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Title: Gas-Engines and Producer-Gas Plants - A Practice Treatise Setting Forth the Principles of Gas-Engines and Producer Design, the Selection and Installation of an Engine, Conditions of Perfect Operation, Producer-Gas Engines and Their Possibilities, the Care of Gas-Engines and Producer-Gas Plants, with a Chapter on Volatile Hydrocarbon and Oil Engines
Author: Mathot, Rodolphe Edgard, 1866-
Language: English
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Gas-Engines and Producer-Gas Plants
A PRACTICE TREATISE SETTING FORTH THE PRINCIPLES OF GAS-ENGINES AND
PRODUCER DESIGN, THE SELECTION AND INSTALLATION OF AN ENGINE, CONDITIONS
OF PERFECT OPERATION, PRODUCER-GAS ENGINES AND THEIR POSSIBILITIES, THE
CARE OF GAS-ENGINES AND PRODUCER-GAS PLANTS, WITH A CHAPTER ON VOLATILE
HYDROCARBON AND OIL ENGINES
BY R. E. MATHOT, M.E.
Member of the Société des Ingénieurs Civils de France, Institution of
Mechanical Engineers, Association des Ingénieurs de l'Ecole des Mines du
Hainaut of Brussels
TRANSLATED FROM ORIGINAL FRENCH MANUSCRIPT BY WALDEMAR B. KAEMPFFERT
WITH A PREFACE BY DUGALD CLERK, M. INST. C.E., F.C.S.
ILLUSTRATED
NEW YORK
MUNN & COMPANY
OFFICE OF THE SCIENTIFIC AMERICAN
361 BROADWAY
1905
PREFACE TO
"MATHOT'S GAS-ENGINES AND PRODUCER-GAS PLANTS"
BY
DUGALD CLERK, M. INST.C.E., F.C.S.
Mr. Mathot, the author of this interesting work, is a well-known Belgian
engineer, who has devoted himself to testing and reporting upon gas and
oil engines, gas producers and gas plants generally for many years past.
I have had the pleasure of knowing Mr. Mathot for many years, and have
inspected gas-engines with him. I have been much struck with the ability
and care which he has devoted to this subject. I know of no engineer
more competent to deal with the many minute points which occur in the
installation and running of gas and oil engines. I have read this book
with much interest and pleasure, and I consider that it deals
effectively and fully with all the principal detail points in the
installation, operation, and testing of these engines. I know of no work
which has gone so fully into the details of gas-engine installation and
up-keep. The work clearly points out all the matters which have to be
attended to in getting the best work from any gas-engine under the
varying circumstances of different installations and conditions. In my
view, the book is a most useful one, which deserves, and no doubt will
obtain, a wide public recognition.
DUGALD CLERK.
_March, 1905._
INTRODUCTION
The constantly increasing use of gas-engines in the last decade has led
to the invention of a great number of types, the operation and care of
which necessitate a special practical knowledge that is not exacted by
other motors, such as steam-engines.
Explosion-engines, driven by illuminating-gas, producer-gas, oil,
benzin, alcohol and the like, exact much more care in their operation
and adjustment than steam-engines. Indeed, steam-engines are regularly
subjected to comparatively low pressures. The temperature in the
cylinders, moreover, is moderate.
On the other hand, the explosion-motor is irregularly subjected to high
and low pressures. The temperature of the gases at the moment of
explosion is exceedingly high. It is consequently necessary to resort to
artificial means for cooling the cylinder; and the manner in which this
cooling is effected has a very great influence on the operation of the
motor. If the cooling be effected too rapidly, the quantity of gas
consumed is considerably increased; if the cooling be effected too
slowly, the motor parts will quickly deteriorate.
In order to reduce the gas consumption to a minimum, a matter which is
particularly important when the motor is driven by street-gas, the
explosive mixture is compressed before ignition. Only if all the parts
are built with joints absolutely gas-tight is it possible to obtain this
compression. The slightest leakage past the valves or around the piston
will sensibly increase the consumption.
The mixture should be exploded at the exact moment the piston starts on
its working stroke. If ignition occurs too soon or too late, the result
will be a marked diminution in the useful effect produced by the
expansion of the gas. All ignition devices are composed of delicate
parts, which cannot be too well cared for.
It follows from what has thus far been said that the causes of
perturbation are more numerous in a gas than in a steam engine; that
with a gas-engine, improper care will lead to a much greater increase in
consumption than with a steam-engine, and will cause a waste in power
which would hardly be appreciable in steam-engines, whether their joints
be tight or not.
It is the purpose of this manual to indicate the more elementary
precautions to be taken in the care of an engine operating under normal
conditions, and to explain how repairs should be made to remedy the
injuries caused by accidents. Engines which are of less than 200
horse-power and which are widely used in a small way will be primarily
considered. In another work the author will discuss more powerful
engines.
Before considering the choice, installation, and operation of a
gas-engine, it will be of interest to ascertain the relative cost of
different kinds of motive power. Disregarding special reasons which may
favor the one or the other method of generating power, the net cost per
horse-power hour will be considered in each case in order to show which
is the least expensive method of generating power in ordinary
circumstances.
R. E. MATHOT.
MARCH, 1905.
TABLE OF CONTENTS
CHAPTER I
PAGE
MOTIVE POWER AND COST OF INSTALLATION 17
CHAPTER II
SELECTION OF AN ENGINE
The Otto Cycle.--The First Period.--The Second Period.--The Third
Period.--The Fourth Period.--Valve Mechanism.--Ignition.--
Incandescent Tubes.--Electric Ignition.--Electric Ignition by
Battery and Induction-Coil.--Ignition by Magnetos.--The Piston.--
Arrangement of the Cylinder.--The Frame.--Fly-Wheels.--Straight
and Curved Spoke Fly-Wheels.--The Crank-Shaft.--Cams, Rollers,
etc.--Bearings.--Steadiness.--Governors.--Vertical Engines.--
Power of an Engine.--Automatic Starting 21
CHAPTER III
THE INSTALLATION OF AN ENGINE
Location.--Gas-Pipes.--Dry Meters.--Wet Meters.--Anti-Pulsators,
Bags, Pressure-Regulators.--Precautions.--Air Suction.--
Exhaust.--Legal Authorization 69
CHAPTER IV
FOUNDATION AND EXHAUST
The Foundation Materials.--Vibration.--Air Vibration, etc.--
Exhaust Noises 87
CHAPTER V
WATER CIRCULATION
Running Water.--Water-Tanks.--Coolers 98
CHAPTER VI
LUBRICATION
Quality of Oils.--Types of Lubricators 111
CHAPTER VII
CONDITIONS OF PERFECT OPERATION
General Care.--Lubrication.--Tightness of the Cylinder.--
Valve-Regrinding.--Bearings.--Crosshead.--Governor.--Joints.--
Water Circulation.--Adjustment 121
CHAPTER VIII
HOW TO START AN ENGINE.--PRELIMINARY PRECAUTIONS
Care during Operation.--Stopping the Engine 128
CHAPTER IX
PERTURBATIONS IN THE OPERATION OF ENGINES AND
THEIR REMEDY
Difficulties in Starting.--Faulty Compression.--Pressure of Water
in the Cylinder.--Imperfect Ignition.--Electric Ignition by
Battery or Magneto.--Premature Ignition.--Untimely
Detonations.--Retarded Explosions.--Lost Motion in Moving
Parts.--Overheated Bearings.--Overheating of the Cylinder.--
Overheating of the Piston.--Smoke arising from the Cylinder.--
Back Pressure to the Exhaust.--Sudden Stops 134
CHAPTER X
PRODUCER-GAS ENGINES
High Compression.--Cooling.--Premature Ignition.--The Governing
of Engines 153
CHAPTER XI
PRODUCER-GAS
Street-Gas.--Composition of Producer-Gases.--Symptoms of
Asphyxiation.--Gradual, Rapid Asphyxiation.--Slow, Chronic
Asphyxiation.--First Aid in Cases of Carbon Monoxide
Poisoning.--Sylvester Method.--Pacini Method.--Impurities of
the Gases 165
CHAPTER XII
PRESSURE GAS-PRODUCERS
Dowson Producer.--Generators.--Air-Blast.--Blowers.--Fans.--
Compressors.--Exhausters.--Washing and Purifying.--
Gas-Holder.--Lignite and Peat Producers.--Distilling-Producers.--
Producers Using Wood Waste, Sawdust, and the like.--
Combustion-Generators.--Inverted Combustion 174
CHAPTER XIII
SUCTION GAS-PRODUCERS
Advantages.--Qualities of Fuel.--General Arrangement.--
Generator.--Cylindrical Body.--Refractory Lining.--Grate and
Support for the Lining.--Ash-pit.--Charging-Box.--
Slide-Valve.--Cock.--Feed-Hopper.--Connection of Parts.--Air
Supply.--Vaporizer.--Preheaters.--Internal Vaporizers.--
External Vaporizers.--Tubular Vaporizers.--Partition
Vaporizers.--Operation of the Vaporizers.--Air-Heaters.--
Dust-Collectors.--Cooler, Washer, Scrubber.--Purifying
Apparatus.--Gas-Holders.--Drier.--Pipes.--Purifying-Brush.--
Conditions of Perfect Operation of Gas-Producers.--
Workmanship and System.--Generator.--Vaporizer.--Scrubber.--
Assembling the Plant.--Fuel.--How to Keep the Plant in Good
Condition.--Care of the Apparatus.--Starting the Fire for the
Gas-Producer.--Starting the Engine.--Care of the Generator
during Operation.--Stoppages and Cleaning 199
CHAPTER XIV
OIL AND VOLATILE HYDROCARBON ENGINES
Oil-Engines.--Volatile Hydrocarbon Engines.--Comparative Costs.--
Tests of High-Speed Engines.--The Manograph.--The Continuous
Explosion-Recorder for High-Speed Engines.--Records 264
CHAPTER XV
THE SELECTION OF AN ENGINE
The Duty of a Consulting Engineer.--Specifications.--Testing the
Plant.--Explosion-Recorder for Industrial Engines.--Analysis of
the Gases.--Witz Calorimeter.--Maintenance of Plants.--Test of
Stockport Gas-Engine with Dowson Pressure Gas-Producer.--Test of
a Winterthur Engine.--Test of a Winterthur Producer-Gas
Engine.--Test of a Deutz Producer-Gas Engine and Suction
Gas-Producer.--Test of a 200-H.P. Deutz Suction Gas-Producer and
Engine 279
CHAPTER I
MOTIVE POWER--COST OF INSTALLATION
The ease with which a gas-engine can be installed, compared with a
steam-engine is self-evident. In places where illuminating gas can be
obtained and where less than 10 to 15 horse-power is needed, street-gas
is ordinarily employed.[A] The improvements which have very recently
been made in the construction of suction gas-generators, however, would
seem to augur well for their general introduction in the near future,
even for very small powers.
The installation of small street-gas-engines involves simply the making
of the necessary connections with gas main and the mounting of the
engine on a small base.
An economical steam-engine of equal power would necessitate the
installation of a boiler and its setting, the construction of a
smoke-stack, and other accessories, while the engine itself would
require a firm base. Without exaggeration it may be asserted that the
installation of a steam-engine and of its boiler requires five times as
much time and trouble as the installation of a gas-engine of equal
power, without considering even the requirements imposed by storing the
fuel (Fig. 1). Small steam-engines mounted on their own boilers, or
portable engines, the consumption of which is generally not economical,
are not here taken into account.
[Illustration: FIG. 1.--30 H.P. Gas-engine and suction gas-producer.]
[Illustration: FIG. 1_A_.--30 H.P. Steam-engine, boiler and smoke-stack.]
So far as the question of cost is concerned, we find that a 15 to 20
horse-power steam-engine working at a pressure of 90 pounds and having a
speed of 60 revolutions per minute would cost about 16-2/3 per cent.
more than a 15 horse-power gas-engine, with its anti-pulsators and other
accessories. The foundation of the steam-engine would likewise cost
about 16-2/3 per cent. more than that of the gas-engine. Furthermore the
installation of the steam-engine would mean the buying of piping, of a
boiler of 100 pounds pressure, and of firebrick, and the erection of a
smoke-stack having a height of at least 65 feet. Beyond a little
excavating for the engine-base and the necessary piping, a gas-engine
imposes no additional burdens. It may be safely accepted that the
steam-engine of the power indicated would cost approximately 45 per
cent. more than the gas-engine of corresponding power.
The cost of running a 15 to 20 horse-power steam-engine is likewise
considerably greater than that of running a gas-engine of the same size.
Considering the fuel-consumption, the cost of the lubricating oil
employed, the interest on the capital invested, the cost of maintenance
and repair, and the salary of an engineer, it will be found that the
operation of the steam-engine is more expensive by about 23 per cent.
This economical advantage of the gas over the steam-engine holds good
for higher power as well, and becomes even more marked when
producer-gas is used instead of street-gas. Comparing, for example, a 50
horse-power steam-engine having a pressure of 90 pounds and a speed of
60 revolutions per minute, with a 50 horse-power producer-gas engine,
and considering in the case of the steam-engine the cost of a boiler of
suitable size, foundation, firebrick, smoke-stack, etc., and in the case
of the gas-engine the cost of the producer, foundation, and the like, it
will be found that the installation of a steam-engine entails an
expenditure 15 per cent. greater than in the case of the producer-gas
engine. However, the cost of operating and maintaining the steam-engine
of 50 horse-power will be 40 per cent. greater than the operation and
maintenance of the producer-gas engine.
From the foregoing it follows that from 15 to 20 up to 500 horse-power
the engine driven by producer-gas has considerably the advantage over
the steam-engine in first cost and maintenance. For the development of
horse-powers greater than 500, the employment of compound
condensing-engines and engines driven by superheated steam considerably
reduces the consumption, and the difference in the cost of running a
steam- and gas-engine is not so marked. Still, in the present state of
the art, superheated steam installations entail considerable expense for
their maintenance and repair, thereby lessening their practical
advantages and rendering their use rather burdensome.
FOOTNOTES:
[A] Recent improvements made in suction gas-producers will probably lead
to the wide introduction of producer gas engines even for small power.
CHAPTER II
THE SELECTION OF AN ENGINE
Explosion-engines are of many types. Gas-engines, of the four-cycle
type, such as are industrially employed, will here be principally
considered.
=The Otto Cycle.=--The term "four-cycle" motor, or Otto engine, has its
origin in the manner in which the engine operates. A complete cycle
comprises four distinct periods which are diagrammatically reproduced in
the accompanying drawings.
=The First Period.=--_Suction:_ The piston is driven forward, creating a
vacuum in the cylinder, and simultaneously drawing in a certain quantity
of air and gas (Fig. 2).
[Illustration: FIG. 2.--First cycle: Suction.]
=The Second Period.=--_Compression:_ The piston returns to its initial
position. All admission and exhaust valves are closed (Fig. 3). The
mixture drawn in during the first period is compressed.
=The Third Period.=--_Explosion and Expansion:_ When the piston has
reached the end of its return stroke, the compressed mixture is ignited.
Explosion takes place at the dead center. The expansion of the gas
drives the piston forward (Fig. 4).
[Illustration: FIG. 3.--Second cycle: Compression.]
[Illustration: FIG. 4.--Third cycle: Explosion and expansion.]
=The Fourth Period.=--_Exhaust:_ The piston returns a second time. The
exhaust-valve is opened, and the products of combustion are discharged
(Fig. 5).
[Illustration: FIG. 5.--Fourth cycle: Exhaust.]
These various cycles succeed one another, passing through the same
phases in the same order.
=Valve Mechanism.=--It is to be noted that in modern motors valves are
used which are better adapted to the peculiarities of explosion-engines
than were the old slide-valves used when the Otto engine was first
introduced. The slide-valve may now be considered as an antiquated
distributing device with which it is impossible to obtain a low
consumption.
In old-time gas-engines rather low compressions were used. Consequently
a very low explosive power of the gaseous mixture, and low temperatures
were obtained. The slide-valves were held to their seats by the pressure
of external springs, and were generously lubricated. Under these
conditions they operated regularly. Nowadays, the necessity of using
gas-engines which are really economical has led to the use of high
compressions with the result that powerful explosions and high
temperatures are obtained. Under these conditions slide-valves would
work poorly. They would not be sufficiently tight. To lubricate them
would be difficult and ineffective. Furthermore, large engines are
widely used in actual practice, and with these motors the frictional
resistance of large slide-valves, moving on extensive surfaces would be
considerable and would appreciably reduce the amount of useful work
performed.
[Illustration: FIG. 6.--Modern valve mechanism.]
By reason of its peculiar operation, the slide-valve is objectionable,
the gases being throttled at the time of their admission and discharge.
As a result of these objections there are losses in the charge; and
obnoxious counter-pressures occur. The necessity of using elements
simple in their operation and free from the objections which have been
mentioned, has naturally led to the adoption of the present valve. This
valve is used both for the suction of the gas and of the air, as well as
for the exhaust, with the result that either of these two essential
phases in the operation of the motor can be independently controlled.
The valves offer the following advantages: Their tightness increases
with the pressure, since they always open toward the interior of the
cylinder (Fig. 6). They have no rubbing surfaces, and need not,
therefore, be lubricated. Their opening is controlled by levers provided
with quick-acting cams; and their closure is effected by coiled springs
almost instantaneous in their action (Fig. 7). Each valve, depending
upon the purpose for which it is used, can be mounted in that part of
the cylinder best suited for its particular function. The types of
valved motors now used are many and various. In order to attain economy
in consumption and regularity in operation they should meet certain
essential requirements which will here be reviewed.
Apart from proportioning the areas properly and from providing a
suitable means of operation, it is indispensable that the valves should
be readily accessible. Indeed, the valves should be regularly examined,
cleaned and ground. It follows that it should be possible to take them
apart easily and quickly.
[Illustration: FIG. 7.--Controlling mechanism of valve.]
It is necessary that the exhaust-valve be well cooled; otherwise the
valve, exposed as it is to high temperatures, will suffer derangement
and may cause leakage. The water-jacket should, therefore, surround the
seat of the exhaust-valve, care being taken that the cooling water be
admitted as near to it as possible (Fig. 8). The motor should control
the air-let valve or that of the gaseous mixture. Hence these valves
should not be actuated simply by springs, because springs are apt to
move under the influence of the vacuum produced by suction.
[Illustration: FIG. 8.--Water-jacketed valve.]
The mixture of gas and air should not be admitted into the cylinder at
too low a pressure; otherwise the weight of the mixture admitted would
be lower than it ought to be, inasmuch as under these conditions the
valve will be opened too tardily and closed prematurely. At the
beginning as well as at the end of its stroke the linear velocity of the
piston is quite inadequate to create a vacuum sufficient to overcome the
resistance of the spring. It is, therefore, generally the practice
separately to control the opening or closing of the one or the other
valve (gas-valve or mixture-valve). Consequently these valves must be
actuated independently of each other. Nowadays they are mechanically
controlled almost exclusively,--a method which is advocated by
well-known designers for industrial motors in particular. Valves which
are not actuated in this manner (free valves) have only the advantage of
simplicity of operation. Nevertheless, this arrangement is still to be
found in certain oil and benzine engines, notably in automobile-motors.
In these motors it is necessary to atomize the liquid fuel by means of
aspired air, in order to produce an explosive, gaseous mixture.
=Ignition.=--In the development of the gas-engine, the incandescent tube
and the electric spark have taken the place of the obsolete naked flame.
The last-mentioned mode of exploding the gaseous mixture will not,
therefore, be discussed.
The hot tube of porcelain or of metal has the indisputable merit of
regularity of operation. The methods by which this operation is made as
perfect as possible are many. Since certainty of ignition is obtained by
means of the tube, it is important to time the ignition, so that it
shall occur exactly at the moment when the piston is at the dead
center. It has been previously stated that premature or belated ignition
of the explosive mixture appreciably lessens the amount of useful work
performed by the expansion of the gas. If ignition occur too soon, the
mixture will be exploded before the piston has reached the dead center
on its return stroke. As a result, the piston must overcome a
considerable resistance due to the premature explosion and the
consequent pressure. Furthermore, by reason of the high temperature of
explosion, the gaseous products are very rapidly cooled. This rapid
cooling causes a sudden drop in the pressure; and since a certain
interval elapses between the moment of explosion and the moment when the
piston starts on its forward stroke, the useful motive effort is the
more diminished as the ignition is more premature.
=Incandescent Tubes.=--In Figs. 9 and 10 two systems most commonly used
are illustrated. In these two arrangements, in which no valve is used,
the length or height to which the tube is heated by the outer flame is
so controlled that the gaseous mixture, which has been driven into the
tube after compression, reaches the incandescent zone as nearly as
possible at the exact moment when ignition and explosion should take
place. The temperature of the flame of the burner, the richness of the
gaseous mixture, and other circumstances, however, have a marked
influence on the time of ignition, so that the mixture is never fired at
the exact moment mentioned.
[Illustration: FIGS. 9-10.--Valveless hot tubes.]
These considerations lead to the conclusion that motors in which the
mixture is exploded by hot tubes provided with an ignition-valve are
preferable to valveless tubes. By the use of a special valve, positively
controlled by the motor itself, the chances of untimely ignition are
lessened, because it is necessary simply to regulate the temperature and
the position of the tube in order that ignition may be surely effected
immediately upon the opening of the valve, at the very moment the
cylinder gases come into contact with the incandescent portion of the
tube (Fig. 11). Many manufacturers, however, do not employ the
ignition-valve on motors of less than 15 to 20 horse-power, chiefly
because of the cheaper construction. The total consumption is of less
moment in a motor of small than of great power, and the loss due to the
lack of an ignition-valve not so marked. In a high-power engine,
premature explosion may be the cause of the breaking of a vital part,
such as the piston-rod or the crank-shaft. For this reason, a valve is
indispensable for engines of more than 20 to 25 horse-power. A breakage
of this kind is less to be feared in a small motor, where the parts are
comparatively stout. The gas consumption of a well-designed burner does
not exceed from 3.5 to 5 cubic feet per hour.
[Illustration: FIG. 11.--Ignition-tube with valve.]
=Electric Ignition.=--Electric ignition consists in producing a spark in
the explosion-chamber of the engine. The nicety with which it can be
controlled gives it an undeniable advantage over the hot tube. But the
objection has been raised, perhaps with some force, that it entails
certain complications in installing the engine. Its opponents even
assert that the power and the rapidity of the deflagration of the
explosive mixture are greater with hot-tube ignition. This reason may
have caused the hot-tube system to prevail in England, where
manufacturers of gas-engines are very numerous and not lacking in
experience.
Electric ignition is effected in gas-engines by means of a battery and
spark-coil, or by means of a small magneto machine which mechanically
produces a current-breaking spark.
[Illustration: FIG. 12.--Electric ignition by spark-coil and battery.]
[Illustration: FIG. 13.--Spark-plug.]
=Electric Ignition by Battery and Induction-Coil.=--The first system is
the cheaper; but it exacts the most painstaking care in maintaining the
parts in proper working condition. It comprises three essential
elements--a battery, a coil, and a spark-plug (Fig. 12). The battery may
be a storage-battery, which must, consequently, be recharged from time
to time; or it may be a primary battery which must be frequently
renewed and carefully cleaned. The induction-coil is fitted with a
trembler or interrupter, which easily gets out of order and which must
be regulated with considerable accuracy. The spark-plug is a
particularly delicate part, subject to many possible accidents. The
porcelain of which it is made is liable to crack. It is hard to obtain
absolutely perfect insulation; for the terminals deteriorate as they
become overheated, break, or become foul (Fig. 13). In oil-engines,
especially, soot is rapidly deposited on the terminals, so that no spark
can be produced. In benzine or naphtha motors, such an accident is less
likely to happen. In automobile-motors, however, the spark-plug only too
often fails to perform its function. The one remedy for these evils is
to be found in the most painstaking care of the spark-plug and of the
other elements of the ignition system.
[Illustration: FIG. 14.--Magneto ignition apparatus.]
[Illustration: FIG. 15.--General view and details of a magneto ignition
apparatus.]
=Ignition by Magnetos.=--Magneto apparatus, on the other hand, are
noteworthy for the regularity of their operation. They may be used for
several years without being remagnetized, and require no exceptional
care. Magneto ignition devices are mechanically actuated, the necessary
displacement of the coil being effected by means of a cam carried on a
shaft turning with half the motor speed (Figs. 14 and 15). At the moment
when it is released by the cam, the coil is suddenly returned to its
initial position by means of a spring. This rapid movement generates a
current that passes through terminals, which are arranged within the
cylinder and which are immediately separated by mechanical means. Thus a
much hotter circuit-breaking spark is produced, which is very much more
energetic than that of a battery and induction-coil, and which surely
ignites the gaseous mixture in the cylinder. The terminals are generally
of steel, sometimes pointed with nickel or platinum (Fig. 16). The only
precaution to be observed is the exclusion of moisture and occasional
cleaning. For engines driven by producer-gas magneto-igniters are
preferable to cells and batteries. In general, electrical ignition is to
be recommended for high-pressure engines.
[Illustration: FIG. 16.--Contacts of a magneto-igniter.]
[Illustration: FIG. 17.--Device for regulating the moment of ignition.]
In order to explain more clearly modern methods of ignition a diagram is
presented, showing an electric magneto-igniter applied to the
cylinder-head of a Winterthur motor, and also a sectional view of the
member varying the make-and-break contacts which are mounted in the
explosion-chamber (Figs. 18 and 19)
1. The magneto _A_ consists of horseshoe-magnets, between the poles of
which the armature rotates. At its conically turned end, the
armature-shaft carries an arm _B_, held in place by a nut.
[Illustration: FIG. 18.--Winterthur electric ignition system.]
2. The igniter _C_ is a casting secured to the cylinder-head by a
movable strap and provided with two axes _D_ and _M_, of which the one,
_D_, made of bronze, is movable, and is fitted with a small interior
contact-hammer, a percussion-lever, and an exterior recoil-spring; the
other, _M_, is fixed, insulated, and arranged to receive the current
from the magneto _A_, by means of an insulated copper wire _E_.
3. The spring _F_ comprises two continuous coils contained in a brass
casing, and actuating a steel striking or percussion-pin.
4. The controlling devices of the magneto include a stem or rod _G_,
slidable in a guide _H_, provided with a safety spring and mounted on an
eccentric spindle, the position of which can be varied by means of a
regulating-lever (_I_). The rod is operated from the distributing-shaft,
on the conical end of which a cam _J_ carrying a spindle is secured.
[Illustration: FIG. 19.--Contacts of the Winterthur system.]
_Regulation of the Magneto._--The position assumed by the armature when
at rest is a matter of importance in obtaining a good spark on breaking
the circuit. The marks on the armature should be noted. The position of
the armature may be experimentally varied, in order to obtain a spark of
maximum intensity, by changing the position of the arm B on the
armature-shaft.
_Control of the Magneto._--The controlling gear should enable the
armature to oscillate from 20 to 25 degrees. The time at which the
breaking of the circuit is effected can be regulated by shifting the
handle (_I_). In starting the engine, the circuit can be broken with a
slight retardation, which is lessened as the engine attains its normal
speed.
_Igniter._--It is advisable that there should be a play of 1/2 mm.
(0.0196 in.) between the lever _Z_ when at rest and the striking-pin.
The axis _D_ of the circuit-breaking device should be easily movable;
and the hammer which it carries at its end toward the interior of the
cylinder should be in perfect contact with the stationary spindle _M_,
which is electrically insulated. This spindle _M_ should be well
enclosed, in order to prevent any leakage that might cause a
deterioration of the insulating material.
The subject of ignition is of such extreme importance that the author
will recur to it from time to time in the various chapters of this book.
Too much stress cannot be laid upon proper timing; otherwise there will
be a needless waste of power. Cleanliness is a point that must be
observed scrupulously; for spark-plugs are apt to foul only too readily,
with the result that short-circuits and misfires are apt to occur. In
oil and volatile hydrocarbon engines the tendency to fouling is
particularly noticeable. In the chapter devoted to these forms of
motors the author has dwelt upon the precautions that should be taken to
forestall a possible derangement of the ignition apparatus. As a general
rule the ignition apparatus installed by trustworthy manufacturers will
be found best suited for the requirements of the engine.
The apparatus should be fitted with a device by which the ignition can
be duly timed by hand during operation (Fig. 17).
[Illustration: FIG. 20.--Design of the piston.]
=The Piston.=--Coming, as it does, continually in contact with the
ignited gases, the piston is gradually heated to a high temperature. The
rear face of the piston should preferably be plane. Curved surfaces are
not to be recommended because they cool off badly. Likewise, faces
having either inserted parts or bolt-heads are to be avoided, since they
are liable to become red-hot and to ignite the mixture prematurely (Fig.
20).
[Illustration: FIG. 21.--Piston with lubricated pin.]
Among the parts of the piston which rapidly wear away because constant
lubrication is difficult, is the connection with the piston-rod (Fig.
21). It is important that the bearing at the piston-pin be formed of two
parts which can be adjusted to take up the wear. The pin itself should
be of case-hardened steel. For large engines, some manufacturers have
apparently abandoned the practice of locking the pin, by set-screws, in
flanges cast in one piece with the piston. Indeed, the piston is often
fractured by reason of the expansion of the pins thus held on two sides.
It seems advisable to secure the pin by means of a single screw in one
of the flanges, fitting it by pressure against the opposite boss. The
use of wedges or of clamping-screws, introduced from without the piston
to hold the pin, should be avoided. It may happen that the wedges will
be loosened, will move out, and will grind the cylinder, causing
injuries that cannot be detected before it is too late. The strength of
the piston-pin should be so calculated that the pressure per square inch
of projected surface does not exceed 1,500 to 2,850 pounds per square
inch. It should be borne in mind that the initial pressure of the
explosion is often equal to 400 to 425 pounds per square inch. Some
manufacturers mount the pin as far to the back of the piston as
possible, so as to bring it nearer the point of application of the
motive force of the explosion. Other manufacturers, on the other hand,
mount the pin toward the front of the piston. No great objection can be
raised against either method. In the former case the position of the
rings will limit that of the pin.
The number of these rings ought not to be less than four or five,
arranged at the rear of the piston. It is to be observed that makers of
good engines use as many as 8 to 10 rings in the pistons of fair-sized
motors.
Piston-rings of gray pig-iron can be adjusted with the greatest nicety
in such a manner that, by means of tongues fitting in their grooves,
they are held from turning in the latter, whereby their openings are
prevented from registering and allowing the passage of gas. As a general
rule, a large number of rings may be considered a distinguishing feature
of a well-built engine. In order to prevent a too rapid wear of the
cylinder, several German manufacturers finish off the front of the
piston with bronze or anti-friction metal in engines of more than 40 to
50 horse-power. It is to be observed, however, that this expedient is
not applicable to motors the cylinders of which are comparatively cold;
otherwise the bronze or anti-friction metal will deteriorate.
=Arrangement of the Cylinder.=--The cylinder shell or liner, in which
the piston travels, and the water-jacket should preferably be made in
separate pieces and not cast of the same metal, in order to permit a
free expansion (Figs. 22 and 23). If for want of care or of proper
lubrication, which frequently occurs in gas-engines, the cylinder should
be injured by grinding, it can be easily renewed, without the loss of
all the connecting parts.
[Illustration: FIG. 22.--Head, jacket and liner of cylinder, cast in one
piece.]
[Illustration: FIG. 23.--Cylinder with independent liner and head.]
For the same reason, the cylinder and its casing should be independent
of the frame. In many horizontal engines, the cylinders overhang the
frame throughout the entire length, by reason of the joining of their
front portions with the frames. Although such a construction is attended
with no serious consequences in small engines, nevertheless in large
engines it is exceedingly harmful. Indeed, in most modern single-acting
engines, the pistons are directly connected with the crank-shaft by the
piston-rod, without any intermediate connecting-rod or cross-head. The
vertical reaction of the motive effort on the piston is, therefore,
taken up entirely by the thrust of the cylinder, which is also vertical
(Fig. 24). This thrust, acting against an unsupported part, may cause
fractures; at any rate, it entails a rapid deterioration of the cylinder
joint.
[Illustration: FIG. 24.--Single-acting engines.]
[Illustration: FIG. 25.--Engine with inclined bearings.]
=The Frame.=--Gas-engines driven as they are, by explosions, giving rise
to shocks and blows, should be built with frames, heavy, substantial,
and broad-based, so as to rest solidly on the ground. This essential
condition is often fulfilled at the cost of the engine's appearance; but
appearance will be willingly sacrificed to meet one of the requirements
of perfect operation. For engines of more than 8 to 10 horse-power,
frames should be employed which can be secured to the masonry foundation
without a separate pedestal or base. Some manufacturers, for the purpose
of lightening the frame, attach but little importance to the foundation
and to strength of construction, and employ the design illustrated in
place of the crank-shaft bearing (Fig. 25); others, in order to
facilitate the adjusting of the connecting-rod bearings, prefer the
second form (Fig. 26). It is evident that, in the first case, a part of
the effort produced by the explosion reacts on the upper portion of the
connecting-rod bearing, on the cap of the crank-shaft bearing, and
consequently on the fastening-bolts. In the second case, if the
adjustment be not very carefully made, or if the rubbing surfaces are
insufficient, the entire thrust due to the explosion will be received
by the meeting parts of the two bushings, thus injuring them and causing
a more rapid wear. In the construction of large engines, some
manufacturers take the precaution of forming the connecting-rod bearings
of four parts, adjustable to take up the wear, so that the effort is
exerted against the parts disposed at right angles to each other. A form
that seems rational is that shown in Fig. 27, in which the reaction of
the thrust is taken up by the lower bearing, rigidly supported by the
braced frame, in the direction opposite to that of the explosive effort.
[Illustration: FIG. 26.--Engine with straight bearings.]
[Illustration: FIG. 27.--Engine with correctly designed bearings.]
The sum of the projecting surfaces of the two bearings should be so
calculated that a maximum explosive pressure of 405 to 425 pounds per
square inch will not subject the bearings to a pressure higher than 425
to 550 pounds per square inch.
=Fly-Wheels.=--In gas-engines particularly, the fly-wheel should be
secured to the crank-shaft with the utmost care. It should be mounted as
near as possible to the bearings; otherwise the alinement of the shaft
will be destroyed and its strength impaired. If the fly-wheel be
fastened by means of a key or wedge having a projecting head, it is
advisable to cover the end of the shaft by a movable sleeve. The
fly-wheel should run absolutely true and straight even if the explosion
be premature. In well-built engines the fly-wheels are lined up and
shaped to the rim. The periphery is slightly rounded in order the better
to guide the belt when applied to the wheel.
[Illustration: FIG. 28.--Single fly-wheel engine with external bearing.]
Furthermore, fly-wheels should be nicely balanced; those are to be
preferred which have no counter-weights cast or fastened to the hub, the
spokes, or the rim. The system of balancing the engine by means of two
fly-wheels, mounted on opposite sides, is used chiefly for the purpose
of equalizing the inertia effects. Special engines, employed for driving
dynamos, and even industrial engines of high power, are preferably
fitted with but a single fly-wheel, with an outer bearing, since they
more readily counteract the cyclic irregularities or variations of speed
occurring in a single revolution (Fig. 28). If in this case a pulley be
provided, it should be mounted between the engine and the outer
bearing. The following advantages may be cited in favor of the single
fly-wheel, particularly in the case of dynamo-driving engines:
1. The single fly-wheel permits a more ready access to the parts to be
examined.
2. It involves the employment of a third bearing, thus avoiding the
overhang caused by two ordinary fly-wheels.
3. It avoids the torsional strain to which the two-wheel crank is
subjected when starting, stopping, and changing the load, the peripheral
resistance varying in one of the fly-wheels, while the other is
subjected to a strain in the opposite direction on account of the
inertia.
4. Two fly-wheels, keyed as they are to projecting ends of the shaft,
will be so affected at the rims by the explosions that the belts will
shake.
The third bearing which characterizes the single-fly-wheel system, is
but an independent support, resting solidly on the masonry bed of the
engine. The bearing with its independent support is sufficiently rigid,
and is not subjected to any stress from the crank at the moment of
explosion, the reaction of the crank affecting only the frame bearings.
With such fly-wheels, reputable firms guarantee a cyclic regularity
which compares favorably with that of the best steam-engines. For a duty
varying from a third of the load to the maximum load, these engines,
when driving direct-current dynamos for directly supplying an
electric-light circuit, will insure perfect steadiness of the light;
and the effectually aperiodic measuring instruments will not indicate
fluctuations greater than 2 to 3 per cent. of the tension or intensity
of the current. The coefficient of the variations in the speed of a
single revolution will thus be not far from 1/60.
[Illustration: FIG. 29.--Curved spoke fly-wheel.]
=Straight and Curved Spoke Fly-Wheels.=--The spokes of fly-wheels are
either straight or curved. In assembling the motor parts it too often
occurs that curved spoke fly-wheels are mounted with utter disregard of
the direction in which they are to turn. It is important that curved
spokes should be subjected to compression and not to traction. Hence the
fly-wheels should be so mounted that the concave portions of the spokes
travel in the direction of rotation, as shown in the accompanying
diagram (Fig. 29). If a single fly-wheel be employed on an engine of the
type in which the speed is governed by the "hit-and-miss" system, the
fly-wheel should be extra heavy to counteract the irregularities of the
motive impulses when the engine is not working at its full load, or in
other words, when no explosion takes place at every cycle.
[Illustration: FIG. 30.--Forged crank-shafts.]
=The Crank-Shaft.=--The crank-shaft should be made of the best mild
steel. Those shafts are to be preferred the cranks of which are not
forged on (Fig. 30), but cut out of the mass of metal; furthermore, the
brackets or supports should be planed and shaped so that they are square
in cross-section.
[Illustration: FIG. 31.--Correct design of crank-shaft.]
