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Title: Gas and Petroleum Engines
Author: Gaffigny, Henry de
Language: English
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*** Start of this LibraryBlog Digital Book "Gas and Petroleum Engines" ***
Electro-Mechanical Series
GAS AND PETROLEUM
ENGINES
_TRANSLATED AND ADAPTED FROM THE FRENCH
OF HENRY DE GRAFFIGNY_
AND EDITED BY
A. G. ELLIOTT, B.Sc.
LONDON
WHITTAKER AND CO.
2 WHITE HART STREET, PATERNOSTER SQUARE
NEW YORK: 66 FIFTH AVENUE
1898
RICHARD CLAY & SONS, LIMITED,
LONDON & BUNGAY.
PREFACE
The great and increasing importance of internal combustion motors
is perhaps scarcely realized by the general public. For industrial
purposes they have for many years been steadily gaining favour, and now
hold an assured position. It is only in the last few years, however,
that we have begun to recognize the drawbacks of horse-drawn vehicles,
and the immense advantage gained by propelling them mechanically.
The suitability of oil engines for the purpose has awakened a
widespread interest in them. The Editor therefore hopes that this
little volume will be especially welcome to non-technical readers who
like to keep ahead of the times in matters of such universal importance.
One chapter deals exclusively with the theory of the gas engine, but
the non-technical mind should have no fear, for mathematics have been
as far as possible avoided. It may also serve to dispel wrongful
notions concerning the practical limits of the efficiency of gas
engines which, we are sorry to say, exist even among persons living in
a scientific atmosphere.
We have not spoken in the text of the extremely interesting results
obtained from the oil engine invented by Herr Diesel of Berlin, because
it has not yet been proved that this motor is strictly practicable.
If, however, it turns out to be a commercial success, we hope to add a
description of it at some future date.
_May 1898._
CONTENTS
CHAP. PAGE
I. HISTORY OF THE GAS ENGINE 1
II. THE WORKING PRINCIPLES OF THE GAS ENGINE 13
III. DESCRIPTION OF EXISTING GAS ENGINES 23
IV. CARBURETTED AIR ENGINE 67
V. PETROLEUM ENGINES 77
VI. GAS GENERATING PLANT 103
VII. ENGINES FOR USE WITH POOR GASES 121
VIII. MAINTENANCE OF GAS AND OIL ENGINES 130
INDEX 139
LIST OF ILLUSTRATIONS
FIG. PAGE
1. Early Lenoir Motor 24
2. Bisschop Motor 25
3. Bénier Motor 26
4. Forest Motor 27
5. Plan of Dugald-Clerk Engine 30
6. Benz Gas Engine 32
7. Otto Gas Engine 36
8. ” ” ” (vertical type) 38
9. Lenoir Gas Engine 39
10. Koerting-Boulet Motor 40
11. Niel Gas Engine 44
12. Martini Motor 45
13. Lablin Three-cylinder Motor 46
14. Crossley Gas Engine (X type) 47
15. Crossley Gas Engine 48
16. Pygmée Gas Engine 50
17. National Gas Engine 52
18-19. De Forest Gas Engines 54
20. De Forest Double Piston Motor 54
21. Diagram of Atkinson Mechanism 58
22. Section of Charon Motor 58
23. Charon Motor 59
24. Roger Vertical Gas Engine 60
25. Vertical Gas Engine of the Compagnie Parisienne du Gaz 62
26. Maurice Motor (de Cadiot) 64
27. Durand Carburetted Air Motor 72
28. De Dion Motor Tricycle 75
29. Campbell Oil Engine 81
30. Section of Grob Motor 83
31. Exterior View of Grob Oil Motor 84
32. Capitaine Gas Engine 86
33. Horizontal “Balance” Motor (Capitaine) 87
34. Capitaine Two-cylinder Gas Engine 88
35. Hornsby-Akroyd Oil Engine (section) 91
36. Exterior View of Hornsby-Akroyd Oil Engine 92
37-38. Sections of Ragot Petroleum Engine 94
39. Carburator of Ragot Oil Engine 96
40. Crossley-Holt Petroleum Engine 99
41-42. Griffin Oil Engine 101
43. Dowson Gas-producing Plant 108
44. Taylor Gas-producing Plant 114
45. Simplex Gas Engine (Delamare-Deboutteville) 123
46-47. Governor of Simplex Engine 123
48. Combined Simplex Engine and Buire-Lencauchez
Gas-producer 124
49-50. Bénier Engine and Gas Plant (sectional plan and
elevation) _face p._ 127
51. Section of Simplex Gas-producing Plant 135
52. Agricultural Oil Locomotive 137
GAS AND PETROLEUM ENGINES
CHAPTER I
HISTORY OF THE GAS ENGINE
The history of gas engines may be said to date from a time when coal
gas and petroleum were unknown. This statement appears at first
somewhat paradoxical, but it arises from the fact that the first
gas engine, invented by the Abbé de Hautefeuille in 1678, used the
explosive force of gunpowder as a motive power. The principle of this
early gas engine, however, is exactly the same as that of its more
modern brothers; that is, the work is done by the expansion and cooling
of a volume of heated gas, the only difference being that gunpowder
contains within its grains the oxygen necessary for its combustion,
while coal gas or petroleum require admixture with the oxygen of the
air before they can be made to explode.
Two years after the Abbé de Hautefeuille had made public his idea, in
a memoir entitled _A Method of Raising Water by means of Gunpowder_,
the Dutch savant Huyghens published a similar work, describing an
apparatus consisting of a cylinder with two leather exhaust pipes,
forming valves; to the bottom of the cylinder was screwed a small box
in which gunpowder was to be ignited. The effect of the explosion was
to drive out a large quantity of heated gas through the valves, which
closed again when it had passed. The gas remaining in the cylinder soon
cooled down, so that the pressure within it fell below that of the
surrounding atmosphere, and caused the piston to be forced down by the
excess of atmospheric pressure.
This operation was certainly very crude, and, as might have been
expected, scarcely came up to the expectations of its inventor. The
idea was, however, not allowed to rest here, and Papin set himself
to find out some better agent to replace the gunpowder, whose action
was uncertain and, to say the least of it, brutal. The result of his
experiments pointed clearly to the condensation of steam as being the
most suitable method of producing a space filled with a gas at a lower
pressure than that of the atmosphere, and many inventors, following in
his footsteps, adopted this process for working pumping engines. In
consequence of the great success of the steam engine, which was due to
the genius of Watt and his successors, the idea of using combustion to
act directly as a motive power was lost sight of for a great number
of years, and it was not till the year 1791 that any suggestion was
made which was an improvement on the engines of De Hautefeuille and
Huyghens. The inventor, this time an Englishman, by name John Barber,
specified in his patent, in somewhat laconic language, the use of a
mixture of a hydrocarbon gas and air, and its explosion in a vessel
which he termed an exploder. Several years later, in 1794, Robert
Street, also an Englishman, took out a patent for the production of
an explosive vapour by means of a liquid and air, ignited by a flame
in a suitable cylinder so as to drive machinery and pumping engines.
Petroleum or any other inflammable liquid was allowed to drip on to
the heated bottom of a cylinder so as to be vaporized and drive up the
piston.
Philip Lebon, of Brachay, the creator of the coal gas industry in
France, took out a patent in 1799, setting forth very clearly the
principle and construction of an engine using the explosion of coal
gas as its motive power. Lebon, in fact, devised his gas-producing
plant with the intention of only using the coal gas in his gas engine,
lighting by its means being quite an afterthought. In a second patent
two years afterwards he describes a more perfect apparatus, in which
a pump is provided for compressing the mixture of coal gas air, and
also an electric machine worked by the engine itself for igniting the
compressed mixture. Unfortunately, the career of this fertile inventor
came to an abrupt end by his assassination in 1804. It is highly
probable, that if he had lived gas engines would have come into general
use at the beginning of the century instead of nearly sixty years later.
From 1799 up till the year 1860, in which the first really practical
gas engine made its appearance, several schemes were put forward,
some of them not lacking in ingenuity, of which the most interesting
were due to Welman, Wright, Johnston, and Barnett. Wright’s machine
was particularly well thought out and constructed. The double-acting
cylinder was placed in a vertical position and the gases were ignited
by a gas-jet. A centrifugal governor regulated the pumps which
compressed the explosive mixture in the cylinder, and at the same
time varied the composition of the explosive mixture so as to always
be proportional to the work which was required to be done. When we
come to consider that this engine was brought out in the year 1833,
it is wonderful that it did not meet with greater success, but this
was probably due to the fact that the steam engine was at that period
coming greatly into favour, and for the time being completely eclipsed
all other forms of motive power.
About this time a double-acting gas engine was devised by Johnston,
using pure hydrogen and oxygen as the explosive mixture, in the
proportion of two volumes of hydrogen to one of oxygen. After the
explosion and driving forward of the piston, the combined gases being
cooled were precipitated as water, and a partial vacuum obtained which
was used during the return stroke. This idea was a highly ingenious
one, but failed owing to the high price of hydrogen and oxygen, but
perhaps some day, when these obstacles have been removed, this idea may
once more be taken up.
In 1838 William Barnett took out a patent for an engine based on the
same principle as that of Lebon. Two pumps compressed separately the
combustible gas and the air and forced the mixture under pressure
into the cylinder. The explosion was caused by a small gas-jet,
communication between it and the cylinder being set up at the right
moment by a revolving valve. The gas-jet was situated in the valve
itself, and was so arranged that during half a revolution it was turned
towards the outside, and was then lighted by a second jet, and during
the remainder of the revolution it communicated with the interior of
the cylinder and ignited the explosive mixture. This was the first gas
motor in which the ignition was from the outside, and in which the
explosive gases were at the same time under pressure. In most modern
gases the same result is obtained, but the original and rather crude
method of obtaining it has of course been much modified and improved.
During the next few years several patents were taken out relating to
the same subject. In 1844 John Reynolds suggested using a battery which
should white-heat a platinum wire in order to ignite the gases, the
ignition taking place at the required moment by means of an automatic
switch closing the battery circuit.
In 1850 Stéphard recommended a magneto-electric machine driven by the
engine itself instead of the primary battery.
Barsanti and Matteucci described in 1857 an atmospheric motor, their
arrangement of the parts being afterwards adopted by Otto and Langen.
A Bunsen cell supplied current to a De la Rive multiplier, causing a
stream of sparks to pass between two fine points situated within the
combustible mixture. In 1858 and 1859 Degrand explained in two patents
a gas engine in which the gases were compressed in the cylinder itself.
Owing to mechanical difficulties his machine was impracticable, but
the idea forms an important step in the history of gas engines.
In 1860, when the Lenoir motor appeared, no other existed which was
capable of regular and comparatively efficient work.
This machine, devised by Lenoir and constructed by Marinoni, had the
appearance of a double-acting horizontal steam engine. The explosive
mixture was ignited by an electric spark produced by a Ruhmkorff coil
and a primary battery. The machine ran smoothly and regularly and its
cost was moderate: among the advantages which it possessed at that time
over other forms of motive power, were the absence of a cumbrous boiler
and costly foundations, and the little care and attention necessary to
keep it in working order. So great was its success at the time, that
many people prophesied that the steam engine would soon become extinct.
In spite of this the Lenoir motor possessed many defects which
engineers were not slow to recognize. The enthusiasm which it had
aroused soon cooled down when it became known that for steam and gas
engines of equivalent power, the steam engine was considerably cheaper.
It required in fact 3000 litres of gas to produce one horse-power
hour, and to cool the cylinder of such a motor a volume of water was
necessary four times as great as that required to produce the steam of
a steam engine of equal power. Besides this, the machine had to be kept
flooded with lubricating oil. In consequence of these various defects
the Lenoir motor disappeared almost as rapidly as it had arisen. In
spite, however, of this apparent failure, it did some good, for it
once more directed the attention of inventors to the problem of a
practical gas engine.
Among the numerous patents taken out in consequence of this reaction,
the most important, filed in 1860 by M. Hugon, related to a gas
motor with a flame ignition, and in which the cylinder was cooled by
injecting into it a very fine spray of cold water. Experiments were
made upon it in 1876 by M. Tresca, and it was found that the motor
consumed 2445 litres of gas per horse-power hour. The temperature of
the exhaust gases was 180° C., while in the Lenoir motor they were
about 280° C. The diminution in temperature was probably due to the
better method of cooling the cylinder, and was found to be a great
improvement, the cylinder requiring much less lubrication. In 1861
Kinder and Kinsey somewhat modified the existing arrangements of the
parts, but otherwise their motor embodied no new ideas. Another motor
was devised about this time by Millon, once more bringing forward
Lebon’s idea of compressing the gases in the cylinder itself.
We have now reached the year 1862, which may be considered a memorable
one in the history of the gas engine, for it was in this year that
a patent was taken out by M. Beau de Rochas, setting forth from a
theoretical point of view the best working conditions for a gas engine.
During the forward stroke of the piston the explosive mixture was to
be drawn into the cylinder, during the return stroke this volume of
gas being compressed; at the dead point at the beginning of the second
forward stroke the explosion was to take place, driving the piston
forward, the gases being expelled during the second return stroke. The
whole principle will be seen to consist of four distinct operations,
forming what is known as the Otto cycle, for reasons which we will
presently explain.
The peculiar part of the patent was its purely theoretical explanation.
Whilst giving all the honour due to the inventor, and recognizing that
he fully understood what he was talking about, we must not forget that
there was nothing whatever in the patent indicating how the ideas
embodied therein might be carried into practice. No drawings were
appended to the text, explaining how the gases were to be ignited, or
how the exhausted gases were to escape; it contained nothing, in fact,
but the plain statement of the most efficient cycle of operations.
M. de Rochas did not construct a machine on this principle, and as he
omitted to pay his patent fee for the second year, the idea became
public property. For these reasons no attention was drawn to it
until ten years afterwards, when it came to light during some patent
litigation undertaken by Dr. Otto in 1878.
In 1867 at the International Exhibition at Paris a vertical atmospheric
motor was to be seen working, based on the primitive principle of
the gunpowder pump of De Hautefeuille. This machine was constructed
by two German engineers, Otto, and Langen of Deutz near Cologne, and
was a perfected form of the Barsanti and Matteucci motor invented ten
years previously. The explosion of the gases in the cylinder only
served to obtain a partial vacuum underneath the piston, which was
therefore forced down by the excess of atmospheric pressure above it.
This arrangement had one great advantage over the Lenoir and Hugon
motors, it only burnt 1350 litres of gas against their 2500 or 3000 per
horse-power hour, and consequently it rapidly came into favour, and the
lucky inventors were able to sell no less than 5000 motors in a few
years.
The motor itself was very rough and had many defects: the gear-wheels
rattled and made a furious noise, the igniting flame kept up a
continuous roar, and above the noise of clanking machinery the
explosion of the gases could be heard like a cannon going off; in fact,
no one could say that the ideal of domestic motors had been attained;
but as the motors constructed in 1872 only consumed 800 litres of gas
per horse-power hour, rendering power produced by this means cheaper
than steam, its success was assured in spite of the defects.
The success of these early attempts stimulated Dr. Otto to further
efforts, and in 1878 he brought out his famous gas engine, which
has earned a world-wide reputation by reason of its incontestable
merits. It was based on the principle explained in the De Rochas
patent which we have spoken of, but Otto undoubtedly knew nothing of
this patent, and his invention was perfectly independent and fresh
as far as the world was concerned. The enormous success to which the
new motor attained naturally led to many unscrupulous imitations,
and legal proceedings were instituted in England and France. In this
country the validity of Otto’s patents were upheld, but in France the
De Rochas patent was for the first time brought to light, and the
verdict went against him. This verdict has been attributed to malice
on the part of the French judges, for at that time the French nation
would have probably conceded as little as possible to a German; but
whether that be so or not, we are indebted to Dr. Otto for having made
the gas motor a really practical engine after many years of patient
experiment and study. At the same time as the Otto engine three other
motors appeared at the Exhibition of 1878: the Bisschop gas engine
constructed by Mignon and Rouart, and two others by Simon and Ravel.
The Simon motor, of which only a very small number were constructed,
was very interesting from the economy point of view. The explosion of
the mixed gas was not allowed to take place suddenly, but proceeded
gradually as the piston moved forward, and the heat which in the Otto
engine is carried off by the water jacket, was made use of, as in the
old Hugon motor, to vaporize a spray of cold water, and thus adding
to the total force behind the piston. This process was so effective,
that on shutting off the supply of gas the motor continued to revolve
for a considerable period by means of the vaporized water. About 800
litres of gas were consumed and four litres of water per horse-power
hour, a very good result. The Ravel motor used even less, about 500
or 600 litres only, but owing to the bad arrangement of the parts the
mechanical efficiency was very low.
Such was the position of the gas engine in 1878. A standard type had
been adopted and worked excellently. It merely required to be perfected
in detail and simplified in order to make it still more economic, and
capable of holding its own against its powerful rival the steam engine.
Many modifications of the Otto gas engine have appeared since that
date, among the most important being those by—Dugald-Clerk, in 1879, a
motor which compressed and exploded the gases once in every revolution;
Lenoir, in 1833, the cylinder being cooled by currents of air; and in
the same year appeared the Griffin gas engine, with a complete cycle of
operations every three revolutions.
At the Antwerp Exhibition of 1884 several new types appeared, among
them the Stockport engine by Andrews, and others by Koerting, Bénier,
and Benz. In the same year a very good motor appeared, called the
_Simplex_, constructed by Powell of Rouen (now Matter et Cie.),
according to the plans of MM. Delamare-Deboutteville and L. Malandin.
This engine was the subject of some litigation, the Otto people
considering it an infringement of their patents, but the improvements
in the design of the working part and the novelty of several details
being apparent, the _Simplex_ gas engine gained the day. In 1885,
after the appearance of the _Simplex_ and the new Lenoir motors, most
makers made use of the Otto cycle, and about this time appeared the
first carburetted gas motors, that is to say, using volatile spirits
and products of petroleum for their source of energy. Such motors have
been devised by Tenting, Koerting-Boulet, Diedrichs, Gotendorf, Noël,
Forest, Ragot, Rollason, Atkinson, etc.
At the International Exhibition in 1889 there were thirty-one
exhibitors and fifty-three machines, with a total power of 1000
horse-power. All except four used the Otto cycle, and for the first
time a motor was to be seen using a gas other than coal gas, namely a
poor gas produced at a very low cost in a special gas-producing plant.
The motor itself was of the single-cylinder _Simplex_ type of 100
horse-power, opening up a new horizon to inventors, and demonstrating
the possibility of using large gas engines supplied with poor gas.
This short history of the gas engine will be seen to consist of three
distinct periods—firstly, from 1700 up to 1860, during which time many
inventors tried and failed to produce anything practical; secondly,
from 1860 to 1889, during which the gas engine became something
really practical; thirdly, from 1889 up to the present date. In
this period gas engines have grown in size, and large units of 200
to 400 horse-power are now constructed, worked by poor gas produced
from special gas plants, and enabling the gas engine to successfully
hold its own against the steam engine, which it may one day entirely
supplant.
CHAPTER II
THE WORKING PRINCIPLES OF THE GAS ENGINE
Assuming that the earth once formed part of the sun, the whole of the
energy at our command for commercial purposes can be traced back to
the sun as source. This energy we have received from it in the form
of heat, and under certain circumstances the heat is stored up in a
latent form in chemical compounds such as coal, petroleum, etc. With
our present knowledge it is exceedingly difficult to extract the latent
energy from coal and petroleum in any other form but heat, and in order
to do so to our greater benefit, it is necessary to study the laws
of heat and heat engines. The law which states the relation between
heat and other forms of energy such as electricity, mechanical work,
is called the principle of the conservation of energy, and forms the
first law of thermodynamics. It is enunciated as follows. Whenever a
body does work or has work done upon it, there is a disappearance or an
appearance of heat, and the amount of heat thus produced or used up is
always exactly proportional to the work which is done. The ratio of the
amount of work which a certain quantity of heat can produce has been
therefore termed the mechanical equivalent of heat.
It has been found by experiment, taking the calorie (C.G.S. unit)
as the unit of heat and the kilogramme metre as the unit of work or
energy, that the mechanical equivalent is 424. That is to say, the heat
necessary to raise the temperature of one kilogramme of pure water at
0° Centigrade through 1° C. (the calorie) is equal to the work done in
raising 424 kilogrammes to a height of one metre.
In nearly all commercial heat engines the heat is converted into the
energy of movement (kinetic energy) by using some body such as water
vapour, gas, or air as an intermediary agent. We do not, however,
know at present how to transform heat into mechanical work without
losing a greater part of it in the process. Even in the most perfect
heat engines at least 70% of the heat is lost, only about 30% being
converted into mechanical energy. This is as yet the most perfect
result which engineers have obtained even with the most elaborate
precautions. As a rule the loss is greater; for instance, many good
machines which we consider efficient burn one kilogramme of coal,
giving out 8000 calories, equivalent to 3,400,000 kilogramme-metres,
and transform only about 400,000 kilogramme-metres into work, the rest,
forming nearly 80%, is lost.
It has been the aim of engineers for many years past to reduce this
extravagant waste by every means possible, and the very fact that such
a waste exists, clearly shows that our vaunted engines are hopelessly
wrong in their principle. There is reason, however, to hope that one
day we may, by converting the chemical energy of coal direct into
electricity, and thereby avoiding the wasteful heat altogether, reclaim
at least 80% of the latent energy which nature has so bountifully
supplied to us.
It can be shown mathematically that the ratio of the quantity of heat
actually converted into work to the total heat used by an engine
depends on the temperature at which the heat was absorbed and on the
temperature at which the waste heat was discharged. For instance, in
a gas engine the efficiency depends on the temperature of the gases
directly after the explosion, and on the temperature of the exhaust
gases after the work has been done. The exact relation is as follows:
the above stated ratio, which is called the theoretical or thermal
efficiency, is equal to the difference between the temperature of the
hot gases immediately after explosion, and the temperature of the
gases of the exhaust divided by the temperature of the hot gases after
explosion. This somewhat cumbrous statement may be expressed more
clearly in algebraic symbols—
W T_{2} - T_{1}
— = —————————————
H T_{2}
where W is the amount of work done by an engine supplied with a
quantity of heat, H, and T_{2} is the temperature of the heated gases
which expand doing work, and are thereby cooled to the temperature
T_{1}, at which they are exhausted.