Such a design involves fine workmanship and speaks well for the
construction of the whole engine. Moreover, it enables the bearings to
be brought nearer each other, reduces to a minimum that part of the
crank-shaft which may be considered the weakest, and permits a rational
and exact counterbalancing of the moving parts, such as the crank and
the end of the connecting-rod. The best manufacturers have adopted the
method of fastening to the cranks balancing weights secured to the
brackets, especially for high-speed engines or for engines of high
power. The projecting surface of the crank-pin should, as a rule, be
calculated for a pressure of 1,400 pounds per square inch.
[Illustration: FIG. 32.--Crank-shaft with balancing weight.]
=Cams, Rollers, etc.=--The cams, rollers, thrust-bearings, as well as
the piston-pin in particular, should be made of good steel,
case-hardened to a depth of at least .08 of an inch. Their hardness and
the degree of cementation may be tested by means of a file. This is the
method followed by the best manufacturers.
=Bearings.=--All the bearings and all guides should be adjustable to
take up the wear. They are usually made of bronze or of the best
anti-friction metal.
=Steadiness.=--The steadiness of engines may be considered from two
different standpoints.
[Illustration: FIG. 33.--Inertia governor.]
1. _Variation of the Number of Revolutions at Different Loads._--This
depends chiefly on the sensitiveness of the governor, which should be of
the "inertia" or of the "ball" (or centrifugal) type. The first form is
rarely employed, except in small engines up to 10 horse-power, and is
applicable only to engines in which the "hit and miss" system is
employed (Fig. 33). The second form is more widely used, and is
applicable to engines having "hit-and-miss" or variable admission
devices. In the first form, the governor simply displaces a very light
member, whatever may be the size of the engine, for which reason the
dimensions are very small. In the second form, on the other hand, the
governor acts either on a conical sleeve or on some other regulating
member offering resistance. Evidently, in order to overcome the
reactions to which it is subjected, it must be as heavy and powerful as
a steam-engine governor. Sufficient allowance is made in a good engine
for variation in the number of revolutions between no load and full
load, not greater than two per cent. if the admission be of the
"hit-and-miss" type, and five per cent. if it be of the variable type.
2. _Cyclic Regularity._--This term means simply that the speed of the
engine is constant in a single revolution. In practice this is never
attained. Allowance is made in engines used for driving direct-current
dynamos for a variation of about 1/60; while in industrial engines a
variation of 1/25 is permissible. Cyclic variation depends only on the
weight of the fly-wheel; whereas variation in the number of revolutions
is determined chiefly by the governor.
=Governors.=--Diagrams are here presented of the principal types of
governors--the inertia governor, the ball or centrifugal governor
controlling an admission-valve of the "hit-and-miss" type (Fig. 34), and
the ball or centrifugal governor controlling a variable gas-admission
valve (Fig. 35).
In distinguishing between the operation of the two last-mentioned types,
it may be stated that the former bears the same relation to the
hit-and-miss gear as it does, for example, to the valve gear of a
Corliss steam-engine. In other words, it is an apparatus that
_indicates_ without _inducing_, admission or cut-off. The second type,
on the other hand, operates by means of slides and the like, as in the
Ridder type of engine, in which it controls the displacement of the
cut-off or distribution slide-valve and is subjected to variable forces,
depending on the pressure, lubrication, the condition of the
stuffing-boxes, and the like.
In gas as well as in steam engines, designs are to be commended which
shield the delicate mechanism from strains and stresses that are likely
to destroy its sensitiveness, as is the case in the automatic cut-off of
the Corliss steam-engine.
[Illustration: FIG. 34.--"Hit-and-miss" governor.]
Governors should be provided with means to permit the manual variation
of the speed while the engine is in operation.
For small motors, one of the most widely used admission devices is that
of the "hit-and-miss" type. As its name indicates, this admission
arrangement allows a given quantity of gas to enter the cylinder for a
number of consecutive intervals, until the engine is about to exceed its
normal speed. Thereupon the governor cuts off the gas entirely. The
result is that, in this system, the number of admissions is variable,
but that each admitted charge is composed of a constant proportion of
gas and air.
The governors employed for the "hit-and-miss" type are either "inertia"
or "centrifugal" governors.
Inertia governors (Fig. 33) are less sensitive than those of the
centrifugal type. They are generally applied only to industrial engines
of small power, in which regularity of operation is a secondary
consideration.
Centrifugal governors employed for gas-engines with "hit-and-miss"
regulation are, as a general rule, noteworthy for their small size,
which is accounted for by the fact that, in most systems, merely a
movable member is placed between the admission-controlling means and the
valve-stem (Fig. 34). It follows that this method of operation relieves
the governor of the necessity of overcoming the resistance of the weight
of moving parts, more or less effectually lubricated, and subjected to
the reaction of the parts which they control.
In engines equipped with variable admission devices for the gas or the
explosive mixture, the governor actuates a sleeve on which the
admission-cam is fastened (Fig. 35). Or, the governor may displace a
conical cam, the reaction of which, on contact with the lever, destroys
the stability of the governor. These conditions justify the employment
of powerful governors which, on account of the inertia of their parts,
diminish the reactionary forces encountered.
The centrifugal governor should be sufficiently effectual to prevent
variations in the number of revolutions within the limits of 2 to 3 per
cent. between no load and approximately full load. Under equivalent
conditions, the inertia governor can hardly be relied upon for a
coefficient of regularity greater than 4 to 5 per cent.
[Illustration: FIG. 35.--Variable admission governor.]
The manner of a governor's operation is necessarily dependent on the
admission system adopted. And the admission system varies essentially
with the size, the purpose of the engine, and the character of the fuel
employed.
[Illustration: FIG. 36.--Vertical engine.]
[Illustration: FIG. 37.--Section through an engine of the vertical or
"steam-hammer" type.]
=Vertical Engines.=--For some years past there seems to have been a
tendency in Europe to use horizontal instead of vertical engines,
especially since engines of more than 10 or 15 horse-power have been
extensively used for industrial purposes. The vertical type is used for
1 to 8 horse-power engines, with the cylinder in the lower part of the
frame, and the shaft and its fly-wheel in the upper part (Fig. 36). The
only merit to be attributed to this arrangement is a great saving of
space. It is evident, however, that beyond a certain size and power,
such engines are unstable. In America particularly, many manufacturers
of high-power engines (50 to 100 horse-power or more) prefer the
vertical or "steam-hammer" arrangement, which consists in placing the
cylinder in the upper part, and the shaft in the lower part of the frame
as close to the ground as possible (Figs. 37 and 38). The problem of
saving space, as well as that of insuring stability, is thus solved, so
that it is easily possible to run up the speed of the engine. There is
also the advantage that the shaft of a dynamo can be directly coupled
up with the crank-shaft of the engine, thus dispensing with a belt,
which, at the least, absorbs 4 to 6 per cent. of the total power. It
should, nevertheless, be borne in mind that the direct coupling of
electric generators to engine-shafts implies the use of extremely large
and, therefore, of extremely costly dynamos. Furthermore, by reason of
this arrangement, groups of electro-generators can be disposed in a
comparatively small amount of space. Some English manufacturers are also
beginning to adopt the "steam-hammer" type of engine for high powers,
the result being a marked saving in material and lowering of the cost of
installation.
[Illustration: FIG. 38.--Side and end elevations of a vertical or
"steam-hammer" engine.]
=Power of the Engine.=--The first thing to be considered is that the
power of a gas-engine is always given in "effective" horse-power, and
that the power of a steam-engine is always given in "indicated"
horse-power in contracts of sale. In England and in the United States,
the expression "nominal" horse-power is still employed. It may be
advisable to define these various terms exactly, since unscrupulous
dealers, to the buyer's loss, have done much to confuse them.
"Indicated" horse-power is a designation applied to the theoretical
power produced by the action of the motive agent on the piston. The work
performed is measured on an indicator card, by means of which the
average pressure to be considered in the computation of the theoretical
power is ascertained.
The "effective" or brake horse-power is equal to the "indicated"
horse-power, less the energy absorbed by passive resistance, friction of
the moving parts, etc.
The "effective" work is an experimental term applied to the power
actually developed at the shaft. This work is of interest solely to the
engine user.
In a well-built motor, in which the passive resistance by reason of the
correct adjustment and simplicity of the parts, is reduced to a minimum,
the "effective" horse-power is about 80 to 87 per cent. of the
"indicated" horse-power, when the engine runs under full load. This
reduced output is usually called the "mechanical efficiency" of the
engine.
"Nominal" horse-power is an arbitrary term in the sense in which it is
used in England and America, where it is quite common. The manufacturers
themselves do not seem to agree on its absolute value. A "nominal"
horse-power, however, is equal to anything from 3 to 4 "effective"
horse-power. The uncertainty which ensues from the use of the term
should lead to its abandonment.
In installing a motor, the determination of its horse-power is a matter
of grave importance, which should not be considered as if the motor were
a steam-engine or an engine of some other type. It must not be forgotten
that, especially at full load, explosion-engines are most efficient, and
that, under these conditions, it will generally be advisable to
subordinate the utility of having a reserve power to the economy which
follows from the employment of a motor running at a load close to its
maximum capacity. On the other hand, the gas-engine user is unwilling to
believe that the stipulated horse-power of the motor which is sold to
him is the greatest that it is capable of developing under industrial
conditions. Business competition has led some firms to sell their
engines to meet these conditions. It is probably not stretching the
truth too far to declare that 80 per cent. of the engines sold with no
exact contract specifications are incapable of maintaining for more than
a half hour the power which is attributed to them, and which the buyer
expects. It follows that the power at which the engine is sold should be
both industrially realized and maintained, if need be, for an entire
day, without the engine's showing the slightest perturbation, or
faltering in its silent and regular operation. To attain this end, it is
essential that the energy developed by the engine in normal or constant
operation should not exceed 90 to 95 per cent. of the maximum power
which it is able to yield, and which may be termed its "utmost power".
As a general rule, especially for installations in which the power
fluctuates from the lowest possible to double this, as much attention
must be paid to the consumption at half load as at full load; and
preference should be given to the engine which, other things being
equal, will operate most economically at its lowest load. In this case
the consumption per effective horse-power is appreciably higher.
Generally, this consumption is greater by 20 to 30 per cent. than that
at full load. This is particularly true of the single-acting engines so
widely used for horse-powers less than 100 to 150.
In some double or triple-acting engines, according to certain writers,
the diminution in the consumption will hardly be proportional to the
diminution of the power, or at any rate, the difference between the
consumption per B.H.P. at full load and at reduced load will be less
than in other engines. It should be observed, however, that this
statement is apparently not borne out by experiments which the author
has had occasion to make. To a slight degree, this economy is obtained
at the cost of simplicity, and consequently, at the cost of the engine.
At all events, the engines have the merit of great cyclic regularity,
rendering them serviceable for driving electric-light dynamos; but this
regularity can also be attained by the use of the extra heavy fly-wheels
which English firms, in particular, have introduced.
=Automatic Starting.=--When the gas-engine was first introduced,
starting was effected simply by manually turning the fly-wheel until
steady running was assured. This procedure, altogether too crude in its
way, is attended with some danger. In a few countries it is prohibited
by laws regulating the employment of industrial machinery. If the engine
be of rather large size one, moreover, which operates at high
pressure--such a method of starting is very troublesome. For these
reasons, among others, manufacturers have devised automatic means of
setting a gas-engine in motion.
Of such automatic devices, the first that shall be mentioned is a
combination of pipes, provided with cocks, by the manipulation of which,
a certain amount of gas, drawn from the supply pipe, is introduced into
the engine-cylinder. The piston is first placed in a suitable position,
and behind it a mixture is formed which is ignited by a naked flame
situated near a convenient orifice. When the explosion takes place the
ignition-orifice is automatically closed, and the piston is given its
motive impulse. The engine thus started continues to run in accordance
with the regular recurrence of the cycles. In this system, starting is
effected by the explosion of a mixture, without previous compression.
Some designers have devised a system of hand-pumps which compress in the
cylinder a mixture of air and gas, ignited at the proper time by
allowing it to come into contact with the igniter, through the
manipulation of cocks (Fig. 39).
These two methods are not absolutely effective. They require a certain
deftness which can be acquired only after some practice. Furthermore,
they are objectionable because the starting is effected too violently,
and because the instantaneous explosion subjects the stationary piston,
crank, and fly-wheel to a shock so sudden that they may be severely
strained and may even break. Moreover, the slightest leakage in one of
the valves or checks may cause the entire system to fail, and,
particularly in the case of the pump, may induce a back explosion
exceedingly dangerous to the man in charge of the engine.
These systems are now almost generally supplanted by the compressed-air
system, which is simpler, less dangerous, and more certain in its
effect.
The elements comprising the system in question include essentially a
reservoir of thick sheet iron, capable of resisting a pressure of 180 to
225 pounds and sufficient in capacity to start an engine several times.
This reservoir is connected with the engine by piping, which is disposed
in one of two ways, depending upon whether the reservoir is charged by
the engine itself operatively connected with the compressor, or by an
independent compressor, mechanically operated.
[Illustration: FIG. 39.--Tangye starter.]
In the first case, the pipe is provided with a stop-cock, mounted
adjacent to the cylinder, and with a check-valve. When the engine is
started and the gas cut off, the air is drawn in at each cycle and
driven back into the reservoir during the period of compression. When
the engine, running under these conditions by reason of the inertia of
the fly-wheel, begins to slow down, the check-valve is closed and the
gas-admission valve opened, so as to produce several explosions and to
impart a certain speed to the engine in order to continue the charging
of the reservoir with compressed air. This done, the valve on the
reservoir itself is tightly closed, as well as the check-valve, so as to
avoid any leakage likely to cause a fall in the reservoir's pressure.
In the second case, which applies particularly to engines of more than
50 horse-power, the charging pipe connected with the reservoir is
necessarily independent of the pipe by means of which the motor is
started. The reservoir having been filled and the decompression cam
thrown into gear, starting is accomplished:
1. By placing the piston in starting position, which corresponds with a
crank inclination of 10 to 20 degrees in the direction of the piston's
movement, from the rear dead center, immediately after the period of
compression;
2. By opening the reservoir-valve;
3. By allowing the compressed air to enter the cylinder rapidly, through
the quick manipulation of the stop-cock, which is closed again when the
impulse is given and reopened at the corresponding period of the
following cycle, this operation being repeated several times in order to
impart sufficient speed to the motor;
4. By opening the gas-valve and finally closing the two valves of the
compressed-air pipe.
The pipes and compressed-air reservoirs should be perfectly tight. The
reservoirs should have a capacity in inverse ratio to the pressure under
which they are placed, _i.e._, they increase in size as the pressure
decreases. If, for example, the reservoirs should be operated normally
at a pressure of 105 to 120 pounds per square inch, their capacity
should be at least five or six times the volume of the engine-cylinder.
If these reservoirs are charged by the engine itself, the pressure will
always be less by 15 to 20 per cent. than that of the compression.
CHAPTER III
THE INSTALLATION OF AN ENGINE
In the preceding chapter the various structural details of an engine
have been summarized and those arrangements indicated which, from a
general standpoint, seem most commendable. No particular system has been
described in order that this manual might be kept within proper limits.
Moreover, the best-known writers, such as Hutton, Hiscox, Parsell and
Weed, in America; Aimé Witz, in France; Dugald Clerk, Frederick Grover,
and the late Bryan Donkin, in England; Güldner, Schottler, Thering, in
Germany, have published very full descriptive works on the various types
of engines.
We shall now consider the various methods which seem preferable in
installing an engine. The directions to be given, the author believes,
have not been hitherto published in any work, and are here formulated,
after an experience of fifteen years, acquired in testing over 400
engines of all kinds, and in studying the methods of the leading
gas-engine-building firms in the chief industrial centers of Europe and
America.
=Location.=--The engine should be preferably located in a well-lighted
place, accessible for inspection and maintenance, and should be kept
entirely free from dust. As a general rule, the engine space should be
enclosed. An engine should not be located in a cellar, on a damp floor,
or in badly illuminated and ventilated places.
=Gas-Pipes.=--The pipes by which fuel is conducted to engines, driven by
street-gas, and the gas-bags, etc., are rarely altogether free from
leakage. For this reason, the engine-room should be as well ventilated
as possible in the interest of safety. Long lines of pipe between the
meter and the engine should be avoided, for the sake of economy, since
the chances for leakage increase with the length of the pipe. It seldom
happens that the leakage of a pipe 30 to 50 feet long, supplying a 30
horse-power engine, is much less than 90 cubic feet per hour. The
beneficial effect of short supply pipes between meter and engine on the
running of the engine is another point to be kept in mind.
An engine should be supplied with gas as cool as possible, which
condition is seldom realized if long pipe lines be employed, extending
through workshops, the temperature of which is usually higher than that
of underground piping. On the other hand, pipes should not be exposed to
the freezing temperature of winter, since the frost formed within the
pipe, and particularly the crystalline deposition of naphthaline,
reduces the cross section and sometimes clogs the passage. Often it
happens that water condenses in the pipes; consequently, the piping
should be disposed so as to obviate inclines, in which the water can
collect in pockets. An accumulation of water is usually manifested by
fluctuations in the flame of the burner. In places where water can
collect, a drain-cock should be inserted. In places exposed to frost, a
cock or a plug should be provided, so that a liquid can be introduced to
dissolve the naphthaline. To insure the perfect operation of the engine,
as well as to avoid fluctuations in nearby lights, pipes having a large
diameter should preferably be employed. The cross-section should not be
less than that of the discharge-pipe of the meter, selected in
accordance with the prescriptions of the following table:
GAS-METERS.
Table Headings--
Column A: Capacity.
Column B: Normal hourly flow.
Column C: Height.
Column D: Width.
Column E: Depth.
Column F: Diameter of pipe.
Column G: Power of engine to be fed.
_________________________________________________________________
| | |
| | Dimension in inches. |
| |_______________________________________|
| | | | | |
A. | B. | C. | D. | E. | F. | G.
________|_________|_________|__________|__________|_______|______
| | | | | |
burners | cu. ft. | | | | | h.-p.
3 | 14.726 | 13 | 11 | 9-13/16 | 0.590 | 1/2
5 | 24.710 | 18 | 13-3/4 | 10-5/8 | 0.787 | 3/4
10 | 49.420 | 21-1/4 | 18-1/2 | 12-9/16 | 0.984 | 1-2
20 | 98.840 | 23-3/16 | 19-11/16 | 15-5/16 | 1.181 | 3-4
30 | 148.260 | 25-5/8 | 21-11/16 | 18-3/16 | 1.456 | 5-6
50 | 247.100 | 29-1/2 | 24-5/16 | 20-7/16 | 1.592 | 7-10
60 | 296.520 | 30-5/16 | 25-5/8 | 25-5/8 | 1.671 | 11-14
80 | 395.360 | 33-5/16 | 30-5/16 | 27-1/8 | 1.968 | 15-19
100 | 494.200 | 35 | 33-7/16 | 29-15/16 | 1.968 | 20-25
150 | 741.300 | 40-3/16 | 40-3/16 | 33-13/16 | | 30-40
________|_________|_________|__________|__________|_______|______
The records made are exact only when the meters (Fig. 40) are installed
and operated under normal conditions. Two chief causes tend to falsify
the measurements in wet meters: (1) evaporation of the water, (2) the
failure to have the meter level.
Evaporation occurs incessantly, owing to the flowing of the gas through
the apparatus, and increases with a rise in the temperature of the
atmosphere surrounding the meter. Consequently this temperature must be
kept down, for which reason the meter should be placed as near the
ground as possible. The evaporation also increases with the volume of
gas delivered. Hence the meter should not supply more than the volume
for which it was intended. In order to facilitate the return of the
water of condensation to the meter and to prevent its accumulation, the
pipes should be inclined as far as possible toward the meter. The
lowering of the water-level in the meter benefits the consumer at the
expense of the gas company.
[Illustration: FIG. 40.--Wet gas-meter.]
Inclination from the horizontal has an effect that varies with the
direction of inclination. If the meter be inclined forward, or from left
to right, the water can flow out by the lateral opening at the level,
and incorrect measurements are made to the consumer's cost.
During winter, the meter should be protected from cold. The simplest way
to accomplish this, is to wrap substances around the meter which are
poor conductors of heat, such as straw, hay, rags, cotton, and the like.
Freezing of the water can also be prevented by the addition of alcohol
in the proportion of 2 pints per burner. The water is thus enabled to
withstand a temperature of about 5 degrees F. below zero. Instead of
alcohol, glycerine in the same proportions can be employed, care being
taken that the glycerine is neutral, in order that the meter may not be
attacked by the acids which the liquid sometimes contains.
[Illustration: FIG. 41.--Dry gas-meter.]
=Dry Meters.=--Dry meters are employed chiefly in cold climates, where
wet meters could be protected only with difficulty and where the water
is likely to freeze. In the United States the dry meter is the type most
widely employed. In Sweden and in Holland it is also generally
introduced (Fig. 41).
In the matter of accuracy of measurement there is little, if any,
difference between wet and dry meters. The dry meter has the merit of
measuring correctly regardless of the fluctuations in the water level.
On the other hand, it is open to the objection of absorbing somewhat
more pressure than the wet meter, after having been in operation for a
certain length of time. This is an objection of no great weight; for
there is always enough pressure in the mains and pipes to operate a
meter.
[Illustration: FIG. 42.--Section through a dry gas-meter.]
In many cases, where the employment of non-freezing liquids is
necessary, the dry meter may be used to advantage, since all such
liquids have more or less corroding effect on sheet lead and even tin,
depending upon the composition of the gas.
[Illustration: FIG. 43.--Section through a dry gas-meter.]
The dry meter comprises two bellows, operating in a casing divided into
two compartments by a central partition. The gas is distributed on one
or the other side of the bellows, by slides _B_. The slides _B_ are
provided with cranks _E_, controlled by levers _M_, actuated by
transmission shafts _O_, driven by the bellows. The meter is adjusted by
a screw which changes the throw of the cranks _E_ and consequently
affects the bellows. The movement of the crank-shaft _D_ is transmitted
to the indicating apparatus. In order to obviate any leakage, this shaft
passes through a stuffing-box, _G_. The diagrams (Figs. 42-43) show the
construction of a dry meter, the arrows indicating the course taken by
the gas.
[Illustration: FIG. 44.--Rubber bag to prevent fluctuations of the
ignition flame.]
[Illustration: FIG. 45.--Rubber bags on gas-pipes.]
Care should be taken to provide the gas-pipe with a drain-cock, at a
point near the engine. By means of this cock, any air in the pipe can be
allowed to escape before starting; otherwise the engine can be set in
motion only with difficulty. If the engine be provided with an
incandescent tube, the gas-supply pipe of the igniter should be fitted
with a small rubber pouch or bag, in order to obviate fluctuations in
the burner flame, caused by variations in the pressure (Fig. 44). As a
general rule, the supply-pipe should be connected with the main pipe on
the forward side of the bags and gas-governors. The main pipe and all
other piping near the engine should extend underground, so that free
access to the motor from all sides can be obtained, without possibility
of injury.
=Anti-pulsators, Bags, Pressure-Regulators.=--The most commonly employed
means of preventing fluctuation of nearby lights, due to the sharp
strokes of the engine, consists in providing the gas-supply pipe with
rubber bags (Fig. 45), which form reservoirs for the gas and, by reason
of their elasticity, counteract the effect produced by the suction of
the engine. Nevertheless, in order to insure a supply of gas at a
constant pressure, which is necessary for the perfect operation of the
engine, there are generally used, in addition to the bags, devices
called gas-governors, or anti-pulsators (Fig. 46).
Although these devices are constructed in different ways, the underlying
principle is the same in all. They comprise a metallic casing,
containing a flexible diaphragm of rubber or of some fabric impermeable
to gas. Suction of the engine creates a vacuum in the casing. The
diaphragm bends, thereby actuating a valve, which cuts off the gas
supply. During the three following periods (compression, explosion, and
exhaust) the gas, by reason of its pressure on the diaphragm, opens the
valve and fills the casing, ready for the next suction stroke.
[Illustration: FIG. 46.--An anti-pulsator.]
Other devices, which are never sold with the engine, but are rendered
necessary by reason of the conditions imposed by the gas supply are sold
under the name "pressure-regulators" (Fig. 47). They consist of a bell,
floating in a reservoir containing water and glycerine (or mercury), and
likewise actuate a valve which partially controls the flow of gas. This
valve being balanced, its mechanical action is the more certain. Such
devices are very effective in maintaining the steadiness of lights. On
the other hand, they are often an obstacle to the operation of the
engine because they reduce the flow and pressure of the gas too much. In
order to obviate this difficulty, a pressure-regulator should be chosen
with discrimination, and of sufficiently large size to insure the
maintenance of an adequate supply of gas to the engine. Frequent
examinations should be made to ascertain if the bell of the regulator is
immersed in the liquid. In the case of anti-pulsators, care should be
taken that they are not spattered with oil, which has a disastrous
effect on rubber. Anti-pulsators are generally mounted about 4 inches
from a wall, in order that the diaphragm may be actuated by hand, if
need be.
[Illustration: FIG. 47.--A pressure-regulator.]
=Precautions.=--In order not to strain the rubber of the bags or of the
anti-pulsators, it is advisable to place a stop-cock in advance of these
devices so that they can not be filled while the motor is at rest.
The capacity of the rubber bags that can be bought in the market being
limited, it is necessary to place one, two, or three extra bags in
series (Figs. 48 and 49), for large pipes; but it should be borne in
mind that the total section of the branch pipes should be at least equal
to that of the main pipe. It is also advisable to extend the tube
completely through the bag as shown in Figs. 48 and 49.
[Illustration: FIGS. 48-49.--Arrangement of rubber bags.]
If there be two branch pipes the minimum diameter which meets this
requirement is ascertained as follows: Draw to any scale a semicircle
having a diameter equal or proportional to that of the main pipe (Fig.
50). The sides of the isosceles triangle inscribed within this
semicircle give the minimum diameter of each of the branch pipes.
Sometimes engines are provided with a cock having an arrangement by
means of which the gas feed is permanently regulated, according to the
quality and pressure of the gas and according to the load at which the
engine is to run. This renders it possible to open the cock always to
the same point (Fig. 51).
[Illustration: FIG. 50.]
[Illustration: FIG. 51.]
=Air Suction.=--In a special chapter the precautions to be taken to
counteract the influence of the suction of the engine in causing
vibration will be treated. The manner in which the suction of air is
effected necessarily has as marked an influence on the operation of the
engine as the supply of gas, since air and gas constitute the explosive
mixture.
Resistance to the suction of air should be carefully avoided, for which
reason the length of the pipe should be reduced to a minimum, and its
cross-section kept at least equal to that of the air inlet of the
engine. Since the quality of street-gas varies with each city, the
proper proportions of gas and air are not constant. In order that these
proportions may be regulated, it is a matter of some importance to fit
some suitable device on the pipe. Good engines are provided with a plug
or flap valve. Generally the air-pipe terminates either in the hollowed
portion of the frame, or in an independent pot, or air chest. The first
arrangement is not to be recommended for engines over 20 to 25
horse-power. Accidents may result, such as the breaking of the frame by
reason of back firing, of which more will be said later. If an
independent chest be employed, its closeness to the ground renders it
possible for dust easily to pass through the air-holes in the walls at
the moment of suction, and even to enter the cylinder, where its
presence is particularly harmful, leading, as it does, to the rapid wear
of the rubbing surfaces. This evil can be largely remedied by filling
the air-chest with cocoa fiber or even wood fiber, provided the latter
does not become packed down so as to prevent the air from passing
freely. Such fibers act as air-filters. Regular cleaning or renewal of
the fiber protects the cylinder from wear. In a general way, care should
be taken, before fitting both the gas and air pipes, to tap the pipes,
elbows, and joints lightly with a hammer on the outside in order to
loosen whatever rust or sand may cling to the interior; otherwise this
foreign matter may enter the cylinder and cause perturbations in the
operation of the engine. Under all circumstances, care should be taken
not to place the end of the air-pipe under the floor or in an enclosed
space, because leakage may occur, due to the bad seating of the
air-valve, thereby producing a mixture which may explode if the flame
leaps back, as we shall see in the discussion of suction by pipes
terminating in the hollow of the frame. On the other hand, sand or
sawdust should not be sprinkled on the floor.
=Exhaust.=--For the exhaust, cast-iron or drawn pipes as short as
possible should be used. Not only the power of the engine, but also its
economic consumption, can be markedly affected by the employment of long
and bent pipes. Resistance to the exhaust of the products of combustion
not only causes an injurious counter-pressure, but also prevents the
clearing of the cylinder of burnt gases, which contaminate the aspired
mixture and rob it of much of its explosiveness. The necessity of
evacuating the cylinder as completely as possible is, nevertheless, not
always reconcilable with local surroundings. To a certain extent, the
objections to long exhaust-pipes are overcome by rigorously avoiding the
use of elbows. Gradual curves are preferable. In the case of very long
pipes it is advisable to increase their diameter every 16 feet from the
exhaust. The exhaust-chest should be placed as near as possible to the
engine; it should never be buried; for the joints of the inlet and
outlet pipes of the exhaust-chest should be easily accessible, so that
they may be renewed when necessary. The author recommends the placing
of the exhaust-chest in a masonry pit, which can be closed with a
sheet-metal cover. For engines of 20 horse-power and upward, these
joints should be entirely of asbestos. Pipes screwed directly into the
casting are liable to rust. Exposed as they are to the steam or water of
the exhaust, they cannot be detached.
[Illustration: FIG. 52.--Method of mounting pipes.]
The water, which results from the combination of the hydrogen of the gas
with the oxygen of the air, is deposited in most cases at the bottom of
the exhaust-chest. It is advisable to fit a plug or iron cock in the
base of the chest. Alkaline or acid water will always corrode a bronze
cock. In order that the pipes may not also be attacked, they are not
disposed horizontally, but are given a slight incline toward the point
where the water is drained off. If pipes of some length be employed,
they should be able to expand freely without straining the joints, as
shown in the accompanying diagram (Fig. 52), in which the exhaust-chest
rests on iron rollers which permit a slight displacement.
For the sake of safety, at least that portion of the piping which is
near the engine should be located at a proper distance from woodwork and
other combustible material. By no means should the exhaust discharge
into a sewer or chimney, even though the sewer or chimney be not in use;
for the unburnt gases may be trapped, and dangerous explosions may ensue
at the moment of discharge.
The joints or threaded sleeves employed in assembling the exhaust-pipe
should be tested for tightness. The combined action of the moisture and
heat causes the metal to rust and to deteriorate very rapidly at leaky
spots.
When several engines are installed near one another, each should be
provided with a special exhaust-pipe; otherwise it may happen, when the
engines are all running at once, that the products of combustion
discharged by the one may cause a back pressure detrimental to the
exhaust of the next.
It is possible to employ a pipe common to all the exhausts if the pipe
starts from a point beyond the exhaust-chests, in which case Y-joints
and not T-joints are to be used.
The manner of securing the pipes to walls by means of detachable
hangers, lined with asbestos, is shown in a general way in the
accompanying Fig. 53. The object of this arrangement is to render
detachment easy and to prevent the transmission of shocks to the
masonry.
The precautions to be taken for muffling the noise of the exhaust will
be discussed later.
The end of the exhaust-pipe should be slightly curved down in order to
prevent the entrance of rain. Exhaust-pipes are subjected to
considerable vibration, due to the sudden discharge of the gases. To
protect the joints, the pipes should be rigidly fastened in place.
[Illustration: FIG. 53.--Method of securing pipes to walls.]
=Legal Authorization.=--In most countries gas-engines may be installed
only in accordance with the provision of general or local laws, which
impose certain conditions. These laws vary with different localities,
for which reason they are not discussed here.
CHAPTER IV
FOUNDATION AND EXHAUST
The reader will remember from what has already been said that a
gas-engine is a motor which, more than any other, is subjected to
forces, suddenly and repeatedly exerted, producing violent reactions on
the foundation. It follows that the foundation must be made particularly
resistant by properly determining its shape and size and by carefully
selecting the material of which it is to be built.
=The Foundation Materials.=--Well-hardened brick should be used. The top
course of bricks should be laid on edge. It is advisable to increase the
stability of the foundation by longitudinally elongating it toward the
base, as shown in the accompanying diagram (Fig. 54).
As a binding material, only mortar composed of coarse sand or river sand
and of good cement, should be used. Instead of coarse sand, crushed
slag, well-screened, may be employed. The mortar should consist of 2/3
slag and 1/3 cement. Oil should not in any way come into contact with
the mortar; it may percolate through the cement and alter its resistant
qualities.
As in the construction of all foundations, care should be taken to
excavate down to good soil and to line the bottom with concrete, in
order to form a single mass of artificial stone. A day or two should be
allowed for the masonry to dry out, before filling in around it.
When the engine is installed on the ground floor above a vaulted cellar,
the foundation should not rest directly on the vault below or on the
joists, but should be built upon the very floor of the cellar, so that
it passes through the planking of the ground floor without contact.
[Illustration: FIG. 54.--Method of building the foundation.]
When the engine is to be installed on a staging, the method of securing
it in place illustrated in Fig. 55 should be adopted.
Although a foundation, built in the manner described, will fulfill the
usual conditions of an industrial installation, it will be inadequate
for special cases in which trepidation is to be expected. Such is the
case when engines are to be installed in places where, owing to the
absence of factories, it is necessary to avoid all nuisance, such as
noise, trepidations, odors, and the like.
[Illustration: FIG. 55.--Elevated foundation.]
=Vibration.=--In order to prevent the transmission of vibration, the
foundation should be carefully insulated from all neighboring walls. For
this purpose various insulating substances called "anti-vibratory" are
to be recommended. Among these may be mentioned horsehair, felt packing,
cork, and the like. The efficacy of these substances depends much on the
manner in which they are applied. It is always advisable to interpose a
layer of one of these substances, from one to four inches thick, between
the foundation and the surrounding soil, the thickness varying with the
nature of the material used and the effect to be obtained. Between the
bed of concrete, mentioned previously, and the foundation-masonry and
between the foundation and the engine-frame, a layer of insulating
material may well be placed. Preference is to be given to substances not
likely to rot or at least not likely to lose their insulating property,
when acted upon by heat, moisture or pressure.
Here it may not be amiss to warn against the utilization of cork for the
bottom of the foundation; for water may cause the cork to swell and to
dislocate the foundation or destroy its level.
The employment of the various substances mentioned does not entail any
great expense when the foundations are not large and the engines are
light. But the cost becomes considerable when insulating material is to
be employed for the foundation of a 30 to 50 horse-power engine and
upwards. For an engine of such size the author recommends an arrangement
as simple as it is efficient, which consists in placing the foundation
of the engine in a veritable masonry basin, the bottom of which is a bed
of concrete of suitable thickness. The foundation is so placed that the
lateral surfaces are absolutely independent of the supporting-walls of
the basin thus formed. Care should be taken to cover the bottom with a
layer of dry sand, rammed down well, varying in thickness with each
case. This layer of sand constitutes the anti-vibratory material and
confines the trepidations of the engine to the foundation.
As a result of this arrangement, it should be observed that, being
unsupported laterally, the foundation should be all the more resistant,
for which reason the base-area and weight should be increased by 30 to
40 per cent. The expense entailed will be largely offset by saving the
cost of special anti-vibratory substances. In places liable to be
flooded by water, the basin should be cemented or asphalted.
When the engine is of some size and is intended for the driving of one
or more dynamos which may themselves give rise to vibrations, the
dynamos are secured directly to the foundation of the engine, which is
extended for that purpose, so that both machines are carried solidly on
a single base.
The foregoing outline should not lead the proprietor of a plant to
dispense with the services of experts, whose long experience has brought
home to them the difficulties to be overcome in special cases.
It should here be stated, as a general rule, that the bricks should be
thoroughly moistened before they are laid in order that they may grip
the mortar.
After having been placed on the foundation and roughly trimmed with
respect to the transmission devices, the engine is carefully leveled by
means of hardwood wedges driven under the base. This done, the bolts are
sealed by very gradually pouring a cement wash into the holes, and
allowing it to set. When the holes are completely filled and the bolts
securely fastened in place, a shallow rim, or edge of clay, or sand is
run around the cast base, so as to form a small box or trough, in which
cement is also poured for the purpose of firmly binding the engine frame
and foundation together. When, as in the case of electric-light engines,
single extra-heavy fly-wheels are employed, provided with bearings held
in independent cast supports, the following rule should be observed to
prevent the overheating due to unlevelness, which usually occurs at the
bushings of these bearings: That part of the foundation which is to
receive such a support should rest directly on the concrete bed and
should be rigidly connected at the bottom with the main foundation. When
the foundation is completely blocked up, the fly-wheel bearing with its
support is hung to the crank-shaft; and not until this is effected is
the masonry at the base of the support completed and rigidly fixed in
its proper position.
For very large engines, the foundation-bolts should be particularly well
sealed into the foundation. In order to attain this end the bricks are
laid around the bolt-holes, alternately projected and retracted as shown
in Fig. 54. Broken stone is then rammed down around the fixed bolt; in
the interstices cement wash is poured.
=Air Vibration, etc.=--Vibration due chiefly to the transmission of
noises and the displacement of air by the piston should not be confused
with the trepidations previously mentioned.
The noise of an engine is caused by two distinct phenomena. The one is
due to the transmitting properties of the entire solid mass constituting
the frame, the foundation, and the soil. The other is due to vibrations
transmitted to the air. In both cases, in order to reduce the noise to a
minimum, the moving parts should be kept nicely adjusted, and above all,
shocks avoided, the more harmful of which are caused by the play between
the joint at the foot of the connecting-rod and the piston-pin, and
between the head of the connecting-rod and the crank-shaft.
Although smooth running of the engine may be assured, there is always an
inherent drawback in the rapid reciprocating movement of the piston. In
large, single-acting gas-engines, a considerable displacement of air is
thus produced. In the case of a forty horse-power engine having a
cylinder diameter and piston-stroke respectively of 13-3/4 inches and
21-3/5 inches, it is evident that at each stroke the piston will
displace about 2 cubic feet of air, the effect of which will be doubled
when it is considered that on the forward stroke back pressure is
created and on the return stroke suction is produced.