It is therefore evident, that to make an engine work perfectly
efficiently we must obtain an amount of work from it exactly equivalent
to the heat put in. That is to say, W must equal H in the above
equation. We therefore have the efficiency of such a perfect engine
T_{2} - T_{1} W
= ————————————— = — = 1.
T_{2} H
It must not be forgotten that T_{2} and T_{1} are reckoned not in the
ordinary scales of temperature such as Fahrenheit and Centigrade, but
on the absolute scale, absolute zero being that temperature at which a
body has no molecular motion.
Calculations based upon various considerations point to the fact that
absolute zero corresponds to about -273° C.
We have just pointed out that in a perfectly efficient engine
T_{2} - T_{1}
= ————————————— = 1.
T_{2}
In order that this may be so, we must have T_{1} = 0, the absolute zero.
In practice it is impossible to make the temperature of the exhausted
gases as low as this, and so the only way to obtain more efficient
engines is to make T_{2} as large as possible, that is to say, the
initial temperature of the gases must be high.
It is, however, just as possible to turn all the heat supplied to a
heat engine into work as it is to use up all the energy of a waterfall
in a turbine, because the level from which the zero of the potential
of the energy water is measured is the centre of earth, which is as
inaccessible as absolute zero of temperature.
It therefore behoves us to make the ratio of the initial and final
temperatures of the gas which does work in a gas engine as large as
possible, and it is for this reason that gas engines can be made more
efficient than steam engines, for in the former a momentary initial
temperature of 1500° C. may be obtained by the combustion, whilst steam
at 200 lbs. on the square inch is at about ⅒th of that temperature.
There are practical difficulties which prevent higher initial
temperatures being used, residing chiefly in the fact that at 400° C.
iron is red-hot, so that any lubricant coming into contact with it is
decomposed and loses its lubricating properties. Even at 300° C. most
lubricating oils in contact with the air become oxidized and destroyed.
This difficulty of lubrication, by limiting the temperature, at the
same time limits the efficiency, and not till some new lubricant is
discovered which defies heat will there be much improvement in this
direction.
Even as it is, it is necessary to cool the sides of the vessel or
cylinder in which the gases expand, and in doing so we lose a great
deal of heat.
Hot-air engines using ordinary air as the expansible gas have been
devised from time to time, but they have not met with much success
owing to their weight and the large amount of space they take up,
neither are they as efficient as a good modern gas engine. We will not,
therefore, study the theory of hot-air engines, but further consider
the details of gas engines, whose superiority over all other heat
engines we think we have sufficiently pointed out.
It seems at the present date almost impossible to conceive anything
fresh in the cycle of operation of a motor using explosive gases,
so numerous and varied are the already existing types. All possible
combinations appear to have been considered, and even repeated, for in
many recent patents old ideas have once more been brought forward which
date back to the early attempts of Lebon, Barnett, Beau de Rochas. The
greater number of existing types are based in principle on two or three
fundamental ideas, and their improvement is rather to be found in their
mechanical design than in the conception of a new cycle.
This fact enables us to classify gas engines very much more easily,
because, apart from some perfection of detail, they fall naturally
into several groups, which will prevent the reader from losing his way
in what otherwise might be chaos. We shall therefore, in describing
individual engines later on in this book, follow a systematic course,
and arrange the different systems into four classes, which we shall
consider in turn.
Motors using (1) coal gas.
(2) carburetted gas.
(3) petroleum.
(4) water gases.
And in order to classify them according to the principles of their
cycle of operations, irrespective of their fuel, M. Witz places them in
four groups—
(1) Explosion of the gases without compression.
(2) Explosion of the gases with compression.
(3) Combustion of the gases with compression.
(4) Atmospheric motors.
The first group of this second classification is formed by motors
which have developed the idea conceived in 1860 by M. Lenoir. For the
first half of the forward stroke the piston draws in a mixture of gas
and air; the valves being then closed, and ignition taking place, the
explosion drives the piston to the end of the stroke. The return stroke
is made use of to expel the gases through the exhaust. Before igniting
the gases which have been drawn in they may be compressed either by a
separate pump, or in a chamber forming a continuation of the cylinder.
The arrangement is characteristic of the second group. This again can
be modified to form the third group, by allowing the gases to burn
under constant pressure throughout the stroke instead of violently
exploding at the commencement. Engines using this sort of progressive
combustion have been designed by Simon and Brayton.
Finally, in the fourth group the explosion is merely used for obtaining
a partial vacuum under the piston, and the work is done by the excess
of atmospheric pressure acting on its external surface. It is almost
unnecessary to state that this method has been completely abandoned,
and has been replaced by a sort of combination type, in which the
explosion is used in the forward stroke and atmospheric pressure in the
return stroke, such a motor as the Bisschop gas engine being therefore
practically double-acting.
The table on page 20, which we have borrowed from M. Witz’s very
complete work on gas engines, shows at a glance the cycle of operations
in the cylinders of the different types: they are arranged in parallel
columns, in order to make it more easy for the reader to compare the
operations undergone by the gases before and after their combustion.
It is necessary to subdivide the motors of the second group into three,
according as the cycle of operations is completed in one, two, or three
complete revolutions of the fly-wheel. Perhaps this subdivision is
somewhat unnecessary, because the employment of a second cylinder for
compressing the gases does not alter the character of the cycle, but
we think that it will make the classification clearer if we proceed in
this manner.
+----------------+----------------+----------------+-----------------+
| Group I. | Group II. | Group III. | Group IV. |
| Without | With | Combustion | Atmospheric. |
| compression. | compression. | and | |
| | | compression. | |
+----------------+----------------+----------------+-----------------+
| 1. Explosive | 1. Explosive | 1. Explosive | 1. Explosive |
| mixture enters | gases enter | mixture enters | mixture enters |
| the cylinder | the cylinder | the cylinder | the cylinder at |
| at atmospheric | at atmospheric | at atmospheric | atmospheric |
| pressure | pressure | pressure | pressure |
+----------------+----------------+----------------+-----------------+
| | 2. Compression | 2. Compression | |
| | of the gaseous | of the gaseous | |
| | mixture | mixture | |
+----------------+----------------+----------------+-----------------+
| 2. Explosion | 3. Explosion at| 3. Combustion | 2. Explosion at |
| at constant | constant | at constant | constant volume |
| volume | volume | pressure | |
+----------------+----------------+----------------+-----------------+
| 3. Expansion | 4. Expansion | | 3. Piston |
| of gases in | of gases | | driven back by |
| cylinder | | | the pressure of |
| | | | the atmosphere |
+----------------+----------------+----------------+-----------------+
| 4. Products of | 5. Products | 4. Products of | 4. Products of |
| combustion | of combustion | combustion | combustion |
| expelled from | expelled from | expelled from | expelled from |
| the cylinder | the cylinder | the cylinder | the cylinder |
+----------------+----------------+----------------+-----------------+
Group I.
Explosion without compression.
Lenoir
Kinder & Kinsey
Hugon
Ravel
Turner
Bénier
Parker
Hutchinson
Forest
Baker
Economic motor
Crown
Laviornery
Lentz
Group II.
Explosion with compression.
(1) _Two-cycle type._
Dugald-Clerk
Koerting-Lieckfeld
Wittig & Hees
Andrews (Stockport)
Benz
Ravel
Baldwin
Taylor (Midland)
Campbell
Bénier
(2) _Four-cycle type._
Millon
Otto
Linford
Crossley
Maxim
Martini
Lenoir
Simplex
Koerting-Boulet
Lombard
Durand
Daimler
Varchalouski
Atkinson
Tenting
Diedrichs
Adam
Ragot
Forest
Noël
Charon
Niel
Lablin
Poussant
Roger
Letombe
Lacoin
Cronan
Cadiot
Dürkopp
Brouhot
Levasseur
Fielding
Delahaye
Acmé
Cuinat
Group III.
Combustion with compression.
Brayton
Hoch
Simon, et fils
Livesay
Crowe
Gardie
Overmand
Group IV.
Atmospheric motors.
Otto & Langen
Bisschop
Gilles
Hallevell
Robson
François
Carburetted Air Engines.
Lenoir
Forest
Tenting
Daimler
Le Marcel (Cadiot)
Durand
De Dion-Bouton
Bollée
Pelloree
Le Pygmée
Klause
Oil Engines.
Brayton
Priestman
Ragot
Otto
Crossley-Holt
Niel (Atlas)
Hornsby-Akroyd
Grob-Capitaine
Merlin
Knight-Weyman
Griffin
Pinkney
Levasseur
Root
Rationnel
Dawson
The “Gnome”
On page 21 we give a table embracing all the best known types of gas
engines, which will also help to avoid the confusion arising from the
fact that some motors exist which belong to neither one nor another,
but are combinations of one or more groups. Such hybrid motors have
been devised amongst others by Schweizer and Siemens. In the former
the power of the explosion is used to compress a considerable volume
of air, which is then used for working a compressed air engine. In the
latter the gas heats a quantity of air which drives a hot-air motor.
In this table we have also, specially grouped apart, engines using
carburetted air (air which has been passed through a volatile spirit
such as benzoline) and petroleum. The list may be found somewhat
incomplete, as more than 250 gas engines have been devised and patented
in the last twenty-five years; but on the other hand, many of these
have been failures, and we have only included those motors which can
undoubtedly be considered commercial successes. These we will now
study.
CHAPTER III
DESCRIPTION OF EXISTING GAS ENGINES
_Early Lenoir engine_ (1860).—The motor (Fig. 1) resembled in external
appearance a horizontal double-acting steam engine. This design was in
great favour at that time, being copied from the steam engine, and was
to a certain extent suitable for use with an explosive gas instead of
steam. The valve chest is cylindrical and the valves themselves flat,
and work off two eccentrics; ignition is effected by an electric spark
from a Ruhmkorff coil, which passes through the gas in the cylinder
when the piston is commencing the second half of the forward stroke.
The exploded gases having done their work are driven out through the
exhaust in the return stroke, during which work is being done by a
similar explosion on the other side of the piston. A water jacket
prevents the cylinder walls from becoming overheated. This arrangement
is therefore double-acting, but a compression of the explosive gas
is not possible without the use of a second cylinder. It has been
abandoned because regularity of working is only obtained at the expense
of economy, and by using both sides of the piston as explosive
chambers it is found that the quantity of gas used is quite out of
proportion to the power developed.
[Illustration: FIG. 1.—Early Lenoir Motor (1860).]
_The Bisschop gas engine._—This motor (Fig. 2), based on a mixed
principle, uses the explosion to do work during the forward stroke,
and in the return the atmosphere exerts an excess of pressure on the
other side of the piston, as in the Otto and Langen atmospheric engine
which we have previously mentioned. In its time the Bisschop gas engine
obtained a great measure of success, but it has now almost completely
disappeared. It was, however, well thought out and constructed; the
cylinder was vertical, and relied on longitudinal corrugations, and the
air to keep it cool. Above the cylinder was placed a cylindrical guide;
a connecting rod and cross-head formed the attachment between the
piston rod and crank. The machine was principally constructed for small
workshops requiring small powers of from a quarter to one horse-power,
the cost of fuel for the half horse-power size being about one penny
per hour. The inventor received a prize of 1000 francs from the Société
d’Encouragement for the best small motor applicable to home industries.