The air motion caused by the engine is the more readily felt as the
engine-room is smaller. If the room, for example, be 9 feet by 15 feet
by 8 feet, the volume will be 1,080 cubic feet. From this it follows
that the 2 cubic feet of air in the case supposed will be alternately
displaced six times each second, which means the displacement of 12
cubic feet at short intervals with an average speed of 550 feet per
minute. Such vibrations transmitted to halls or neighboring rooms are
due entirely to the displacement of the air.
In installations where the air-intake of the engine is located in the
engine-room, a certain compensation is secured, at the period of
suction, between the quantity of air expelled on the forward stroke of
the piston and the quantity of air drawn into the cylinder. From this it
follows that the vibration caused by the movement of the air is felt
less and occurs but once for two revolutions of the engine.
This phenomenon is very manifest in narrow rooms in which the engine
happens to be installed near glass windows. By reason of the elasticity
of the glass, the windows acquire a vibratory movement corresponding in
period with half the number of revolutions of the engine. It follows
from the preceding that, in order to do away with the air vibration
occasioned by the piston in drawing in and forcing out air in an
enclosed space, openings should be provided for the entrance of large
quantities of air, or a sufficient supply of air should be forced in by
means of a fan.
The author ends this section with the advice that all pipes in general
and the exhaust-pipe in particular be insulated from the foundation and
from the walls through which they pass as well as from the ground, as
metal pipes are good conductors of sound and liable to carry to some
distance from the engine the sounds of the moving parts.
=Exhaust Noises.=--Among the most difficult noises to muffle is that of
the exhaust. Indeed, it is the exhaust above all that betrays the
gas-engine by its discharge to the exterior through the exhaust-pipe.
The most commonly employed means for rendering the exhaust less
perceptible consists in extending the pipe upward as far as possible,
even to the height of the roof. This is an easy way out of the
difficulty; but it has a bad effect on the operation of the engine. It
reduces the power generated and increases the consumption, as will be
explained in a special paragraph.
Expansion-boxes, more commonly called exhaust-mufflers, considerably
deaden the noise of explosion by the use of two or three successive
receptacles. But this remedy is attended with the same faults that mark
the use of extremely long pipes. The best plan is to mount a single
exhaust-muffler near the discharge of the engine in the engine-room
itself, where it will serve at least the purpose of localizing the
sound.
[Illustration: FIG. 56.--Exhaust-muffler.]
The employment of pipes of sufficiently large cross-section to
constitute expansion-boxes in themselves will also muffle the exhaust. A
more complete solution of the problem is obtained by causing the
exhaust-pipe, after leaving the muffler, to discharge into a masonry
trough having a volume equal to twelve times that of the engine-cylinder
(Fig. 56). This trough should be divided into two parts, separated by a
horizontal iron grating. Into the lower part, which is empty, the
exhaust-pipe discharges; in the upper part, paving-blocks or hard stones
not likely to crumble with the heat, are placed. Between this layer of
stones and the cover it is advisable to leave a space equal to the
first. Here the gases may expand after having been divided into many
parts in passing through the spaces left between adjacent stones. The
trough should not be closed by a rigid cover; for, although efficient
muffling may be attained, certain disadvantages are nevertheless
encountered. It may happen that in a badly regulated engine, unburnt
gases may be discharged into this trough, forming an explosive mixture
which will be ignited by the next explosion, causing considerable
damage. Still, the explosion will be less dangerous than noisy. It may
be mentioned in passing that this disadvantage occurs rarely.
A second arrangement consists in superposing the end of the exhaust-pipe
upon a casing of suitable size, which casing is partitioned off by
several perforated baffle-plates. This casing is preferably made of
wood, lined with metal, so that it will not be resonant. The size of the
casing, the number of partitions and their perforations, and the manner
of disposing the partitions have much to do with the result to be
obtained. Here again the experience of the expert is of use.
Various other systems are employed, depending upon the particular
circumstances of each case. Among these systems may be mentioned those
in which the pipe is forked at its end to form either a yoke (Fig. 57)
or a double curve, each branch of which terminates in a muffler (Fig.
58).
[Illustration: FIG. 57.]
[Illustration: FIG. 58.--Two types of exhaust-mufflers.]
It should be observed that, under ordinary conditions, noises heard as
hissing sounds are often due to the presence of projections, or to
distortion of the pipes near the discharge opening. Consequently, in
connecting the pipes, care should be taken that the joints or seams have
no interior projections. Occasionally, water may be injected into the
exhaust-muffler in order to condense the vapors of the exhaust, the
result being a deadening of the noises; but in order to be truly
efficient this method should be employed with discretion, for which
reason the advice of an expert is of value.
CHAPTER V
WATER CIRCULATION
Circulation of water in explosion-engines is one of the essentials of
their perfect operation. Two special cases are encountered. In the one
the jacket of the engine is supplied with running water; in the other,
reservoirs are employed, the circulation being effected simply by the
difference in specific gravity in a thermo-siphon apparatus. Coolers are
also used.
=Running Water.=--A water-jacket fed from a constant source of running
water, such as the water mains of a town, is certainly productive of the
best results, the supply, moreover, being easily regulated; but the
system is not widely used because the water runs away and is entirely
lost. If running water be employed, the outlet of the jacket is so
disposed that the water gushes out immediately on leaving the cylinder,
and that the flow is visible and accessible, in order that the
temperature may be tested by the hand. Apart from the relatively great
cost of water in towns, the use of running water is objectionable on
account of its chemical composition. Though it may be clear and limpid,
it frequently contains lime salts, carbonates, sulphates, and silicates
which are precipitated by reason of the sudden change of temperature to
which the water is subjected as it comes into contact with the walls of
the cylinder. That part of the water-jacket surrounding the head or
explosion-chamber, where the temperature is necessarily the highest,
becomes literally covered with calcareous incrustations, which are the
more harmful because they are bad conductors of heat and because they
reduce and even obstruct the passage exactly at the point where the
water must circulate most freely to do any good. If the circulating
water be pumped into the jacket, it is preferable, wherever possible, to
use cistern water, which is not likely to contain lime salts in
suspension. If river water be used, it should be free from the
objections already mentioned, which are all the more grave if the water
be muddy, as sometimes happens. The water-jacket can be easily freed
from all non-adhering deposits by flushing it periodically through the
medium of a conveniently placed cock. It is always preferable to pass
the water through a reservoir where its impurities can settle, before it
flows to the cylinder. In the case considered, the water usually has an
average temperature of 54 to 60 degrees F., under which condition the
hourly flow should be at least 5-1/2 gallons per horse-power per hour,
the temperature rising at the outlet-pipe of the cylinder to 140 and 158
degrees F., which should not be surpassed. However, in engines working
with high compression, 104 to 122 degrees F. should not be exceeded.
If the water-jacket be fed by a reservoir, it is essential that the
reservoir comply with the following conditions:
In horizontal engines the water-inlet is always located in the base of
the cylinder, while the outlet is located at the top. By providing the
inlet-pipe extending to the cylinder with a cock, the circulation of
water can be regulated to correspond with the work performed by the
engine. Another cock at the end of the outlet-pipe near the reservoir
serves, in conjunction with the first, to arrest the circulating water.
When the weather is very cold or when the cylinder must be repaired,
these two cocks may be closed, and the pipe and water-jacket of the
cylinder drained by means of the drain-cock _V_ (Fig. 59), mounted at
the inlet of the engine's water-jacket. In order that the pressure of
the atmosphere may not prevent the flowing of the water, the highest
part of the pipe is provided with a small tube, _T_, communicating with
the atmosphere.
[Illustration: FIG. 59.--Thermo-siphon cooling system.]
On account of the importance of preventing losses of the charge in the
pipes the author recommends the utilization of sluice-valves of the type
shown in Fig. 60, instead of the usual cone or plug type.
[Illustration: FIG. 60.--Vanne sluice-cock.]
=Water-Tanks.=--The reservoir is mounted in such a way that its base is
flush with the top of the cylinder; it should be as near as possible to
the cylinder in order to obviate the use of long inlet and return pipes.
This fact, however, does not necessarily render it advisable to place
the reservoir in the engine-room; for such a disposition is doubly
disadvantageous in so far as it does not permit a sufficiently rapid
cooling of the circulating water by reason of the high temperature of
the surrounding air, and in so far as it is liable to cause the
formation of vapors which injuriously affect the engine. Consequently,
the reservoir should be placed in as cool a place as possible,
preferably even in the open air; for the water is not likely to freeze,
except when it has been allowed to stand for a considerable time. The
reservoir should be left uncovered so as to facilitate cooling by the
liberation of the vapors formed on the surface of the water.
Circulation being effected solely by the difference in specific gravity
or density between the warmer water emerging from the cylinder and the
cooler water which flows in from the reservoir, the slightest
obstruction will impede the flow. Hence, the cross-section of the pipes
should not be less than that of the inlet and outlet openings of the
cylinder of the engine. Good circulation cannot be attained if the water
must overcome inclines or obstacles in the pipes themselves. Instead of
elbows, long curves of great radius, limited to the smallest possible
number, should be employed. This is particularly true of the return-pipe
extending from the cylinder back to the reservoir. For this pipe a
minimum incline of 10 to 15 per cent. should be allowed, in order that
the water may run up into the reservoir. The height of the water in the
reservoir should be from 2 to 4 inches above the discharge of the
return-pipe. In order to maintain this level it is advisable to use some
automatic device such as a float-valve, in which case the reservoir
should not be allowed to become too full.
[Illustration: FIG. 61.--Correct arrangement of tanks and piping.]
The size of a reservoir is determined by the engine; it should be large
enough to enable the engine to run smoothly at its maximum load for
several hours consecutively. Under these conditions, the reservoir
should have a capacity of 45 to 55 gallons per horse-power for engines
with "hit-and-miss" admission, and 55 to 65 gallons for engines
controlled by variable admission. It is not advisable to employ
reservoirs having a capacity of more than 330 to 440 gallons, the usual
diameter being about 3 feet.
[Illustration: FIG. 62.--Incorrect arrangement of tanks and piping.]
If the power of the engine be such that several reservoirs are
necessary, then the reservoirs should be connected in such a manner that
the top of the first communicates with the bottom of the next and so
on, the first reservoir receiving the water as it comes from the
cylinder (Fig. 61).
Intercommunication of the reservoirs by means of a common top tube (_a_)
is objectionable; and simultaneous intercommunication at top and bottom
(_a_ and _b_) is ineffective, so far as one of the reservoirs is
concerned (Fig. 62).
[Illustration: FIG. 63.--Tanks connected by inclined pipes.]
The reservoirs are true thermo-siphons. Consequently the water should be
methodically circulated; in other words, the hottest water, flowing from
the engine into the top of the first reservoir and having, for example,
a temperature of 104 degrees F., is cooled off to 86 degrees F. and
drops to the bottom of the reservoir, thence to be driven, at a
temperature sensibly equal to 86 degrees F., to the second reservoir,
where a further cooling of 18 degrees F. takes place. In passing on to
the following reservoirs the temperature is still further lowered, until
the water finally reaches its minimum temperature, after which it flows
back to the engine-cylinder.
[Illustration: FIG. 64.--Circulating pump with by-pass.]
In order to effect this cooling, the reservoirs can be connected in
several ways. The most common method, as shown in Fig. 63, consists in
connecting the reservoirs by oblique pipes. This is open to criticism,
however, since leakage occurs, caused by the employment of elbows which
retard the circulation. A less cumbrous and more efficient method of
connection consists in joining the reservoirs by a single pipe at the
top, as shown in Fig. 61; but care must be taken to extend this pipe at
the point of its entrance into the adjoining reservoir by means of a
downwardly projecting extension, or to fit its discharge-end with a box,
closed by a single partition, open at the bottom.
In order to prevent incrustation of the water-jacket surrounding the
cylinder, a pound of soda per 17 cubic feet of the reservoir capacity is
monthly introduced, and the jacket flushed weekly by a cock conveniently
mounted near the cylinder (Fig. 59). The jacket is thus purged of
calcareous sediments, which are prevented by the soda from adhering to
the metal. The flushing-cock mentioned also serves to drain the
water-jacket of the cylinder in case of intense or persistent cold,
which would certainly freeze the water in the jacket, thereby cracking
the cylinder or the exposed pipes.
In order to regulate the circulation of the water in accordance with the
work performed by the engine, a cock should be fitted to the water
supply pipe at a convenient place.
In engines of large size, driven at full load for long periods, cooling
by natural circulation is often inadequate. In such cases, circulation
is quickened by a small rotary or reciprocating pump, driven from the
engine itself and fitted with a by-pass provided with a cock. This
arrangement permits the renewal of the natural thermo-siphon circulation
in case of accident to the pump (Fig. 64).
[Illustration: FIG. 65.--Water-cooler in which tree branches are
employed.]
=Coolers.=--The arrangement which is illustrated in Fig. 65, and which
has the merit of simplicity, will be found of service in cooling the
water. It comprises a tank _B_ surmounted by a set of trays _E_, formed
of frames to which iron rods are secured, spaced 1 to 2 feet apart, so
as to form superimposed series separated by 1-1/2 to 2-1/3 feet. On
these trays bundles of tree branches are placed. The cold water at the
bottom of the tank is forced by the pump _P_i into the water-jacket,
from which it emerges hot, and flows through the pipe _T_, which ends in
a sprinkler _G_, formed of communicating tubes and perforated with a
sufficient number of holes to enable the water to fall upon the trays in
many drops. Thus finely divided, the water falls from one tray to
another, retarded as it descends by the bundles of tree branches. It
finally reaches the tank in a very cold condition and is then ready to
be pumped to the engine. Birch branches are to be preferred on account
of their tenuity.
Great care should be taken to cover the tank with a sheet-metal closure
in order to prevent twigs and foreign bodies from entering and from
being drawn into the pump.
[Illustration: FIG. 66.--Fan-cooler.]
In the following table the dimensions of an operative apparatus of this
kind are given,--an apparatus, moreover, that may be constructed of wood
or of iron:--
Table Headings--
Column A: Horse-power.
Column B: Volume in cubic ft.
Column C: Base.
Column D: Height.
Column E: Height of tray-base.
Column F: Pump--Capacity in gals. per min.
______________________________________________
| | | |
| | Tank. | |
| |____________________| |
| | | | |
A. | B. | C. | D. | E. | F.
_____|_____|_____________|______|______|______
| | | | |
30 | 105 | 4.9' x 4.9' | 4.4' | 6.6' | 16.71
40 | 154 | 5.2' x 5.2' | 5.6' | 7.4' | 18.69
50 | 190 | 5.7' x 5.7' | 6.4' | 8.1' | 21.99
75 | 350 | 6.6' x 6.6' | 8.1' | 9.1' | 35.18
100 | 490 | 7.4' x 7.4' | 9.1' | 9.1' | 43.98
_____|_____|_____________|______|______|______
In order that the water may not drop to one side, the base of the
apparatus should be made 10 to 12 inches less in width than the tank.
The size of these apparatus may be considerably reduced by constructing
them in the form of closed chests, into the bottom of which air maybe
injected by means of fans in order to accelerate cooling (Fig. 66).
CHAPTER VI
LUBRICATION
Lubrication is a subject that should be studied by every gas-engine
user. So far as the piston is concerned it is a matter of the utmost
importance. The piston does its work under very peculiar conditions. It
is driven at great linear velocities; and it is, moreover, subjected to
high temperatures which have nothing in common with good lubrication if
care be not exercised.
The piston is the essential, vital element of an engine. Upon its
freedom from leakage depends the maintenance of a proper compression,
and, consequently, the production of power and economical consumption.
As it travels forward and as it recedes from the explosion-chamber, it
uncovers more and more of the frictional surface constituting the
interior wall of the cylinder. This surface, as a result, is regularly
brought into contact with the ignited, expanding gases after each
explosion. For this reason the oil which covers the wall is constantly
subjected to high temperatures, by which it is likely to be volatilized
and burned. Therefore, the first condition to be fulfilled in properly
lubricating the piston is a constant and regular supply of oil.
=Quality of Oils.=--For cylinder lubrication only the very best oils
should be used; perfect lubrication is of such importance that cost
should not be considered. Besides, the surplus oil which is usually
caught in the drip-pan is by no means lost. After having been filtered
it can be used for lubricating the bearings of the crank, the cam-shaft,
and like parts.
Cylinder-oil should be exceedingly pure, free from acids, and composed
of hydrocarbons that leave no residue after combustion. Only mineral
oils, therefore, are suitable for the purpose. Those oils should be
selected which, with a maximum of viscosity, are capable of withstanding
great heat without volatilizing or burning. The point at which a good
cylinder-oil ignites should not be lower than 535 degrees F.
Whether an oil possesses this essential quality is easily enough
ascertained in practice without resorting to laboratory tests. All that
is necessary is to heat the oil in a metal vessel or a porcelain dish.
In order that the temperature may be uniform the vessel is shielded from
the direct flame by interposing a piece of sheet metal or a layer of dry
sand. As soon as gases begin to arise a lighted match is held over the
oil. When the gases are ignited the thermometer reading is taken, the
instrument being immersed in the oil. The temperature recorded is that
corresponding with the point of ignition.
For cylinder lubrication American mineral oil is preferable to Russian
oil. The specific gravity should lie somewhere between .886 and .889 at
70 degrees F. Oil of this quality begins to evaporate at about 365
degrees F. Ignition occurs at 535 degrees F. The point of complete
combustibility lies between 625 and 645 degrees F. Oil of this quality
solidifies at 39 or 41 degrees F. Its color is a reddish yellow with a
greenish fluorescence. Compared with water its degree of viscosity lies
between 11.5 and 12.5 at a temperature of 140 degrees F.
Before lubricating other parts of the engine with oil that has been used
for the piston, heavy particles and foreign matter, such as dust,
bearing incrustations, and the like, should be filtered out. The
piston-pivot and the connecting-rod head are preferably lubricated with
fresh oil, because their constant movement renders inspection difficult
and the control of lubrication irksome. A good, industrial mineral oil
of usual market quality will be found satisfactory. In order to bring
home the importance of employing good cylinder-oil and of proper
lubrication the author can only state that in his personal experience he
has frequently detected losses varying from 10 to 15 per cent. in the
power developed by engines poorly lubricated.
=Types of Lubricators.=--Among the more common apparatus employed for
automatically lubricating the cylinder, the author mentions an English
oiler of the type pictured in Fig. 67 which is driven simply by a belt
from the intermediary shaft, and which rotates the pulley _P_ secured on
the shaft _a_ of the apparatus, at a very slow speed. The shaft _a_ is
provided at its end with a small crank, from which a small iron arm _f_
is suspended, which arm dips in the oil contained in the cup _G_ of the
oiler. When the shaft _a_ is turned this arm, as it sweeps through the
oil-bath, collects a certain quantity of oil which it deposits on the
collector _b_. From this spindle the oil passes through an outlet-pipe
opening into the bottom of the oiler, and thence to the cylinder. The
entire apparatus is closed by a cover _D_ which can be easily removed in
order to ascertain the quantity of oil still remaining in the apparatus.
Many other systems are utilized which, like the one that has been
described, enable the feed to be controlled. Often small force-pumps are
employed as cylinder-lubricators. Whatever may be the type selected,
preference should be given to that in which the feed is visible (Fig.
68).
[Illustration: FIG. 67.--An automatic English oiler.]
If the oil be fed under pressure the cylinder is more constantly
lubricated. Pressure-lubricators are nowadays widely used on large
engines. It is advisable to add a little salt to the water contained in
sight-feed lubricators so that the drop of oil is easily freed.
These oil-pumps are provided with small check-valves at their outlets as
well as at the inlets of cylinders. In order that pressure-lubricators
may operate perfectly they should be regularly inspected and the
check-valves ground from time to time.
The lubrication of the crank-shaft and of the two connecting-rod heads
should receive every attention.
[Illustration: FIG. 68.--Sight-feed lubricating-pump.]
[Illustration: FIG. 69.--Method of oiling the piston and end of the
connecting-rod.]
Lubricating devices should be employed which, besides being efficient,
do not necessitate the stopping of the engine in order to oil the
bearings. The foot of the connecting-rod at the point where it is
pivoted to the piston is generally lubricated with cylinder-oil which is
supplied by a tube mounted in the proper place across the piston-wall
(Fig. 69). This arrangement may be adequate enough for small engines;
but it is not sufficiently sure for engines of considerable size. An
independent lubricating system should be employed, lubrication being
effected either by a splasher mounted in front of the cylinder or by a
lubricator secured to the connecting-rod by which the pivot is
lubricated through the medium of a small tube supplying special oil
(Fig. 21). The head of the connecting-rod where it meets the crank, must
also be carefully lubricated because of the important nature of the work
which it must perform, and because of the shocks to which it is
subjected at each explosion. For motors of high power the system which
seems to give most satisfactory results is that illustrated in Fig. 70.
The arrangement there shown consists of an annular vessel secured at one
side of the crank and turning concentrically on its axis; the vessel
being connected with a long tube extending into a channel formed in the
crank and discharging at the surface of the crank-pin within the bearing
at the head of the connecting-rod. An adjustable sight-feed lubricator
conducts the oil along a pipe to the vessel. Turning with the shaft, the
vessel retains the oil in the periphery so that the feed in the
previously mentioned channel in the connecting-rod head, is constant.
[Illustration: FIG. 70.--Method of oiling the crank-shaft.]
The main crank-shaft bearings are more easily lubricated. Among the
systems commonly used with good results may be mentioned that shown in
Fig. 71, in which the half section represents a small tube starting from
the bearing and terminating in the interior of an oil recess or
reservoir cast integrally with the bearing-cap. This reservoir is filled
up to the level of the tube opening. A piece of cotton waste held on a
small iron wire is inserted in the tube, part of the cotton being
allowed to hang down in the reservoir. This cotton serves as a kind of
siphon and feeds the bearing by capillary attraction with a constant
quantity of oil, the supply being regulated by varying the thickness of
the cotton. When the motor is stopped, the cotton should be removed in
order that oil-feeding may not uselessly continue. Glass, sight-feed
lubricators with stop-cocks, are very often used on crank-shafts. They
are cleaner and much more easily regulated. Of all shaft-bearing
lubricators, those which are most to be recommended are of the
revolving-ring type (Fig. 72). They presuppose, however, bearings of
large size and a special arrangement of bushings which renders their
application somewhat expensive. Furthermore, the revolving-ring system
can hardly be used in connection with engines of less than 20
horse-power. Since the system is applied almost exclusively to
dynamo-shafts, it need not here be described in detail. As its name
indicates, it consists of a metal ring having a diameter larger than
that part of the shaft from which it is suspended and by which it is
rotated. The lower part of the ring is immersed in an oil bath so that
a certain quantity of lubricant is continually transferred to the shaft.
[Illustration: FIG. 71.--Cotton-waste lubricator.]
The revolving ring bearing should be fitted with a drain-cock and a
glass tube in order to control the level of the oil in the bearing.
Many manufacturers have adopted lubricating devices for valve-stems, and
especially for exhaust-valves. The system adopted consists of a small
tube curved in any convenient direction and discharging in the
stem-guide. The free end is provided with a plug. A few drops of
petroleum are introduced once or twice a day.
[Illustration: FIG. 72.--Ring type of bearing oiler.]
The lubrication of an engine entails certain difficulties which are
easily overcome. One of these is the splashing of oil by the
connecting-rod head. In order that this splashed oil may be collected in
the base of the engine a suitably curved sheet-metal guard is mounted
over the crank. A more serious difficulty is presented when the oil from
a crank-bearing finds its way to the hub of the fly-wheel, whence it is
driven by the centrifugal force to the rim. The oil is not only splashed
against the walls of the engine-room, but it also destroys the adhesion
of the belt if the fly-wheel be employed as a pulley. In order to
overcome this objection the oil is prevented from spreading along the
shaft by means of a circular guard (Fig. 73) mounted on that portion of
the shaft toward the interior of the bearing.
[Illustration: FIG. 73.--Shaft with oil-guard.]
The problem of lubrication is of particular importance if the engine is
driven for several days at a time without a stop. This happens in the
case of mill and shop engines. Lubricators of large volume or
lubricators which can be readily filled without stopping the engine
should be employed.
CHAPTER VII
THE CONDITIONS OF PERFECT OPERATION
=General Care.=--Gas-engines, as well as most machines in general,
should be kept in perfect condition. Cleanliness, even in the case of
parts of secondary importance, is indispensable. Unpainted and polished
surfaces such as the shaft of the engine, the distributing cam-shafts,
the levers, the connecting-rod and the like, should be kept in a
condition equal to that when they were new. The absence of all traces of
rust or corrosion in these parts affords sufficient evidence of the care
taken of the invisible members such as the piston, the valves, ignition
devices, and the like.
=Lubrication.=--The rubbing surfaces of a gas-engine should be regularly
and perfectly lubricated. The absence of lost motion and backlash in the
bearings, guides, and joints is of particular importance not only
because of its influence on steady and silent running, but also on the
power developed and on the consumption. As we have already seen in the
chapter on lubrication, a special quality of oil should be employed for
the lubrication of the cylinder. The feed of the lubricator supplying
this most vital part of the engine is so regulated that it meets the
actual requirements with the utmost nicety possible. In a subsequent
chapter, in which faulty operation will be discussed, it will be shown
how too much and too little oil may cause serious trouble.
=Tightness of the Cylinder.=--The amount of power developed depends
principally on the degree of compression to which the explosive mixture
is subjected. The economical operation of the engine depends in general
upon perfect compression. It is, therefore, necessary to keep those
parts in good order upon which the tightness of the cylinder depends.
These parts are the piston, the valves, and their joints, and the
ignition devices whether they be of the hot-tube or electrical variety.
In order to prevent leakage at the piston, the rings should be protected
from all wear. It is of the utmost importance that the surfaces both of
the piston and of the cylinder, be highly polished so that binding
cannot occur. In cleansing the cylinder, emery paper or abrasive powder
should not be employed; for the slightest particle of abrasive between
the surfaces in contact will surely cause leakage. The oil and dirt,
which is turned black by friction and which may adhere to the piston
rings, should be washed away with petroleum. Similarly the other parts
of the cylinder should be cleaned to which burnt oil tends to adhere.
=Valve-Regrinding.=--The valves should be regularly ground. Even in
special cases where they may show no trace of rapid wear they should be
removed at least every month. In order to avoid any accident, care
should be taken in adjusting the valves after the cap has been unbolted
not to introduce a candle or a lighted match either in the
valve-chambers or in the cylinder, without first closing the gas-cock.
Furthermore, a few turns should be given to the engine, in order to
drive out any explosive mixture that may still remain in the cylinder or
the connected passages. The exhaust-valve, by reason of the high
temperature to which the disk and the seat are subjected, should receive
special attention. The valve should be ground on its seat every two or
three months at least, depending upon the load of the engine.
=Bearings and Crosshead.=--The bushings of the engine shaft should
always be held tightly in place. The looseness to which they are liable,
particularly in gas-engines on account of the sharp explosions, tends to
unscrew the nuts and to hasten the wear of the brass, which is the
result of frequent tightening. The slightest play in the bearings of the
engine-shaft as well as in the bearings of connecting-rods increases the
sound that engines naturally produce.
=Governor.=--The governor should receive careful attention so far as its
cleanliness is concerned; for if its operation is not easy it is apt to
become "lazy" and to lose its sensitiveness. If the governor be of the
ball type, or of the conical pendulum type operated by centrifugal
force, it is well to lubricate each joint without excess of oil. In
order to prevent the accumulation and the solidification of oil, the
governor should be lubricated from time to time with petroleum. If the
governor is actuated by inertia, which is the case in most engines of
the hit-and-miss variety, it needs less care; still, it is advisable to
keep the contact at which the thrust takes place well oiled.
The operation of any of these governors is usually controlled by the
tension of a spring, or by a counterweight. In order to increase the
speed of the engine, or in other words, to increase the number of
admissions of gas in a given time, all that is usually necessary is to
tighten up the spring, or to change the position of the counterweight.
It should be possible to effect this adjustment while the engine is
running in such a manner that the speed can be easily changed.
=Joints.=--In most well-built engines the caps of the valve-chests and
other removable parts are secured "metal on metal" without interposing
special joints. In other words, the surfaces are themselves sufficiently
cohesive to insure perfect tightness. In engines which are not of this
class, asbestos joints are very frequently employed, particularly at the
exhaust-valve cap and the suction-valve.
In some engines, where for any reason it is necessary frequently to
detach the caps, certain precautions should be taken to protect the
joints so that they may not be exposed to deterioration whenever they
are removed. For this purpose, they are first immersed in water in order
to be softened, then dried and washed with olive or linseed oil on the
side upon which they rest in the engine. On the cap side they are dusted
with talcum or with graphite. Treated in this manner, the joint will
adhere on one side and will be easily released on the other.
Joints that are liable to come in contact with the gases in the
explosion-chamber should be free from all projections toward the
interior of the cylinder; for during compression these uncooled
projections may become incandescent and may thus cause premature
ignition. As a general rule when the cap is placed in position the joint
should be retightened after a certain time, when the surfaces have
become sufficiently heated. In order to tighten the joints the bolts and
nuts should not be oiled; otherwise the removal of the cap becomes
difficult.
=Water Circulation.=--In a previous chapter, the importance of the water
circulation and the necessity of keeping the cylinder-jacket hot, have
been sufficiently dwelt upon. As the cylinder tends to become hotter
with an increase in the load, because of the greater frequency of
explosions, it is advisable to regulate the flow of the water in order
to prevent its becoming more than sufficient in quantity when the engine
is lightly loaded; for under these conditions the cylinder will be cold
and the explosive mixture will be badly utilized. A suitable temperature
of 140 to 158 degrees F. is easily maintained by adjusting the
circulation of the water. This can be accomplished by providing the
water-inlet pipe leading to the cylinder with a cock which can be opened
more or less, as may be necessary. The temperature of 140 to 158 degrees
F., which has been mentioned, may, at first blush, seem rather high
because it would be impossible to keep the hand on the outlet-pipe. The
cylinder, however, will not become overheated so long as it is possible
to hold the hand beneath the jacket near the water-inlet. This relates
only to engines having a compression of 50 to 100 lbs. per square inch.
For engines of higher compression, a lower running temperature will be
safer. On this matter the instructions of the engine maker should be
carried out.
=Adjustment.=--Gas-engines, at least those which are built by
trustworthy firms, are always put to the brake test before they are sent
from the shops, and are adjusted to meet the requirements of maximum
efficiency. But since the nature and quality of gas necessarily vary
with each city, it is evident that an engine adjusted to develop a
certain horse-power with a gas of a certain richness, may not fulfil all
expectations if it is fed with a gas less rich, less pure, hotter, and
the like. The altitude also has some influence on the efficiency of the
engine. As it increases, the density of the mixture diminishes; that is
to say, for the same volume the engine is using a smaller amount. From
this it follows that a gas-engine ought to be adjusted as a general rule
on the spot where it is to be used.
The fulfilment of this condition is particularly important in the case
of explosion-engines, because an advancement or retardation of only
one-half a second in igniting the explosive mixture will cause a
considerable loss in useful work. From this it would follow that
gas-engines should be periodically inspected in order that they may
operate with the highest efficiency and economy. As in the case of
steam-engines, it is advisable to take indicator records which afford
conclusive evidence of the perturbations to which every engine is
subject after having run for some time.
Most gas-engine users either have no indicating instruments at their
disposal or else are not sufficiently versed in their employment and the
interpretation of their records to study perturbations by their means.
For this reason the advice of experts should be sought,--men who
understand the meaning of the diagrams taken and who are able by their
means to effect a considerable saving in gas.
CHAPTER VIII
HOW TO START AN ENGINE--PRELIMINARY PRECAUTIONS
The first step which is taken in starting an engine driven by street-gas
is, naturally, the opening of the meter-cock and the valves between the
meter and the engine. When the gas has reached the engine, the rubber
bags will swell up and the anti-pulsator diaphragm will be forced out.
The drain-cock of the gas-pipe is then opened. In order to ascertain
whether the flow of gas is pure, a match is applied to the outlet of the
cock. The flame is allowed to burn until it changes from its original
blue color to a brilliant yellow.
If the hot-tube system of ignition be employed, the Bunsen burner is
ignited, care being taken that the flame emerging from the tube is blue
in color. If necessary the admission of air to the burner is regulated
by the usual adjusting-sleeve. A white or smoky flame indicates an
insufficient supply of air to the burner. A characteristic sooty odor is
still other evidence of the same fact. Sometimes a white flame may be
produced by the ignition of the gas at the opening of the
adjusting-sleeve. A blue or greenish flame is that which has the highest
temperature and is the one which should, therefore, be obtained. About
five or ten minutes are required to heat up the tube, owing to the
material of which it is made. When the proper temperature has been
attained the tube becomes a dazzling cherry red in color. While the tube
is being heated up, it is well to determine whether the engine is
properly lubricated and all the cups and oil reservoirs are duly filled
up. The cotton waste of the lubricators should be properly immersed, and
the drip lubricators examined to determine whether they are supplying
their normal quantity of oil.
The regulating-levers of the valves should be operated in order to
ascertain whether the valves drop upon their seats as they should. The
stem of the exhaust-valve should be lubricated with a few drops of
petroleum.
If the ignition system employed be of the electric type, with batteries
and coils, tests should be made to determine whether the current passes
at the proper time on completing the circuit with the contact mounted on
the intermediary shaft. This contact should produce the characteristic
hum caused by the operation of the coil.
If a magneto be used in connection with the ignition apparatus, its
inspection need not be undertaken whenever the engine is started,
because it is not so likely to be deranged. Still, it is advisable, as
in the case of ignition by induction-coils, to set in position the
device which retards the production of the spark. This precaution is
necessary in order to avoid a premature explosion, liable to cause a
sharp backward revolution of the fly-wheel.
After the ignition apparatus and the lubricators have been thus
inspected, the engine is adjusted with the piston at the starting
position, which is generally indicated by a mark on the cam-shaft. The
starting position corresponds with the explosion cycle and is generally
at an angle of 40 to 60 degrees formed by the crank above the horizontal
and toward the rear of the engine. The gas-cock is opened to the proper
mark, usually shown on a small dial. If there be no mark, the cock is
slowly opened in order that no premature explosion may be caused by an
excess of gas.
The steps outlined in the foregoing are those which must be taken with
all motors. Each system, however, necessitates peculiar precautions,
which are usually given in detailed directions furnished by the builder.
As a general rule the engines are provided on their intermediary shafts
with a "relief" or "half-compression" cam. By means of this cam the
fly-wheel can be turned several times without the necessity of
overcoming the resistance due to complete compression. Care should be
taken, however, not to release the cam until the engine has reached a
speed sufficient to overcome this resistance.
Engines of considerable size are commonly provided with an automatic
starting appliance. In order to manipulate the parts of which this
appliance is composed, the directions furnished by the manufacturer
must be followed. Particularly is this true of automatic starters
comprising a hand-pump by means of which an explosive mixture is
compressed,--true because in the interests of safety great care must be
taken.
The tightness and free operation of the valves or clacks which are
intended to prevent back firing toward the pump should be made the
subject of careful investigation. Otherwise, the piston of the pump is
likely to receive a sudden shock when back firing occurs.
When the engine has been idle for several days, it is advisable, before
starting, to give it several turns (without gas) in order to be sure
that all its parts operate normally. The same precaution should be taken
in starting an engine, if a first attempt has failed, in order to
evacuate imperfect mixtures that may be left in the cylinder. Before
this test is made, the gas-cock should, of course, be closed in order to
prevent an untimely explosion. It is advisable in starting an engine not
to bend the body over the ignition-tube, because the tube is likely to
break and to scatter dangerous fragments.
Under no condition whatever should the fly-wheel be turned by placing
the foot upon the spokes. All that should be done is to set it in motion
by applying the hand to the rim.
=Care During Operation.=--When the engine has acquired its normal speed,
the governor should be looked after in order that its free operation may
be assured and that all possibility of racing may be prevented. After
the engine has been running normally for a time, the cocks of the water
circulation system should be manipulated in order to adjust the supply
of water to the work performed by the engine. In other words the
cylinder should be kept hot, but not burning, as previously explained in
the paragraph in which the water-jacket is discussed. The maintenance of
a suitable temperature is extremely important so far as economy is
concerned. All the bearings should be inspected in order that hot boxes
may be obviated.
=Stopping the Engine.=--The steps to be taken in stopping the engine are
the following:
1. Stopping the various machines driven by the engine,--a practice which
is followed in the case of all motors;
2. Throwing out the driving-pulley of the engine itself, if there be
one;
3. Closing the cock between the meter and the gas-bags in order to
prevent the escape of gas and the useless stretching of the rubber of
the bags or of the anti-pulsating devices;
4. Actuating the half-compression or relief cam as the motor slows down,
in order to prevent the recoil due to the compression;
5. Closing the gas-admission cock;
6. Shutting off the supply of oil of free flowing lubricators, and
lifting out the cotton from the others.
If the engine be used to drive a dynamo, particularly a dynamo provided
with metal brushes, the precaution should be taken of lifting the
brushes before the engine is stopped in order to prevent their injury
by a return movement of the armature-shaft;
7. Shutting off the cooling-water cock if running water is used.
If the engine is exposed to great cold, the freezing of the water in the
jacket is prevented while the engine is at rest, either by draining the
jacket entirely, or by arranging a gas jet or a burner beneath the
cylinder for the purpose of causing the water to circulate. If such a
burner be used the cocks of the water supply pipe should, of course, be
left open.
CHAPTER IX
PERTURBATIONS IN THE OPERATION OF ENGINES AND THEIR REMEDY
In this chapter will be discussed certain perturbations which affect the
operations of gas-engines to a more marked degree than lack of care in
their construction. In previous chapters defects in operation due to
various causes have been dwelt upon, such as objectionable methods in
the construction of an engine, ill-advised combination of parts, defects
of installation, and the like; and an attempt has been made to determine
in each case the conditions which must be fulfilled by the engine in
order to secure efficiency and economy at a normal load.