[Illustration: FIG. 2.—Bisschop Motor.]
_François motor._—This type, which is now quite obsolete, was somewhat
similar in character to the last, but rather more complicated and
perfect. The crank shaft was not in a line with the cylinder, and was
connected by two connecting rods to the cross-head. Two fly-wheels
were placed one on each side of the cylinder and connected by toothed
wheels. The machine was on the whole too complicated, and although its
consumption of fuel was comparatively small and its speed constant, it
did not succeed in ousting the Bisschop motor from its position.
_Bénier gas engine._—This motor was the first conceived by the
inventors of the combined gas plant and engine which we will describe
later, and is extremely simple. This piston rod is connected to the
crank in a manner similar to a beam engine (Fig. 3). Both the admission
of the gases and their ignition are accomplished by a single spring
valve worked by a cam on the crank-shaft. The cylinder, which is
vertical and inverted, draws in the gases for half the forward stroke,
and then the valve, which has moved still further forward, brings a
flame opposite the admission port and ignites the mixture; a small
auxiliary gas-jet re-ignites the flame at each stroke. The gases
escape from the cylinder by a second port with a special valve and cam.
A water jacket for the cylinder is provided to carry off the surplus
heat. The consumption is high, being about 1400 litres per horse-power
hour, but owing to the extreme simplicity of the working parts this
motor met with a certain amount of success about 1880.
[Illustration: FIG. 3.—Bénier Motor.]
_Forest gas engine_ (Fig. 4).—This motor, being of the single-acting
type without compression, had at one time a considerable sale, being
used where only a small power was required. The rectilinear motion
is changed into a rotary one by means of an Oliver Evans beam, and
a connecting rod which returned alongside of the cylinder to the
crank-shaft and fly-wheel, which are placed at the back. Ignition is
obtained by a burner which is re-lit by a smaller one at each stroke,
and the cylinder is cooled not by a water jacket but by a helical
groove, which increases the surface. This helix is formed by a thin
plate cast on the cylinder. The fuel consumed was about 1400 litres
of gas per horse-power hour, which may be considered good for such an
engine.
[Illustration: FIG. 4.—Forest Motor.]
_Economic motor._—Constructed in New York. This engine is another
example of the early attempts to obtain economy without compression. As
a rule they were not constructed of more than half horse-power size,
and the general arrangement is ingenious, but rather more complicated
than those which we have so far spoken of. The piston rod is guided by
being attached to one end of a lever, connected with crank by means of
a vertical connecting rod. The cylinder is grooved, and cooled by the
circulation of the air round it, and constancy of speed is obtained by
a centrifugal governor, which cuts off the supply of gas when the speed
is too high. The engine seems to have given some very fair results.
_Lentz gas engine._—It is difficult to conceive a more simple mechanism
than is to be found in this motor. The supply of gas is drawn into the
cylinder by an open valve, and a gas flame situated in this admission
port ignites the explosive gases. The force of the explosion closes the
admission valve, and on the return stroke a cam opens an exhaust port
situated underneath the cylinder. There is no water jacket, but the
cylinder is formed of two parts connected together by a non-conducting
joint. In order to smooth down the jerk of the explosion the head of
the connecting rod slides in a groove, and is kept pressed against the
crank-pin by a spring, the result being that the connecting rod is
longitudinally elastic and deadens the shock of the explosion.
GROUP II., CLASS I.—ONE CYCLE PER REVOLUTION.
_Dugald-Clerk gas engine._—In the ideal motor we should have at least
one explosion per revolution of the fly-wheel, which is not the case in
the Otto cycle. For this reason many inventors have tried to construct
gas engines with one cycle per revolution, but experience has taught
us that though they may be mechanically more simple, they lose in
efficiency what they gain in simplicity, and in spite of many eminent
inventors attempting to solve the problem. Even the best-designed
motors of this type have been unable to hold their own against the Otto
cycle because they are not as efficient.
The first attempt was made by Dugald-Clerk in 1881. His engine is
simple in the extreme, containing no gear-wheels, and working steadily
and noiselessly at a fairly constant speed (Fig. 5).
There are two cylinders of equal diameter placed side by side, and
projecting over the end of a cast-iron bed-plate. The first of these
is the motive cylinder in which the explosion takes place; the other
is used for compressing the explosive mixture, this compression taking
place in the Otto cycle in the motive cylinder itself.
This secondary cylinder also serves for another purpose; it draws in a
certain volume of air directly after the explosion, which is afterwards
driven through the motive cylinder, effectively clearing out the waste
gases. The advantage which this arrangement of double cylinders has
over the Otto cycle, lies in the fact that one explosion can take place
during each revolution of the crank, and consequently such very heavy
fly-wheels as are used for the Otto type of engine are not necessary.
The great disadvantage which the Dugald-Clerk motor possesses is the
extreme suddenness of the explosion, which is practically complete
before the piston begins to move. In spite of this defect the machines
have a fairly high efficiency. The gases are ignited by a gas-jet
situated in a sliding valve. A water jacket is used for cooling the
cylinder, and in some of these motors a mechanism is attached for
converting the engine from simple to compound. The compression cylinder
then becomes double-acting, and the gases are further expanded in what
was previously the motor cylinder only.
[Illustration: FIG. 5.—Plan of Dugald-Clerk Engine.]
Owing to the fact that this motor was not as efficient as those of the
Otto type it never became a commercial success, and it is doubtful if
any are working at the present date.
_Early Stockport gas engine._—The working of this motor affords a good
example of British ingenuity. The compression cylinder is situated
behind the motive cylinder, being a prolongation of it on the same
axis; the two are firmly bolted together end on. The active piston is
in front and connected to the crank, drawing behind it the piston of
the compression chamber. Each cylinder has a separate sliding valve.
The rear cylinder having aspirated and compressed a volume of the
explosive gases, they are passed into the motive cylinder through a
sliding valve which also serves to ignite them. The waste gas escapes
into the air by a special valve. The aspiration and compression take
place in the auxiliary cylinder once in every revolution of the crank,
and besides, the motive piston also compresses the gases a trifle
before the explosion takes place. The exhaust valve is made to open
slightly before the piston reaches the end of its stroke. The motor
was rather inefficient, and since its appearance a new type has been
brought out with an Otto cycle which we will describe later on.
_Benz motor_ (Fig. 6).—In this motor the inventor attempts to drive out
the whole of the exhaust gases before the second half of the backward
stroke of the piston is reached. To do this he injects a certain volume
of air under pressure, driving out the burnt gases and substituting
itself in their place. Before the end of this return stroke a small
auxiliary pump introduces the requisite amount of coal gas, which is
then compressed during the rest of the stroke. The ignition is effected
by a small magneto machine driven by the engine itself, the sparks
being generated between two fine metallic points in the cylinder.
The jet of air required to drive out the product of the combustion
is furnished from a reservoir, pressure in it being maintained by
using the other side of the piston as an air-pump. This arrangement
is an advantage, because cold air is being continually drawn into the
cylinder which keeps it cool, and enables the lubrification to take
place more effectively. There is also an external cooling apparatus in
the form of a water jacket, which uses about 40 litres of water per
horse-power hour, and keeps the cylinder at about 75° C. The Benz
motor is very well known on the Continent, and much of its success is
due to the fact that it seems to work as well with gasoline as with
coal gas! It is constructed by M. Roger of Paris, and in consequence of
the extreme constancy of its speed, it has been successfully applied to
driving dynamos, and also to launches, motor cars, etc.
[Illustration: FIG. 6.—Benz Gas Engine.]
_Baldwin gas engine._—The cycle of this engine is somewhat similar to
that of the Benz motor, one side of the piston being used for expansion
and the other side for compression. Part of the bed-plate casting is
arranged so as to form a reservoir for the compressed gases. The coal
gas is also admitted into this vessel, so that it contains an explosive
mixture. As the vessel is only made of cast-iron this arrangement
is rather dangerous. There are three valves, the admission valve
being regulated by the governor. The power developed is, therefore,
always kept proportional to the demand, and the constancy of speed is
sufficient to warrant the use of these engines for running dynamos for
electric light. The ignition is by an electric spark, and is generally
obtained from some extra apparatus, such as accumulators or batteries,
and an induction coil. The engine is constructed by Messrs. Otis Bros.
of New York.
_De Ravel motors._—The first motor constructed by M. de Ravel was
exhibited in Paris in 1878, and was of the oscillating cylinder
type, with a variable centre of gravity. The explosion drove up a
heavy piston whose rod was directly connected to the crank-pin. The
revolution of the crank-pin caused the whole cylinder to move in the
same manner as that of the early oscillating steam engines. This
movement was used as a means of opening and closing the ports. The
efficiency of the engine was low, using some 600 to 700 litres of
gas per horse-power hour; and besides the motor had, owing to faulty
mechanism, the unhappy knack of suddenly stopping dead. These defects
caused M. de Ravel to abandon this type and to bring out a second motor
in 1885, performing one cycle per revolution. This new motor only had
one cylinder, whose rear half acted as a compression chamber during the
backward stroke of the piston, whilst the explosion took place in the
front end of the cylinder. The consumption of gas was slightly more
than an Otto engine, and the motor ran exceedingly silently and evenly,
but this advantage was not of much service in the struggle against the
all-conquering Otto motor.
_Midland motor (Taylor)._—Constructed in Nottingham, this engine is
of the horizontal double-cylinder type. One cylinder compresses the
explosive mixture and passes it on to the other, where it is ignited
and does work. The cranks connected to the two pistons are placed
65° apart, and a complete cycle in the cylinders is performed every
revolution. The makers of this engine claim a consumption of only 600
litres of gas per horse-power hour.
_Campbell gas engine._—The mechanism of this engine is very much
like that of the Dugald-Clerk motor, two cylinders being placed side
by side. The utilization of the heat is, however, far superior, and
only about 500 litres of coal gas per horse-power hour are required.
A result which the inventor of this type of cycle never succeeded in
obtaining, but as far as we know the motor has never had any official
trial, and the above figures are only taken from the makers prospectus.
However, there is only a hardly perceptible shock from the explosion,
and the motor can be safely recommended to anybody requiring a silent
gas engine. There still exist gas engines worked on this same cycle
per revolution principle, such as the Conelly, Day, De Ravel motors,
descriptions of which must be sought elsewhere. The limited space at
our disposal prevents us from discussing all those types which have
only obtained a very small measure of success. The only remaining
engine based on this principle worth mentioning is the Bénier motor,
which is exceedingly instructive, but we shall speak of it later under
the head of poor-gas engines. We shall at present pass on to the
consideration of engines based in principle on the patent of Beau de
Rochas, and first practically realized in 1877 by Dr. Otto.
_Otto gas engine_ (Fig. 7).—The principle on which this engine is based
is known as the Otto cycle, named after Dr. Otto, but first suggested
by Beau de Rochas. Since the patents have expired numerous copies and
imitations have been brought out, but very few surpass or even equal
some of the earlier types.