=Difficulties in Starting.=--The preliminary precautions to be taken in
starting an engine having been indicated, it is to be assumed that the
advice given has been followed. Nevertheless various causes may prevent
the starting of the engine.
=Faulty Compression.=--Defective compression, as a general rule,
prevents the ignition of the explosive mixture. Whether or not the
compression be imperfect can be ascertained by moving the piston back to
the period corresponding with compression, in other words, that position
in which all valves are closed. If no resistance be encountered, it is
evident that the air or the gaseous mixture is escaping from the
cylinder by way of the admission-valve, the exhaust-valve, or the
piston. The valves, ordinarily seated by springs, may remain open
because their stems have become bound, or because some obstruction has
dropped in between the disk and the seat. In a worn-out or badly kept
engine the valves are likely to leak. If that be the case grinding is
the only remedy. If a valve be clogged, which becomes sufficiently
evident by manipulating the controlling levers, it is necessary simply
to clean the stem and its guides in order to remove the caked oil which
accumulates in time. If the engine be new, the binding of the
valve-stems is often caused by insufficient play between the stems and
their guides. Should this prove to be the case, the defect is remedied
by rubbing the frictional surface of the stem with fine emery paper and
by lubricating it with cylinder-oil. The exhaust-valve, however, should
be lubricated only with petroleum.
It is not unlikely that the exhaust-valve may leak for two other
reasons. In the first place, the tension of the spring which serves to
return the valve may have lessened and may be insufficient to prevent
the valve from being unseated during suction. Again, the screw or roller
serving as a contact between the lever and the valve-stem, may not have
sufficient play, so that the lengthening of the stem on account of its
expansion may prevent the valve from falling back on its seat. The
first-mentioned defect is remedied by renewing the spring, or by the
provision of an additional spring or of a counterweight in order to
prevent the stoppage of the motor. The second defect can be remedied by
regulating the contact.
Leakage past the piston may be caused by the breaking of one or more
rings, by wear or binding of the rings, or by wear or binding of the
cylinder. The whistling caused by the air or the mixture as it passes
back proves the existence of this fault.
=Presence of Water in the Cylinder.=--It may sometimes happen that water
may find its way into the cylinder with the gas by reason of the bad
arrangement of the piping. It may also happen that water may enter the
cylinder through the water-jacket joint. Again, the presence of water in
the cylinder may be due to condensation of the steam formed by the
chemical union of the hydrogen of the gas and the oxygen of the air,
which condensation is caused by the cool walls of the cylinder. The
water may sometimes accumulate in the exhaust pipe and box, when they
have been improperly drained, and may thus return to the cylinder.
Whatever may be its cause, however, the presence of water in the cylinder
impedes the starting of the engine, because the gases resulting from the
explosion are almost spontaneously chilled, thereby diminishing the
working pressure.
If electric ignition be employed, drops of water may be deposited
between the contacts, thereby causing short circuits which prevent the
passing of the spark.
If there be no drain-cock on the cylinder, the difficulty of starting
the engine can be overcome only by ceaseless attempts to set it in
motion. The leaky condition of a joint as well as the presence of a
particle of gravel in the cylinder-casting, through which the water can
pass from the jacket, is attested by the bubbling up of gas in the
water-tank at the opening of the supply tube. These bubbles are caused
by the passage of the gas through the jacket after the explosion. If
such bubbles be detected, the cylinder should be renewed or the defect
remedied. In order to obviate any danger, the stop-cocks of the
water-jacket, which have already been described in a previous chapter,
should be closed while the engine is idle.
=Imperfect Ignition.=--The difficulties encountered in starting an
engine, and caused by imperfect ignition, vary in their nature with the
character of the ignition system employed, whether that system, for
example, be of the electric, or of the incandescent or hot tube type.
Frequently it happens that in starting an engine a hot tube may break.
If the tube be of porcelain the accident may usually be traced to
improper fitting or to the presence of water in the cylinder. If the
tube be of metal, its breaking is caused usually by a weakening of the
metal through long use--an accident that occurs more often in starting
the engine than in normal operation, because the explosions at starting
are more violent, owing to the tendency of the supply-pipes to admit an
excess of gas at the beginning.
A misfire arising from a faulty tube in starting may be caused by an
obstruction or by leaks at the joints or in the body of the tube
itself, thereby allowing a certain quantity of the mixture to escape
before ignition. This defect in the tube is usually disclosed by a
characteristic whistling sound.
A tube may leak either at the bottom or at the top. In the first case,
starting is very difficult, because the part of the mixture compressed
toward the tube will escape through the opening before it reaches the
incandescent zone. In the second case, ignition may be simply retarded
to so marked an extent that a sufficient motive effect cannot be
produced. An example of this retardation, artificially produced to
facilitate the starting and to obviate premature explosions, is found in
a system of ignition-tubes provided with a small cock or variable valve
(Figs. 74 and 75).
[Illustration: FIG. 74.]
[Illustration: FIG. 75.--Ignition-tubes provided with needle valves to
facilitate starting.]
The mere enumeration of defects caused by leakage is sufficient to
indicate the remedy to be adopted. It may be well to recall in this
connection the important part played by the ignition-valve. If it be
leaky, or if its free operation be impeded, starting will always be
difficult.
=Electric Ignition by Battery or Magneto.=--If the electric ignition
apparatus, whatever may be the method by which the spark is produced, be
imperfect in operation, the first step to be taken is to ascertain
whether the spark is produced at the proper time, in other words,
slightly after the dead center in the particular position given to the
admission device at starting. If a coil and a battery be employed, it is
advisable to remove the plug and to place it with its armature upon a
well-polished metal surface to produce an electrical contact,
preventing, however, the contact of the binding post with this metallic
surface. The same method of inspection is adopted with the
make-and-break apparatus of an electric magneto. In both cases it should
be ascertained whether or not there is any short-circuiting. The
contacts should be cleaned with a little benzine if they are covered
with oil or caked grease.
If no spark is produced at the plug or at the make-and-break device it
may be inferred that the wires are broken or that the generating
apparatus is out of order. A careful examination will indicate what
measures are to be taken to cure the defects.
=Premature Ignition.=--It has several times been stated that the moment
of ignition of the gaseous mixture has a pronounced influence on the
operation of gas-engines and upon their economy.
Premature ignition takes place when there is a violent shock at the
moment when the piston leaps from the rear dead center to the end of the
compression stroke. The violent effects produced are all the more
harmful because they tend to overheat the interior of the engine and
thereby to increase in intensity.
Premature ignition may be due to several causes. If a valveless hot tube
be employed it may happen that the incandescent zone is too near the
base. If the tube be provided with a valve, it very frequently happens
that the valve leaks or that it opens too soon. In the case of electric
ignition, the circuit may be completed before the proper time, because
of faulty regulation. The suggestions made in the preceding chapters
indicate the method of remedying these defects.
Faulty ignition may have its origin not only in the method of ignition
employed, but also in excessive heating of the internal parts of the
engine, caused by continual overloading or by inadequate circulation of
water.
Passing to those cases of premature ignition of a special nature which
are not due to any functional defect in the engine, but which are purely
accidental in origin, such as the uncleanliness of the parts within the
cylinder or the presence of some projecting part which becomes heated to
incandescence during compression, it should first be stated that these
ignitions, usually termed spontaneous, often occur well in advance of
the end of the compression stroke. They are characterized by a more
marked shock than that caused by ordinary premature ignition and
usually result in bringing the engine to a complete stop in a very short
time. These spontaneous explosions counteract to such an extent the
impulse of the compression period, during which the piston is moving
back, that they have a tendency to reverse the direction in which the
engine is running. In such cases a careful inspection and a scrupulous
cleaning of the cylinder and of the piston should be undertaken.
The bottom of the piston is particularly likely to retain grease which
has become caked, and which is likely to become heated to incandescence
and spontaneously to ignite the explosive mixture.
=Untimely Detonations.=--The sound produced by the explosions of a
normally operating engine can hardly be heard in the engine-room.
Untimely detonations are produced either at the exhaust, or in the
suction apparatus, near the engine itself. These detonations are noisier
than they are dangerous; still, they afford evidence of some fault in
the operation which should be remedied.
Detonations produced at the exhaust are caused by the burning of a
charge of the explosive mixture in the exhaust-pipe, which charge, for
some reason, has not been ignited in the cylinder, and has been driven
into the exhaust-pipe, where it catches fire on coming into contact with
the incandescent gases discharged from the cylinder after the following
explosion.
Detonations produced in the suction apparatus of the engine, which
apparatus is either arranged in the base itself or in a separate chest,
are often noisier than the foregoing. They are caused by the accidental
backward flowing of the explosive mixture, and by its ignition outside
of the cylinder. The accident may be traced to three causes:
1. The suction-valve of the mixture may not be tight and may leak during
the period of compression, allowing a certain quantity of the mixture to
pass into the suction-chest or into the frame. When the explosion takes
place in the cylinder that part of the mixture which has passed back is
ignited, as we have just seen, thereby producing a very loud
deflagration. The obvious remedy consists in making the suction-valve
tight by carefully grinding it.
2. It may happen that at the end of the exhaust stroke incandescent
particles may remain in the cylinder, which particles may consist of
caked oil or may be retained by poorly cooled projections. The result is
that the mixture is prematurely ignited during the suction period.
3. The engine is so regulated, particularly in the case of English-built
engines, as to effect what is technically called "scavenging" the
products of combustion. In order to obtain this result, the
mixture-valve is opened before the end of the exhaust stroke of the
piston and the closing of the exhaust-valve. Owing to the inertia and
the speed acquired by the products of combustion shot into the
exhaust-pipe after explosion, a lowering of the pressure is produced in
the cylinder toward the end of the stroke, causing the entrance of air
by the open admission-valve and consequently effecting the scavenging of
the burnt gases, part of which would otherwise remain in the cylinder.
It is evident that if a charge of the mixture has not been normally
exploded, either because its constituents have not been mingled in the
proper proportion, or because the ignition apparatus has missed fire,
this charge at the moment of exhausting will pass out of the cylinder
without any acquired speed, and will flow back in part at the end of the
exhaust stroke past the prematurely opened admission-valve, thereby
lodging in the air suction apparatus. Despite the suction which takes
place immediately following the re-entrance of the gas into the
cylinder, a certain quantity of the mixture is still confined in the
suction-pipe and its branches, where it will catch fire at the end of
the exhaust stroke after the opening of the mixture-valve.
In order to avoid these detonations it is necessary simply to see to it
that the mixture is regularly ignited. This is accomplished by mixing
the gas and air in proper proportions or by correcting the ignition
time.
=Retarded Explosions.=--Retarded explosions considerably reduce the
power which an engine should normally yield, and sensibly increase the
consumption. They are due to three chief causes: (1), faulty ignition;
(2), the poor quality of the mixture; (3), compression losses. The
existence of the defect cannot be ascertained with any certainty without
the use of an indicator or of some registering device which gives
graphic records. Nevertheless, it is possible in some degree to detect
retarded explosions, simply by observing whether there is a diminution
in the power or an excessive consumption, despite the perfect operation
and good condition of all the engine parts.
In order to remedy the defect it should be ascertained if the
compression is good, if the supply of gas is normal, and if the
conditions under which the mixture of air and gas is produced have not
been changed. Lastly, the ignition apparatus is gradually adjusted to
accelerate its operation until a point is reached when, after explosion,
shocks are produced which indicate an excessive advance. The ignition
apparatus is then adjusted to a point slightly ahead of the
corresponding position. Recalling the descriptions already given of the
various systems of ignition, the manner of regulating the moment of
ignition in each case may be summarized as follows:
1. For the valveless incandescent tube, provided with a burner the
position of which can be varied, ignition can be accelerated by bringing
the burner nearer to the base. Retardation is effected by moving the
burner away from the base.
2. In the case of the incandescent tube of the fixed burner type, the
moment of ignition will depend upon the length of the tube. The
retardation will be greater as the tube is shorter, and _vice versa_.
3. If the tube be provided with an ignition-valve, the time of ignition
having been regulated by the maker, regulation need not be undertaken
except if the valve-stem be worn or the controlling-cam be distorted.
If these defects should be noted, the imperfect parts should be repaired
or renewed.
4. In electric igniters the controlling apparatus is generally provided
with a regulating device which may be manipulated during the operation
of the motor. If the manual adjustment of the regulating apparatus be
unproductive of satisfactory results, it is advisable to ascertain
whether the spark is being produced normally. Before the engine has come
to a stop, one of the valve-casings is raised, and through the opening
thus produced it is easily seen whether the spark is of sufficient
strength, the engine in the meanwhile being turned by hand. Care should
always be taken to purge the cylinder of the gas that it may contain, in
order to prevent dangerous explosions. If the spark should prove to be
too feeble, or if there be no spark at all, despite the fact that every
part of the mechanism is properly adjusted, it may be inferred that the
fault lies with the current and is caused by
1. Imperfect contact with the binding-posts, with the conducting wire,
or with the contact-breaking members;
2. A short circuit in one of the dismembered pieces;
3. The presence of a layer of oil or of caked grease forming an
insulator, injurious to induction, between the armature and the magnets;
4. A deposit of oil or moisture on the contact-breaking parts;
5. The exhaustion of the magnets, which, however, occurs only after
several years of use, except when the magneto has been subjected for a
long time to a high temperature.
The mere discovery of any of these defects sufficiently indicates the
means to be adopted in remedying them.
=Lost Motion in Moving Parts.=--Lost motion of the moving parts is due
to structural errors. Its cause is to be found in the insufficient size
of the frictional bearing surfaces, and improper proportioning of
shafts, pins, and the like. The result is a premature wear which cannot
be remedied. Imperfect adjustment, lack of care, and bad lubrication,
may also hasten the wear of certain parts. This wear is manifested in
shocks, occurring during the operation of the engine,--shocks which are
particularly noticeable at the moment of explosion.
Besides the inconveniences mentioned, wearing of the gears and of the
moving parts leads to derangement of the power-transmitting members.
So far as the admission and exhaust valves are concerned, the wearing of
the cams, rollers, and lever-pivots is evidenced by a retardation in the
opening of these valves and an acceleration in their closing.
The ignition, whatever may be the system employed, is affected by lost
motion and is retarded. The engine appreciably loses in power, and its
consumption becomes excessive.
=Overheated Bearings.=--Apart from the imperfect adjustment of a member,
it may happen that the bushings of the main bearings of the ends of the
connecting-rod, and of the piston-pivot, may become heated because of
excessive play, or of too much tightening, or of a lack of oil, or of
the employment of oil of bad quality. The overheating may lead to the
binding of frictional surfaces and even to the fusion of bushings if
they be lined with anti-friction metal. In order to avoid the
overheating of parts, it is advisable, while the engine is running, to
touch them from time to time with the back of the hand. As soon as the
slightest overheating is felt, the temperature may be lowered often by
liberal oiling. If this be inadequate and if for special reasons it is
impossible to stop the engine, the overheated part may be cooled by
spraying it with soapy water.
If the overheating has not been detected or reduced in time, a
characteristic odor of burnt oil will be perceived, accompanied by
smoke. The part overheated will then have attained a temperature so high
that it cannot be touched with the hand. Should this occur, it is
inadvisable to employ oil, because it would immediately burn up and
would only aggravate the conditions. Cotton waste should be carefully
applied to the overheated member, and gradual spraying with soapy water
begun.
In special cases where the lubricating openings or channels are not
likely to be obstructed, a little flowers of sulphur may be added to the
oil, if this be very fluid. Castor oil may also be successfully
employed.
If the binding of the rubbing surfaces should prevent the reduction of
the overheated member's temperature, the engine must necessarily be
stopped, and the parts affected detached. All causes of binding are
removed by means of a steel scraper. The surfaces of the bushings and of
the shaft which they receive are smoothed with a soft file and then
polished with fine emery paper. Before the parts are replaced, the
precaution of ascertaining whether they touch at all points should be
taken. Careful inspection and copious lubrication should, of course, be
undertaken when the engine is again started.
=Overheating of the Cylinder.=--The overheating of the cylinder may be
due to a complete lack of water in the jacket or to an accidental
diminution in the quantity of water supplied. If this discovery is made
too late, and if the cylinder has reached a very high temperature, the
circulation of the water should not be suddenly re-established, because
of the liability of breaking the casting. It is best to stop the engine
and to restore the parts to their normal condition.
It is well to recall at this point that if the calcareous incrustation
of the water-jacket or the branch pipes should hinder the free
circulation of water, cleaning is, of course, necessary. The jacket may
be washed several times with a twenty per cent. solution of hydrochloric
acid. After this treatment the jacket should, of course, be rinsed with
fresh water before the piping of the water-circulating apparatus is
again connected.
=Overheating of the Piston.=--If the overheating of the piston is not
due to faulty adjustment, it may be caused by lack of oil or to the
employment of a lubricant not suitable for the purpose. In a previous
chapter the importance of using a special oil for cylinder lubrication
has been insisted upon. The overheating of the piston can also result
from that of the piston-pin. Should this be the case it is advisable to
stop the engine, to ascertain the condition and the degree of
lubrication of this member and its bearing. Overheating of the piston is
manifested by an increase of the temperature of the cylinder at the
forward end. If this overheating be not checked, binding of the piston
in the cylinder is likely to result.
=Smoke Arising from the Cylinder.=--This is generally a sign either of
overheating, which causes the oil to evaporate, or of an abnormal
passage of gas, caused by the explosion. Abnormal passage of gas may
result from wear or from distortion of the cylinder, or from wear or
breakage of the piston-rings. The result is always the overheating of
the cylinder and a reduction in compression and power.
If the engine is well kept and shows no sign of wear, leakage may be
caused simply by the fouling of the piston-rings, which then adhere in
their grooves and have but insufficient play. This defect is obviated by
cleaning the rings in the manner explained in Chapter VII.
Lubrication is faulty when the quantity of lubricant supplied is either
insufficient or too abundant, or when the oils employed are of bad
quality. It has already been shown that insufficient lubrication and the
utilization of bad oils leads to the overheating of the moving parts.
Insufficient lubrication may be caused by imperfect operation of the
lubricators, or, particularly during cold weather, by too great a
viscosity or congelation of the oil. If a lubricator be imperfect in its
operation, the condition of its regulating mechanism should be
ascertained, if it has any, and an examination made to discover any
obstruction in the oil-ducts. Such obstructions are very likely to occur
in new devices which have been packed in cotton waste or excelsior, with
the result that the particles of the packing material often find their
way into openings.
An oil may be bad in quality because of its very nature, or because of
the presence of foreign bodies. In either case an oil of better quality
should be substituted.
The freezing of oil by intense cold may be retarded by the addition of
ordinary petroleum to the amount of 10 to 20 per cent.
An excess of oil in the bearings results simply in an unnecessary waste
of lubricant, and the splashing of oil on the engine and about the room.
If too much oil be used in the cylinder, grave consequences may be the
result; for a certain quantity of the oil is likely to accumulate within
the cylinder, where it burns and forms a caky mass that may be heated to
incandescence and prematurely ignite the explosive mixture. Especially
in producer-gas engines is an excess of cylinder-lubricant likely to
cause such accidents. Indeed, the temperature of explosion not being as
high as in street-gas engines, the excess oil cannot be so readily
removed with certainty by evaporation or combustion. On the other hand,
the compression of the mixture being generally higher, premature
ignition is very likely to occur.
=Back Pressure to the Exhaust.=--How the pipes and chests for the
exhaust should be arranged in order not to exert a harmful influence on
the motor has already been explained. Even if the directions given have
been followed, however, the exhaust may not operate properly from
accidental causes. Among these causes may be mentioned obstructions in
the form of foreign bodies, such as particles of rust, which drop from
the interior of the pipes after the engine has been running for some
time and which, accumulating at any place in the pipe, are likely to
clog the passage. Furthermore, the products of combustion may contain
atomized cylinder oil which finds its way into the exhaust-pipe. This
oil condenses on the walls of the elbows and bends of the pipe in a
deposit which, as it carbonizes, is converted into a hard cake and which
reduces the cross-section of the passage, thereby constituting a true
obstacle to the free exhaust of the gases.
These various defects are manifested in a loss in engine power as well
as in an abnormal elevation of the temperature of the parts surrounding
the exhaust opening.
=Sudden Stops.=--Sudden stops are occasioned by faulty operation of the
engine, and by imperfect fuel supply. Among the first class the chief
causes to be mentioned are the following:
1. Overheating, which has already been discussed and which may block a
moving part.
2. Defective ignition.
3. Binding of the admission-valve or of the exhaust-valve, preventing
respectively suction or compression.
4. The breaking or derangement of a member of the distributing
mechanism.
5. A weakening of the exhaust-valve spring, so that the valve is opened
by the suction of fresh quantities of mixture.
These faults are due to carelessness and improper inspection of the
engine.
So far as the fuel supply of the engine is concerned, the causes of
stoppage will vary if street-gas or producer-gas be employed. In the
former case the difficulty may be occasioned by the improper operation
of the meter, by the formation of a water-pocket in the piping, by the
binding of an anti-pulsator valve, by the derangement of a
pressure-regulator, or by a sudden change in the gas pressure when no
pressure-regulator is employed. If producer-gas be used, stoppages may
be occasioned by a sudden change in the quality, quantity, or
temperature of the gas. These defects will be examined in detail in the
chapter on Gas-Producers.
CHAPTER X
PRODUCER-GAS ENGINES
Thus far only street-gas or illuminating-gas engines have been
discussed. If the engine employed be small--10 to 15 horse-power, for
instance--street-gas is a fuel, the richness, purity and facility of
employment of which offsets its comparatively high cost. But the
constantly increasing necessity of generating power cheaply has led to
the employment of special gases which are easily and cheaply generated.
Such are the following:
Blast-furnace gases,
Coke-oven gases,
Fuel-gas proper,
Mond gas,
Mixed gas,
Water-gas,
Wood-gas.
The practical advantages resulting from the utilization of these gases
in generating power were hardly known until within the last few years.
The many uses to which these gases have been applied in Europe since
1900 have definitely proved the industrial value of producer-gas engines
in general.
The steps which have led to this gradually increasing use of
producer-gas have been learnedly discussed and commented upon in the
instructive works and publications of Aimé Witz, Professor in the
Faculty of Sciences of Lille, in those of Dugald Clerk, of London, F.
Grover, of Leeds, and Otto Güldner, of Munich, and in those of the
American authors, Goldingham, Hiscox, Hutton, Parsell and Weed, etc. The
new tendencies in the construction of large engines may be regarded as
an interesting verification of the forecasts of these men--forecasts
which coincide with the opinion long held by the author. Aimé Witz has
always been an advocate of high pressures and of increased piston speed.
English builders who made experiments in this direction conceded the
beneficial results obtained; but while they increased the original
pressure of 28 to 43 pounds per square inch employed five or six years
ago to the pressure of 85 to 100 pounds per square inch nowadays
advocated, the Germans, for the most part, have adopted, at least in
producer-gas engines, pressures of 114 to 170 pounds per square inch and
more.
=High Compression.=--In actual practice, the problem of high pressures
is apparently very difficult of solution, and many of the best firms
still seem to cling to old ideas. The reason for their course is,
perhaps, to be found in the fact that certain experiments which they
made in raising the pressures resulted in discouraging accidents. The
explosion-chambers became overheated; valves were distorted; and
premature ignition occurred. Because the principle underlying high
pressures was improperly applied, the results obtained were poor.
High pressures cannot be used with impunity in cylinders not especially
designed for their employment, and this is the case with most engines of
the older type, among which may be included most engines of English,
French, and particularly of American construction. In American engines
notably, the explosion-chamber, the cylinder and its jacket, are
generally cast in one piece, so that it is very difficult to allow for
the free expansion of certain members with the high and unequal
temperatures to which they are subjected (Fig. 22).
Some builders have attempted to use high pressures without concerning
themselves in the least with a modification of the explosive mixture.
The result has been that, owing to the richness of the mixture, the
explosive pressure was increased to a point far beyond that for which
the parts were designed. Sudden starts and stops in operation,
overheating of the parts, and even breaking of crank-shafts, were the
results. The engines had gained somewhat in power, but no progress had
been made in economy of consumption, although this was the very purpose
of increasing the compression.
High pressures render it possible to employ poor mixtures and still
insure ignition. A quality of street-gas, for example, which yields one
horse-power per hour with 17.5 cubic feet and a mixture of 1 part gas
and 8 of air compressed to 78 pounds per square inch, will give the same
power as 14 cubic feet of the same gas mixed with 12 parts of air and
compressed to 171 pounds per square inch.
"Scavenging" of the cylinder, a practice which engineers of modern
ideas seem to consider of much importance, is better effected with high
pressures, for the simple reason that the explosion-chamber, at the end
of the return stroke, contains considerably less burnt gases when its
volume is smaller in proportion to that of the cylinder.
In impoverishing the mixture to meet the needs of high pressures, the
explosive power is not increased and in practice hardly exceeds 365 to
427 pounds per square inch. With the higher pressures thus obtained
there is consequently no reason for subjecting the moving parts to
greater forces.
[Illustration: FIG. 76.--Method of cooling the cylinder-head.]
=Cooling.=--The increase in temperature of the cylinder-head and of the
valves, due wholly to high compression, is perfectly counteracted by an
arrangement which most designers seem to prefer, and which, as shown in
the accompanying diagram (Fig. 76), consists in placing the mixture and
exhaust-valves in a passage forming a kind of antechamber completely
surrounded by water. The immediate vicinity of this water assures the
perfect and equal cooling of the valve-seats. This arrangement, while it
renders it possible to reduce the size of the explosion-chamber to a
minimum, has the additional mechanical advantage of enabling the builder
to bore the seats and valve-guides with the same tool, since they are
all mounted on the same line. From the standpoint of efficiency, the
design has the advantage of permitting the introduction of the explosive
mixture without overheating it as it passes through the admission-valve,
which obtains all the benefit of the cooling of the cylinder-head,
literally surrounded as it is by water.
In large engines the cooling effect is even heightened by separately
supplying the jackets of the cylinder-head and of the cylinder. In
engines of less power the top of the cylinder-head jacket is placed in
communication with that of the cylinder, so that the coldest water
enters at the base of the head and, after having there been heated,
passes around the cylinder in order finally to emerge at the top toward
the center. The water having been thus methodically circulated, the
useful effect and regularity of the cooling process is increased.
Notwithstanding the care which is devoted to water circulation, it is
advisable to run the producer-gas engine "colder" than the older
street-gas types, in which the more economic speed is that at which the
water emerges from the jacket at about a temperature of 104 degrees F.
It would seem advisable to meet the requirements of piston lubrication
by reducing to a minimum the quantity of heat withdrawn by the
circulating water. Indeed, the personal experiments of the author bear
out this principle.
For street-gas engines, however, the cylinders should be worked at the
highest possible temperature consistent with the requirements of
lubrication. It should not be forgotten that, in large engines fed with
producer-gas, economy of consumption is a secondary consideration,
because of the low quantity of fuel required. The cost, moreover, may
well be sacrificed to that steadiness of operation which is of such
great importance in large engines furnishing the power of factories; for
in such engines sudden stops seriously affect the work to be performed.
For this reason engine builders have been led to the construction of
motors provided with very effective cooling apparatus. Since the
circulation of the water around the explosion-chamber and the cylinder
is not sufficient to counteract the rise of temperature, it has become
the practice to cool separately each part likely to be subjected to
heat. The seats of the exhaust-valves, the valves themselves, the
piston, and sometimes the piston-rod, have been provided with
water-jackets.
=Premature Ignition.=--Returning to the causes of the discouragements
encountered by some designers who endeavored to use high pressures, it
has already been mentioned that premature ignition of the explosive
mixture in cylinders not suited for high pressures is one reason for the
bad results obtained. An explanation of these results is to be found in
the high theoretical temperature corresponding with great pressures and
in the quantity of heat which must be absorbed by the walls of the
explosion-chamber. These two circumstances are in themselves sufficient
to produce spontaneous ignition of excessively rich mixtures, compressed
in an overheated chamber unprovided with a sufficient circulation of
water. A third cause of premature ignition may also be found in the old
system of ignition which, in most English engines, consists of a
metallic or porcelain tube, the interior of which communicates with the
explosion-chamber, an exterior flame being employed to heat the tube to
incandescence. In tubes of this type which are not provided with a
special ignition-valve, the time of ignition is dependent only on the
moment when the explosive mixture, driven into the tube, comes into
contact, at the end of the compression stroke, with the incandescent
zone, thereby causing the ignition. This very empirical method leads
either to an acceleration or retardation of the ignition, depending upon
the temperature of the tube, the position of the red-hot zone, its
dimensions, and the temperature of the mixture, which is determined by
the load of the engine. Although this system, the only merit of which is
its simplicity, may meet the requirements of small engines, there is not
the slightest doubt that it is quite inapplicable to those of more than
20 to 25 horse-power, for in such engines greater certainty in operation
is demanded. Even if only the more improved of the two types of hot-tube
ignition be considered, with or without valves, it must still be held
that they are inapplicable to high compression engines. The
ignition-valve is the part which suffers most from the high temperature
to which it is subjected. Its immediate proximity to the incandescent
tube, and its contact with the burning gas when it flares up, render it
almost impossible to employ any cooling arrangement. Although with the
exercise of great care it may work satisfactorily in engines of normal
pressure, it is evident that it cannot meet the requirements of high
pressure engines, because the temperature of the compressed mixture is
such that the charge is certain to catch fire by mere contact with the
overheated valve. In industrial engines of small size, premature
ignition has little, if any, effect except upon silent operation and
economic consumption. This does not hold true, however, of large
engines. Besides the inconveniences mentioned, there is also the danger
of breaking the cranks or other moving parts. The inertia of these
members is a matter of some concern, because of their weight and of the
linear speed which they attain in large engines. Some idea of this may
be obtained when it is considered that in a producer-gas or
blast-furnace-gas engine having a piston diameter of 24 inches and an
explosive pressure of 299 pounds per square inch, the force exerted at
the moment of explosion is about 132,000 pounds. Naturally, engine
builders have adopted the most certain means of avoiding premature
ignition and its grave consequences.
The method of ignition which at present seems to be preferred to any
other for producer-gas is that employing a break-spark obtained with
the magneto apparatus previously described. Some builders of large
engines, particularly desirous of assuring steadiness of running, have
provided the explosion-chamber with two independent igniters. It may be
that they have adopted this arrangement largely for the purpose of
avoiding the inconveniences resulting from a failure of one of the
igniters, rather than for the purpose of igniting the mixture in several
places so as to obtain a more uniform ignition and one better suited for
the propagation of the flame.
=The Governing of Engines.=--Various methods have been adopted for the
purpose of varying the motive power of an engine between no load and
full load, still preserving, however, a constant speed of rotation.
These methods consist in changing either the quantity or the quality of
the mixture admitted into the cylinder. Thus it may happen that an
engine may be supplied:
1. With a mixture constant in quality and in quantity;
2. With a mixture variable in quality and constant in quantity;
3. With a mixture constant in quality and variable in quantity.
1. _Mixture Constant in Quality and Quantity._--This method implies the
use of the hit-and-miss system of admission, in which the number of
admissions and explosions varies, while the value or the composition of
each admitted charge remains as constant as the compression itself (Fig.
34). This system has already been referred to and its simplicity fully
set forth. By its use a comparatively low consumption is obtained, even
when the engine is not running at full load. On the other hand, it has
the disadvantage of necessitating the employment of heavy fly-wheel to
preserve cyclic regularity.
2. _Mixture Variable in Quality and Constant in Quantity._--The
governing system most commonly employed to obtain a mixture variable in
quality and constant quantity is based upon the control of the
gas-admission valve by means of a cam having a conical longitudinal
section, as shown in Fig. 35. This cam, commonly called a "conical cam,"
is connected with a lever actuated from the governor. As the lever
swings under the action of the governor, the cam is shifted along the
half-speed shaft of the engine. The result is that the gas-admission
valve is opened for a longer or shorter period.
In another system a cylindrical valve is mounted between the chamber in
which the mixture is formed and the gas-supply pipe, the valve being
carried on the same stem as the mixture-valve itself. The cylindrical
valve is displaced by the governor so as to vary the quantity of gas
drawn in with relation to the quantity of air.
When the engines are fed with producer-gas the parts which have just
been described should be frequently inspected and cleaned; for they are
only too easily fouled.
Engines thus governed should be run at high pressure so as to insure
the ignition of the producer-gas mixtures formed when the position of
the cam corresponds with the minimum opening of the gas-valve. Powerful
governors should be employed, capable of overcoming the resistance
offered by the cylindrical valve or the cam.
It may often happen that variations in the load of the engine render it
necessary to actuate the air valve, so as to obtain a mixture which will
be ignited and exploded under the best possible conditions.
3. _Mixture Constant in Quality and Variable in Quantity._--In supplying
an engine with a mixture constant in quality and variable in quantity,
the compression does not remain constant. The quantity of mixture drawn
in by the cylinder may even be so far reduced that the pressure drops
below the point at which ignition takes place. For that reason engines
of this type should be run at high pressures.
The variation of the quantity of mixture may be effected in various
ways. The simplest arrangement consists in mounting a butterfly-valve in
the mixture pipe, which valve is controlled by the governor and
throttles the passage to a greater or lesser degree. A very striking
solution of the problem consists in varying the opening of the
mixture-valve itself. To attain this end the valve is moved by levers.
The point of application of one of these levers is displaced under the
action of the governor so as to vary the travel of the valve within
predetermined limits. Under these conditions a mixture of constant
homogeneity is introduced into the cylinder, so proportioned as to
insure ignition even at low pressures.
[Illustration: FIG. 76_a_.--Governing system for producer-gas engines.]
In recent experiments conducted by the author it was proved that with
this governing system ignition still takes place even though the
pressure has dropped to 43 pounds per square inch. This system has the
merit of rendering it possible to employ ordinary governors of moderate
size, since the resistance to be overcome at the point of application of
the lever is comparatively small. In the accompanying illustration the
Otto Deutz system is illustrated.
CHAPTER XI
PRODUCER-GAS
It may here be not amiss to point out the differences between
illuminating gas and those gases which are called in English "producer"
gases, and in French "poor" gases, because of their low calorific value.
=Street-Gas.=--This gas, the composition of which varies with different
localities, has a calorific value, which is a function of its
composition, and which varies from 5,000 to 5,600 calories per cubic
meter (19,841 to 24,896 B.T.U. per 35.31 cubic feet) measured at
constant pressure and corrected to 0 degrees C. (32 degrees F.) at a
pressure of 760 millimeters (29.9 inches of mercury, or atmospheric
pressure), not including the latent heat of the water of condensation.
The following table gives the average volumetric composition of
illuminating gas in various cities:
____________________________________________________________________
|
| Cities.
|______________________________________________
| | | | |
| | Manches- | New | |
| London. | ter. | York. | Paris. | Berlin.
_____________________|_________|__________|_______|________|________
| | | | |
Hydrogen | 48 | 46 | 40 | 52 | 50
Carbon monoxide | 4 | 7 | 4 | 6 | 9
Methane | 38 | 35 | 37 | 32 | 33
Various hydrocarbons | 4 | 6 | 7 | 6 | 5
Carbon dioxide | | 4 | 3 | | 2
Nitrogen | 5 | 2 | 8 | 4 | 1
Oxygen | 1 | ... | 1 | ... | ...
|_________|__________|_______|________|________
| | | | |
| 100 | 100 | 100 | 100 | 100
_____________________|_________|__________|_______|________|________
Furthermore, these constituents vary within certain limits. This is also
true of the calorific value. Experiments made by the author have
demonstrated that in the same place at an interval of a few hours,
variations of approximately ten per cent. occur.
=Composition of Producer-Gases.=--The average chemical composition of
producer-gases varies with the conditions under which they are generated
and the nature of the fuel. The following are the proportions of its
constituents expressed volumetrically:
Table Headings--
A: Blast Furnace.
B: Producer.
C: Mond.
D: Mixed (Fichet).
E: Water (Stache).
F: Wood (Riché).
________________________________________________________________________
|
| Gas.
|_________________________________________________
| | | | | |
| A. | B. | C. | D. | E. | F.
______________________|_______|_______|_______|________|________|_______
| | | | | |
Nitrogen and oxygen | 60 | 59 | 42 | 50 | 5 | 1
Carbon monoxide | 24 | 25 | 11 | 20 | 40 | 29
Carbon dioxide | 12 | 5 | 16 | 7 | 4 | 11
Hydrocarbons | 2 | 2 | 2 | 3 | 1 | 15
Hydrogen | 2 | 9 | 29 | 20 | 50 | 44
|_______|_______|_______|________|________|_______
| | | | | |
| 100 | 100 | 100 | 100 | 100 | 100
|_______|_______|_______|________|________|_______
Calorific value | | | | | |
in calories. | 950 | 1,100 | 1,400 | 1,300 | 2,400 | 2,960
Average weight of a | | | | | |
cubic meter in kilos| 1.30 | 1.1 | 1.02 | 1.05 | 0.680 | 0.824
Or of a cubic foot | | | | | |
in pounds | 0.008 | 0.007 | 0.006 | 0.0068 | 0.0042 | 0.0051
______________________|_______|_______|_______|________|________|_______
Blast-furnace gas has been used for generating power by means of
gas-engines for about ten years. At the present time it is used in
engines of very high power, a discussion of which engines more properly
belongs to a work on metallurgy, and has no place, therefore, in a
manual such as this.
Producer-gas, in the true sense of the term, is generated in special
apparatus either under pressure or by suction in a manner to be
described in the following chapters.
Mond gas is produced in generators of the blowing or pressure type from
bituminous coal, necessitating the employment of special purifiers and
permitting the collection of the by-products of the fractional
distillation of the coal. Mond gas plants are, therefore, rather
complicated and can be advantageously utilized only for large engines.
More exhaustive information can be obtained from the descriptions
published by the builders of Mond gas generators.
Mixed gas is generated in apparatus arranged so that the retort is kept
at a high temperature, thereby producing a gas richer in hydrogen than
that made by producers. It should be observed that in practice the
generators at present used yield a producer-gas, the calorific value of
which fluctuates between 1,000 and 1,400 calories per cubic meter (3,968
to 5,158 B.T.U. per 35.31 cubic feet); and the composition varies
accordingly, in the manner that has already been indicated in the tables
for producer-gas and mixed gas. There is no necessity, therefore, for
drawing a distinction between these two qualities of gas.
Water-gas should theoretically be composed of 50 per cent. carbon
monoxide and 50 per cent. hydrogen, resulting from the decomposition of
steam by incandescent coal. In practice, however, it contains a little
nitrogen and carbon dioxide. The gas is obtained from generators in
which air is alternately blown in to fan the fire and then steam to
produce gas. Water-gas is employed in soldering on account of its
reducing properties and of the high temperature of its flame. The great
quantity of carbon monoxide which it contains renders it very poisonous
and exceedingly dangerous, because it is generated under pressure. From
the economical standpoint, its generation is more expensive than that of
producer-gas, for which reason its employment in gas-engines is hardly
of much value.
Wood-gas, the composition of which has already been given, is generated
in apparatus of the Riché type, the principle of which consists in
heating a cast retort charged with any kind of fuel, namely wood, and
vertically mounted on a masonry base.
This apparatus should be of particular interest to the proprietors of
sawmills, furniture factories, and the like, since it offers a means of
using the waste products of their plants.
The relatively high proportion of carbon monoxide in producer-gas is
objectionable from a hygienic standpoint, so much so, indeed, that it
has attracted the attention of manufacturers. Carbon monoxide, the
specific gravity of which is 0.967, is a gas peculiarly poisonous and
dangerous. It cannot be breathed without baneful effects, and is even
more dangerous than carbonic-acid gas, which eventually causes
asphyxiation by reducing the quantity of oxygen in the air. For this
reason, it is necessary to take the utmost precaution in efficiently and
continuously ventilating the rooms in which the gas-generators and their
accessories are installed. This suggestion should be followed, above
all, when the apparatus in question are installed in cellars and
basements. As a further precaution, where the plant is rather large a
workman should not be allowed to enter the generator room alone.
Blowing-generators, or those in which the gas is produced under
pressure, are more dangerous than suction-generators. In the former a
leaky joint may cause the vitiation of the surrounding air as the
producer-gas escapes; in the suction apparatus the same fault simply
causes more air to be drawn in.
Dr. Melotte recommends the following procedure in cases of carbon
monoxide asphyxiation:
CARBON MONOXIDE ASPHYXIATION
Cases of poisoning by carbon monoxide are both frequent and dangerous.
The gas is extremely poisonous, and all the more dangerous because it is
odorless, colorless and tasteless. When it comes into contact with the
blood, it forms a combination so stable that it is reacted upon by the
oxygen of the air only with difficulty. It follows, therefore, that with
each respiration of air charged with carbon monoxide, a certain quantity
of blood is poisoned. In consequence of this, there is a possibility of
poisoning in open air.
=Symptoms.=--The symptoms observed will vary with the manner in which
the blood has been poisoned. There are two ways in which this poisoning
can occur. The one depends upon whether the atmosphere contains an
excess of carbon monoxide; the other whether the air breathed contains
only traces of the gas.
=Gradual, Rapid Asphyxiation.=--At first a vague sickness is felt,
rapidly followed by violent headaches, vertigo, anxiety, oppression,
dimness of vision, beating of the pulse at the temples, hallucinations,
and an irresistible desire to sleep. If at this stage the patient has a
sufficient idea of danger to prompt him to open a window or door, he
will escape death.
In the second stage, the victim's legs are paralyzed, but he can still
move his arms and his head. The mind still preserves its clearness, and
in a measure assists the further process of asphyxiation because of its
impotency. Then follow coma and death.
=Slow, Chronic Asphyxiation.=--Slow, chronic asphyxiation is not
infrequent. Its symptoms are often difficult to detect. Poisoning is
manifested by weakness, cephalalgia, vomiting, pallor, general anemia,
lassitude, and local paralysis. If any of these symptoms appear in the
men who work in the vicinity of the producers, immediate steps should be
taken to prevent the possibility of carbon monoxide asphyxiation.
FIRST AID IN CASES OF CARBON MONOXIDE POISONING
It has already been stated that the oxygen of the air has no oxidizing
effect upon blood contaminated by carbon monoxide. Only a liberal
current of pure oxygen can oxidize the combination formed and render
hematosis possible. This liberal current can be obtained from an oxygen
tank of the portable variety, provided with a tube carrying at its free
end a mask which is held over the mouth and the nostrils. The
absorption of gas takes place by artificial respiration, which is
effected in several ways. The most practical of these are the Sylvester
and Pacini methods.
=Sylvester Method.=--The patient is laid on his back. His arms are
raised over his head and then brought back on each side of the body.
This operation is repeated fifteen times per minute approximately. The
method is very frequently employed and is excellent in its results.
=The Pacini Method.=--Four fingers are placed in the pit of the arm,
with the thumb on the shoulder. The shoulder is then alternately raised
and lowered, producing a marked expansion of the chest. This method is
the more effective of the two. The movements described are repeated
fifteen to twenty times each minute very rhythmically.
One or the other of these two methods of treatment should be immediately
applied in serious cases. Certain preliminary precautions should be
taken in all cases, however. The patient should be carried to a
well-ventilated and moderately heated room, stripped of his clothes, and
warmed by water-bottles and heated linen. Reflex action should be
excited, the peripheral nervous system stimulated in order to contract
the heart and the respiratory muscles, and the precordial region
cauterized. In addition to this treatment, the region of the diaphragm
should be rubbed and pinched, the skin rubbed, cold showers given,
flagellations administered, urtications (whipping with nettles)
undertaken, the skin and the mucous membranes excited, the mucous
membrane of the nose and of the pharynx titillated with a feather dipped
in ammonia, alcohol, vinegar, or lemon juice. Rhythmic traction of the
tongue is effective when carried out as follows: The tongue is seized
with a forceps and kept extended by means of a coarse thread. It is then
pulled out from the mouth sharply and allowed to reenter after each
traction. These movements should be rhythmic and should be repeated
fifteen to twenty times a minute.
All these efforts should be continued for several hours. When the
patient has finally been revived, he should be placed in a warm bed.
Stimulants such as wine, coffee, and the like should be administered. If
the head should be congested, local blood-letting should be resorted to
and four or six leeches applied behind the ears. It should be borne in
mind that the various steps enumerated are to be taken pending the
arrival of a physician.
IMPURITIES OF THE GASES
Most of the coal used in generating producer-gas contains sulphur.
Sulphuretted hydrogen is thus produced, which mixes with the gas and
imparts to it its characteristic odor. In some gas-generators, purifiers
are employed in which sawdust mixed with iron salts is utilized, with
the result that a combination is formed with the sulphuretted hydrogen,
thereby removing it from the producer-gas. In other forms of generators
a more summary method of purification is adopted, so that traces of
sulphuretted hydrogen still remain. Since this gas attacks copper, the
employment of this metal is not advisable for the following apparatus:
Generator (openings, cock for testing the gas); piping (gas-pressure
cocks, drain and pet cocks); engine (gas-admission cock, lubricating
joint in the cylinder, valves and cocks of the compressed-air
starting-pipe).
The distillation of coal in generators results in the formation of
ammonia gas. This also has a corrosive action on copper and its alloys;
but owing to its great solubility, it is eliminated by the waters of the
"scrubber" and does not reach the engine.
PRODUCTION AND CONSUMPTION
The quantity of gas produced in most generators varies from 6.4 to 8.2
pounds per cubic foot of raw coal burnt in the generator. The engine
consumes per horse-power per hour 70 to 115 cubic feet of gas, depending
upon its richness.
CHAPTER XII
PRESSURE GAS-PRODUCERS
As we have already seen, producer-gas as a fuel for engines may be
generated in two kinds of apparatus, the one operating under pressure,
and the other by suction.
=Dowson Gas-Producers.=--The first pressure-generators were introduced
by Dowson of London and necessitated installations of quite a
complicated nature. Later improvements made by the designers contributed
much to the general employment of their system. Many installations
varying from 50 to 100 horsepower and more may be found in the United
Kingdom, all of them made by Dowson. Indeed, for a long time the name of
Dowson was coupled with producer-gas itself. The Dowson system
necessitates the utilization of anthracite or of comparatively hard
coal, such as that mined in Wales and Pennsylvania. Owing to the
necessity of employing this special quality of coal the Dowson system
and the systems that sprang from it were burdened with cooling, washing,
and purifying apparatus, which complicated the installations to such an
extent that they resembled gas works. The generator that took the place
of the retort was fed with air and steam, blown in under pressure,
necessitating the employment of a boiler. Furthermore, the production
of the gas under pressure necessitated the use of a gasometer for its
collection before it was supplied to the engine-cylinder. Such
Installations were evidently costly, and were, moreover, difficult to
maintain in proper working order. Nevertheless, there are many cases in
which they must be industrially employed.
[Illustration: FIG. 77.--A complete Dowson producer-gas plant.]
[Illustration: FIG. 78.--A Simplex producer-gas plant.]
Among these may be cited works in which producer-gas is employed as a
furnace fuel or as a soldering or roasting medium. Still other cases are
those in which the producer-gas must be piped to some distance from a
central generating installation to various engines, in the manner
rendered familiar in gas-lighting practice.
Most pressure gas-generators have been copied from the original type
invented by Dowson. These include a generator in which the gas is
produced; an injector fed by a boiler; a fan or a compressor by means of
which a mixture of steam and air is blown under the generator-furnace;
washing apparatus termed "scrubbers"; gas-purifying apparatus; and a
gas-holder (Fig. 77).
=Generators.=--The generator consists of a retort made of refractory
clay, vertically mounted, and cylindrical or conical in form. This
retort is protected on its exterior by a metal jacket with an
intermediate layer of sand which serves to reduce the heat lost by
radiation. The fuel is charged through the top of the retort, which is
provided with a double closure in order to prevent the entrance of air
during the charging operation. The generator rests on a grid arranged at
the base of the retort, upon which grid the ashes fall. The outlet of
the injector-pipe opens into the ash-pit, and this injector constantly
supplies a mixture of steam and air. The mixture is generally
superheated by passing it through a coil arranged in the fire-box of the
boiler, in the generator, or in the outlet for burnt gases. Sometimes
the air is subjected to a preliminary heating by recuperating in some
way the waste heat of the apparatus.
The chief features in the arrangement of generators which have received
the attention of manufacturers are the following: Good distribution of
the fuel in charging; easy descent of the fuel; reduction of the
destructive action of the clinkers on the walls; means for cleaning the
grate without interfering with the generation of gas; prevention of
leakage. Many devices have been employed to fulfil these requisites.
A perfect distribution of the fuel during charging is attained chiefly
by the form of the hopper, and of its gate, which is generally conical.
In most apparatus the gate opens toward the interior of the generator,
and the inclination of its walls causes a uniform scattering of the fuel
in the retort. It is all the more necessary to disperse the fuel in this
manner when the cross-section of the retort is small compared with its
height.
_The facility of the fuel's_ descent is dependent largely upon the
nature and the size of the coal employed. Porous coal gives better
results than dense and compact coal. It is therefore preferable to
employ screened coal free from dust in pieces each the size of a
hazel-nut. The various sections given to the interior, including as they
do cylindrical forms, truncated at the summit or the base, partially
truncated toward the base and the like, would lead to the conclusion
that this question is not of the importance which some writers would
have us believe. Still, it must be considered that if the fuel drops
slowly, its prolonged detention within the walls of the hopper and its
transformation into fusible slag may result in a disintegration of the
refractory lining of the furnace.
The quantity of steam injected, greater or less, according to the nature
of the fuel, renders it possible to obtain friable slags and
consequently to prevent grave injury to the retort. Red-ash coal is in
general fusible, containing as it does some iron. Its temperature of
fusion varies between 1,832 to 2,732 degrees F.
_Cleanliness_ is most important so far as the operation of the generator
is concerned. It should be possible to scrape the generator during
operation without changing the composition of the gas, when the
incandescent zone is chilled, or an excess of air is introduced, or the
steam-injector be momentarily thrown out of operation. Mechanical
cleaners with movable grates or revolving beds have the merit of causing
the ashes to drop without interfering with the operation of the
apparatus. The same meritorious feature is characteristic of ash-pits
having water-sealed joints.
Pressure gas-generators need not be as perfectly gas-tight as suction
apparatus. Leakage of gas, which is usually manifested by a
characteristic odor, results in a loss of consumption and renders the
air unfit to breathe.
A generator should be provided in its upper part with openings through
which a poker can easily be introduced in order to shake up the fuel and
to dislodge the clinkers which tend to form and which cause the
principal defects in operation, particularly with fuels that tend to
swell, cake, and adhere to the furnace walls when heated. Many
apparatus, moreover, are provided with lateral openings having mica
panes through which the progress of combustion can be observed (Fig.
79).
[Illustration: FIG. 79.--Fichet-Heurtey producer with rotating
bed-plate.]
=Air-Blast.=--The system by which air and steam are injected
necessitates the employment of a steam-boiler of 75 pounds pressure.
This method of blowing, which is rather complicated, has the
disadvantage of varying in feed with the pressure of the steam in the
boiler, which pressure is not easily maintained at a given number of
pounds per square inch. Moreover, when more or less resistance is
offered by the fuel in the generator the quantity of air which is
injected is likely to be diminished in quantity while the quantity of
steam remains the same. The result is a change in speed which follows
from the modification of the proportions of the two elements. For these
reasons some manufacturers have resorted of late years to the employment
of fans and blowers.
[Illustration: FIG. 80.--Koerting blower.]
=Blowers.=--The fans or blowers employed vary considerably in
arrangement. Most of them are based on the Koerting system (Fig. 80),
and comprise essentially (1) a tube through which the steam is supplied
under pressure, and (2) a cylindro-conical blast-pipe. The tube is
placed in the axis of the blast-pipe at its outer opening. As it escapes
under pressure the steam is caught in the blast-pipe and draws with it a
certain quantity of air, which can be regulated. It is important that
these injection blowers should operate in such a manner that the
pressure and the feed of air and steam can be controlled.
=Fans.=--Mechanical blowers have the advantage of dispensing with the
employment of steam under pressure and the consequent installation of a
boiler (Fig. 78). Driven by the engine itself or from some separate
source of power, these apparatus are easily placed in position, require
no great amount of attention, and utilize but little energy. They are
either of the centrifugal type or of the rotary type, exemplified in the
Root blower (Fig. 81). The latter system has the advantage of high
efficiency, and of enabling comparatively high pressures--19 to 27
inches of water--to be attained, which, however, are used only for
special fuels, such as lignite, peat, and the like. The air supplied by
the blower, before reaching the fire-box, is superheated, either before
or after it is charged with steam.
[Illustration: FIG. 81.--Root blower.]
=Compressors.=--In some installations air is supplied by compressor
under the high pressure of 70 to 90 pounds per square inch, and seem
well adapted to the production of a gas of good quality. Moreover,
neither tar nor ammoniacal waters are produced. The Gardie producer may
be considered typical of this class of apparatus (Fig. 82). The chief
feature of this producer is to be found in simple washing and purifying
apparatus. It may be well to state here that the compression of air at
high pressure occasions some complications, and a considerable
expenditure of power.
[Illustration: FIG. 82.--Gardie producer.]
=Exhausters.=--Some designers have invented devices which draw gas into
the generator whence it is supplied to the engines, these suction
apparatus being connected with the blowers or used separately. But with
the exception of a few special instances, such arrangements are not
widely used--at least not for the production of motive power alone.
Whatever may be the arrangement employed for the introduction of a
mixture of air and steam under the grate of the generator, the
blast-pipe as a general rule discharges toward the center of the
apparatus. Still, in large producers it becomes desirable to provide a
means for varying the quantity of air and steam within wide limits so as
to regulate the heat of the fire. For that reason several outlets are
symmetrically arranged below the fuel.
[Illustration: FIG. 83.--Sawdust purifier.]
=Washing and Purifying.=--In pressure producers the gas is generally
washed and purified with much more care than in suction apparatus. Given
a sufficient pressure, the gas can be driven through the different
apparatus and the spaces between the material which they contain without
any difficulty. The gases emerge from the generator highly heated, and
this heat is used either to warm the injection water or to generate the
steam fed to the furnace. The gases then enter the washing apparatus,
which most frequently consists of a succession of contrivances in which
the gas is washed either by causing it to bubble up through the water,
or by subjecting it to superficial friction against a sheet of water, or
by systematically circulating it in a mass of continuously besprinkled
inert material. The object of washing is to remove the dust contained in
the gas and to precipitate it in the form of a slime which can be
removed by flushing.
[Illustration: FIG. 84.--Moss or fiber purifier.]
Physical purification thus begun is completed by passing the gas through
a filtering bed consisting of fiber, sawdust, or moss (Figs. 83 and 84).
Chemical purification if it is necessary, is effected by means of
calcium hydrate, iron oxide, or, still better, by a mixture of lime and
iron sulphate. This filtering material must necessarily be renewed after
it is exhausted.
[Illustration: FIG. 85.--Combined gas-holder and washer.]
=Gas-Holder.=--The gas-holder is composed essentially of a tank and a
bell. Sometimes, for the purpose of simplifying the apparatus, the tank
is so arranged as to take the place of a washer or scrubber (Fig. 85).
The bell should be provided with mechanism which, when the bell is full,
automatically diminishes or stops the generation of gas. It is advisable
to provide the bell with a blow or flap valve opening toward the
interior. If, therefore, it should happen that the gas supply is cut off
while the engine still continues to run, the suction of the engine will
not draw the water from the tank of the gas-holder.
When engines are employed the horse-power of which does not exceed 50,
it is sometimes customary to use the water of the tank (placed at a
higher elevation than the engine) to cool the cylinder. In this manner
the cost of installing special reservoirs is saved. If such an
arrangement be employed, however, the quantity of water contained in the
tank should be at least double that ordinarily contained in reservoirs.
If this precaution be not observed, the water may become excessively
heated and expand the gas in the bell.
The volume of the bell of the gas-holder should preferably be
not less than about 3 cubic feet per effective horse-power of the
engine to be supplied. Under these circumstances the bell acts as a
pressure-regulator, assures a sufficient homogeneity of the remaining
gas, and renders it possible to supply the engine during the short
intervals in which it is necessary to stop the blast to poke the fire.
But if the engine consumes 60 to 80 cubic feet of producer-gas per
horse-power per hour, the bell must be very much larger in size if the
generation of gas is to be checked for some time.
It may be well to recall here that coal is not the only fuel which lends
itself to the generation of gas suitable for driving engines, but that
some generators are able to utilize lignite, peat, and the like. In
others, straw, wood, shavings and sawdust, tannery waste, and other
organic matter is burnt with an efficiency very much higher than that
which they would give in the fireboxes of steam-boilers.
[Illustration: FIG. 86.--Otto Deutz lignite-producer.]
=Lignite and Peat Producers.=--Lignite and peat generators (Fig. 86)
cannot operate on the suction principle because of the resistance
offered to the passage of gas by the layer of fuel. This resistance is
considerable and extremely variable. Consequently, lignite and peat
generators must operate on the pressure principle by utilizing a blast
of air or a steam injector, depending upon the amount of water contained
in the lignite. As a general rule a Root blower operating at a pressure
of 8 to 27 inches of water, depending upon the quality of the lignite,
is employed. These generators are not to be recommended for powers less
than 50 horse-power, for the cost of the apparatus becomes too great.
The best lignite is that which, after combustion, leaves a fine ash and
no agglomerated clinker. Lignite has the peculiarity of forming dust
which ignites very easily when air is admitted into the generator. For
this reason the generator should not be scraped during operation, in
order to avoid the production of a flame which may escape from the
apparatus.
The scrubber is simply a column without coke, and is provided with an
interior sprinkler. The coke is too rapidly clogged with tar. Much of
this tar is deposited in a chamber which precedes the gas-holder.
Several quarts of tar may be tapped from the chamber daily.
The gas-holder serves merely to regulate the production of gas. The
pipes leading to the engine should be cleaned several times each month,
in order to remove the thin layer of tar which is deposited within them.
There are many kinds of lignite, and the gas-generator should be
constructed to meet the peculiar requirements of the variety employed.
The layer of fuel should be such in thickness that the gas as it emerges
from the generator has a temperature of about 77 degrees F. This is the
temperature of the gas which leaves the scrubber in the case of
anthracite-generators. If the lignite contains much water, the greater
part is retained in the washer by the gas in the form of drops.
Sometimes the water drips through the grate of the generator.
Lignite-generators may also be operated with peat, and even with town
refuse, with slight modifications. The consumption per horse-power per
hour is 3.3 pounds of lignite containing 2,400 calories (9,424.9
B.T.U.). In order to generate the same power with a boiler and
steam-engine, 8.8 pounds would be required. An engine driven unloaded
with fuel furnished by a lignite-generator will consume 50 per cent. of
the weight of the fuel required at full load. This depends upon the
proportion of water contained in the lignite and on losses of heat by
radiation from the generator. In street-gas engines running without
load, the absorption is 20 per cent., in anthracite-generators 40 per
cent. of the consumption at full load.
Passing now to the utilization of wood, of which something has already
been said in Chapter XI, two entirely distinct processes are
successfully employed in apparatus of the Riché type, these processes
depending upon the form of the wood used--whether, in other words, the
wood be consumed in the form of sticks or blocks or in the form of
chips, sawdust, bark, and the like, all of them the wastes of factories
in which wood is used.
=Distilling-Producers.=--If the wood consists of logs, it is burnt in a
generator comprising a fire-box and a distilling retort. The fire-box is
charged with ordinary coal which serves to heat the retort to redness.
The wood is discharged through the top of the retort, and the gas,
produced by the distillation, escapes through the bottom and passes to
the washing apparatus. The base of the retort is heated to about 1,652
degrees F., while at the top this temperature is reduced to 752 degrees
F. The wood thus treated is transformed into charcoal, which is a
by-product of some value.
[Illustration: FIG. 87.--Riché distilling-producer.]
The lower part of this cast retort (Fig. 87) is lined with charcoal, the
residue of previous distillations. The wood which is introduced in the
upper part of the retort is distilled in the chamber. The retort is held
by its own weight in a socket on the foot, which socket is lined with a
special refractory cement, made of silicate, asbestos forming the joint.
The products of combustion, issuing from the furnace, pass by way of
the flue to the lower part of the casing, and raise the temperature of
the retort and the charcoal it contains to that of a cherry red (1,652
degrees F.). These products of combustion then float to the upper part
of the casing and heat the top of the retort to a temperature of about
752 degrees F., in which part the wood or the wooden waste to be
distilled is enclosed. Thence the products of combustion pass through a
horizontal flue, provided with a damper, into a collecting flue by which
they are led to the smoke-stack. The products of distillation formed in
the chamber, having no outlet at the top of the retort, must traverse
the zone filled with incandescent carbon. The condensible products are
conducted as permanent gases (carbonic-acid gas in the state of carbon
monoxide) and are collected in the receptacle, after having passed the
funnel and the bell of the purifying apparatus.
A gas-furnace is formed by grouping in a single mass of masonry a
certain number of elements of the kind just described. It is essential
that the retorts should be vertically placed, that they be made only of
cast metal and not of refractory clay, and, finally, that their diameter
be not much more than 10 inches, which size has been found most
expedient in practice. The gas collected in the bell or in one or more
of the receptacles passes into the gasometer and then into the service
pipes. If 2.2 pounds of wood be distilled by burning in the furnace 8/9
of a pound of coal of average quality or 2.2 pounds of wood (either
sawdust or waste), 24.5 to 28 cubic feet of gas will be generated
having a thermal value of 3,000 to 3,300 calories per cubic meter
(11,904 to 13,094 B.T.U. per 35.31 cubic feet), and a residue 44 pounds
of charcoal will be left.
In practice only the wood of commerce containing in the green state 20
to 40 per cent. of water, depending upon the variety, is used. Hornbeam
contains the least water (18 per cent.), while elmwood and spruce
contain the most (44 to 45 per cent.).
The blast apparatus of the generator being started, the gas is supplied
under pressure. By reason of its permanent composition and its richness,
it is an excellent substitute for street-gas in incandescent lighting, a
good furnace fuel reducing agent.
_Producers Using Wood Waste, Sawdust, and the Like._--If waste wood in
the form of shavings, sawdust, straw, bark, and the like, should be
employed, a still higher efficiency is obtained with self-reducing
generators of the Riché type.
_Combustion-Generators._--In combustion-generators (Fig. 88) the fuel is
burnt and not distilled. The generator comprises two distinct elements.
The first is the generator proper, in which the combustion takes place.
Upon it is placed a hopper or fuel supply box. The Second element is the
reducer, in which by an independent process the reduction of the
carbonic-acid gas, the dissociation of the steam, and the transformation
of the hydrocarbons takes place. The generator is provided at its base
with a grate having oblique bars in tiers, which grate is furnished with
a channel in which the water for the generation of hydrogen flows. On a
level with this grate, at the opposite side, is a flue communicating
with the reduction column of coke. The incandescent zone of the
generator should not extend above the level of the grate. Instead of
passing through the layers of fresh fuel and out by way of the top, the
gas generated flows directly into the reduction column where it heats
the coke to incandescence. The high temperature to which the coke is
subjected, coupled with the injection of air, effects useful reactions.
This additional air, however, is not used if the fuel is free from all
products of distillation.
[Illustration: FIG. 88.--Riché combustion-producer.]
Experience has shown that gas of 1,000 to 1100 calories per cubic meter
(3,968 to 4,365 B.T.U. per 35.31 cubic feet), which heat content is
necessary to develop one horse-power per hour, can be obtained with 3.96
pounds of wood in the form of shavings and sawdust containing 30 per
cent. of water. The corresponding quantity of coke consumed in the
reduction column is insignificant, and may be placed at about 0.112
pounds per horse-power per hour.
It has been proven in actual practice that, both in the distilling and
combustion types of apparatus, the wood, either in the green state or in
the form of saw-mill waste, may contain as much as 60 per cent. of
water. Either of the two systems can be operated under pressure with an
air-blast, in which case a gas-holder and bell must be employed. The gas
as it passes from the generator to the gas-holder is conducted through a
cooler and washer and through a moss filter, which removes traces of the
products that may have escaped the distillation.
=Inverted Combustion.=--With a few exceptions the pressure-generators
which have been described, as well as suction gas-producers which will
be later discussed, are fed with anthracite coal or with coke. They
cannot be operated with moderately soft or bituminous coal. For this
reason they limit the employment of producer-gas engines. Manufacturers
have long sought generators in which any fuel whatever can be consumed.
Among the producers which seem to overcome the objections cited to a
certain degree, are those which are based on the principle of inverted
combustion. These apparatus embody the ideas of Ebelmen, the products of
distillation being decomposed by passing them over layers of
incandescent fuel.
[Illustration: FIG. 89.--Deschamps inverted-combustion producer.]
Many writers place in the class of inverted combustion producers,
apparatus of the Riché, Thwaite, and Duff type, in which this idea is
also carried out. Riché employs an independent incandescent mass to
reduce the products of distillation of another mass. Thwaite employs two
vessels which serve alternately as distilling retorts and reducing
columns. Duff draws in the products of distillation for the purpose of
blowing them under the fire. All these generators can hardly be said to
be of the inverted combustion type.
[Illustration: FIG. 90.--Fangé-Chavanon inverted-combustion producer.]
The generators of Deschamps (Fig. 89) and of Fangé and Chavanon (Fig.
90), on the other hand, are producers in which the combustion is really
inverted, and which are worked continuously. The air enters at the upper
part of the retort, passes through the entire mass of fuel, carrying
with it the distilled volatile products, and when the mixture reaches
the incandescent zone, chemical reactions occur that result in the
production of a gas entirely free from tar and other impurities.
CHAPTER XIII
SUCTION GAS-PRODUCERS
The high cost and the complicated nature of the pressure gas-generators
which have just been discussed have led manufacturers to attempt in some
other way the generation of producer-gas intended for operating motors.
Several inventors, among whom we will mention Bénier and A. Taylor (in
France), made some praiseworthy although not immediately very successful
attempts to simplify the manufacture of producer-gas.
=Advantages.=--In these systems the suction occasioned by the motor
itself has taken the place of a forced draft, produced in the generator
by an air-injector or a fan, so that the gas, instead of being stored
under pressure in a gas-holder, is kept in the apparatus under a
pressure below that of the atmosphere.
As the device for producing a draft by means of boiler pressure or of a
fan, and the gas-holder, are dispensed with, the result is a saving,
first in the cost of installation, consumption, and floor space.
Furthermore, the cooler and washer are supplanted by a single scrubber.
Manufacturers have succeeded in devising apparatus remarkable for the
simplicity of the processes employed and yielding economical results
which would never be obtained with pressure-generators employing
gas-holders and boilers, considering that the boiler alone calls for a
consumption of from 15 to 30 per cent. of the total amount of coal used
for making the gas.
The best results obtained by the author with pressure gas-producers have
indicated a consumption of not much less than 1 to 1-1/4 pounds of
anthracite per horse-power per hour at the motor, while with
suction-generators, under similar conditions and with the same grade of
fuel, he has repeatedly found a consumption of from 9/10 pounds per
effective horse-power per hour. In either case, the gas obtained
developed between 1,100 and 1,300 calories (4,365 and 5,158 B.T.U. per
35.31 cubic feet) if produced from anthracite yielding from 7,500 to
8,000 calories (29,763 to 31,746 B.T.U.) per 2.2 pounds.
The suction apparatus will also work very well with inferior coal
containing up to 6 to 8 per cent. of volatile matter and from 8 to 10
per cent. of ash. This great advantage added to all the others explains
the favorable reception which European manufacturers at once gave to
suction-producers. The petroleum engine itself will find a serious
competitor in the new system.
As regards the possibility of employing suction gas generators with
respect to the somewhat peculiar properties of the fuel, it may be said
at the outset that coke from gas works yielding from 6,000 to 6,500
calories (22,911 to 24,995 B.T.U.) and also charcoal are perfectly
available.
One horse-power per hour is obtained with a consumption of 1.1 to 1.3
pounds of coke.
Blast-furnace coke may be used in case of need, but its employment is
not to be recommended on account of the sulphides it contains, which
sulphides, being carried along by the gas, are liable to form sulphuric
acid with the steam, the corrosive action of which would soon destroy
the cylinder and other important parts of the engine.
=Qualities of Fuel.=--Anthracite coal is, upon the whole, so far the
best available fuel for generators. However, it should possess certain
qualities which will now be briefly indicated.
In suction gas-generators, above all, it is important that no harmful
resistance should be opposed to the passage of the air and of the gas
produced. It is therefore necessary to employ coal of a size that will
answer the foregoing condition, without being too expensive.
The size of the pieces, to a certain extent, determines the price; and
with coal of the same properties, pieces 1.1 to 2 inches may cost 1.4 of
the price for the ordinary size of 0.59 to 0.98 inches, which is very
well adapted for gas-generators. This is the size of a hazel-nut.
Moreover, it will be advisable to select the dryest coals, containing a
minimum of volatile matter and having no tendency to coke or to cohere,
in order that the volatilized products may not by distillation obstruct
the interstices through which the gases must pass. For the same reason
coal which breaks up and becomes pulverized under the action of the
fire is not to be recommended. The coal should also be such as to avoid
the formation of arches which would interfere with the proper settling
of the fuel during its combustion. It may be stated as a rule that, with
coal that does not cohere, the content of volatile matter should not
exceed 5 to 8 per cent.
Coal which contains more than 10 to 15 per cent. of ash should not be
used, for the reason that it chokes up and obstructs generators in which
the dropping and discharge of the ashes is done automatically, a fact
which should not pass unnoticed. The furnace cannot be cleaned safely
with a fire of this kind, where combustion takes place in an enclosed
space, without hindering the production of gas. Here again a point may
be raised very much in favor of suction gas-producers. In a good
generator, the ash-pit can be cleaned and the fire stoked without
interrupting the liberation of the gas drawn in and without appreciably
impairing the quality of the gas. These considerations are of importance
so far as the gas-generator itself is concerned. Other conditions which
should be noticed affect the engine fed by the generator, the grade of
coal used, and the purification of the gas obtained from it.
Unless special chemical cleaners and purifiers are employed, thereby
complicating the plant, the coal utilized should yield as little tar as
possible during distillation; for the tendency of the tar to choke up
the pipes and to clog the valves is one of the chief causes of defective
operation of producer-gas engines.
Tar changes the proper composition of the explosive mixture. When it
catches fire in the cylinder it causes premature ignition, which is so
dangerous in large engines.
From what has been said in the foregoing, it follows that, in the
present state of the art, the satisfactory operation of gas-generators
depends no longer on the use of pure anthracite, such as Pennsylvania
coal in America and Welsh coal in England, containing an amount of
carbon as high as 90 to 94 per cent. and having a thermal value of
33,529 B.T.U. On the contrary, good dry coal yielding from 29,763 to
31,746 B.T.U. is quite suitable for the generation of producer-gas.
A final, practical advantage which speaks in favor of a generator and
motor plant as compared with a steam-engine, is the small amount of
water required. Apart from the water used for cooling the engine, which
may be used over and over again if cooled, any water, whether it forms
scale or deposits, may be employed for cooling and washing the gas in
the scrubber.
According to the author's personal experience, an average of 3.3 gallons
of water per effective horse-power per hour is sufficient for this
purpose. This is about one-half of the amount required by a
non-condensing slide-valve engine of from 15 to 30 horse-power. The
difference in the consumption of water is quite important in city
plants, where water is rather expensive as a rule.
=General Arrangement.=--A suction gas-generator plant of the character
we have been discussing is shown in Fig. 91.
[Illustration: FIG. 91.--Engine and suction gas-producer.]
The apparatus _A_ is the generator proper, in which combustion takes
place. The gas produced passes into the apparatus _B_ through a series
of tubes, to be conveyed to the washer _C_. In the apparatus _B_, which
is the vaporizer, the water admitted at the top under atmospheric
pressure is vaporized by contact with a series of tubes, heated by the
gas coming from the generator. The steam, together with air, is drawn
into the lower part of the generator to support combustion. This
vaporizer is provided with an overflow for the outlet of the water which
has not been vaporized. The producer-gas pipe which leads from the
vaporizer to the washer has a branch _D_, for the temporary escape to
the atmosphere of the gas produced before and after the operation of the
engine. In the washer, as the drawing shows, the gas enters at the
bottom and leaves at the top to pass to the gas expansion-chamber _E_
and thence to the motor. The gas thus passes through the body of coke
in the opposite direction to the wash water, which then flows to the
waste-pipe. The coke and the water free the gas not only from the dust
carried along, but from the ammonia and other impurities contained in
the gas.
When firing the generator, a small hand ventilator _G_ is used for
blowing in air to fan the fire. The gas obtained at first, being
unsuitable for combustion, is allowed to escape through the branch _D_.
After injecting air for about 10 to 15 minutes, the engine can be
started after closing the branch _D_. The suction of the engine itself
will then gradually bring about the proper conditions for its regular
running, and after a quarter of an hour or half an hour the gas is rich
enough to run the engine under a full load.
The apparatus just described is the original type, upon which many
improvements have been made for the purpose of securing a uniform gas
production and of diminishing the interval of time elapsing between the
firing of the generator and the running of the engine under a full load.
Each of the elements of this apparatus--to wit, the generator,
vaporizer, super-heater, and washer--have been modified and improved
more or less successfully by the manufacturers; and in order that the
reader may perceive the merits and the drawbacks of the various
arrangements adopted, the most important ones will be separately
discussed.
=Generator.=--With respect to the general arrangement of parts,
generators may be divided into two classes:
First.--Generators with internal vaporizers, such as the Otto Deutz and
Wiedenfeld generators.
[Illustration: FIG. 92.--Old type of Winterthur producer.]
Second.--Generators with external vaporizers, such as the Taylor,
Bollinckx, Pintsch, Kinderlen, Benz, Wiedenfeld, Hille, and Goebels
generators.
=Cylindrical Body.=--The generator consists essentially of a mantle made
of sheet-iron or cast-iron and containing a refractory lining which
forms a retort, a grate, and an ash-pit. In the small size apparatus the
cast-iron mantle is often used, whereas in large sizes the mantle is
made of riveted sheet-iron so as to reduce its weight and its cost. In
the latter case the linings are securely riveted or bolted.
The Winterthur generator (Figs. 92 and 93), the Taylor generator (Fig.
94), and the Benz generator (Fig. 97), are made of cast-iron; the
Wiedenfeld generator (Fig. 95), the Pintsch generator (Fig. 96), are
made of sheet-iron; the Bollinckx (Fig. 98) is made partly of sheet-iron
and partly of cast-iron.
The different parts of a generator, if made of sheet-iron, are held
together by means of angle-irons forming yokes, and a sheet of asbestos
is interposed. If the parts are made of cast-iron, they are connected
after the manner of pipe-joints and packed with compressed asbestos.
This latter way of assembling the parts presents the advantage of
allowing them to be dismembered readily. Therefore, it allows the
several parts to expand freely and facilitates the securing of tight
joints. This last consideration is exceedingly important, particularly
for the joints which are beyond the zone in which the distillation of
the fuel takes place. Any entrance of air through these joints would
necessarily impair the quality of the gas, either by mingling therewith,
or by combustion. The air so admitted would also be liable to form an
explosive mixture which might become ignited in case of a premature
ignition of the cylinder charge during suction or through some other
cause.
[Illustration: FIG. 93.--New type of Winterthur producer.]