[Illustration: FIG. 7.—Otto Gas Engine.]
The explanation of the working of the Otto motor, which we are about
to give, will save us from returning to it in the descriptions of
analogous types brought out after this famous system. The cylinder is
continued in a backward direction so as to form a compression chamber,
into which the mixture of gas and air is drawn during the forward
stroke of the piston. The mixture is compressed during the return
stroke in this chamber, the pressure rising at the end of the stroke to
about 3 or 4 atmospheres. At this point in the cycle a flame is brought
into contact with the compressed gases and they explode. This explosion
raises the temperature of the gases to 1500° C., and drives forward the
piston under a pressure of about 150 lbs. to the square inch. During
the second return stroke, corresponding to the latter half of the
second revolution of the crank, the piston drives out the products of
the combustion into the air under a pressure of about an atmosphere.
The heating of the cylinder is avoided by keeping water automatically
circulating through a jacket surrounding it. This is necessary, because
if the cylinder walls became heated, the oil upon them would become
decomposed, and lose its lubricating properties. Dr. Otto paid special
attention to the efficiency of the engine, and in order to increase
it, he diluted the air and gas drawn into the cylinder with a portion
of the gases already burnt in the previous stroke. Consequently the
explosion at the beginning of the stroke is less violent, and the
gases continue burning while the piston moves forward. The cause of
this slow combustion has been wrongly attributed to stratification
of superimposed layers of gas and air, but it is probably due to the
action of the cylinder walls.
The Otto gas engine is a marvel of simplicity from a mechanical
point of view, very much more so than a Corliss steam engine for
instance. The admission and exhaust valves are worked by cams, and the
ignition takes place under pressure. The governor is sometimes of the
centrifugal type, and at others of the inertia type, but in both it
is a case of all or nothing, the supply being completely shut off if
the engine is going too fast. The connecting rod joins the crank to
the piston rod by a cross-head running into a bored out-guide. It is
necessary to have a heavy fly-wheel, because, as only one explosion
takes place per two revolutions, the fly-wheel must store up enough
energy during that explosion to carry it through the rest of the cycle.
Many different types of Otto gas engines now exist, some having two
cylinders and a single crank, and others two fly-wheels, in order
to ensure constancy of speed for driving dynamos. Dr. Otto devised
a compound gas engine, but it did not succeed, and also a cheaper
vertical type (Fig. 8), which is very convenient for small workshops.
Since the invention of carburetted air the creator of the Otto cycle
has devised another motor for use with gasoline instead of coal gas.
Otto devised the first practical gas engine and opened up the path for
others, who, following in his footsteps, have confined their attention
to improvement of detail. Some have undoubtedly succeeded, and by
avoiding waste of heat, and by raising the initial temperature of the
gases, they have considerably reduced the consumption of fuel. We shall
now discuss different types of motors which have appeared during the
last fifteen years, confining ourselves to the really successful ones.
[Illustration: FIG. 8.—Otto Gas Engine (vertical type).]
_Second Lenoir motor._—Twenty-five years separated the appearances of
the first and second Lenoir motors, and during this time M. Lenoir
gained a great deal of practical experience, so that if reference be
made to Figs. 1 and 9 they will be seen to have very little in common.
In the later type the cylinder projects over the back of the bed-plate,
and is provided with deep circular grooves on the outside to increase
the cooling surface. Ignition is obtained by the spark from a coil
supplied by a battery as in the early form. The consumption of gas is
about 800 litres per horse-power hour. Later on we shall discuss a
petroleum motor for motor cars, and also a stationary petroleum engine
by the same inventor. These engines were originally constructed by
Mignon and Rouart, but later by the Compagnie Parisienne du Gaz, and
are very well designed and constructed.
[Illustration: FIG. 9.—Lenoir Gas Engine (second type).]
_Koerting-Lieckfeld motor._—The first of these motors was constructed
in 1877, and was based on the Dugald-Clerk cycle. The original type
has, however, been abandoned, and the firm of Brûlé et Cie. of Paris
now construct these engines on the Otto system. All the moving parts
are attached to a vertical frame of cast-iron (Fig. 10), the lower half
containing the cylinder. The admission and exhaust valves are situated
in front and near the base. The governor is of the centrifugal type and
acts directly on the levers of the valves. The flame ignition makes it
necessary to occasionally clean out the valves, but otherwise the motor
has few drawbacks, and is very neat and compact. The consumption of
coal gas for engines of 8 horse-power and upwards is about 800 litres
per horse-power hour. The crank-shaft is placed horizontally across
the top of the frame, and the cams acting upon the valves are rotated
by a bevel gear enclosed in a case, driving a thin supplementary shaft
on which they are placed. The motor is self-lubricating, and is also
constructed as a horizontal gas engine.
[Illustration: FIG. 10.—Koerting-Boulet Motor.]
_Andrews’ motor._—The governing apparatus in this engine is exceedingly
simple and ingenious, consisting of a weight fixed to an oscillating
lever which controls the admission valve. The position which the weight
takes up depends upon the rapidity with which the lever oscillates, and
consequently upon the speed of the engine. If, therefore, the engine
is running too fast or too slow the weight takes up a new position,
and the effect upon the admission valve is to either slow down or
quicken the speed. The gases are ignited by means of a tube kept
red-hot by a gas flame. This engine possesses the special advantage
of being self-starting, that is to say, it is not necessary, as in
many other motors, to start the engine by giving the fly-wheel a few
rapid turns by hand. The motor is stopped with the crank in a position
slightly in advance of the point corresponding to ignition. The gas is
allowed to enter by a small auxiliary valve, which closes after the
first explosion. This volume of gas entering the cylinder mixes with
the air already in it, forming an explosive mixture. This explosive
mixture then begins to escape by similar automatic self-closing valves
situated at the top of the red-hot ignition tube. Ignition takes place,
and is communicated to the rest of the gas in the cylinder, closing the
two small valves by the force of the explosion. The piston is therefore
driven forward, and the energy of this combustion is sufficient to
start the engine. It must be understood that this operation is only
performed once at starting, for immediately afterwards the engine
falls into its normal cycle of operations. Two fly-wheels are as a
rule provided to ensure constancy of speed. The consumption of gas is
as low as 580 litres per horse-power hour in the large units of 100
horse-power.
The Andrews gas engine is also constructed of a special type for
consuming poor gas produced by the Dowson process, and gives very
good results. As a rule, about 600 to 800 grammes of anthracite are
necessary to produce one horse-power hour. In one particular plant
generating electricity, the cost has been certified to be as low as one
penny per kilowatt hour, including lubrication.
_Fielding gas engine._—The characteristic point in these engines is
the extreme simplicity of the valve gear, only one valve being ever
subjected to pressure. Even in the small engines of this type all
sliding valves are replaced by those of the spring pattern, in fact,
the valve mechanism consists simply of two spring-valves, one of which
fulfils two functions, controlling the admission and the escape of the
gases. The two valves are moved by a double lever actuated by a single
cam. The cycle is that of Dr. Otto. When the piston is starting on the
return stroke after an explosion has taken place, the lever lifts
one of the valves, and the products of the combustion escape into a
circular space situated below. In the next forward stroke this valve
is still further lifted, opening the admission port, while at the same
moment the exhaust port is closed by the second valve; a new charge is
therefore drawn into the cylinder. At the end of the admission stroke
the valves are released by the lever, and the compression can now take
place during the second return stroke. The movement causing the lifting
of the valve continuously throughout one whole revolution is effected
by means of a cam with two prominences on it, which act in succession
on the lever. There is only one valve, therefore, which is subjected
to pressure, and even this is well provided against risk of leakage by
the second valve being placed behind it, acting as a double seating.
A chamber is also provided in which the gases are first mixed, and
this mixing is regulated by a second lever and a special valve. The
governor is of the inertia type, and is attached to the upper side of
the double lever. It consists of a straight rod with a ball at one end
and a knife edge at the other, pivoted at its centre to the end of the
valve lever. As this lever is thrown forward the knife edge strikes the
end of the spring-valve admitting gas to the mixing chamber. If the
speed is too great the sudden jerk on the ball at the other end of the
knife edge causes it to miss the valve, and no gas is admitted till
the speed is reduced to the normal number of revolutions per minute.
This arrangement is very sensitive, and keeps the speed exceedingly
constant. Mr. Fielding has constructed some large gas engines of 350
horse-power which are started by compressed air, this air having been
previously stored up under pressure when the motor was stopping.
_Niel motor._—As will be seen from Fig. 11, the valves are actuated
by cams rotating on a supplementary shaft placed parallel to the
cylinder. A pair of toothed wheels transmit the rotation of the crank
to this valve-shaft, and it is arranged so as to give one rotation to
every two of the crank. The cycle of operations is somewhat similar
to the Otto cycle; gas is only admitted to the cylinder for two-thirds
of the forward stroke, so that the compression on the back stroke is
somewhat lessened. It is doubtful whether there is much advantage in
this method, but the Niel motors have had a large sale, which is a
sufficient proof of their good qualities.
[Illustration: FIG. 11.—Niel Gas Engine (elevation and sectional plan).]
_Lombart, Martini_ (Fig. 12), _Adam, Le Parisien, and Le Kientzy
motors._—All these motors, each of which is constructed by a different
maker, are based in principle on the Otto engine, and except for slight
modifications of the working parts, they do not call for any particular
notice. The small amount of space at our disposal only admits of our
mentioning them.
[Illustration: FIG. 12.—Martini Motor.]
_Lablin motor_ (Fig. 13).—M. Lablin of Nantes set himself to produce
a motor which should correspond with the Brotherood and Westinghouse
steam engine, that is to say, a motor developing the maximum of
power for the minimum of space and weight. This might be termed the
dynamic density of the motor, which M. Lablin sought to increase. He
has succeeded in constructing gas motors of ½ horse-power weighing
about 90 lbs., and of 8 horse-power weighing 7 cwt. Unfortunately
they consume a rather large quantity of fuel—about 1000 litres of
coal gas, or 500 grammes of gasoline per horse-power hour. There are
three cylinders grouped at equal distances round the same shaft,
and all attached to one single crank. By this arrangement a more
constant torque or twisting movement on the shaft is obtained, and
consequently the weight of the fly-wheel can be considerably reduced.
Three explosions are produced during every revolution, that is to say,
each cylinder performs a complete cycle of operations during every
revolution, a fact which accounts for the low efficiency. Ignition
is obtained by a platinum tube heated to incandescence when using
coal gas, and by an electric spark when carburetted air is used. The
governor is centrifugal, and controls the admission of gas.
[Illustration: FIG. 13.—Lablin Three-cylinder Motor.]
_Crossley Bros. gas engine_ (Figs. 14, 15).—This engine is from the
cycle point of view purely and simply an Otto gas engine. A light
shaft runs parallel to the cylinder, being driven by a worm-gear of
the crank-shaft. On it are situated the cams which force open the four
spring-valves, controlling respectively the admission of air gas and
the ignition and exhaust.
[Illustration: FIG. 14.—Crossley Gas Engine (X type).]
[Illustration: FIG. 15.—Crossley Gas Engine.]
The pressure of the gases is raised during compression to about four
atmospheres, and immediately after the explosion it rises to about 180
lbs. on the square inch; during the exhaust it averages about 10 lbs.
per square inch. Ignition is obtained by a tube heated to a bright red
incandescence by a Bunsen flame. At the right moment a valve is opened,
placing the explosive mixture in contact with it and causing the
explosion. When starting the machine the ignition is retarded or takes
place a little after passing the dead point, so that the machine cannot
start the wrong way by mistake. Two or three other features call for
special notice, especially the device for lubricating the cylinder. In
the illustration (Fig. 14) will be seen a small bell-shaped receptacle.
This vessel contains oil, and also a small crank inside driven by a
belt off the valve-shaft. As this crank rotates it dips into the oil at
the bottom of the vessel, and at the top of its path it wipes off the
oil which it has gathered on to a cup which allows it to flow into the
cylinder.
The water jacket is cast separately from the cylinder, and not, as in
many engines, in one piece with it. There is an advantage in this,
because there is less likelihood of flaws or blow-holes in the cylinder
wall passing unobserved when the engine is leaving the maker’s hands.
The governor in some of the sizes is centrifugal, and in others of the
inertia type similar to that described in the Fielding gas engine.
_Pygmée motor (Lefebvre)._—This motor, shown in Fig. 16, gives one the
idea of solidity and compactness. It possesses the peculiar property of
working equally well in any position, either horizontal or vertical.
This is due to the fact that it is particularly well balanced, and when
running does not vibrate at all. Easily started, these engines run at
a very constant speed, and their power in relation to their size is
truly remarkable, hence the name Pygmée. They have been especially
designed for self-propelled vehicles, and are not affected by the worst
running conditions, such as inclement weather or bad roads. In this
type they are constructed with two cylinders in order to obtain a more
constant torque, and also have an arrangement by which the speed can be
changed. For stationary purposes the motor is mounted on a cast-iron
stand (Fig. 16). In virtue of their exceedingly small dimensions and
reduced weight they are specially suitable where small-power motors
are required for home industries or small workshops, and also for
driving private electric installations and pumping water. They have
economically replaced steam engines in agricultural operations, both on
a large and small scale. The working parts being entirely enclosed they
stand a good deal of rough usage, and will work in positions in which
other motors would be useless. Where it is necessary to bring the motor
to the work it is required to perform they are bolted to a carriage
instead of a cast-iron base.
[Illustration: FIG. 16.—Pygmée Gas Engine.]
_The “National” gas engine._—As a gas engine this machine is
constructed in all sizes, from one horse-power up to large units
requiring a gas plant of their own. As petroleum motors they range from
one to ten horse-power. They are all provided with two fly-wheels,
which keep them well balanced and steadies their speed. They have
besides been especially designed with a view to economy of coal gas
or petroleum. An idea of the general arrangement of the parts will be
obtained by glancing at Fig. 17. The petroleum motors are provided in
addition with a vaporizer and a petroleum lamp placed at the front end
of the machine, and the oil reservoir is situated immediately above the
cylinder. M. Herckenrath has specially devoted himself to simplifying
the mechanism and making it more self-contained and less unsightly. Up
to 50 horse-power only one cylinder is found necessary, and for larger
powers two are provided. The patent governor is centrifugal and rather
novel in construction, and to it is partly due the high efficiency of
these engines. The large sizes are as easily started as the smaller
ones, and the lubrication is perfectly automatic. Besides these
advantages they require a minimum of attention, in fact, a skilled
attendant can be dispensed with, a few explanations and instructions
being all that is necessary to enable a boy or labourer to take
competent charge of them.
[Illustration: FIG. 17.—Herckenrath National Gas Engine.]
_Forest motor_ (Figs. 18, 19, 20).—We have already described the
earlier attempts of M. Forest to produce a practical gas engine. The
idea embodied in the motor depicted in Fig. 20, if not particularly
advantageous, is none the less highly original. The ends of the single
cylinder are open, and within it are two pistons, between which the
explosive mixture is introduced. The explosion drives these pistons
out in different directions, but by means of a suitable mechanism they
are each connected to one of two cranks on the same shaft. The whole
forms a very neat and compact arrangement. In another type by the same
inventor (Figs. 18, 19), also working on the Otto cycle, the cylinders
are vertical, there being one, two, or four placed side by side. In
the last case two explosions per revolution are obtained, ensuring a
very constant torque throughout. M. Forest has, however, particularly
applied himself in collaboration with M. Gallice to designing petroleum
engines for small boats. These two inventors have conceived a highly
ingenious arrangement for reversing the direction of rotation of the
engine, which is absolutely necessary in the propulsion of boats. All
the cams which actuate the valves are grouped together on a light
shaft, and by a simple twisting of this shaft from one end by a handle
the engine is reversed. The engines are self-starting, and are so
especially suitable for the propulsion of boats that they have been
adopted by the French navy, who at the present date have a number of
small vessels propelled by this motive power.
[Illustration: FIG. 18. FIG. 19. De Forest Gas Engines.]
[Illustration: FIG. 20.—De Forest Double Piston Motor.]
_Cuinat gas engines._—These engines are constructed in four types.
The A type is vertical with the cylinder above and fly-wheel and
shaft below. This is a more stable arrangement than placing them in
the reversed order, as is more frequently done. For small engines
the vertical type is undoubtedly the best, space, or rather lack of
space, being very often an important consideration to the purchaser.
The B type is similar to the previous one, except that two fly-wheels
are provided so as to make it suitable for small electric light
installations. The C type is horizontal, having all the valves placed
vertically, which plan seems to work better for engines of power
greater than 10 horse-power. The D type is also horizontal, but has
two fly-wheels, having been specially designed for electric lighting
purposes. In order to take up as little space as possible the dynamo
is situated underneath the projecting cylinder, both the engine and
dynamo being bolted down on to a special bed-plate. This arrangement is
more stable than placing them on separate foundations. In the petroleum
engines an electric spark is used to ignite the gases, and in the gas
engines both electricity and a gas flame.
It is best not to use animal or vegetable oils for lubricating the
inside of the cylinder, because they decompose, forming fatty acids
which have a corrosive action. Besides this, when they have fulfilled
their function of lubrication they settle down to a thick paste, which
has a most injurious effect on the working of the engine. It is best,
therefore, to use nothing but perfectly pure mineral oils and to avoid
all others. This does not only apply to the type of engine we have just
been describing, but to all gas engines. The Cuinat gas and petroleum
motors do not mix a portion of their exhausted gases with the fresh
charge as is frequently done, but completely sweep away the products
of the explosion before admitting a new charge. The result is, that
combustion is more complete but at the same time rather more violent.
An examination of an indicator diagram taken from one of these engines
shows that the combustion takes place at once as an explosion, and
that the final expanded pressure is as low as it is possible to get
it. These being the conditions necessary for a high efficiency, it is
needless to state that the consumption of fuel in these engines is as
low as in any other engine.
_Noël motor._—This type, constructed at Provins, has the advantage of
being exceedingly simple. The entries to the cylinder are controlled by
spring-valves, and the gases are ignited by electricity. From the ¼
up to the 2 horse-power size the cylinder is not provided with a water
jacket, and the general arrangement is either vertical or horizontal.
These engines work equally well with coal gas or carburetted air; in
the latter case the carburator is placed inside the cast-iron frame of
the motor. The guaranteed consumption of fuel is about 900 litres of
gas or 500 grammes of gasoline per horse-power hour, which is quite
satisfactory.
_Tenting motor._—This is a horizontal motor with the cylinder cooled
atmospherically, and the gases ignited by electricity. The governor
acts upon the exhaust valve; the products of the explosion remain in
the cylinder if the speed is too great, and then the admission valve,
which is automatic, no longer rises to admit a fresh charge until the
speed has once more fallen to the normal. This little motor is one of
the most practical small-power engines existing, partly because of the
great simplicity of the mechanism. It works well with carburetted air,
and the vertical type has been successfully applied to the propulsion
of small pleasure-boats.
_Atkinson motor_ (Figs. 21, 22).—This apparatus, constructed by the
British Gas Engine Company, was until recently the most efficient
heat engine in existence, its indicated efficiency being 22·8%. Mr.
Atkinson, the inventor, has arrived at this result by making the gases
burn gradually and by shortening the compression stroke. The discharge
of the residual gases is complete, this being directly opposite to Dr.
Otto’s procedure, for he diluted his explosive mixture largely with
the exhausted gases. In order, however, to make the piston execute two
strokes relative to the cylinder of different lengths, the inventor has
had to devise a rather complicated mechanism (Fig. 21). The result,
however, quite neutralizes this slight disadvantage.
[Illustration: FIG. 21.—Diagram of Atkinson Mechanism.]
[Illustration: FIG. 22.—Section of Charon Motor.]
_Charon motor_ (Fig. 23).—M. Charon has attempted to obtain a
prolonged combustion without the complicated devices resorted to by
Atkinson. He has obtained the same result by means of a regulator
controlling a double cam, one half of which actuates the admission
valve and the other half an auxiliary valve, which opens into a tube
forming a sort of reservoir, into which part of the explosive mixture
passes during the compression. After the explosion this stored-up
mixture is gradually allowed to re-enter the cylinder and prolong the
combustion. By this means a considerable gain in economy is obtained,
so that engines of this type only use about 500 litres of coal gas
per horse-power hour. In appearance the motor much resembles the
Otto motor, the crank-shaft and valve-shaft and valves being placed
in the same relative positions. Although these motors are rather
more expensive than others working with the Otto cycle, they are
nevertheless widely used. This is due to the fact that if cost of coal
gas in a particular district is high it is cheaper in the end to pay a
higher price for an efficient engine than to buy a less expensive and
at the same time less economical machine.
[Illustration: FIG. 23.—Charon Motor (latest type).]
_Roger motor._—This excellent little engine (Fig. 24) was especially
designed for small workshops. The extreme simplicity of the working
parts in no way lessens the efficiency, for the two horse-power only
burns 700 litres of gas per horse-power hour. The simple design also
keeps the cost of construction low, and the price averages about £30
per horse-power.
[Illustration: FIG. 24.—Roger Vertical Gas Engine.]
The governor controls the admission valve. Ignition is obtained by
means of an incandescent tube; the cylinder is cooled by a water
jacket; the mean speed is about 200 revolutions per minute, and this
speed is constant enough to allow the engine to drive a dynamo for
electric lighting. The motor has been very favourably received abroad,
but is not much known in this country.
_Motor of the Compagnie Parisienne du Gaz_ (Fig. 25).—Owing to its very
large consumption of gas the engine can only be used if the price of
gas is low, but it has several advantages which to a certain extent
neutralize this defect. It runs at a high speed of 400 revolutions per
minute, and the parts are arranged so as to be easily accessible.
[Illustration: FIG. 25.—Vertical Gas Engine of the Compagnie Parisienne
du Gaz.]
_Letombe motor._—Constructed by the firm of Mollet-Fontaine of Lille,
this engine presents several interesting features which we will briefly
enumerate. The cylinder is double-acting, giving one impulse to the
piston during every revolution. The speed is therefore maintained
fairly constant. The efficiency is high owing to the gases in the
cylinder being made to burn slowly as in the Charon motor. The machine
on the whole works exceedingly satisfactorily and reflects great credit
on its inventors.