[Illustration: FIG. 94.--The A. Taylor producer.]
[Illustration: FIG. 95.--Wiedenfeld producer.]
[Illustration: FIG. 96.--Pintsch producer.]
[Illustration: FIG. 97.--Benz producer.]
[Illustration: FIG. 98.--Bollinckx producer.]
[Illustration: FIG. 99.--Lencauchez producer.]
=Refractory Lining.=--The interior lining of the generator should be
made of refractory clay of the best quality. It would seem advisable, in
order to facilitate repairs, to employ retorts made of pieces held
together instead of retorts made of a single piece. In the first case
the assembling should preferably be made by means of refractory cement,
and the inner surface should be covered with a coating so as to form a
practically continuous stone surface.
[Illustration: FIG. 100.--Goebels producer.]
Some manufacturers, in order to allow for the renewal of the part most
liable to be burnt, employ at the bottom of the tank a refractory
moulded ring (Lencauchez, Fig. 99).
It is always advisable to place between the shell or mantle of the
generator and the refractory lining a layer of a material which is a bad
conductor of heat as, for instance, asbestos or sand, in order to avoid
as much as possible loss of heat due to external radiation (Fig. 100).
[Illustration: FIG. 101.--Pierson producer.]
=Grate and Support for the Lining.=--These parts, owing to their contact
with the ashes and the hot embers, are liable to deteriorate rapidly. It
is therefore indispensable that they should be removable and easily
accessible, so that they may be renewed in case of need. From this point
of view, grates composed of independent bars would appear to be
preferable. The clearance between the bars depends, of course, on the
kind of ashes resulting from the different grades of fuel. It is
advisable to design the grate so that the free passage for the air is
about 60 to 70 per cent. of the total surface.
In generators having a cup-shaped ash-pit, containing water (Fig. 95),
the grate and the base of the retort are less liable to burn than in
apparatus having dry ash-pits. Certain apparatus, such as those of
Lencauchez (Fig. 99), Pierson (Fig. 101), and Taylor (Fig. 94), have no
grates; the fuel is held in the retort by the ashes, which form a cone
resting on a sheet-iron base, easy of access for cleaning and from which
the fuel slides down gradually.
The Pierson generator (Fig. 101) is provided with a poker comprising a
central fork, which is worked with a lever, in order to stir the fire
from below without entirely extinguishing the cone of ashes.
In some apparatus in which a grate is used (Fig. 92), a space is left
between the grate and the support of the retort. This arrangement has
the merit of allowing only finely divided and completely burnt ashes to
pass to the ash-pit. Moreover, a large surface grate can be employed,
thus facilitating the passage of the mixture of air and steam.
[Illustration: FIG. 102.--Kiderlen producer.]
The space above mentioned is provided with a cleaning-door through which
cinder and slag may be removed.
In other apparatus the grate rests either on the support of the
refractory lining, as in the old type invented by Wiedenfeld (Fig. 95),
or upon a projection embedded in the lining, as, for instance, in the
Kiderlen (Fig. 102) and Pintsch generators (Fig. 96).
In the Riché apparatus (Fig. 103) there is, besides the ordinary grate,
a grate with tiers on which the fuel spreads. This grate consists of
wide, hollow bars containing water. It should be noted that the
apparatus is of the blower type.
[Illustration: FIG. 103.--Riché combustion-producer.]
An interesting arrangement is found in Bénier's generator (Fig. 104).
This consists of a grate formed of projections cast around a cylinder
which can be turned about its axis. The finely divided ashes which are
retained in the spaces between these projections are thus carried into the
ash-pit, and those which adhere to the metal are scraped away by a
metallic comb fastened to the lower part of the apparatus. The "Phoenix"
generator (Fig. 105) is fitted with a grate having a mechanical cleaning
device, worked by a lever from the outside.
[Illustration: FIG. 104.--Bénier producer.]
[Illustration: FIG. 105.--Phoenix producer.]
=Ash-Pit.=--The ash-pits are exposed to the destructive effects of
heat and moisture, and should preferably be constructed of cast-iron,
since sheet-steel is liable to corrode quickly.
[Illustration: FIG. 106.--Otto Deutz producer.]
In most apparatus the ash-pit is hermetically sealed, and the air for
supporting combustion enters below the grate through a pipe leading
from the heater or the vaporizer. This arrangement seems best adapted to
prevent the leakage of gas which tends to take place by reaction after
each suction stroke of the engine.
Ash-pits formed as water-cups, such as the Deutz (Fig. 106), the
Wiedenfeld (Fig. 95), and the Bollinckx (Fig. 98), are fed by the
overflow from the vaporizer. These ash-pits are themselves provided with
an overflow consisting of a siphon-tube forming a water-seal.
Besides providing protection to the grate and other parts by this sheet
of water, a larger proportion of the heat radiated from the furnace is
utilized for the production of steam which contributes to enrich the
gas. The doors of the ash-pits and their fittings are likewise exposed
to a rapid deterioration.
For this reason these parts should be very strongly made, either of
cast-iron or cast-steel. Furthermore, they should, at joint surfaces, be
connected in an air-tight manner, which may be attained by carefully
finishing the engaging surfaces of the frame and the door proper, or by
cutting a dovetail groove in one of the sides of the frame which is
packed with asbestos and adapted to receive a sharp edged rib on the
other part.
The pintles of the hinges should also be carefully adjusted so that the
joint members of the door shall remain true. Hinges with horizontal axes
seem to be preferable in this respect to those having vertical axes. As
a means of closing the door, the arrangement here shown (Fig. 107) seems
to assure a proper engagement of the joint surfaces. It consists of a
yoke which straddles the door, and which, on the one hand, swings about
the hinge, and on the other hand engages a movable hoop. A screw,
fastened to the yoke, serves to tighten the door by pressure on its
center. This screw can also be fastened to the end of the yoke (Fig.
108).
[Illustration: FIGS. 107-108.--Fire-box doors.]
It is very advantageous to provide in each door a hole closed by an
air-tight plug, so that in case of need a tool may be introduced for
cleaning the grate. In this manner the grate may be cleaned without
opening doors and without causing a harmful entrance of air.
The door of the furnace, particularly, should be provided with an iron
counter-plate held by hinged bolts (Fig. 109); or, better still, this
door should be so constructed that it can be lined with refractory
material to protect it against the radiated heat of the fire.
=Charging-Box.=--Like the other parts of the generator the construction
of which has been discussed above, the charging-box should be absolutely
air-tight.
On account of their greater security, preference should be given to
double closure devices, which form a sort of preliminary chamber, owing
to which the filling of the generator is made in two operations. The
first operation consists in filling the preliminary chamber after
opening the outer door. Upon closing this outer door, the second
operation is performed, which consists in moving the inner door so as to
cause the fuel in the preliminary chamber to drop into the generator.
Stress has been laid on the greater safety of this type of charging-box
for the reason that, with devices having a single charging-door, a
sudden gust of air may rush in at the time of charging the furnace, and
bring about an explosion very dangerous to the workman entrusted with
stoking the furnace.
[Illustration: FIG. 109.--Door with refractory lining.]
The closure is generally simply a removable cover, or may be a lid
swinging about a hinge having a horizontal or vertical axis.
As regards the inner door, which is of great importance, in order to
insure an air-tight joint, there are three chief types of closure:
1. The Lift-Valve.
2. The Slide-Valve.
3. The Cock.
=The Lift-Valve.=--The lift-valve is formed by a disk of conical or
spherical shape moved up and down by means of a lever having a
counter-weight for adjustment. The valve is used in the Winterthur (Fig.
92) and Bollinckx (Fig. 98) generators.
This device serves as an automatic closure and insures a tight joint
irrespective of wear. Moreover, it presents the advantage that, at the
moment of opening, it distributes the fuel evenly in the generator; but
on the other hand, it has the drawback of not allowing the fuel to be
examined or shaken through the charging-box. In apparatus provided with
this kind of valve, it is therefore advisable to furnish the upper part
of the generator with agitating holes closed by an air-tight slide.
=Slide-Valve.=--The slide-valve closure consists of a smooth-finished
metallic plate movable below the charging-box proper. Operated as it is
from the outside, it is evident that the slightest play, the wearing of
the pivot, or the weight of the charge, will form spaces between the
plate and its seat through which air may rush in.
Furthermore, the manipulation of the slide-valve may be interfered with
if too much fuel is put in the generator.
The valve or damper may move parallel to itself or swing about the
operating axis. The Taylor apparatus (Fig. 94) and the Bénier apparatus
(Fig. 104) are provided with such valves.
The Pintsch generator (Fig. 96) is provided with a device which,
properly speaking, is not a damper, but which consists of two boxes
movable about a vertical axis and arranged to be displaced alternately
above the shaft to effect the charging. This system effects only a
single closure, but explosions are scarcely to be feared with an
apparatus of this kind, owing to the considerable height of fuel
contained between the charging opening and the gas-producing zone.
=Cock.=--The cock is applied particularly in the modern apparatus of the
Otto Deutz Co. (Fig. 106) and the Pierson generator (Fig. 101). It
consists of a large cast-iron cone, having an operating handle and an
opening. The cone moves in a sleeve formed by the charging-box.
This arrangement appears to be preferable to the others on account of
its simplicity and of the ease with which it can be taken apart for
cleaning. Moreover, the fuel can be poked directly through the
feed-hopper. In apparatus provided with a cock, it is advisable to place
on the outside cover a mica pane through which the condition of the fuel
may be examined without danger.
=Feed-Hopper.=--Below the charging-box is arranged, as a rule, a hopper
tapered conically downward. This part of the generator should serve only
as a storage chamber for fuel. It can therefore be made of cast-iron,
and has the advantage of being removable, easily replaced, and of
allowing ready access to the retort for the purposes of examination and
repair.
The annular space surrounding this feed-hopper generally forms a chamber
for receiving the gas produced, as in the Winterthur (Fig. 92), the
Bollinckx (Fig. 98), and the Taylor apparatus (Fig. 99).
In generators having an internal vaporizing-tank, this tank itself
serves as a feed-hopper, which is the case in the Deutz apparatus (Fig.
106) and Wiedenfeld generator (Fig. 95).
=Connection of Parts.=--In order to facilitate the thorough cleaning of
the retort, preference is given to removable charging-boxes and
feed-hoppers. These are features of apparatus of the Bollinckx type
(Fig. 98), in which the charging-box is secured to the generator by
means of its yoke and by catches provided with knobs, and also of
apparatus of the Winterthur kind (Fig. 92), having a charging-box
pivoted about a vertical axis, or apparatus of the Duplex type (Fig.
110), in which the charging-box can swing about a horizontal hinge.
=Air Supply.=--We have seen that, when starting the generator, the gas
is produced with the aid of a fan. This fan may be operated
mechanically, but is generally operated by hand.
It is customary to convey the air-blast through a pipe leading to the
ash-pit, as in the Winterthur apparatus (Fig. 92). Often, however, the
air supply pipe is directly branched on that which leads from the
vaporizer to the ash-pit, as in the Deutz apparatus (Fig. 106). In this
case a set of valves or dampers permits the disconnection of the fan or
its connection with the ash-pit.
[Illustration: FIG. 110.--Duplex charging-hopper.]
In some apparatus an air inlet is provided immediately adjacent to the
ash-pit. This arrangement is faulty for the reason that it gives rise to
gaseous emanations which take place by reaction after each suction
stroke of the engine. Furthermore, it is advisable that the air supplied
below the ash-pit be as hot as possible. For this reason the employment
of preheaters is desirable. The dry air forced in by the fan stimulates
combustion, and the hot gas produced and mixed with smoke escapes
through a separate flue, generally arranged beyond the vaporizer and
serving as a chimney. This chimney should in all cases be extended to
the outside of the building, and should never terminate in a brick
chimney or similar smoke-flue. The direct escape of such gas and smoke
through a telescopic chimney above the charging-box has been generally
abandoned in modern structures.
[Illustration: FIG. 111.--Bollinckx flue and scrubber.]
[Illustration: FIG. 112.--Winterthur flue and air-reheater.]
The escape-pipe mentioned, being branched on the gas-pipe leading to the
engine, should be capable of disconnection when desired, by a thoroughly
tight system of closure. For this purpose, some employ a simple cock
(Bollinckx, Fig. 111), a three-way cock, a set of cocks, or, still
better, a double valve, as in the Winterthur apparatus (Fig. 112) and
the Deutz apparatus (Fig. 113). A double seated valve is also used, as
is the case in the Benz generator (Fig. 114).
[Illustration: FIG. 113.--Otto Deutz flue.]
[Illustration: FIG. 114.--Benz flue.]
=Vaporizer-Preheaters.=--As has been stated before, there are vaporizers
internal or external, relatively to the generator.
=Internal Vaporizers.=--The Deutz apparatus (Fig. 106), for example,
consists of an annular cast-iron tank mounted above the retort of the
generator.
The hot gases given off by the burning fuel travel around this tank and
vaporize the water which it contains. The air drawn in by the suction of
the engine enters through an opening located above the tank, travels
over the surface of the water which is being vaporized, and thus laden
with steam passes to the ash-pit.
The tank in question is supplied with water by means of a cock having a
sight feed, located on the outside, and the level is kept constant by
means of an overflow tube leading to the ash-pit. It is well to bend
this tube and to place a funnel on its lower member. The amount of
overflow may thus be regulated.
These vaporizers are simple and take up little room; but they are open
to the apparently well-founded objection that they heat up slowly and
require a considerable time to produce the steam necessary to enrich the
gas, this being due to the relatively large mass of cast-iron and the
amount of water contained therein.
The Pierson vaporizer (Fig. 101) and the Chavanon vaporizer (Fig. 115)
both consist of an annular tank forming the base of the generator. Steam
is formed near the outlet of the ashes, which, as has been described
above, leads to the outer air. The development of steam is regulated by
mechanical means controlled by the suction of the engine.
[Illustration: FIG. 115.--Chavanon producer.]
=External Vaporizers.=--External vaporizers are generally formed by a
cylinder with partitions constituting two series of chambers. In one of
these the hot gases from the generator travel, and in the others the
water to be vaporized is contained.
[Illustration: FIG. 116.--Taylor vaporizer.]
[Illustration: FIG. 117.--Deutz vaporizer.]
=Tubular Vaporizers.=--Different types of tubular vaporizers are
manufactured. The vaporizer with a series of tubes, as in Taylor's
apparatus (Fig. 116), Deutz's old model (Fig. 117), or with single tube
like Pintsch's generator (Fig. 118), is formed by three compartments
separated by two tube sheets or by plates which are connected by tubes.
In some cases the gases pass within the tubes, while the water to be
vaporized surrounds them; as in the Pintsch apparatus (Fig. 118), and
Taylor apparatus (Fig. 116), Benz (Fig. 119), and Koerting generators
(Fig. 120).
[Illustration: FIG. 118.--Pintsch vaporizer and scrubber.]
In other cases, the water lies inside and the gas outside. In this
latter case, a longitudinal baffle is employed to compel the gases to
heat the tubes in their whole length, as in the Deutz producer (Fig.
117). In a general way it may be said that such a series of tubes
presents the disadvantage of becoming clogged up rapidly by the deposit
of lime salts contained in water.
[Illustration: FIG. 119.--Benz vaporizer.]
[Illustration: FIG. 120.--Koerting vaporizer.]
If the set of tubes consists of fire-tubes, the deposit will form on the
outer surface, that is, on a portion not accessible for cleaning. From
this point of view, water-tubes are preferable, as they allow the
deposit or scale to be removed through the tubular heads or plates. On
the other hand, such water-tubes have the drawback that their exterior
surfaces are readily covered with pitch and soot. The tubular vaporizers
of the Field type (Bollinckx, Fig. 98) are composed of a single
sheet-iron tube or shell, in which the tubes are arranged, dipping into
a chamber through which the hot gases pass. This arrangement insures a
rapid production of steam, but the Field tubes are even more liable than
the others to become covered with deposits.
It will be seen that these types of vaporizers should all present the
following features: easy access, small quantity of the body of water
undergoing vaporization, and large heating surface with small volume.
The use of copper or brass tubes should be strictly avoided, as they
would be quickly corroded by the action of the ammonia and hydrogen
sulphide contained in the gas.
=Partition Vaporizers.=--Partition vaporizers comprise a cylindrical
shell, generally made of cast-iron and having a double wall in which the
water to be vaporized circulates. The gas coming from the generator
passes into the central portion, where it comes in contact with a hollow
baffle, also containing water (Wiedenfeld, Fig. 121). Vaporizers of this
kind are strong, simple, and easily cleaned.
=Operation of the Vaporizers.=--The general purpose of vaporizers,
whatever their construction may be, is to produce steam under
atmospheric pressure, by utilizing the heat of the generator gases
immediately after their production, or, as in the Chavanon system, by
utilizing the heat radiated from the furnace.
The air drawn by the engine through the generator generally passes
through the vaporizers and becomes laden with a certain amount of steam
which it carries along. The amount thus taken up depends chiefly upon
the temperature and the amount of gases coming from the generator, so
that the greater the amount drawn into the engine, the more energetic
will the vaporization be, and the richer the gas will become. It will be
understood that when a generator is working at its maximum production,
the interior temperature is highest and most favorable to the
decomposition of the largest amount of steam.
[Illustration: FIG. 121.--Wiedenfeld vaporizer.]
It follows that with the very simple vaporizers which have been
reviewed, a practically automatic regulation is obtained. However, some
manufacturers have deemed it advisable to regulate the amount of steam
more accurately, and to make it exactly proportionate to the power
developed by the motor. Thus in the Winterthur gas-producer (Figs. 92
and 112) the manufacturers have omitted the vaporizer proper, and use
instead an air-heater and a super-heater for air and steam.
The heater is formed by a cast-iron box having two compartments, through
one of which the hot gases from the generator pass, while in the other
the air intended to support combustion travels. At the inlet of the
super-heater a pipe terminates, which feeds, drop by drop, water
supplied by a feed device to be described presently. This water is
vaporized immediately upon contact with the wall of the super-heater and
is carried along with the air contained in it.
The super-heater comprises a hollow ring-shaped cast-iron piece arranged
in the chamber of the generator, in which the gases are developed, and
is thus heated to a high temperature. The mixture of air and steam
circulates in this super-heater before traveling to the ash-pit.
The feeder of the Winterthur gas-generator (Fig. 122) is composed of a
receptacle having the shape of a tank or basin containing water and
located below a closed cylindrical box. In this box a piston moves,
which is provided at its lower end with a needle-valve. The upper
portion of the box communicates with the gas-suction pipe through a
small tube. At each suction stroke of the engine, according to the force
of the suction, the needle-valve piston rises more or less and thus
allows a variable amount of water to pass.
[Illustration: FIG. 122.--Winterthur feeders.]
This apparatus--and all those based on the same principle--presents the
advantage of proportioning the amount of water to the work of the
engine; but in view of its rather sensitive operation it must be kept in
perfect repair and carefully watched. Obviously, should the water
contain impurities, the needle-valve will bind or the orifices will be
obstructed, and thus the feeding of the water will be interrupted. This
will not only result in the production of a poorer gas, but will lead to
greater wear of the grates, which in this case are not sufficiently
cooled by the introduction of steam.
[Illustration: FIG. 123.--Hille producer.]
=Air-Heaters.=--The preliminary heating of the air appears to be of
great utility for keeping up a good fire. This heating is very easily
accomplished, and is generally effected by utilizing a portion of the
waste heat of the gases, a procedure which also has the advantage of
cooling the gases before they pass through the washing apparatus.
The heating of the air for supporting combustion takes place either
before the addition of steam (Hille's generator, Fig. 123), or after the
mixture as in Wiedenfeld's apparatus (Fig. 95). In the first case, the
air passes through a sheet-iron shell concentric with the basin of the
generator, is there heated by the radiated heat, and is conveyed to the
ash-pit by a tube into which leads the steam-supply pipe extended from
the vaporizer. In the second type of heater, the mixture of air and
steam is super-heated during its passage through an annular piece
arranged in the ash-pit of the generator.
[Illustration: FIG. 124.--Benz dust-collector.]
=Dust-Collectors.=--Dust-collectors are generally placed between the
generator and the scrubber or washer. They may be formed of baffle-board
arrangements against which the gases laden with dust impinge, causing
the dust to be thrown down into a box provided with a cleaning opening
(Benz, Fig. 124, and Pintsch, Fig. 118).
Some collectors are formed either by the vaporizer itself, terminating
at its base in a tube which dips into water and forms a water-seal, as
in the Wiedenfeld generator (Fig. 121), or by a water-chamber into which
the gas-supply tube slightly dips (Bollinckx, Fig. 111). With this
arrangement, the gas will bubble through the water and will be partly
freed of the dust suspended in it. These water-chambers are generally
fed by the overflow from the spray of the scrubber. There is thus
produced a continuous circulation by which the dust, in the form of
slime, is carried toward the waste-pipe or sewer.
=Cooler, Washer, Scrubber.=--Some manufacturers cool the gas in a tower
with water circulation. Most manufacturers, however, simply cool the gas
in the washer or scrubber. This apparatus comprises a cylindrical body
of sheet-iron or cast-iron formed of two compartments separated by a
wooden or iron grate or perforated partition. The upper compartment up
to a certain level contains either coke, glass balls, stones, pieces of
wood, and the like. The top of the compartment is provided with a water
supply in the nature of a sprinkler or spray nozzle. The lower
compartment of the scrubber serves to collect the wash-water which has
passed through the substance filling the tower. An overflow in the shape
of a siphon, provided with a water seal, carries the water to the
waste-pipe either directly or after it has first passed through the dust
collector.
The gas drawn in enters the washer in the lower compartment either above
the water level (Deutz, Fig. 125; Winterthur, Fig. 126), or through an
elbow which dips slightly into the water (Benz, Fig. 127; Fichet and
Heurtey producer, Fig. 128).
The gas passes through the grate or partition which supports the
material filling the tower, and travels through the interstices in a
direction opposite to that of the water falling from the top. Under
these conditions, the gas is cooled, gives up the ammonia and the dust
which it may still contain in suspension, and is conveyed to the engine
either directly or after passing through certain purifiers. Care should
be taken to place the pieces of most regular shape along the walls, so
that the unevenness of their surfaces may not form upward channels along
the shell, through which channels the gas could pass without meeting the
wash-water.
[Illustration: FIG. 125.--Otto Deutz scrubber.]
[Illustration: FIG. 126.--Winterthur scrubber.]
[Illustration: FIG. 127.--Benz scrubber.]
The material most commonly employed in washers is coke in pieces of from
2-1/2 to 3-1/2 inches in size. This material is cheap and is very well
suited for retaining the impurities of the gas. The largest pieces of
coke should be placed at the bottom of the washer, and smaller pieces
should form at the top a layer from 6 to 8 inches deep. In this manner
the water is distributed more evenly and the gas is more thoroughly
washed. Blast-furnace coke is best suited for this washing, as it is
more porous and less brittle than gas-works coke. It is advisable to
put a baffle-board in front of the gas outlet to reduce the carrying
along of water in the conduits.
[Illustration: FIG. 128.--Fichet-Heurtey scrubber.]
[Illustration: FIG. 129.--Scrubber-doors.]
The tower of the washer should be provided with three openings having
air-tight closures, easily fastened by screws (Fig. 129). One of the
openings is located in the lower compartment, slightly above the water
level, to allow the deposits to be removed and to permit the cleaning of
the orifice of the gas-supply tube, which is particularly liable to be
obstructed. The second opening is placed above the grating which
supports the filtering material. The third opening is provided on the
top of the apparatus to permit the examination and cleaning of the water
feed device and the gas outlet without the necessity of taking the lid
of the washer apart, the joint of which is kept tight with difficulty.
The two openings last mentioned also serve for introducing and removing
the filtering material.
=Purifying Apparatus.=--In some cases, where it is necessary to have
very clean gas or where coal is employed which is softer than anthracite
coal, and which therefore produces an appreciable amount of tar,
supplementary purifying means must be employed. The apparatus for this
purpose may, like the washers, be based upon a physical action or upon a
chemical action. The physical action has for its purpose chiefly to
retain the pitch and the dust which may have passed through the washer.
This is accomplished by means of sawdust or wood shavings arranged in a
thin layer and capable of filtering the gas without opposing too great
a resistance to its passage. These materials are spread on one or more
shelves superposed to form successive compartments in a box closed in an
air-tight manner by an ordinary lid or a water seal cover (Pintsch, Fig.
130; Fichet and Heurtey, Fig. 131). It may be well to point out that the
presence of the water carried along will, in the end, destroy the
efficiency of the precipitated materials, because they swell up and
cease to be permeable to the gas. These materials must therefore be
renewed rather frequently. To obviate this drawback, vegetable moss may
be employed, which is much less affected by moisture than most filters
and keeps its spongy condition for a long time.
[Illustration: FIG. 130.--Pintsch purifier.]
The chemical action has for its chief object to rid the gas of the
carbonic acid and the hydrogen sulphide which certain fuels give off in
appreciable amounts. The purifying material, in this case, is formed
either by a mixture of hydrate of lime and natural iron oxide, or by the
so-called Laming mass, which consists of iron sulphide, slaked lime, and
sawdust, which last serves the purpose of rendering the material looser
and more permeable to the gas. The Laming mass as well as other
purifying materials will become exhausted in the course of chemical
reactions. It can be regenerated merely by exposure to the air.
[Illustration: FIG. 131.--Fichet-Heurtey purifier.]
=Gas-Holders.=--The purifiers by themselves constitute, to a certain
extent, storage chambers for the gas before it is supplied to the
engine; but in plants for the generation of gas without purifiers it is
advisable to provide a gas-holder on the suction conduit near the
engine.
[Illustration: FIG. 132.--Pintsch regulating-bell.]
In order to save floor space the gas-holder may be placed in the
basement. Preferably the capacity of the holder should be at least from
3 to 4 times the volume of the engine-cylinder. The holder should also
be provided with a drain-cock and with a hand-hole located at some
accessible point, so that the slimes and pitch which tend to accumulate
in the holder can be removed. In some cases the gas-holder is formed by
a small regulating bell, the function of which is to insure a uniform
pressure. This bell is emptied during the suction period and is filled
during the three succeeding periods of compression, explosion, and
exhaust (Pintsch, Fig. 132).
[Illustration: FIG. 133.--Types of gas-driers.]
=Drier.=--Sometimes, toward the end of a producer-gas pipe, a drier is
located for the purpose of keeping back the water carried along, the
drier being similar to that employed in steam conduits. It will, of
course, be understood that such driers are useful only in plants having
no purifiers (Fig. 133). The employment of the drier is advisable to
prevent the entrance of moist gas into the cylinder and the condensation
of moisture on the electric igniter.
[Illustration: FIG. 134.--Elbow with closure.]
=Pipes.=--The pipes connecting the several parts of a gas-producing
plant should be disposed with particular care to insure tightness and
cleanliness. It should be borne in mind that the gas is under a pressure
below that of the atmosphere, and that the least leakage will cause the
entrance of air, which will impair the quality of the gas. The greatest
care should therefore be taken in fitting the joints. These joints are
numerous, because there are joints wherever tubes are connected with
each other and with the apparatus. Furthermore, all elbows should be
provided with covers held in place by a yoke and compression screw, this
being done for the purpose of providing for the introduction of a brush
or other implement to remove the dust and pitch (Fig. 134).
For conduits of small diameter the elbows with covers may be replaced
with =T= connections, or connections provided with plugs.
Gas piping in the immediate neighborhood of the cock for admitting gas
to the motor should be provided with a conduit of proper diameter
leading to the open air and serving to clean the apparatus and to fill
them, during the operation of the fan, with gas suitable for combustion.
This conduit should be provided with a stop-cock. Test-cocks for the gas
should be placed on the piping immediately beyond the vaporizers, the
scrubber, and near the engine.
It will also be well to provide water-pressure gages before and after
the scrubber to enable the attendant to ascertain the vacuum in the
conduits and to adjust the running of the apparatus.
=Purifying-Brush.=--As an additional precaution against the carrying of
tar to the engine, metallic brushes are often employed, these brushes
being spiral in form and enclosed in a cast-iron box interposed in the
gas-supply pipe immediately after the engine. The gas will be broken up
into streams by the obstacles formed by these brushes and will be freed
of the suspended tar (Fig. 135). These brushes should be carefully
cleaned at regular intervals. The best way of doing this is to drop them
into kerosene or some other suitable solvent.
[Illustration: FIG. 135.--Metal purifying-brush.]
CONDITIONS OF PERFECT OPERATION OF GAS-PRODUCERS
These conditions depend upon the workmanship or upon the system of the
plant, on the care with which it has been erected, on the nature of the
fuel, on the condition of preservation of the apparatus, and upon the
manner in which the producers have been working.
=Workmanship and System.=--The workmanship itself, which term is meant
to include the choice of materials and the way they have been worked,
presents no difficulty. The producers which we have discussed are very
simple and offer absolutely no difficulties in their mechanical
execution. As regards the system, however, especially with respect to
the relative dimensions of the elements, it does not seem so far that it
is possible to indicate any principle or rule capable of a rigid general
application. It must be taken into account that the use of suction
gas-generators has become general only in the last three or four years;
the problem has therefore scarcely been adequately solved. However, some
hints may be given on this subject.
=Generator.=--In regard to the generator, it is possible to deduce from
the best existing plants the dimensions to be given to the generator
relatively to those of the engine to be supplied, upon the assumption
that the engine is single-acting and runs at a normal speed of from 160
to 230 revolutions per minute. The essential portion of the generator
which contributes to the production of a proper gas is that which
corresponds with the combustion zone. To this portion a cross-section is
given varying in size between one-half and one-quarter of the surface of
the engine-piston, sometimes between one-half and nine-tenths of this
surface, according to the nature and the size of the fuel that is used.
With small apparatus, however, ranging from 5 to 15 horse-power, the
size of the base cannot be reduced below a certain limit, since
otherwise the sinking of the fuel will be prevented. This danger always
exists in small generators and renders their operation rather uncertain,
such uncertainty being also due to the influence of the walls. It is to
be noted that most modern generators are rather too large than
otherwise.
Many manufacturers of no wide experience have been led to make their
apparatus rather large so as to insure a more plentiful production of
gas. As a matter of fact, the fire in such apparatus is liable to be
extinguished when the combustion is not very active. If the principles
of the formation of gas in suction-generators be kept in mind, it is
evident that the gas developed is the richer the "hotter" the operation
of the apparatus. Such operation also permits the decomposition of the
hydrogen and carbon monoxide.
The "hot" operation of a generator is accomplished best with active
combustion; and since this is a function of the rapidity with which the
air is fed, it obviously is advantageous to reduce the area of the
air-passage to a minimum as far as allowed by the amount of fuel to be
treated. As to the height of the fuel in use in the apparatus, this
varies as a rule between 4 and 5 times the diameter at the base.
=Vaporizer.=--The size of the vaporizer varies materially according to
its type. No hard-and-fast rule can therefore be adopted for determining
its heating surface; but this surface should in all cases be sufficient
to vaporize under atmospheric pressure from .66 to .83 pounds of water
per pound of anthracite coal consumed in the generator.
=Scrubber.=--For the scrubbers, the following dimensions may be deduced
from constructions now used by standard manufacturers.
The volume of a scrubber is generally from six to eight times the
anthracite capacity of the generator. A height of from three to four
times the diameter is considered sufficient in most cases. It should be
understood that in this height is included the water-pan chamber located
below the partition or grate, and the upper chamber through which the
gas escapes. The height of these two chambers depends necessarily upon
the arrangement used for leading the gas to the lower portion of the
washer and for the distribution of wash-water at the top.
=Assembling the Plant.=--The author has insisted strongly on the
necessity of having all the apparatus and pipe connections perfectly
tight. In order to ascertain if there is any leakage, the following
procedure may be adopted:
When starting the fire by means of wood, straw, or other fuel producing
smoke, instead of allowing this smoke to escape through the flue during
the operation of the fan, it may be caused to escape through the cock
which generally admits the gas to the motor, the cock being opened for
this purpose. The damper in the outlet flue is closed. In this manner
the smoke will fill all the apparatus and connecting pipes under a
certain pressure and will escape through any cracks, the presence of
which will thus be revealed.
Another test, which is made during the ordinary operation of the
generator, consists in passing a lighted candle along the joints; if
there is any leakage, this will be shown by a deviation of the flame
from a vertical position.
=Fuel.=--We have discussed the subject of fuel in a preceding chapter
(Chapter XIII) and have indicated the conditions to be fulfilled by low
grade or anthracite coal best adapted for use in suction gas-generators.
It may here be added that the coal used in the generator should be as
dry as possible and in pieces of from 1/2 inch to 1 inch. Very small
pieces, and particularly coal dust, are injurious and should be removed
by preliminary screening as far as possible. Screened coal is thrown in
with an ordinary grate shovel.
=How to Keep the Plant in Good Condition.=--In regard to the generator,
apart from the cleaning of the grate and of the ash-pit, which may be
done during operation, it is necessary to empty the apparatus entirely
once a week, if possible, in order to break off the clinkers adhering
to the retort. These clinkers destroy the refractory lining, form rough
projections interfering with the downward movement of the fuel, bring
about the formation of arches, and reduce the effective area of the
retort. At the time of this cleaning, tests are also made as to the
tightness of the doors of the combustion-chamber, of the charging-boxes,
etc.
The vaporizer should be cleaned every week or every other week,
according to the more or less bituminous character of the fuel and the
greater or smaller content of lime in the water used. Lime deposits may
be eliminated, or the salts may be precipitated in the form of
non-adhering slimes, by introducing regularly a small amount of caustic
potash or soda into the feed-water. If the deposits or incrustations are
very tenacious, the use of a dilute solution of hydrochloric acid may be
resorted to. Tar which may adhere to the conduits, pipes or gas
passages, is best removed while the apparatus is still hot, or a solvent
may be employed, such as kerosene, turpentine, etc. The connections
between the vaporizer and the scrubber are particularly liable to become
obstructed by the accumulation of tar or dust carried along by the gas.
It is advisable to examine the several parts of the plant once or twice
a week by opening the covers or the cleaning-plugs.
The lower compartment of the washer keeps back the greater part of the
dust which has not been retained in collectors or boxes provided
especially for this purpose. The dust takes the form of slime, and, in
some arrangements of apparatus, tends to clog up the overflow pipe,
thus arresting the passage of gas and causing the engine to stop. This
portion of the washer should be thoroughly cleaned once or twice a
month.
If very hard blast-furnace coke is used in the washer, it may be kept in
use for over a year without requiring removal. In order to free the
purifying materials from dust and lime sediments carried along by the
wash-water, it is well to let the wash-water flow as abundantly as
possible for about a half-hour at least once a month. At the time of
renewing the purifying material the precautions indicated in the section
dealing with these matters should be observed, and care should be taken
to have shelves or gratings on which the material is supported in layers
not too thick, so as to avoid any resistance to the passage of the gas.
In a general way it is advisable to test the drain-cocks on the several
apparatus daily, and to keep them in perfect condition. If, when open,
one of these cocks does not discharge any gas, water, or steam, a wire
should be introduced into the bore to make sure it is not clogged up.
=Care of the Apparatus.=--Each producer-gas plant will require special
instructions for running it, according to the system, the construction,
and the size of the plant. Such instructions are generally furnished by
the manufacturer. However, there are some general rules which are common
to the majority of suction gas-producers, and these will here be
enumerated.
=Starting the Fire for the Gas Generator.=--This operation calls for
the presence of the engineer of the plant and an assistant. The proper
procedure is as follows:
First: Open the doors of the furnace and of the ash-pit. Then open the
outlet flue and make sure that the grate of the generator is clear of
ashes and clinkers. It should also be seen to that the parts of the
charging-box work well and that the joints are tight.
Second: Ascertain whether there is the proper amount of water in the
vaporizer, in the scrubber, etc., and that the feed works properly.
Third: Through the door of the combustion-chamber introduce straw, wood
shavings, cotton waste, etc.; light them and fill the generator with dry
wood up to one-quarter or one-half of its height; then add a few
pailfuls of coal.
Fourth: Close the doors of the ash-pit and of the combustion-chamber and
start the draft by means of the fan. As soon as the draft is started, it
must be kept up without interruption until the engine begins to run,
which may be ten or twenty minutes after lighting the fire.
Fifth: After the draft has been continued for a few minutes, the coal
becomes sufficiently incandescent to start the production of gas, which
may be ascertained by trying to light the gas at the test-cock near the
generator. Then the opening in the outlet flue is half closed for the
purpose of producing pressure in the apparatus.
Sixth: Open the outlet flue adjacent to the engine for the purpose of
purging the apparatus and the conduits of the air which they contain
until the gas may be lighted at the test-cock placed near the motor.
Seventh: Adjust the normal outflow of wash-water for the scrubber.
Eighth: As soon as the gas burns continuously at the test-cock with an
orange-colored flame the engine may be started.
The gas at first burns with a blue flame; this color indicates that it
contains a certain amount of air. The opening of the test-cock should be
so regulated as to reduce the outlet pressure of the gas sufficiently to
prevent the flame from going out. During the production of the draft, as
well as during the ordinary running of the plant, the filling of the
apparatus with fuel should be done with care to prevent explosions of
gas due to the entrance of air. Particular care should be taken never to
open at the same time the lid of the charging-box and the device, be it
a cock, valve, or damper, which controls the connection of the
charging-box with the generator. All the operations which have been
mentioned above should be carried out as quickly as possible.
STARTING THE ENGINE
The manner of starting the engine depends on the type of the engine and
on the starting device with which it is provided, as we have already
explained in connection with engines working with gas from city mains.
It is, however, important for the production of a good explosive mixture
to regulate the amount of air supplied to the engine according to the
quality of the gas employed. It is advisable to continue the operation
of the fan until several explosions have taken place in the cylinder and
the engine has acquired a certain speed so as to be able to draw in the
normal amount of gas.
Naturally the gas-outlet tube near the admission-cock should be closed
after starting the engine, as well as the opening in the outlet flue of
the generator. When the motor is running properly, the amount of water
fed to the vaporizer and overflowing to the ash-pit is properly
adjusted. The generator is then filled up to the level indicated by the
manufacturer.
=Care of the Generator during Operation.=--As soon as the apparatus is
running under normal conditions, it presents the advantage of requiring
only very slight supervision and very little manual tending. The
supervision consists:
First: In regulating and keeping up a proper feed of water to the
vaporizer.
Second: In seeing to it that in apparatus provided with an overflow
leading to the ash-pit, the water should flow constantly but without
exceeding the proper amount.
Third: In keeping down temperature in the scrubber by properly
regulating the feed of the wash-water. This apparatus may be slightly
warm at its lower part, but must be quite cold at the top.
The manual tending to be done is limited to the regular filling up of
the generator with fuel and to the removal of ashes and clinkers. The
charging is effected at regular intervals, which, according to the
various types of anthracite-generators, vary from one to six hours.
Charging the apparatus at short intervals entails unnecessary labor,
while charging at too long intervals will often interfere with the
uniform production of the gas.
It will be obvious that the amount of fuel introduced will be the
larger, the greater the intervals between two fillings. This fuel is
cold and contains between its particles a certain amount of air;
furthermore, the layer of coal which covers the incandescent zone has
become relatively thin. The excess of air impoverishes the gas, and the
fresh fuel lowers the temperature of the mass undergoing combustion, so
that again the gas in process of formation is weakened. Experience seems
to show that as a rule it is best to fill up the generator at intervals
of from two to three hours, according to the work done by the engine. It
should be noted that the level of the fuel in the generator should not
sink below the bottom of the feed-hopper.
The author wishes again to emphasize that in order to prevent the
harmful entrance of air, the charging operations should be carried out
as quickly as possible; and for this reason the fuel should be
introduced not by means of the shovel, but by means of a pail, scuttle,
or other appropriate receptacle.
Care should be taken to fill the charging box to its upper edge and to
adjust its cover accurately before operating the device which closes the
feed-hopper (valve, cock).
The removal of the ashes and clinkers should be accomplished as
infrequently as possible, since opening the doors of the ash-pit and of
the combustion-chamber necessarily causes an inward suction of cold air
which is harmful.
As a rule with generators employing anthracite coal, it is sufficient to
empty the ash-pit twice daily; this should be preferably done during
stoppages. However, the cleaning of the grate by means of a poker passed
between the grate-bars or over them in order to bring about the falling
of the ashes, should be attended to every two to four hours, according
to the type of the generator and the nature of the fuel. In order that
this cleaning may be done without opening the doors, the latter should
be provided with apertures having closing devices.
This cleaning has for its chief object to allow the free passage of the
air for supporting combustion and to keep the incandescent zone in the
apparatus at the proper height. The accumulation of ashes and clinkers
at the bottom of the retort will shift this zone upward and impair the
quality of gas.
=Stoppages and Cleaning.=--After closing the gas-inlet to the engine,
the damper in the gas-outlet flue of the generator should be opened and
the cocks controlling the feed of water to the scrubber and to the
vaporizer should be closed.
If it is desired to keep up the fire of the generator during the
stoppage so as to be able to start again quickly, the ash-pit door
should be opened so as to produce a natural draft which will maintain
combustion. While the door is open, the clinkers which have accumulated
above the grate may be removed, as they are much more easily taken off
the grate when they are hot.
At least once a week the fire in the generator should be put out and the
generator completely cleaned--that is, when ordinary fuel is employed.
For this purpose, as soon as the apparatus is stopped, a portion
of the incandescent fuel is withdrawn through the doors of the
combustion-chamber, and the retort is allowed to cool before it is
emptied entirely. Too sudden a cooling of the retort may injure its
refractory lining. In order to prevent explosions caused by the entrance
of air, the feed-hopper should remain hermetically closed during the
removal of the incandescent fuel through the doors of the
combustion-chamber.
If the apparatus is placed in a room poorly ventilated, the cleaning
should be attended to by two men, so that one may assist the other in
case he is overcome by the gas. In all cases there should be a strict
prohibition against the use of any light having an exposed flame liable
to set on fire the explosive mixtures which may be formed.
When the generator, after cooling, is completely open, the charging-box
is taken apart, and, if necessary, the feed-hopper also; the grates are
taken out, if necessary; and, by means of a poker inserted from above,
the clinkers and slag adhering to the retort are broken off.
In the foregoing paragraphs the author has indicated how the several
apparatus, such as the vaporizer, the washer, the conduits, etc., should
be attended to and maintained in good working order.
CHAPTER XIV
OIL AND VOLATILE HYDROCARBON ENGINES
Although this book is devoted primarily to a discussion of street-gas
and producer-gas engines employed in various industries, a few words on
oil and volatile hydrocarbon engines may not be out of place.
Oil-engines are those which use ordinary petroleum as a fuel or
illuminating oil of yellowish color, having a specific gravity varying
from 0.800 to 0.820 at a temperature of 15 degrees C. (59 degrees F.),
and boiling between 140 and 145 degrees C. (284 to 297 degrees F.).
Volatile hydrocarbon engines are those which employ light oils obtained
by distilling petroleum. These oils are colorless, have a specific
gravity that varies from 0.680 to 0.720, and boil between 80 degrees and
115 degrees C. (176 to 257 degrees F.). Among these "essences," as they
are called in Europe, may be mentioned benzine and alcohol.
In general appearance, and the way in which they are controlled,
oil-engines differ but little from gas-engines. Their usual speed,
however, is 20 to 30 per cent. greater than that of gas-engines. Except
in some engines of the Diesel and Banki types, the compression does not
exceed 43 to 71 pounds per square inch. In volatile hydrocarbon engines,
on the other hand, the speed is very high, often running from 500 to
2,000 revolutions per minute, while the speed of gas or oil engines
rarely exceeds 250 or 300 revolutions per minute.
=Oil-Engines.=--Oil-engines are employed chiefly in Russia and in
America. Because of the high price of oil in other countries they are to
be found only in small installations in country regions and are used
mainly for driving locomobiles and launches. The improvements which have
been made of late years in the construction of gas-engines supplied by
suction gas-producers for small as well as for large powers, have
hindered the general introduction of oil-engines.
The characteristic feature in the design of many of the oil-engines of
the four-cycle type now in use (to which type we shall confine this
discussion) is to be found in the controlling mechanism employed. The
underlying principle of this mechanism lies not in acting upon the
admission-valve, but in causing the governor to operate the
exhaust-valve in such a manner that it is held open whenever the engine
tends to exceed its normal speed. Some engines, however, are built on
the principle of the gas-engine, with an admission-valve so controlled
by the governor that it is open during normal operation and closed
whenever the speed becomes excessive.
The necessity of producing a mixture of air and oil capable of being
ignited in the engine-cylinder has led to the invention of various
contrivances, which cannot be used if illuminating-gas or producer-gas
be employed. These contrivances are the atomizer, the carbureter, the
oil-pump, the air-pump, the oil-tank, and the oil-lamp. In some
oil-engines all of the elements may be found, but for the purpose of
simplifying the construction and of avoiding unnecessary complications,
manufacturers devised arrangements which rendered it possible to discard
some of them, particularly those of delicate construction and operation.
It is not the intention of the author to enter into a detailed
description of these various devices, since the limitations of this book
would be considerably surpassed. The reader is referred to books on the
oil-engine, published in the United States, England, and France.[B]
Most of the observations which have been made on the construction and
installation of gas-engines, as well as the precautions which have been
advised in the conduct of an engine, apply with equal force to
oil-engines. It will therefore be unnecessary to recur to this phase of
the subject so far as oil-engines are concerned. One point only should
be insisted upon--the necessity of very frequently cleaning the valves
and moving parts of the engine.
Illuminating-oil when burnt produces sooty deposits, particularly if
combustion be incomplete, which deposits foul the various parts and
cause premature ignitions and faulty operation.
The use of oil in atomizers, carbureters, and lamps is accompanied with
the employment of pipes and openings so small in cross-section that the
slightest negligence is attended with the formation of partial
obstructions that inevitably affect the operation of the engine.
=Volatile Hydrocarbon Engines.=--Only those engines will here be treated
which have become of importance in the development of the automobile.
Some designers have attempted to employ the volatile hydrocarbon engine
for industrial and agricultural purposes, and have devised
electro-generator groups, hydraulic groups, and so-called "industrial
combinations" in which belt and pulley transmission is employed. These
applications in particular will here be rapidly reviewed.
The high speed at which engines of this class are driven renders it
possible to operate a centrifugal pump directly and to mount both the
engine and machine which it actuates on the same base. The hydrocarbon
engine has the merit of being very light and of taking up but little
room. Its cost is considerably less than that of an oil or producer-gas
engine of corresponding power. On the other hand, its maintenance is
much more expensive, and the hydrocarbons upon which it depends for fuel
anything but cheap. Furthermore, the engines wear away rapidly, on
account of their high speed. For this reason it is advisable to base
calculations on a life of three to four years, while oil and gas engines
may generally be considered to be still of service at the end of
thirteen years. On the following page a comparison of costs for
installation and maintenance is drawn between the oil and hydrocarbon
engine on the basis of ten horse-power.
=Comparative Costs.=--A 10 horse-power oil-engine, in the matter of
first cost of installation, is about 35 per cent. more expensive than a
volatile hydrocarbon engine of equal power. On the other hand, the
operating expenses of the oil-engine are less by 25 per cent. than they
are for the volatile hydrocarbon engine.
The engines which are here discussed usually have their cylinders
vertically arranged, as in steam-engines of the overhead cylinder type.
The crank-shaft and the connecting-rods are enclosed in a hermetically
sealed box filled with oil, so that the movement of the parts themselves
ensures the liberal lubrication of the piston. The suction-valve is
generally free, although latterly designers have shown a tendency to
connect it with the cam-shaft, with the result that it has become
possible to reduce the speed appreciably without stopping the engine.
The carbureter is operated by the suction of the engine. If the fuel
employed is alcohol, it must be heated.
=Tests of High-speed Engines.=--High-speed engines present various
difficulties which must be contended with in controlling their
operation. Their high speed renders it impossible to take indicator
records as in the case of most industrial engines. Indicator cards,
moreover, at best give but very crude data, which relate to each
explosion cycle only, and which are therefore inadequate in determining
the exact conditions of an engine's operation. Oil, benzine, and other
so-called carbureted-air engines are particularly difficult to control
because of many phenomena which cannot be recorded. In order to test the
operation of high-speed engines, two different types of instruments are
at present employed: the manograph and the continuous explosion
recorder.
=The Manograph.=--The manograph, which is the invention of Hospitalier,
is an optical instrument in which a series of closed diagrams are
superimposed upon a polished mirror similar in form to Watt diagrams.
Because the images persist in affecting the retina of the eye an
absolutely continuous, but temporary, gleam is seen. Still, it is
possible to obtain a photograph or a tracing of these diagrams.
=The Continuous Explosion Recorder for High-speed Engines.=--The author
has devised an explosion and pressure recorder, which is mounted upon
the explosion chamber to be tested and which communicates with the
chamber through the medium of a cock _r_ (Fig. 136). The instrument is
somewhat similar in form to the ordinary indicator. Its record, however,
is made on a paper tape which is continuously unwound. The cylinder _c_
is provided with a piston _p_, about the stem of which a spring _s_ is
coiled. A clock train contained in the chamber _b_ unwinds the strip of
paper from the roll _p'_ and draws it over the drum _p''_, where the
pencil _t_ leaves its mark. The tape is then rewound on the spindle
_p'''_. A small stylus or pencil _f_ traces "the atmospheric line" on
the paper as it passes over the drum _p''_. In order to obviate the
binding of the piston _p_ when subjected to the high temperature of the
explosions, the cylinder _c_ is provided with a casing _e_ in which
water is circulated by means of a small rubber tube which fits over the
nipple _e'_. This recorder analyzes with absolute precision the work of
all engines, whatever may be their speed. It gives a continuous graphic
record from which the number of explosions, together with the initial
pressure of each, can be determined, and the order of their succession.
Consequently the regularity or irregularity of the variations can be
observed and traced to the secondary influences producing them, such as
the section of the inlet and outlet valves and the sensitiveness of the
governor. It renders it possible to estimate the resistance to suction
and the back pressure due to expelling the burnt gases, the chief causes
of loss in efficiency in high-speed engines. Furthermore, the influence
of compression is markedly shown from the diagram obtained.
[Illustration: FIG. 136.--R. Mathot's continuous explosion recorder.]
[Illustration: FIG. 137.--12 H.P. Oil-engine.]
[Illustration: FIG. 138.--6 H.P. Volatile Hydrocarbon Engine.]
[Illustration: FIG. 139.--Effect of size of section and exhaust ports.]
The recorder is mounted on the engine; its piston is driven back by each
of the explosions to a height corresponding with their force; and the
stylus or pencil controlled by the lever _t_ records them side by side
on the moving strip of paper. The speed with which this strip is unwound
conforms with the number of revolutions of the engine to be tested, so
that the records of the explosions are placed side by side clearly and
legibly. Their succession indicates not only the number of explosions
and of revolutions which occur in a given time, but also their
regularity, the number of misfires. The atmospheric pressure of the
explosions is measured by a scale connected with the recorder-spring. By
employing a very weak spring which flexes at the bottom simply by the
effect of the compression in the engine-cylinder, it is possible to
ascertain the amount of the resistance to suction and to the exhaust. It
is simply sufficient to compare the explosion record with the
atmospheric line, traced by the stylus _f_. By means of this apparatus,
and of the records which it furnishes, it is possible analytically to
regulate the work of an engine, to ascertain the proportion of air, gas,
or hydrocarbon, which produces the most powerful explosion, to regulate
the compression, the speed, the time of ignition, the temperature, and
the like (Figs. 137, 138 and 139).
In order to explain the manner of using this recorder several specimen
diagrams are here given.
I. _Determination of the Amount of Compression._--A spring of average
power is employed, the total flexion of which corresponds almost with
the maximum compression so as to obtain a curve of considerable
amplitude. The engine is first revolved without producing explosions,
driving it from the dynamo usually employed in shops, at the different
speeds to be studied. The compression of the mixture varies in inverse
ratio to the number of revolutions of the shaft, owing to the
resistances which are set up in the pipes and the valves and which
increase with the speed. The accompanying cut (Fig. 140) shows two
distinct records taken in two different cases, namely:
A.--Speed of engine, 950 revolutions per minute; amount of compression,
68.9 pounds per square inch.
B.--Speed of engine, 1,500 revolutions per minute; amount of
compression, 61 pounds per square inch, or 11.5 per cent. less.
[Illustration: FIG. 140.]
II. _Determination of the Resistance to Suction and Exhaust._--Influence
of the tension of the spring of the suction valve and of the section of
the pipe. Effect of the section of the exhaust-valve and of the length
and shape of the exhaust-pipe:
A very light spring is utilized, the travel of which is limited by a
stop so as to obtain on a comparatively large scale the depressions and
resistance respectively represented by the position of the corresponding
curve, above or below the atmospheric line (Fig. 141).
[Illustration: FIG. 141.]
C.--Tension of the suction-valve: 2.9 pounds. Resistance to suction: 1/7
of an atmosphere (2.7 pounds).
D.--Tension of the suction-valve: 2.17 pounds. Resistance to suction:
2/7 of an atmosphere (5.4 pounds).
E.--A chest is used for the exhaust. Resistance to exhaust: 2/7 of an
atmosphere (5.4 pounds).
F.--The exhausted gases are discharged into the air, the pipe and the
chest being discarded. Resistance to the exhaust is zero (Fig. 142).
[Illustration: FIG. 142.]
The depression graphically recorded is partly due to the inertia of the
spring of the explosion-recorder, which spring expands suddenly when the
exhaust is opened.
III. _Comparison of the Average Force of the Explosions by Means of
Ordinates._--A powerful spring is employed. The paper band or tape of the
recorder is moved with a small velocity of translation so as to
approximate as closely as possible the corresponding ordinates
representing the explosions (Fig. 143).
[Illustration: FIG. 143.]
G.--Pure alcohol. Explosive force, 369.72 to 426.6 pounds per square
inch.
H.--Carbureted alcohol. Explosive force, 397.6 to 510.8 pounds per
square inch.
I.--Volatile hydrocarbon. Explosive force, 483.48 to 531.92 pounds per
square inch.
IV. _Analysis of a Cycle by Means of Open Diagrams Representing the Four
Periods._--A powerful spring is employed, and the paper is moved with
its maximum speed of translation. The four phases of the cycle are
easily distinguished as they succeed one another graphically from right
to left in other words, in a direction opposite to that in which the
paper is unwound. A diagram is made which reproduces exactly the values
of the corresponding pressures at different points in the travel of the
piston (Fig. 144). The periods of the cycle are reproduced as faithfully
as if the ordinary indicator which gives a closed curved diagram had
been employed. There is no difficulty in reading the record, since the
paper is not in any way connected with the engine-piston. Some attempts
have been made to secure open diagrams in which the motion of
translation given to the paper is controlled by the engine itself; but
these apparatus as well as the ordinary indicators cannot be used when
the speed of the engine exceeds 400 to 500 revolutions per minute.
[Illustration: FIG. 144.]
J.--Speed, 1,200 revolutions; carbureted alcohol; average force of the
explosions, 426.6 pounds per square inch. Average compression, 92.43
pounds per square inch. Pressure at the end of the expansion, 21.33
pounds per square inch.
V. _Analysis of the Inertia of the Recorder. Selection of the Spring to
be Employed._--Given the rapidity with which the explosions succeed one
another in automobile engines, it is readily understood that the inertia
of the moving parts of the recorder will be graphically reproduced (Fig.
144). The effect of this inertia is a function of the weight of the
moving parts and of the extent of their travel.
The moving masses are represented by the piston and its rod, the spring
and the levers of the parallelogram stylus. The effects due to inertia
have been considerably lessened by reducing the weight of the various
parts to a minimum. A hollowed piston, a hollowed rod and short and
light levers have been adopted. The traditional pencil has been
displaced by a silver point which traces its mark upon a metallically
coated paper. For the heavy springs with their long travel, light but
powerful springs with small amplitudes have been substituted. Since the
perfect lubrication of the recorder-cylinder is of great importance, a
simple oiling device certain in its action has been adopted. The recess
of the piston forms a cup that can be filled with oil whenever the
spring is changed.
At each explosion the violent return of the piston splashes oil against
the cylinder walls and thus insures perfect lubrication. It should be
observed that if the directions given are not followed, particularly in
the choice of a spring suitable for each experiment, inertia effects
will be produced. These can easily be detected on the record and cannot
be confused with the curves which interpret the phenomena occurring in
the cylinder of the engine. At a height equal to the end of the piston's
stroke, the cylinder of the recorder is provided with a water-jacket
which keeps the temperature down to a proper point and prevents the
binding of the piston.
The explosion-chamber of automobile engines being rather small in
volume, should not be sensibly increased in order that the record
obtained may conform as nearly as possible with actual working
conditions on the road. In order to attain this end the cylinder of the
recorder is so disposed that the piston travels to the height of the
connecting-cock. As a result of this arrangement the field of action of
the gases is reduced to a minimum. Since these gases have no winding
path to follow, they are subjected neither to loss of quantity nor to
cold.
FOOTNOTES:
[B] Hiscox, Gas and Oil Engines, Norman W. Henley Pub. Co., New York.
Parsell and Weed, Gas and Oil Engines, 1900, Norman W. Henley Pub. Co.,
New York. Goldingham, 1900, Spon & Chamberlain, London. Dugald Clerk,
1897, Longmans, London. Grover, 1902, Heywood, Manchester. Aimé. Witz,
1904, Barnard, Paris. H. Güldner, 1903, Springer, Berlin.
CHAPTER XV
THE SELECTION OF AN ENGINE
The conditions which must be fulfilled both by engines and gas-producers
in order that they may industrially operate with regularity and economy
have been dwelt upon at some length. Unfortunately it often happens that
engines are not installed as they should be, with the result that they
run badly and that the reputation of gas-engines suffers unjustly. The
use of suction gas-producers in particular caused considerable trouble
at first owing to inexperience, so that even now many hesitate to adopt
them despite their great economical advantages. The reason assigned for
this hesitation is the supposed danger attending their operation.
The factory proprietor who intends to install a gas-engine in his plant
is not usually able to appreciate the intrinsic value of one engine when
compared with another, or to determine whether the plans for an
installation conform with the best practice. The innumerable types of
engines offered to him by manufacturers and their agents, each of whom
claims to have a better engine than his rivals, plunges the purchaser
into hesitation and doubt. Not knowing which engine to select, he
usually buys the cheapest. Very often he learns, as time goes by, that
his installation is far from being perfect. Finally he begins to
believe that he ought to consult an expert. The author's personal
experience has convinced him that eight times out of ten the factory
owner who has picked out an engine for himself has not obtained an
installation which meets the requirements which the manufacturers of
gas-engines should fulfil. Many of these requirements could be complied
with were it not for the fact that the manufacturer has dropped certain
details which appeared superfluous, but which were in reality very
important in obtaining perfect operation. The author therefore suggests
that the services of a competent expert be retained by those who intend
to install a gas-engine in their plants.
=The Duty of a Consulting Engineer.=--An expert fills the same office as
an architect, and impartially selects the engine best suited to his
client's peculiar needs. His examination of the engines offered to him
will proceed somewhat according to the following programme:
1. He will first study the installation from the mechanical point of
view, and also the local conditions under which that installation is to
operate, in order that he may not order an engine too large or too
small, or a type incompatible with the foundations at his disposal, or
unable to fulfil all the requirements of his client.
2. He will examine the precautions which have been taken to avoid or
reduce to a minimum certain inconveniences which attend the operation of
explosion-engines.
3. He will draw up specifications, with the terms of which gas-engine
makers must comply, so that he can compare on the basis of these
specifications the merits of the engines submitted to him.
4. He will prepare an estimate of cost and also a contract which is not
couched in terms altogether in the gas-engine maker's favor, and which
gives the purchaser important warranties.
5. He will supervise the technical installation of the engine or plant.
6. He will make tests after the engine is installed and see to it that
the maker has fulfilled his warranties.
=Specifications.=--Since engines and gas-producers are constructed for
commercial ends, it naturally follows that their manufacturers seek to
make the utmost possible profit in selling their installations. Prices
charged will necessarily vary with the quality of material employed, the
care taken in constructing the engine and generator, the number of
apparatus of the same type which are manufactured, the arrangement of
the parts and that of the installations. Since there is considerable
rivalry among gas-engine builders, selling prices are often cut down so
far that little or no profit is left. It is very difficult--indeed
impossible--to convince a purchaser that it is to his interest to pay a
fair price in order to obtain a good installation, especially when other
manufacturers are offering the same installation at a less price with
the same warranties. As a result of this state of affairs, engine
builders, in order that they may not lose an order, are willing, to
reduce their prices, hoping to make up in the quality of the
workmanship and the material what they would otherwise lose. Often they
will deliver an engine too small in size but operating at a higher speed
than that ordered; or they will select an old type, or carry out certain
details with no great care.
This, to be sure, is not always the case; for there are a few builders
of engines who place their reputation above everything else and who
would rather lose an order than execute it badly. Others, unfortunately,
prefer to have the order at all costs.
By retaining a consulting engineer, all these difficulties are overcome.
In the first place, the engineer draws up a scale of prices and
specifications which must be complied with in their entirety as well as
in all details. Rival engine builders are thus compelled to make their
estimates according to the same standard, so that one engine can readily
be compared with another with the utmost fairness. In these
specifications, penalties will be provided for by the engineer which
will be levied if the warranties of the maker are not fulfilled.
Otherwise the warranties are worth nothing.
The first consequence of engaging a consulting engineer is to render the
matter of cost a secondary one. A factory owner who employs a consulting
engineer and pays him for his services, is impelled chiefly by the
desire to obtain a good installation which will perform what he expects
of it. For that reason necessary sacrifices will be made to comply with
the client's wishes.
If the purchaser considers the question of cost most important to him,
he need not engage an expert to supervise the installation of his
engines. He has simply to pick out the cheapest engine. Unfortunately,
however, the money which he will save by such a procedure will be more
than compensated for by the trouble which he will later experience when
his motor stops or when it breaks down, because it has been cheaply
built in the first place.
The advice of a consulting engineer is therefore of importance to the
purchaser, because an engine will be installed which will in every way
meet his requirements. The gas-engine builder will also prefer to deal
with an engineer, because the engineer can appreciate at their true
worth good material and good workmanship and place a fair valuation upon
them. The specifications of a gas-engine and gas-producer expert are
accepted by most engine builders, because an expert will not introduce
conditions which cannot be fulfilled. Some manufacturers refuse to
consider the conditions imposed by specifications seriously, or else
they fix different prices and make tenders on the basis of these with or
without specifications. In either case the purchaser may be sure that he
is not receiving what he has a right to exact.
=Testing the Plant.=--When the engine has been selected the consulting
engineer supervises its installation, and, after this is completed,
carries out tests in order to determine whether or not the guaranteed
power and consumption are attained. The methods employed in testing a
gas-engine are both complex and delicate. The quality of the gas, the
proportions of the elements forming the mixture, the time and the
method of ignition, the temperature of the cylinder-walls, the
temperature and the pressure of the gas drawn into the cylinder, all
these are factors which have a decided bearing upon the results of a
test. If these factors be not carefully considered the conclusions to be
drawn from the test may be absolutely wrong.
Indicators of any type should not be indiscriminately employed; only
those specially designed for gas-engine purposes should be used.
Indicator cards are in themselves inadequate, and should be supplemented
by the records of explosion-recorders.
The calorific value of the gas should be measured either by the Witz
apparatus or by means of any other calorimeter.
In interpreting the diagrams and records some difficulty will be
encountered. Sometimes it happens that a particular form of curve is
attributed to a cause entirely different from the real one. It happens
not infrequently that engineers, whose experience is confined to engines
of one make and who have not had the opportunity to make sufficient
comparisons, draw such erroneous conclusions from cards.
To recapitulate what has already been said, the testing of gas-engines
requires considerable experience and cannot be lightly undertaken.
Special instruments of precision are necessary. The author has very
often been called upon to contradict the results obtained by experts
whose tests have consisted simply in ascertaining the engine power
either by means of a Prony brake, or by means of a brake-strap on the
fly-wheel. The brake gives but crude results at best; it is a means of
control, and not an instrument of scientific investigation.
Something more than the mere power produced by an engine should be
ascertained. The tests made should throw some light upon the reasons why
that power cannot be exceeded, and show that the necessary changes can
be made to cause the engine to operate more economically and to yield
energy of an amount which its owner has a right to expect. The indicator
and the recorder are testing instruments which clearly indicate
discrepancies in operation and the means by which they may be corrected.
The tests made should determine whether the power developed is not
obtained largely by means of controlling devices which cause premature
wearing away of the engine parts.
It is not the intention of the author to describe indicators of the
well-known Watt type. It is simply his purpose to call attention to the
explosion-recorder which he has devised to supplement the data obtained
by means of the indicator.
[Illustration: FIG. 145.--Mathot explosion-recorder.]
=Explosion-Recorder for Industrial Engines.=--The explosion-recorder
illustrated in Fig. 145 can be adapted to any ordinary indicator. It is
composed of a supporting bracket _B_ upon which a drum _T_ is mounted.
This drum is rotated by a clock-train, the speed of which is controlled
by means of a special compensating governor. The entire system is
pivotally mounted upon the supporting screw _O_, so that the drum _T_,
about which a band of paper is wound, may be swung against a stylus
_C_, which records upon the paper the number and power of the
explosions. These explosions are measured according to scale by a spring
connected with an indicator. The records obtained disclose for any given
cycle the amount of compression as well as the force of the explosion,
and render it possible to study the phenomena of expansion, exhaust, and
suction. They are, however, inadequate in showing exactly how an engine
runs in general. Indeed, in most gas-engines, as well as oil and
volatile hydrocarbon engines, each explosion differs from that which
follows in character and in power; and it is absolutely essential to
provide some means of avoiding these variations. The explosion-recorder
gives a graphic record from which the number of explosions can be read,
and also the initial pressure of each explosion, the number of
corresponding revolutions, the order in which the explosions succeed one
another, and consequently the regularity of certain phenomena caused by
secondary influences, such as the section of the distributing members,
the sensitiveness of the governor, and the like.
The explosion-records can be taken simultaneously with ordinary
diagrams. In order to attain this end, the recorder is allowed to swing
around the pivot _O_, so that the drum carrying the paper band is
brought into engagement, or swung out of engagement with the stylus, as
it is influenced by each explosion, thereby leaving its record on
the paper. The ordinary diagram may be traced on the drum of the
indicator, as it continues to operate in its usual way. Thus the
explosion-recorder renders it possible to control the operation of
engines, to obtain some idea of the cause of defects and to attribute
them to the proper force. Improvements can then be made which will
ensure a greater efficiency. A number of records herewith reproduced
illustrate the defects in the controlling apparatus and in the
construction of certain engines, and also the result of improvements
which have been made on the basis of the records obtained. The smaller
lines indicate the compression, which is usually constant in engines in
which the "hit-and-miss" system of governing is employed, while the
larger lines indicate the explosions. These records are only part of the
complete data normally drawn on the paper in the period of 120 seconds
corresponding with an entire revolution of the recorder-drum.
[Illustration: FIG. 146.--Record with automatic starter.]
[Illustration: FIG. 147.--Gas-engine running at one-half load.]
[Illustration: FIG. 148.--Record made after correcting faults.]
[Illustration: FIG. 149.--Record made after correcting faults.]
The first record was taken while starting up an engine provided with an
automatic starting device and supplied with explosive mixture without
previous compression (Fig. 146). The gradual lessening of the distances
of the ordinates or lines representing the explosions shows that the
speed of the motor was slowly increasing, and also indicates the time
which elapsed before the engine was running smoothly. The records that
follow (Figs. 147, 148 and 149) show the results which can be obtained
with the recorder by correcting the errors due to faults in installing
the engine and its accessories. The fifth record is particularly
interesting because it shows the influence of the ignition-tube on the
power of the deflagration of the explosive mixture (Fig. 150). This
record was obtained with an engine provided with two contiguous tubes.
The communication of each of these tubes with the explosion-chamber
could be cut off at will at any moment. The last record (Fig. 151) was
obtained at a time when the effective load of the engine was changed at
two different intervals. This record shows how regularly the engine was
running and how constant were the initial pressures. These pressures,
however, which is the case in most engines, manifestly diminish when the
explosions succeed one another without idle strokes of the piston. This
shows, also, the influence of "scavenging" the products of combustion
and the effect it has on the efficiency of explosion-engines.
=Analysis of the Gases.=--It has already been stated that one of the
tests which should be made consists in measuring the calorific value of
the gas. Just what the calorific value of the gas may be it is necessary
to know in order to obtain some idea of the thermal efficiency of the
installation. If a suction gas-producer be employed (an apparatus in
which the nature of the gas generated changes at each instant),
calorimetrical analyses are indispensable in appreciating the conditions
under which a generator operates.
These analyses are made by means of calorimeters which give the
calorific value either at a constant pressure or at a constant volume.
Constant-volume instruments give a somewhat weaker record than
constant-pressure instruments; but according to Professor Aimé Witz, the
inventor of an excellent calorimeter, the constant-volume type is almost
indispensable in gaging the efficiency of explosion-engines.
[Illustration: FIG. 150.]
[Illustration: FIG. 150_b_.]
[Illustration: FIG. 151.--Record made when effective load was changed at
two different intervals.]
[Illustration: FIG. 152.--The Witz calorimeter.]
=The Witz Calorimeter.=--The accompanying diagram (Fig. 152) illustrates
Professor Witz's instrument. Its elements are a steel cylinder having an
interior diameter of 2.36 inches, about a thickness of 0.078 inch and a
height of about 3.54 inches, so that its capacity is about 15.1 cubic
inches, and two covers screwed on the cylinder to seal it hermetically,
oiled paper being used as a washer. The upper cover carries a
spark-exciter; the lower cover is provided with a valve which discharges
into a cylindrical member 1.06 inches in diameter. This second cover is
downwardly inclined at its circumference toward the center to insure
complete drainage of the mercury used for charging the calorimeter. All
surfaces are nickel plated. The proportions of nickel and of steel are
fixed by the manufacturer so as to render it possible to calculate the
displacement of the apparatus in water. The calorimeter having been
completely filled with mercury is inverted in this liquid in the manner
of a test tube. The explosive mixture is then introduced, being fed
from a bell in which it has previously been prepared. A rubber tube
connects the bell with the instrument. The gas is forced from the bell
to the calorimeter by the pressure in the bell. The conical form of the
bottom causes the calorimeter to be emptied rapidly and to be refilled
completely with explosive gas at a pressure slightly above that of the
atmosphere. Equilibrium is re-established by manipulating the valve,
during a very short interval, so as to permit the excess gas to escape.
During this operation the calorimeter must be maintained in the vertical
position shown in the diagram. The atmospheric pressure is read off to
one-tenth of a millimeter (0.003936 inches) on a barometer. The
temperature of the gas may be taken to be that of the mercury-vessel.
The explosive mixture is prepared in the water reservoir, the glass bulb
shown in the accompanying illustration being employed. This bulb is
closed at its upper end by means of a cock and is tapered at its lower
end. The gas or air enters at the top by means of a rubber tube and
gradually displaces the water through the lower end. The bulbs have a
volume varying from 200 to 500 cubic centimeters (12 to 30 cubic
inches), and the error resulting from each filling of a bulb is
certainly less than 15 cubic millimeters (0.0009 cubic inches). The
contents are emptied into a bell by lowering the bulb into the water and
opening the cock. If seven bulbfuls of air be mixed with one bulbful of
gas, an explosive mixture of 1 to 7 is produced, this being the
proportion commonly employed for street-gas. For producer-gases the
preferred proportion is 1 to 1, oxygen being often added to the air in
order to insure complete combustion.
The calorimeter, after having been filled, is placed in a vessel
containing a liter (1.7598 pints) of water so that it is completely
immersed. A spark is then allowed to pass. The explosion is not
accompanied by any noise; the temperature rises a fixed number of
degrees, so that the quantity of heat liberated can easily be computed.
Each division of the thermometer is equal to 0.01502 C. The scale
reading is minute, each interval being divided by ten, so that readings
to the 1,500th part of a degree can be taken.
It should be observed that the mixture generated in the reservoir is
saturated with water vapor at the temperature of the reservoir.
Consequently, the vapor generated by the explosion must condense in the
calorimeter if the final temperature of the calorimeter is the same as
that of the water reservoir. If, on the other hand, the temperature be
slightly different, a correction must be made; but the error is
negligible for differences in temperature of from 2 to 3 degrees C. (3.6
to 5.4 degrees F.). This, however, is never likely to occur if the
operation is conducted under favorable conditions.
This apparatus is exceedingly simple and practical. It does not require
the manipulation of a pump. The pressure of the mixture is read off on
the barometer; the calorimeter is entirely immersed in the water of the
outer vessel, so that all corrections of doubtful accuracy are obviated.
The method requires but a very slight correction for temperature. Air,
alone or mingled with oxygen, or a mixture of air and oxygen, can be
easily tested with.
=Maintenance of Plants.=--If it should be necessary to retain a
consulting engineer to install an engine capable of filling all
requirements, it is also necessary to select a careful attendant in
order that the engine may be kept in good condition. It is a rather
widespread belief that a gas-engine can be operated without any care or
inspection. This belief is all the more prevalent because of the
employment of street-gas engines, which, by reason of their simplicity
of construction and regularity of fuel supply, often run for several
hours, and even for an entire day, without any attention whatever. But
this negligence, particularly in the case of engines driven from
producers, is likely to produce disastrous results. Although engines of
this type do not require constant inspection during operation, still
they require some attention in order that the speed may be kept at a
fixed number of revolutions. Moreover, the care of the engine, the
cleaning of the valves and of the various parts which are likely to
become dirty, and the examination and cleaning of pipes, should be
accomplished with great care and at regular intervals. This task should
be entrusted only to a man of intelligence. A common workman who knows
nothing of the care with which the parts of an engine should be handled
is likely to do more harm than good.
The factory owner who follows the instructions which have been given in
this book will avoid most of the stoppages and the trouble incurred in
engine and generator installations, and may count upon a steadiness of
operation comparable with that of a steam-engine.
TEST OF A "STOCKPORT" GAS-ENGINE WITH DOWSON PRESSURE GAS PLANT
Made by R. Mathot at the Works of the "Union Electrique" C^{ie},
Brussels, June 27, 1901
Piston Diameter: 15-1/2". Piston stroke, 22".
Normal number of revolutions, 210.
1. Calorific value of the coal 12750 B.T.U.
2. Nature and origin of fuel: Anthracite coal
of Charleroi (Belgium).
3. Cost of fuel per ton at the mine $5.50
4. Cost of fuel per ton at the plant $6.39
5. Fuel consumption per hour in the generator 46.3 lbs.
6. Fuel consumption per hour in the boiler 7 lbs.
7. Proportion of ash in the coal 6 per cent.
8. Weight of steam at 66 lbs. generated per hour 42.7 lbs.
9. Average brake horse-power 53 B.H.P.
10. Fuel consumption for gas per B.H.P. per
hour 0.875 lbs.
11. Fuel consumption for steam per B.H.P. per hour 0.133 lbs.
12. Total fuel consumption 1.008 lbs.
13. Steam consumption at 66 lbs. pressure 0.81 lbs.
14. Gas pressure at the engine 1-3/8 inches
15. Weight of water per B.H.P. per hour for
cooling the cylinder entering at 68° F.
and leaving at 105° F. 51.5 lbs.
16. Corresponding heat absorbed in cooling 1970 B.T.U.
17. Average initial explosive pressure on piston 324 lbs.
18. Average pressure on piston per square inch 72 lbs.
19. Average indicated horse-power with 85 per
cent. misses 92.5 I.H.P.