_Robuste (Levasseur) motor._—The composition, admission, and ignition
of explosive mixture are regulated by a sliding valve as in the Otto
motor; in this case, however, it is a piston-valve and not a flat one.
The valve-chest is at the back of the cylinder. The governor is of
the inertia type, and suppresses the admission if the speed becomes
higher than the normal. A double water jacket is provided for cooling
the cylinder walls. Although not presenting any new features, this
motor fully merits its name, and its solid construction enables it to
withstand a surprising amount of bad handling.
_Richardson and Norris gas engine._—Yet another high-speed engine,
running at a speed of 230 revolutions per minute. Roby & Co. construct
this machine especially for driving dynamos, and for this purpose
two fly-wheels are provided in order to make it run smoothly without
variation of speed. The gases are ignited through a valve with a double
seating by means of a red-hot tube. The motor is reversible, which
is an advantage under certain conditions. Poor gas can also be used
instead of coal gas, consuming about 510 grammes of anthracite per
horse-power hour for an 86 horse-power engine supplied with Dowson gas.
This works out to a thermal efficiency of 21%, a result which places
this engine above criticism.
_H. C. motor._—This is an enclosed motor for use in mines or dusty
places, the fly-wheel alone of the moving parts being visible. It
works equally well with coal gas, carburetted air, or petroleum, and
is constructed in sizes from ½ to 60 horse-power. In spite of its
original features it has not met with much success up to the present
time.
_Le Marcel and Le Maurice motors (Cadiot)_ (Fig. 26).—The smallest
types of the Marcel motors are of one man-power, and the largest of
one horse-power, so that they are only suitable for small operations.
One impulse is given to the piston every two revolutions, the cycle
being that of Dr. Otto. The gas is compressed in a red-hot tube
during half of the backward stroke. There are only two valves, one
for the admission and the other for the escape of the gases, actuated
by a single cam on the crank-shaft. The cylinder is cooled by a water
jacket. The governor works on the all or nothing principle, the supply
of gas being completely shut off if the speed rises above the normal of
350 revolutions per minute.
[Illustration: FIG. 26.—Maurice Motor (de Cadiot).]
The Maurice motors are somewhat similar in construction, but are
designed for operating dynamos. For this purpose two fly-wheels are
provided. Many of these little motors are to be seen about the country
working fans, lathes, pumps, etc.
_Various._—We have described about thirty different sorts of motors,
selected from the best-known and most original types. About one hundred
other motors exist in Europe, which are similar in one way or another
to those already described, such as the engines of Dürkopp, Forward,
Brouhot, Debry de Soissons, Narjot, Archat, Wertenbruch, the “Acmé”
motor, and many others. But we are obliged to limit our descriptions,
and to conclude the chapter by a couple of examples of motors
performing one cycle of operations per three revolutions.
_Griffin motor._—In this engine we have only two explosions over three
revolutions, but as it is double-acting this number is reduced to one
explosion per revolution and a half. The different operations are as
follows:—(1) gases drawn into the cylinder, (2) compression of gases,
(3) ignition and expansion, (4) products of combustion driven out of
the cylinder, (5) a volume drawn into it to completely sweep away any
residue of the exhaust gases, (6) this volume of air drawn out.
Admission and ignition are obtained by the action of a sliding valve
and eccentric. The governor causes the gas admission valve to remain
open for a shorter or longer time, so as to ensure constancy of
speed. The exhaust gases escape by two valves actuated by a pair of
cams, opening them at every turn and a half, so that the gases are
alternately discharged from the back and front parts of the cylinder.
The consumption of fuel for a 12 horse-power motor was about 792 litres
of coal gas per horse-power hour in an official trial. The speed is
very constant in spite of the long cycle.
_Rollason gas engine._—This is also an engine using a long cycle of
operations, the arrangement of the parts being copied off the Otto
motor. The governor is electric, and acts on the admission valve,
varying the amount of gas admitted to the cylinder in proportion to the
demand for power. In the larger size of from 20 to 100 horse-power a
self-starting arrangement has been added. This engine, like the Griffin
motor, has proved that it is possible, by completely getting rid of
the products of combustion, to use a very dilute explosive mixture,
which would be impossible in the Otto motor. The Rollason engine is
constructed by Messrs. Beck and Co. of Newcastle-on-Tyne.
CHAPTER IV
CARBURETTED AIR ENGINE
If cold air be saturated with the vapour of volatile spirits such
as gasoline, or distillates of petroleum of about ·65 mean specific
gravity, an explosive mixture is formed with similar properties to that
produced by coal gas mixed with air. This carburetted air can be used
as fuel for heat engines of the explosive type. About twenty different
methods of carburating air are in existence, some of which are more
practical than others. We shall proceed to describe the best known of
these.
_Mille carburetted gas._—In this system air is drawn into a reservoir
containing a petroleum spirit by the volatilization and fall of the
petroleum vapour, this vapour being heavier than air. The reservoir
is placed on a higher level, and an indiarubber tube connected to its
base leads the explosive mixture to the cylinder. The success of this
arrangement encouraged inventors to perfect it. One of the earliest
carburators by Lafroque was provided with a tiny hot-air engine, which
helped to obtain a more perfect saturation of the air with the volatile
spirit. In the Eclipse motors, and also in the Phœbus motors of Pluyer
and Muller of Birmingham, the air and spirit vapour are mixed by an
injector. The vapour is first obtained by heating the liquid spirit in
a small still; it then passes by a fine nozzle across a space drawing
air with it after the manner of the Giffard injector. The explosive
mixture thus obtained passes into a reservoir.
_Faignot apparatus._—The air is drawn in by a revolving pump and forced
into a vessel, divided into several compartments, one above the other,
separated by porous partitions and containing gasoline; several taps or
valves cause the compartments to be alternately opened or closed, so
that the mixture can always be drawn off rich in hydrocarbon vapour.
This apparatus appeared in 1885 at the Antwerp Exhibition, and supplied
a Bénier motor with carburetted air. It is suitable for lighting
villages, country houses, etc., in fact, any places where coal gas is
not laid on. The apparatus has been imitated by Polack of Hamburg and
others.
_Lenoir carburetted air motor._—Carburators for producing fuel for
motive power have been carefully studied during the last ten years
by reason of the rapidly extended use of gas motors. One of the
most ingenious is due to M. Lenoir, constructed for a special motor
designed by himself and constructed by Messrs. Rouart _frères_. This
carburator consists of a horizontal cylinder rotated by a pinion wheel,
and performing five or six revolutions a minute. Vertical perforated
partitions divide the cylinder internally into several compartments,
and the interior wall of the cylinder has attached to it a number of
small buckets which draw up the spirit like a water-wheel, and pour it
out again when they reach the summit of their path. The air and vapour
are thus thoroughly mixed, and pass from thence into the cylinder.
Motors supplied by such carburators have been used for agricultural
operations, and also for driving small pleasure vessels, the cost of
maintenance per horse-power hour being about 2½_d._
_Schrab carburator._—The idea of this apparatus is quite original.
The jacket for cooling the motive cylinder is filled not with water
but with the hydrocarbon to be vaporized. From thence it passes
at a temperature of about 180° F. into a carburator containing
several compartments, and through which pass part of the products of
combustion; these gases passing through the already boiling liquid
hydrocarbon become saturated with its vapour, but require admixture
with air before they are capable of being exploded. The inventor
states that the waste gases only take up 1/16 part of that which pure
air would in passing through the hot liquid fuel, and thus explains
the extraordinary economy of fuel which is obtained by these motors,
only ⅒th of a litre of gasoline being necessary to produce one
horse-power hour. This is a very remarkable result, and if it is
correct places this combined plant in the foremost rank of carburetted
air engines.
_Meyer carburator._—This apparatus has the advantage of allowing
heavier and cheaper oils to be used, at the same time completely
volatilizing them. The heavy hydrocarbons are allowed to fall drop by
drop into a steel chamber about eight centimetres diameter and four
centimetres in height, heated by a flame. The vapour is produced at
a high pressure, and escapes through a fine nozzle at high speed
drawing the necessary air with it. Entering a reservoir this explosive
mixture is prevented from returning by a check-valve. The apparatus
is so arranged, that when the pressure in the reservoir has reached
a certain point, the flame heating the vaporizer is turned down and
prevents further explosive mixture being formed. The apparatus is
therefore self-regulating, the supply of carburetted air being always
proportional to the demand.
_Delamare carburator._—M. Delamare-Deboutteville has devised a very
compact carburator for use with his Simplex motor. Gasoline is
contained in an upper vessel, from which it flows in a fine stream
from a tap on to a horse-hair brush, and is there met by a similar
stream of warm water coming from the water jacket of the cylinder. The
heat obtained from this source tends to vaporize the hydrocarbon, and
the two liquids fall together into a closed vessel. The gasoline rids
itself of its impurities and floats on the surface of the water, which
is withdrawn from underneath it by a siphon. The hydrocarbon vapour
produced during the fall, and afterwards by the heat of the substratum
of water, passes by a check-valve to the motor. It is found that the
cleansing effect of the water renders the cylinder much less liable to
become fouled by tarry products.
_Lothhammer carburator._—Experience has shown that vapour of petroleum
when mixed with air soon separates out; the vaporizer must therefore be
placed as close to the engine as possible. In this motor it has been
the aim of the inventor to obtain an exceedingly perfect mixture of the
explosive gases. In order to do this the air enters the vaporizer near
its base, and passes through it in a number of exceedingly fine streams
of bubbles. The petroleum spirit is at the same time heated by a flame,
and the result is a very close mixture of the gases. The inventor
claims that he thereby obtains much more complete combustion.
_Tenting motor._—M. Tenting has arranged his gas engine, which we
have already described on page 57, for use also as an oil engine. The
carburator is composed of three superposed vessels, through each of
which the oil flows in turn. The upper vessel acts as a reservoir and
will hold a day’s consumption of oil, and the lower one is traversed
by the exhaust pipe, which supplies the heat necessary to obtain the
change of state of the oil from liquid to gas. Although this carburator
is rather crude it gives a very fair practical result.
_Durand carburetted air engine_ (Fig. 27).—M. Durand has set himself to
produce a motor which should work equally well with gas or petroleum,
and which should require a minimum of attention at the same time,
keeping in view such points as regularity of speed, rigidity, economy
of space, and above all low price. This ideal he has, however, failed
to reach, although his engine has many good points. He fails chiefly
because the mechanism is too complicated. The motor works with an
Otto cycle, and the ignition is by an electric spark generated by a
small magneto machine. The regulation of the speed is obtained by
throttling the admission, and the air is drawn through a tube heated
by the waste gases; this arrangement allows a slight economy to be
effected. The carburator is automatic, consisting of a closed cylinder
placed vertically over the motor cylinder. Within it is placed the
oil fuel, and also a spongy mass of cork which soaks up the heavier
impurities found in the oil, and thereby allows cheaper oils to be
used. Air is drawn through the spongy mass, becoming carburetted in the
process; these gases are mixed with a further quantity of pure air in a
distributing chamber before entering the cylinder.
[Illustration: FIG. 27.—Durand Carburetted Air Motor.]