20. Corresponding mechanical efficiency 84 per cent.
21. Corresponding electric load 31.950 K.W.
22. Cost of B.H.P. per hour in anthracite $0.0029
23. Cost of kilowatt per hour in anthracite $0.0048
24. Electric power generated per B.H.P. 602.8 W.
25. Thermal efficiency at 53 B.H.P. with 85
per cent. explosions 18.5 per cent.
TEST OF A 20 H.P. WINTERTHUR ENGINE
With Winterthur Suction-Producer made by R. Mathot at Winterthur,
June 4 and 5, 1902
DATA OF TESTS WITH ILLUMINATING GAS AND WITH FUEL GAS
Dimensions of Winterthur Engine--Piston diameter: 10-3/8". Stroke:
16-7/8". Compression: 177 pounds per square inch. Regulation: hit and
miss. Ignition: electro-magnetic. Fly-wheel: normal, with external
bearing. Lubrication of piston: with oil-pump. Of main bearings, with
rings (as in dynamos).
FULL LOAD WITH STREET-GAS
1. Number of revolutions per minute 200
2. Corresponding number of explosions 96 per cent.
3. Net load on brake 120 lbs.
4. Corresponding effective power 22 B.H.P.
5. Mean initial explosive pressure on piston
per square inch 455 lbs.
6. Average pressure on piston per square inch 78 lbs.
7. Gas consumption per B.H.P. at 24° C. and
721 mm. mean pressure 15.5 cubic feet
8. Gas consumption per B.H.P. reduced to 0° C.
and 760 mm. mean pressure 13.5 cubic feet
HALF LOAD WITH STREET-GAS
9. Number of revolutions per minute 204
10. Corresponding number of explosions 60 per cent.
11. Net load on brake 60 lbs.
12. Corresponding effective power 11.6 B.H.P.
13. Gas consumption per B.H.P. per hour at 24° C.
and 721 mm. mean pressure. 21 cubic feet
14. Gas consumption per B.H.P. per hour at 0° C.
and 760 mm. mean pressure. 18.3 cubic feet
RUNNING WITH NO LOAD WITH STREET-GAS
15. Number of revolutions per minute 206
16. Corresponding number of explosions 22 per cent.
17. Total gas consumption per hour at 24° C.
and 721 mm. mean pressure. 106 cubic feet
18. Maximum calorific power of gas per cubic foot 598 B.T.U.
19. Thermal efficiency with 96 per cent. explosions 31 per cent.
20. Mechanical efficiency with 96 per cent.
explosions 82 per cent.
21. Temperature of water at the jacket-inlet 75 degs. F.
22. Temperature of water at the jacket-outlet 130 degs. F.
23. Compression per square inch on piston surface 178 lbs.
24. Pressure after expansion 37 lbs.
TEST OF WINTERTHUR PLANT WITH PRODUCER-GAS
1. Nature of fuel. Belgian anthracite, "Bonne
Esperance et Batterie"; size, 3/4 inch.
2. Chemical composition: Carbon, 86.5 per cent.;
hydrogen, 3.5 per cent.; oxygen and nitrogen,
4.65 per cent.; ash, 5.35 per cent.
3. Calorific value per pound of coal 14200 B.T.U.
4. Net calorific value per pound of fuel 15050 B.T.U.
5. Price of anthracite delivered at the plant $3.50 per ton
6. Number of revolutions of engine per minute 200
7. Corresponding number of explosions 91 per cent.
8. Load on brake 106 lbs.
9. Corresponding effective horse-power 20.2 B.H.P.
10. Fuel consumption at the generator per hour 16.4 lbs.
11. Fuel consumed per B.H.P. per hour 0.81 lbs.
12. Proportion of ash resulting from the tests 6 per cent.
13. Mean initial explosive pressure per square
inch 419.5 lbs.
14. Average pressure on piston per square inch 72.5 lbs.
15. Indicated horse-power with 91 per cent.
explosions 25.4 I.H.P.
16. Mechanical efficiency 79 per cent.
17. Thermal efficiency at the producer 22 per cent.
18. Water consumption per hour in the scrubber 66 gals.
19. Cost per B.H.P. per hour in anthracite 62 gals.
TEST OF A 60 B.H.P. GAS-ENGINE, TYPE G 9, WITH A SUCTION-GAS
PLANT OF THE GASMOTOREN FABRIK DEUTZ
(Made at Cologne, March 15, 1904, by R. Mathot.)
DATA OF THE TESTS
Diameter of Piston = 16.5". Piston Stroke = 18.9"
FULL LOAD
1. Average number of revolutions per minute 188.66
2. Corresponding effective work 65.11 B.H.P.
3. Average compression per square inch 176 lbs.
4. Average initial explosive pressure per square
inch 397 lbs.
5. Average final expansion pressure 25 lbs.
6. Vacuum at suction 4.4 lbs.
7. Average pressure on piston 81 lbs.
8. Corresponding indicated horse-power 77 I.H.P.
FUEL
9. Nature of fuel: Anthracite coal 0.4" to 0.8"
10. Origin: Coalpit of Zeihe, Morsbach at Aix-la-Chapelle.
11. Chemical composition of coal:
Carbon 83.22%
Hydrogen 3.31%
Nitrogen and Oxygen 3.01%
Sulphur 0.44%
Ash 7.33%
Water 2.69%
12. Calorific value. 13650 B.T.U.
GAS
13. Chemical composition of gas:
Carbonic acid 6.60%
Oxygen 0.30%
Hydrogen 18.90%
Methane 0.57%
Carbon monoxide 24.30%
Nitrogen 49.33%
14. Calorific value of gas, combination water,
at 59° F. constant volume reduced to 32° F.
and atmospheric pressure 140 B.T.U.
TEMPERATURES
_Engine_
15. Cooling water at the inlet of the
cylinder-head 55.4 deg. F.
Temperature at the outlet 109.5 deg. F.
16. Temperature at outlet of cylinder 127.5 deg. F.
_Gas-Generator_
17. Temperature of water in the vaporizer 158.3 deg. F.
EFFICIENCIES AND CONSUMPTION
18. Mechanical efficiency 84.6%
19. Gross consumption of coal per B.H.P. per hour 0.86 lbs
20. Thermal efficiency in proportion to the
effective work and the gross consumption
of coal in the gas-generator 24.3%
HALF LOAD
WORK
1. Average number of revolutions per minute 195.5
2. Corresponding effective work 33.85 B.H.P.
3. Corresponding average compression 125 lbs.
4. Average initial explosive pressure 258 lbs.
5. Average final expansion 18 lbs.
6. Vacuum at suction 6.8 lbs.
7. Average mean pressure on piston 46.2 lbs.
8. Corresponding indicated power 45. I.H.P.
9. Speed variation between full and half load 3.5%
CONSUMPTION
10. Gross consumption of coal per B.H.P. per hour 1.155 lbs.
RUNNING WITH NO LOAD
1. Average number of revolutions per minute 199
2. Minimum corresponding compression 95.55 lbs.
3. Average initial explosive pressure 220 lbs.
4. Average final expansion 0 lbs.
5. Vacuum at suction 8.8 lbs.
6. Average pressure on piston 11.2 lbs.
7. Corresponding indicated horse-power. 11 I.H.P.
8. Speed variation between full load and no load 5.2%
TEST OF A GAS PLANT OF A FOUR-CYCLE DOUBLE-ACTING
ENGINE OF 200 H.P. AND A SUCTION-PRODUCER IN THE
WORKS OF THE GASMOTOREN FABRIK DEUTZ, COLOGNE
March 14 and 15, 1904, by Messrs. A. Witz, R. Mathot, and de Herbais
DATA OF THE TESTS
Piston Diameter: 21-1/4". Stroke: 27-9/16". Diameter of Piston-Rods:
front, 4-3/4"; rear, 4-5/16"
ENGINE
_Full Load Tests_
1. Average number of revolutions per minute 151.29 and 150.20
2. Corresponding effective load 214.22 B.H.P.
and 222.83 B.H.P.
3. Duration of the tests 3 hours and 10 hours
4. Average temperature of water after cooling
the piston 117.5 deg. F.
5. Average temperature of water after cooling
the cylinder and valve-seats 135 deg. F.
6. Water consumption per hour for cooling the
piston 39 gal.
PRODUCER
7. Nature and Origin of Fuel: Anthracite coal
"Bonne-Esperance et Batterie" Herstal,
Belgium.
8. Calorific value of fuel 14650 B.T.U.
9. Consumption of fuel per hour (plus 53 lbs.
on the night of the 14th for keeping the
generator fired during 14 hours, the
engine being stopped) 199 lbs.-160 lbs.
10. Water consumption per hour in the vaporiser 14.2 gals.
11. Water consumption per hour in the scrubbers 318 gals.
12. Average temperature of gas at the outlet
of the generator 558 deg. F.
13. Average temperature of gas at the outlet
of the scrubbers 62.5 deg. F.
EFFICIENCIES
14. Gross consumption of coal per B.H.P. per hour 0.927 lbs.-0.720 lbs.
15. Consumption of coal per B.H.P. after deduction
of the water 0.907 lbs.-0.705 lbs.
16. Thermal efficiency relating to the effective
H.P. and to the dry coal consumed in the
generator 19%-24.4%
17. Water consumption per B.H.P. hour:
For the cylinder, stuffing-boxes and
valve-seat jackets 4.65 gals.
For the piston and piston-rods 1.75 gals.
For the vaporizer 0.0655 gals.
For washing the gas in the scrubbers 1.42 gals.
18. Water converted in steam per lb. consumed
in the generator 0.193 gals.
INDEX
A
Adjustment of gas-engine, 126
Adjustment of moving parts, imperfect, 146
Admission-valve, binding of, 152
Admission, variable, 55, 56
Air-blast, 180
Air-chest, 82
Air, displacement of, 92
Air, exclusion of, in producers, 207
Air, filtration of, 82
Air-heater, Winterthur, 236
Air-heaters, 238
Air-pipe, 82
Air-pipe, location of, 83
Air-pump, 266
Air, regulation of supply, 82
Air suction, 81
Air suction, resistance to, 82
Air supply of producer, 225
Air-valve, control by engine, 25
Air vibration, 92
Alcohol as engine fuel, 264
Anthracite, consumption of, in producers, 200
Anthracite in producers, 190, 201
Anti-pulsators, 77
Anti-pulsators, disconnection of, in stopping engine, 132
Anti-pulsators, precautions to be taken with, 79
Anti-vibratory substances, 89
Ash-pit, 214, 217
Ash-pit, Bollinckx, 220
Ash-pit, cleaning of, 261
Ash-pit, Deutz, 220
Ash-pit, door of, 220
Ash-pit, Wiedenfeld, 220
Asphyxiation, 169
Atomizer of oil-engines, 265
B
Back firing, 82, 131
Back pressure to exhaust, 151
Bags, arrangement of, 80
Bags, capacity of, 79
Bags, precautions to be taken with, 79
Bags, rubber, 77
Bark as producer fuel, 193
Batteries for ignition, 31
Bearings, adjustability of, 5
Bearings, adjustment of, 44
Bearings, care of, 123
Bearings, lubrication of, 117
Bearings, material of, 51
Bearings of fly-wheels, 92
Bearings, overheated, 146
Bearings, over-lubricated, 150
Bearings, position of, 44
Bell, gas-holder, 187
Bell, Pintsch, 248
Bell, volume of, 187
Belts, prevention of adhesion by oil, 120
Bénier, E., 199
Benzin as engine fuel, 264
Binding, 147
Blast in producers, 180, 193, 225
Blower, Koerting, 181
Blower, Root, 182, 188
Blowers for producers, 181
Blowing-generators, 169
Bolts of foundation, 91
Bomb, Witz, 284, 292
Boughs for coolers, 108
Box, charging, 221
Box, double closure for charging, 222
Box, removable charging, 225
Brake tests, 284
Branch pipes, minimum diameter of, 81
Bricks for foundation, 91
Brushes, lifting of, when dynamo-engine is stopped, 132
Brush, purifying, 250
Burner of hot tube, how ignited, 128
Burner, regulation of fixed, 144
Bushings, care of, 123
Bushings, fusion of, 147
Bushings (see also Bearings)
C
Calorimeter, Witz, 292
Calorimeters, 284, 290
Cam, half-compression, 130, 132
Cam, relief, 130
Cams, 51
Caps of valve-chests, 124
Carbureter, 266
Care during operation of engine, 131
Casing, independence of frame, 42
Charging a producer, 221
Charging the generator, 259
Chest for exhaust, 83
Circulation of water, 98, 125
Circulation of water, how effected, 102
Circulation of water in tanks, 105
Circulation of water, regulation of, 107
Cleaning of producer, 261
Cleanliness, necessity of, 121
Cleanliness of producers, 179
Closures for charging-boxes, 223
Coal in producers, 201
Coal in producers, bituminous, 195
Coal, Pennsylvania, 203
Coal (see also Anthracite)
Coal, Welsh, 203
Cock, Deutz, 224
Cock, Pierson, 224
Cock for charging-box, 223, 224
Coke in producers, 201
Coke in washers, 242
Combustion-generators, 193
Combustion, inverted, 195
Compression, determination of, 273
Compression, faulty, 134
Compression, high, 154
Compression in Banki engine, 264
Compression in Diesel engine, 264
Compression, losses in, 143
Compression period, 21
Compression, relation to power developed, 122
Compressors for producers, 182
Connecting-rod bearings, 45
Connecting-rod bearings, rational design of, 45
Connecting-rod, lubrication of, 113, 115
Consulting engineer, advisability of retaining, 282
Consumption at half load and full load, 62
Consumption at various loads, 62
Consumption in double or triple acting engines, 62
Consumption of gas, 173
Consumption of gas in burner, 30
Consumption of suction-producers, 200
Consumption per effective horse-power, 62
Cooler for gas, 199
Cooler, for producer, 240
Coolers, 107
Coolers, size of, 109
Cooling of cylinder, 98, 100, 156
Cooling of producer-gas engines, 203
Cooling, thermo-siphon, 100
Cost of oil and volatile hydrocarbon engines, 268
Crank-pin, tensile strength of, 51
Crank-shaft, 50, 51
Crank-shaft bearings, 44
Crank-shaft bearings, design of, 46
Crank-shaft, effect of premature explosion on, 30
Crank-shaft lubrication, 117
Crank-shaft, material of, 50
Crosshead, care of, 123
Cycle, analysis of, 276
Cylinder, arrangement of, 41
Cylinder, cleaning of, 122
Cylinder, cooling of, 156
Cylinder, evacuation of, 83, 131
Cylinder, gravel in, 137
Cylinder, grinding of, 42
Cylinder, incandescent particles in, 142
Cylinder, independence of casing, Compression in, 42
Cylinder-jacket (see Water-jacket)
Cylinder lubrication, 112
Cylinder-oil, 112, 149
Cylinder, overhang in horizontal engines, 42
Cylinder, overheating of, 148
Cylinder, presence of water in, 136
Cylinder-shell, 41
Cylinder, smoke from, 149
Cylinder, temperature during operation of engine, 132
Cylinder, thrust of, 43
Cylinder, tightness of, 122
D
Damper, Pintsch, 224
Dampers, 223
Detonations, untimely, 141
Distributing mechanism, derangement of, 152
Drain-cock in gas-pipes, 70, 75
Drain-cocks, testing of, 256
Drier for producer-gas, 248
Dust-collector, 239
Dust-collector, Benz, 239
Dust-collector, Bollinckx, 239
Dust-collector, Pintsch, 239
Dust-collector, Wiedenfeld, 239
Dynamo, lifting brushes from, in stopping engine, 132
E
Ebelmen principle, 195
Engine, Banki, 264
Engine, Diesel, 264
Engine, producer-gas and steam, compared, 203
Engine, selection of, 279
Engine, starting a producer-gas, 258
Engineer, duty of a consulting, 281
Engines, governing oil, 265
Engines, oil, 264, 265
Engines, producer-gas, 153
Engines, producer-gas, temperature of, 157
Engines, specifications of, 281
Engines, speed of oil, 264
Engines, tests of, 268
Engines, volatile hydrocarbon, 264, 267
Engines, writers on oil, 266
Escape-pipes, 228
Essences, 264
Exhaust, 83
Exhaust, back pressure to, 151
Exhaust, determination of resistance to, 274
Exhaust into sewer or chimney, 85
Exhaust, noises of, 94, 141
Exhaust period, 22
Exhaust, water in, 136
Exhausters, 183
Exhaust-chest, 83
Exhaust-muffler, 86, 94
Exhaust-pipe, 83, 85
Exhaust-pipe, design of, 96, 97
Exhaust-pipe, joints for, 85
Exhaust-pipe, oil in, 151
Exhaust-valve, binding of, 152
Exhaust-valve, cooling of, 25
Expansion-boxes, 95
Expansion period, 22
Expert, necessity of an, 282, 283
Explosion, spontaneous, 140
Explosion-engines (see Gas-engines)
Explosion period, 22
Explosion-recorder, analysis of inertia of, 277
Explosion-recorder for industrial engines, 285
Explosion-recorder, the continuous, 269
Explosions, comparison of average force of, 275
Explosion-records, 288
Explosions, retarded, 143
F
Fans for producers, 181
Feeder, Winterthur, 236
Feed-hopper, 224
Fire-box, door of, 221
Flues, escape, 228
Fly-wheel, oil on, 120
Fly-wheel, starting the, 131
Fly-wheels, 46
Fly-wheels as pulleys, 46
Fly-wheels, balancing of, 46
Fly-wheels, curved spoke, how mounted, 49
Fly-wheels, fastening of, 46
Fly-wheels, proper mounting of, 46
Fly-wheels, rim of, 46
Fly-wheels, single, 48, 92
Fly-wheels, single, for dynamo-engines, 46
Fly-wheels, straight and curved spoke, 49
Fly-wheels with hit-and-miss system, 50
Foundation, 44, 87
Foundation, design of, 88, 89
Foundation, excavation for, 88
Foundation, insulation of, 89, 90
Foundation of dynamo-engine, 91
Frame, 43
Frame, method of securing, to foundation, 44
Fuel of producers, 178, 187, 254
Fuel, qualities of, 201
Fuel (see also Lignite, Peat, Sawdust, Wood, Coal, etc.)
Fuel, size of, 201
Fuel, smoke-producing, 254
G
Gas, ascertaining purity of, 128
Gas, blast-furnace, 153
Gas, calorific value of, 284
Gas, calorific value of producer, 200
Gas, coke-oven, 153
Gas consumption, 173
Gas consumption of burner, 30
Gas, effect of quality, 152
Gas-engine, balancing of, 46
Gas-engine, care during operation, 131
Gas-engine, cost of installation, 19
Gas-engine, cost of operation, 19
Gas-engine, difficulties in starting, 134
Gas-engine, how to start a, 128
Gas-engine, how to stop a, 132
Gas-engine, installation of a, 68
Gas-engine, location of a, 68
Gas-engine, selection of a, 21
Gas-engine, simplicity of installation, 17
Gas-engine, the four-cycle, 21
Gas-engines, adjustment of, 126
Gas-engines, care of, 121
Gas-engines, "Steam-Hammer," 57
Gas-engines, temperature of, 158
Gas-engines, tests of, 283
Gas-engines, vertical, 56
Gas-engines, writers on, 68
Gas, fuel, 153
Gas-holder, 186, 189
Gas-holders, 247
Gas-holder, combined with washer or scrubber, 186
Gas, illuminating (see Street-gas)
Gas, impurities of, 172
Gas, Mond, 153, 167
Gasometer (see Gas-holder)
Gas, producer (see Producer-gas)
Gas production, 173
Gas, purification of wood, 195
Gas supply, necessity of coolness, 69
Gas-valve, necessity of independent operation of, 27
Gas, water, 153, 169
Gas, wood, 153, 168
Gases, analysis of, 290
Generator (see also Producer)
Generator, Benz, 207
Generator, Bollinckx, 207
Generator, care of, 259
Generator, charging the, 259
Generator, construction of, 177, 207
Generator, dimensions of, 252
Generator, Dowson, 177
Generator, firing the, 205, 256
Generator, hot operation of, 252
Generator of suction producer, 205
Generator, operation of, 251
Generator, Pierson, 215
Generator, Pintsch, 207
Generator, Taylor, 207
Generator, Wiedenfeld, 207
Generator, Winterthur, 207
Generator with internal vaporizer, 206
Generators, blowing, 169
Generators, pressure, 169, 177
Governor, ball, 52, 53
Governor, care during operation, 131
Governor, hit-and-miss, 52, 54
Governor, inertia, 53
Governor, sensitiveness of, 52
Governors, 53
Governors, adjustment of, 124
Governors, care of, 123
Governors, centrifugal, 56
Governors, centrifugal, with hit-and-miss regulation, 55
Governors for oil-engines, 265
Governors for producer-gas engines, 161
Governors, hit-and-miss, 54
Governors, variable admission, 56
Grate, Bénier's, 216
Grate of generator-lining, 214
Grate, Kiderlen, 216
Grate, Pintsch, 216
Grate, Wiedenfeld, 216
H
Heater, air, 238
Hit-and-miss regulation (see Governors)
Holders, gas, 247
Hopper, Bollinckx, 225
Hopper, Deutz, 225
Hopper for generator, 224
Hopper, removable feed, 225
Hopper, Taylor, 225
Hopper, Wiedenfeld, 225
Hopper, Winterthur, 225
Horse-power, definition of, 60
Horse-power, determination of, 61
Horse-power (see also Power)
Hot tubes (see Tubes)
Hydrocarbons, volatile, for engine fuel, 264
I
Ignition, 27, 122
Ignition, adjustment of, 144
Ignition by battery and coil, 31
Ignition by magneto, 33
Ignition, curing defects of electric, 145
Ignition, defective, 152
Ignition, disadvantages of belated, 28
Ignition, disadvantages of premature, 28
Ignition, effect of lost motion, 146
Ignition, effect of mixture composition on, 28
Ignition, effect of temperature of flame on, 28
Ignition, effect of water on, 136
Ignition, electric, 30, 139
Ignition, electric, regulation of, 145
Ignition, faulty, 143
Ignition for high-pressure engines, 35
Ignition, hot-tube, 159
Ignition, imperfect, 137
Ignition, objections to electric, 31
Ignition of producer-gas, 160
Ignition, premature, 139, 142
Ignition, premature, in high-pressure engines, 158
Ignition, prevention of, by faulty compression, 134
Ignition, proper timing of, 27
Ignition, spontaneous, 140, 159
Ignition, tests prior to starting engine, 129
Ignition-tubes (see Tubes)
Incrustation of water-jacket, 98, 148
Incrustation, prevention of, 107
Incrustations, 255
Indicators, 285
Indicator-records, 127
Induction-coil, 32
Installation, laws governing gas-engine, 86
J
Joints, 125
Joints, care of, 124
L
Laming mass, 246
Laws governing gas-engines, 86
Leakage of pipes, 69
Lift-valve for charging-box, 223
Lignite in producers, 188
Lining, refractory, 211
Lining, support for generator, 214
Loads, consumption at half and full, 62
Location of engine, 68
Lubricate (see Oils)
Lubricating-pumps, 115
Lubrication, 111, 121
Lubrication, difficulties entailed by, 119
Lubrication, faulty, 149
Lubrication of crank-shaft, 117
Lubrication of high-power engine, 116
Lubrication of valve-stem, 119
Lubricator, cotton-waste, 117
Lubricators, automatic, 113
Lubricators, disconnection of, when stopping engine, 132
Lubricators, examination of, before starting, 129
Lubricators, feed of, 121
Lubricators, revolving-ring, 118
Lubricators, sight-feed, 118
Lubricators, types of, 113
M
Magneto, adaptability for producer-gas, 35
Magneto, control of, 38
Magneto, efficiency of, 34
Magneto-igniter, construction of, 35
Magneto ignition, 33
Magneto ignition, precautions to be taken, 34
Magneto, inspection of, before starting engine, 129
Magneto, mechanical control of, 33
Magneto, operation of, 33
Magneto, regulation of, 37
Maintenance of plants, 295
Manograph, 269
Mass, Laming, 246
Meters, capacity of, 70
Meters, dry, 72
Meters, evaporation in wet, 70
Meters, falsification of records, 70
Meters, inclination of, 71
Meters, size of, 71
Misfire, 137
Mixture, effect of high compression in, 155
Mixture, effect of high pressure on, 156
Mixture, governing by varying the, 161-164
Mixture, poorness of, 143
Mixture, pressure of, 26
Mixture-valve, necessity of independence of operation of, 27
Mortar for foundation, 87
Motion, lost, 146
Muffler for exhaust, 86, 94
N
Naphthalene in gas-pipes, 70
Noises, cause of, 92
Noises of exhaust, 94
O
Oilers (see Lubricators)
Oiling (see Lubrication)
Oil, addition of sulphur to, 147
Oil, cylinder, 149
Oil-engines, 264, 265
Oil-engines, governing, 265
Oil-engines, speed of, 264
Oil-engines, writers on, 266
Oil for engine fuel, 264
Oil, freezing of, 150
Oil-guard for fly-wheel, 120
Oil-lamp, 266
Oil, prevention of spreading on fly-wheel, 120
Oil-pumps, 115, 226
Oil, quality of, 150
Oil, splashing of, 119
Oil-tank, 266
Oils, how tested, 112
Oils, mineral for lubrication, 112
Oils, purification of, 113
Oils, quality of, 112
Oils, requisites of, 112
Operation, steadiness of, 52
Otto cycle, 21
Overheating, 152
Overheating, prevention of, 147
P
Pacini treatment, 171
Peat in producers, 188
Perturbations, 134
Petrol (see Oil)
Pipe-hangers, 86
Pipes, 69
Pipes, cross-section of, 70
Pipes, disposition of, 77
Pipes, escape, 228
Pipes, exposure to cold, 69
Pipes for exhaust, 83
Pipes for producer-gas, 249
Pipes for water-tanks, 102, 103, 105
Pipes, hanging of, 86
Pipes, insulation from foundations and walls, 94
Pipes, leakage of, 69
Pipes, minimum diameter of branch, 81
Pipes, proper size of, 70
Piston, 39, 122
Piston, avoidance of insertions or projections, 39
Piston, cleaning of, 141
Piston, curved faces inadvisable, 39
Piston, direct connection with crank-shaft, 43
Piston, finish of, 41
Piston, importance of, 111
Piston, leakage of, 136
Piston, overheating of, 148
Piston, position of, in starting, 130
Piston, rear face of, 39
Piston-pin, construction of bearing at, 40
Piston-pin, location of, 41
Piston-pin, locking of, 40
Piston-pin, lubrication of, 113
Piston-pin, material of, 40, 51
Piston-pin, strength of, 40
Piston-rings, fouling of, 149
Piston-rings, material of, 41
Piston-rings, number of, 41
Piston-rod, effect of premature explosion on, 30
Piston-wear, 40
Poisoning, carbon monoxide, 170
Porcelain of spark-plug, 32
Power, definition of, 60
Power, measuring engine, 285
Power, "Nominal," 61
Precautions to be taken in starting, 128
Pressure, back, to exhaust, 151
Pressure-generators, 169, 177
Pressure in producer-gas engines, 160
Pressure-lubricators, 114
Pressure-producers, 174
Pressure-regulator, bell as, 187
Pressure-regulators, 77
Pressure-regulators, their construction, 78
Pressures, high, in producer-gas engines, 154
Preheaters, 229
Producer, assembling, 253
Producer, Bénier, 216
Producer, Benz, 228, 239, 240
Producer, Bollinckx, 206, 220, 225, 228, 234, 239
Producer, Chavanon, 229
Producer, cleaning of, 261
Producer, Dawson, 174
Producer, Deschamps, 198
Producer, Deutz, 206, 220, 224, 225, 228, 229, 240
Producer, Deutz, 231, 232
Producer, Deutz lignite, 188
Producer, Duff, 195
Producer, Fangé-Chavanon, 198
Producer, Fichet-Heurty, 240, 245
Producer, Gardie, 183
Producer-gas, 153
Producer-gas, 165
Producer-gas as a furnace fuel, 177
Producer-gas, calorific value of, 200
Producer-gas, composition of, 166
Producer-gas plants, tests of, 297
Producer-gas, writers on, 154
Producer, general arrangement of suction, 204
Producer, Goebels, 206
Producer, Hille, 206, 239
Producer, Kiderlen, 206
Producer, Kiderlen, 216
Producer, Koerting, 232
Producer, Lencauchez, 212, 214
Producer, Phoenix, 217
Producer, Pierson, 224, 229
Producer, Pintsch, 206, 216, 224, 231, 232, 239, 245, 248
Producer, Riché, 168, 190, 193, 195, 216
Producer (see also Generator)
Producer, stoppage of, 261
Producer, Taylor, 206, 214, 225, 231, 232
Producer, test by smoke, 254
Producer, test of Deutz, 298
Producer, test of Dowson, 296
Producer, tests of Winterthur, 297
Producer, Thwaite, 195
Producer, Wiedenfeld, 206, 216, 220, 225, 234, 239
Producer, Winterthur, 225, 228, 236
Producers, advantages of suction, 199
Producers, combustion, 193
Producers, conditions of perfect operation, 251
Producers, consumption of suction, 200
Producers, distilling, 190
Producers, efficiency of, 201
Producers, efficiency of lignite, 190
Producers, efficiency of wood, 194
Producers, lignite, 188
Producers, maintenance of, 254
Producers, peat, 188
Producers, pressure, 174
Producers, self-reducing, 193
Producers, specifications of, 281
Producers, suction, 199
Producers, suction (see also Suction-producers)
Producers, tests of, 297
Producers with external vaporizers, 206
Production of gas, 173
Pulley, disconnection of, in stopping engine, 132
Pump, circulating with by-pass, 106
Purifier, fiber, 185
Purifier, Fichet-Heurtey, 245
Purifier, material for, 245
Purifier, moss, 185
Purifier, Pintsch, 245
Purifier, sawdust, 185
Purifiers for gas, 184
Purifiers for producer-gas, 244
R
Recorder, analysis of inertia of explosion, 277
Recorder, explosion, for industrial engines, 285
Recorder, the continuous explosion, 269
Records of engines, 284
Records of explosions, 288
Records, indicator, 127
Regrinding of valves, 122
Regularity, cyclic, 48, 53
Remagnetization of magnetos, 33
Resuscitation after asphyxiation, 171
Retort, cleaning of, 225
Retort of producer, 190
Retort, support, 214
Revolutions, variations in number of, 52
Rollers, 51
Running, steadiness of, 52
S
Sand for foundation, 87
Sawdust in producers, 193
Scavenging, 142, 155
Scrubber, 189, 199
Scrubber, combined with gas-holder, 186
Scrubber for producer-gas, 240
Scrubber, size of, 253
Selection of gas-engine, 21
Shavings in producers, 193
Slide-valve for charging-box, 223
Slide-valve, its disadvantages, 23
Sluice-valves, 101
Smoke from cylinder, 149
Spark-plug, 32
Specifications of engines, 281
Specifications of producers, 281
Speed, how to increase, 124
Speed of oil-engines, 264
Speed of volatile hydrocarbon engines, 264
Speed, variation of, with load, 52
Spokes of fly-wheels, 49
Spring for valves (see Valves)
Springs, selection of, for explosion-recorder, 277
Starter, Tangye, 65
Starting an engine, 128
Starting, automatic, 63, 130
Starting by compressed air, 64
Starting by hand, 63
Starting by hand-pumps, 64
Starting, difficulties in, 134
Starting, how accomplished, 66
Starting of producer-gas engine, 258
Steadiness, 52
Steam-engine, cost of installation, 19
Steam-engine, cost of operation, 19
Stoppage of producer, 261
Stopping the engine, 132
Stops, sudden, 151
Straw in producers, 193, 254
Street-gas, 165
Suction, determination of resistance to, 274
Suction, noises caused by, 141
Suction of air, 81
Suction period, 21
Suction-producer, general arrangement of, 204
Suction-producers, 199
Suction-producers, advantages of, 199
Suction-producers, efficiency of, 201
Suction-valve, leakage of, 142
Super-heater, Winterthur, 236
Sylvester treatment, 171
T
Tanks, connection of, 105
Tanks, design of, 103
Tanks, location of, 102
Tanks for water-jacket, how mounted, 101
Tar in producer-plants, 200
Tar, removal of, 250
Tar (see also Scrubber, Purifier, etc.)
Taylor, A., 199
Terminals of magneto apparatus, 34
Tests of gas-engine plants, 283
Tests of high-speed engines, 268
Tests of producer-gas engines, 297
Thrust-bearings, 51
Tongue, traction of, in asphyxiation cases, 172
Tower, washer, 244
Town-gas (see Street-gas)
Tree branches for coolers, 107
Trepidations, 92
Tube, gas-supply pipe of incandescent, 77
Tube, incandescent, 27
Tube, incandescent, adjustment of, 144
Tube, incandescent, breakage of, 137
Tube, incandescent, danger of breaking, 131
Tube, incandescent, how started, 128
Tube, incandescent, leakage of, 138
Tubes as vaporizers, 231
Tubes, incandescent, 28, 159
Tubes, incandescent, valved, 29
Tubes, use of special valves with incandescent, 29
Tubes, valveless ignition, 28
V
Valve-chests, 124
Valve mechanism, slide, 23
Valve-regrinding, 122, 135
Valve-stem lubrication, 119
Valves, 122
Valves, accessibility of, 25
Valves, cooling of, 25
Valves, cooling of, in high-pressure engines, 156
Valves, defective operation of, 135
Valves, free, 27
Valves, mechanical control of, 27
Valves, modern, 24
Valves, necessity of cleanliness, 25
Valves, regulation of, before starting, 129
Valves, requisites of, 25
Valves, retardation in action of, 146
Vaporizer, Bollinckx, 234
Vaporizer, Chavanon, 229, 234
Vaporizer, Deutz, 231, 232, 229, 225
Vaporizer, Field, 233
Vaporizer, internal, 206
Vaporizer, Koerting, 232
Vaporizer, maintenance of, 255
Vaporizer, operation of, 234
Vaporizer, Pierson, 229
Vaporizer, Pintsch, 231, 232
Vaporizer-preheaters, 229
Vaporizer, size of, 253
Vaporizer, Taylor, 231, 232
Vaporizer, Wiedenfeld, 225, 234
Vaporizers, external, 206, 230
Vaporizers, internal, 229
Vaporizers, partition, 234
Vaporizers, regulation of, 236
Vaporizers, tubular, 231
Ventilation in engine-room, 69
Vibration, 89
Vibration of air, 92
Vibration, prevention of, 89, 90
W
Water circulation, 98, 107, 125
Water circulation by pump, 107
Water circulation, care during operation, 132
Water circulation, how effected, 102
Water circulation, prevention of freezing, 133
Water-coolers, 106
Water-coolers, size of, 109
Water for circulation, 99
Water for producer-gas engines, 203
Water-gas, 153, 167
Water in cylinder, 136
Water in exhaust, 136
Water-jacket, 41, 98, 125, 157
Water-jacket, incrustation of, 148
Water-jacket, outlet of, 98
Water-jacket, prevention of incrustation, 107
Water-pipe, 102
Water, purification of, for circulation, 98
Water, running, for jacket, 98
Water-tanks, 101
Water-tanks, connection of, 103, 105
Water-tanks, design of, 103
Water-tanks, location of, 102
Washer, Benz, 240
Washer, combined with gas-holder, 186
Washer, Deutz, 240
Washer, Fichet-Heurtey, 240
Washer for gas, 199
Washer for producer-gas, 240
Washer, maintenance of, 256
Washer, material employed in, 242
Washer, Winterthur, 240
Washers, 184
Wear, premature, 146
Witz apparatus, 284
Wood as fuel, 254
Wood, calorific value, 194
Wood-gas, 153, 168
Wood-gas, purification of, 195
Wood in producers, 190, 192, 193
Work, definition of effective, 60
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Transcriber's Notes
Blank pages have been deleted. Illustrations may have been moved.
The following publishers' errors and inconsistencies were corrected
as noted:
Fig. 59: "Thermo-siphon" was "Thermo-syphon".
Page viii: "If ignition occurs too" was "If ignition occur too"
Page 18: "smoke-stack" was "smokestack".
Page 19: Split illustrations and titled one "Fig. 1a".
Page 70: Rearranged table.
Page 83: "sawdust" was "saw-dust".
Page 83: "9 feet by 15 feet" was "9 feet by 75 feet" (math error).
Page 92: "crank-shaft" was "crankshaft".
Page 92: "fly-wheel" was "flywheel".
Page 105: "thermo-siphons" was "thermo-syphons".
Page 128: "gas-pipe" was "gaspipe".
Page 174, 200, 203(2 places): "horse-power" was "horsepower".
Page 205: "super-heater" was "superheater".
Page 220: "air-tight" was "airtight".
Page 239: "superheated" was "super-heated".
Page 255: "potash" was "postash".
Page 264: "59 degrees F." was "490 degrees F." (conversion error).
Page 269: "drum p''" was "drum p'".
Page 291: Fig. 150 has been split into two figures.
Page 297: "Stroke" was "Stoke".
Page 300: "Ziehe was "Zi he".
Page 301: "Messrs." was "Me rs.".
Page 323: "FOR" was "FOF".
Index: "Fire-box" was "Firebox".
Index: "Governors, ... hit-and-miss" was "hit-and miss".
Index: "Piston ... crank-shaft" was "crankshaft".
Advertisements: Chapter header "ADVERTISEMENTS" added.
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*** End of this LibraryBlog Digital Book "Gas-Engines and Producer-Gas Plants - A Practice Treatise Setting Forth the Principles of Gas-Engines and Producer Design, the Selection and Installation of an Engine, Conditions of Perfect Operation, Producer-Gas Engines and Their Possibilities, the Care of Gas-Engines and Producer-Gas Plants, with a Chapter on Volatile Hydrocarbon and Oil Engines" ***
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