Such a Durand motor sins only by the number of its parts, the
inconvenience of which is noticeable not only by the amount of
lubrication they require, but also by their rapid deterioration.
_Daimler motor._—This motor, constructed by Panhard and Levassor, has
become especially famous for its application to power-driven road
vehicles. It gained nearly all the best prizes in the automobile
races organised in 1894 between Paris and Rouen, and again in 1895
between Paris and Bordeaux. MM. Panhard and Levassor also construct
their motors as fixed engines, but except for slight modifications,
the mechanism is the same in both; we shall therefore describe the
automobile type.
There are two single-acting cylinders working on the same crank-shaft.
A central valve allows compressed air to be admitted which completely
drives out the products of combustion. The admission and exhaust
valves are enclosed in a chest also containing the incandescent tube
which ignites the mixture. The governor on the crank-shaft prevents
the exhaust gases from escaping when the normal speed is exceeded. The
gases remaining in the cylinder prevent a fresh charge from entering,
and during the next revolution no explosion takes place. The whole
mechanism of the engine, together with the fly-wheels, are enclosed
in an air-tight case communicating with the outside air by a valve
opening inwards. The pistons during the backward stroke draw in air
through this valve and compress it during the forward stroke; this
forms the supply of compressed air for the explosive mixture. The
carburetted air is obtained by the suction of heated air through oil
placed in a vaporizing vessel. The motor cylinder is kept cool by a
stream of water, which is itself cooled by travelling through a long
annular pipe which runs completely round the carriage. The heat which
it has absorbed from the cylinder is rapidly extracted from it by the
circulation of the air on both the inside and outside of the tube.
_Brouhot gas and carburetted air engine._—The firm of Brouhot of
Vierzon construct an engine capable of working either by coal, gas,
or petroleum, and which has been especially designed for agricultural
operations. The general appearance of the engine is of the usual type;
the cylinder projects over the bed-plate and is cooled by a water
jacket. The explosive mixture is ignited by an electric spark produced
from a battery of cells whose charge lasts from 120 to 130 hours, or by
a small magneto machine driven by the motor itself. When working with
petroleum a carburator is attached filled with a very volatile mineral
spirit. The air is carburetted by being sucked through it directly into
the cylinder. A second vessel is provided, which serves as a reservoir
for oil feeding the carburator automatically, and keeping the oil in
it at a constant level. The whole machine, though not presenting any
novel features, is strongly constructed and thoroughly suitable for the
work it has to perform.
_Carburetted air motors for horseless carriages._—Although not to such
a great extent in England, self-propelled vehicles have within the last
two years come rapidly into favour on the Continent, and the success
which has attended them has caused inventors and makers to concentrate
their efforts on building the motors as light and as practicable as
possible, as much for purposes of locomotion as for a host of other
uses. We have already spoken of the Daimler motor, which is used to
drive several different types of motor cars; we will now speak of more
recent developments in the same direction. Among many of the same
character, the most noticeable is the high-speed motor of MM. de Dion
and Bouton, who have applied them with great success to the propulsion
of tricycles (Fig. 28).
[Illustration: FIG. 28.—De Dion Motor Tricycle.]
The cooling is effected by radiating cast-iron ribs offering a
considerable surface to the air. The ignition is obtained by an
induction coil and accumulator with a contact mechanism, invented by
Captain de Place. The rotation of the crank-shaft is transmitted to the
wheel-shaft of the tricycle by a reduction gear.
Among other motors we must mention the benzoline engines for
self-propelled vehicles of Lepape, Gautier, the Gladiateur tricycles
and quadricycles constructed by the Société des Voitures sans Chevaux;
also the exceedingly light motors of the Kane-Pennington type; and
lastly, the voiturette-tandem of M. Leon Bollée, some of whose vehicles
have shown a remarkable speed with a very small consumption of fuel.
A few monstrosities have also appeared in the shape of a five-cylinder
motor driving a bicycle called the “bicyclette Soleil Millet,” and
a heavy and complicated mechanism by Wolfmüller, also driving a
bicycle and using petroleum. These motors have not, however, obtained
any success, nor will they at a future date, by reason of their
complication and weight. It is almost unnecessary to state, that any
of the above types may be equally well used for driving a dynamo and
producing electric energy or light.
CHAPTER V
PETROLEUM ENGINES
There is a great deal of difference, from an economic point of view,
between spirit or carburetted air engines which we have just described
and motors using ordinary commercial petroleum oil. As a rule such
oil is much less dangerous, having a lower flashing-point, while at
the same time it is cheaper than the more artificial products such as
benzoline, naphtha, etc. We shall presently give a table comparing the
cost of power produced by various systems of motors, and which will
explain why the petroleum engine is gradually ousting the carburetted
air motor from its place.
The first motor using ordinary petroleum was brought out twenty-six
years ago by Brayton in 1872, and may be said to be the father of the
large family of motors which consume oils varying from naphtha to
others which have boiling-points as high as 150° C.
_Ready motor (Brayton)._—This motor belongs to the third group of the
table on page 21 (combustion and compression). There are two cylinders,
one motive the other auxiliary, and used for compressing air. The
compressed air passes through a space filled with some absorbent
material such as felt, and kept saturated with petroleum injected
into it by a special pump. The carburation of the air proceeds as
follows: the high-pressure jet of air causes the petroleum to froth
up, and in passing through it draws along a quantity of oil in the
shape of finely-divided particles. This petroleum mist passes on to
the cylinder. The advantage of this method of obtaining an explosive
mixture is that it matters not what oil is used, in fact, the heavier
oils are even to be preferred, as their partial condensation in the
cylinder helps to lubricate it. One volume of petroleum will by this
process produce 24,000 of explosive mixture.
The motor is constructed in both the horizontal and vertical form, the
auxiliary being superposed upon the motor cylinder. The admission of
the pulverized petroleum lasts for one-third of the forward stroke, and
the return stroke expels the burnt gases. The engine is double-acting,
using both sides of the piston.
A reservoir of compressed air is used for starting the engine, and
saves the trouble of turning the heavy fly-wheel round by hand to give
it the necessary impetus.
The Brayton motors are constructed by an American firm from 1 to 10
horse-power. The cost of maintenance and fuel is moderate, rendering
them exceedingly practicable where coal gas or the lighter petroleum
are unobtainable. A later type than the one we have just described
appeared in 1890 which is slightly more economic, single-acting, and
uses the Otto cycle. The process for obtaining a spray of oil is also
much improved. Both the auxiliary and the motor cylinders are connected
by a beam and connecting rods to the shaft. A red-hot platinum tube
ignites the explosive mixture.
_Sécurité petroleum motor._—This engine was patented in 1887 by MM.
Belmont Chabout and Diedrichs, and appeared at the Paris Exhibition of
1889. An Otto cycle is used, and ignition is obtained by a platinum
capsule heated to incandescence by a jet of carburetted air which
passes through a spiral coil warmed by the waste heat of the cylinder.
This ignition tube is situated at the back of the cylinder, and is
placed in communication with it by a port and valve, which determines
the exact instant at which the explosion takes place. The petroleum is
vaporized by passing through pipes coiled up in a vessel traversed by
the heated products of combustion. The vapour thus formed has a high
enough pressure to draw air along with it as it passes across an air
space between two nozzles; an explosive mixture is therefore formed.
The motor is started by carburating a small quantity of air by means of
a reservoir containing a light oil, and this supplies sufficient energy
to work the motor until the spiral coils are hot enough to vaporize
the petroleum. The whole apparatus is rather complicated, especially
as there are two separate vaporizers using different oils. This
disadvantage, combined with only a moderate efficiency and a high prime
cost, has severely handicapped the engine.
_Priestman oil engine._—The first patent of this interesting engine
was taken out in 1886 by Messrs. Dent and Priestman. The engine as
a whole represents probably the highest point of perfection which
it is possible to attain to in this class of motor, and the general
arrangement is somewhat similar to that of Dr. Otto’s engines, but in
addition there is a very ingenious apparatus for working with heavy
petroleum oils. A single-stroke pump, driven by an eccentric keyed to
an auxiliary shaft turning half as fast as the main shaft, compresses
the air to a standard pressure (depending in value, on the size of
the engine) in a reservoir supplied with a governing valve and placed
near the front of the engine. This reservoir contains petroleum, and
the pressure of the air forces it up into a spray-maker, where it is
pulverized. From thence the petroleum spray passes to a vaporizer
heated by the waste gases, and becomes mixed with a certain volume of
air forming an explosive mixture, which is admitted to the cylinder
by an automatic valve. Compression and ignition take place in the
cylinder, and the waste gases escape through a valve worked by the
same eccentric which drives the air-pump. The number of parts of the
mechanism is by this means reduced to a minimum, and it is found that
this peculiar vaporizing process completely prevents the cylinder from
being fouled, as is usual when petroleum is heated to such a high
temperature, often decomposing it. The Priestman engine gave a fresh
lease to the life of oil motors, which had at one time been almost
abandoned by engineers. It is well adapted for all kinds of industrial
operations requiring powers of from 1 to 50 horse-power, and large
vertical engines have been constructed for marine purposes up to 100
horse-power, and have always given complete satisfaction to persons
using them. A few minutes are required for the apparatus to become
sufficiently heated to be able to start, after which the consumption of
fuel is about 380 to 500 grammes of petroleum per horse-power hour, or
about ·85 lb. The six-horse size weighs about 1½ tons. Ignition can
be had either electric or by a flame, according to the wishes of the
purchaser.
_Campbell gas engine._—Fig. 29 shows a very compact engine, built
by the Campbell Gas Engine Co. There are only three valves; the
admission valve is regulated by a centrifugal governor. The petroleum
is gasified in a vaporizer heated by a lamp. The speed is very
constant and the motor easily started.
[Illustration: FIG. 29.—Campbell Oil Engine.]
_Grob motor._—This engine is constructed in Leipzig and uses the Otto
cycle, and, like the motors already described, works well with ordinary
petroleum. The arrangement (Fig. 30) is vertical; the cylinder and
valve gear are supported on a hollow cast-iron column, which in turn is
bolted to a circular bed-plate. The shaft has on one side a fly-wheel
and on the other a pulley. The working valve parts are all situated
on the outside so as to be easily got at. The oil-pump marked in the
figure drives, the petroleum into a vaporizer, where it is broken up
into very minute drops. This oil spray becomes mixed with air, and
passes through a vaporizing tube heated by a flame. In the state of
vapour the explosive mixture passes into the cylinder, where it is
ignited at the right moment by a red-hot tube. In consequence of the
compression during a quarter of the cycle, the combustion is very
rapid, the power of these engines being very great for their size.
Ignition, and therefore the explosion, only takes place when the speed
falls below the normal. This regulation is obtained by a pendulum
governor, and ensures a very constant speed. The cylinder walls are
warm enough to make sure of ignition happening.
[Illustration: FIG. 30.—Section of a Grob Motor.]
All heat engines based on the principle of the explosion of a volume
of gas require an arrangement for drawing superfluous heat from the
cylinder, otherwise it would soon become red-hot. This cooling is
obtained in small engines by the circulation of air about a large
surface especially attached to the cylinder walls, but in larger
engines this means is insufficient, and it becomes necessary to use
water as a cooling agent. If water is laid on there is no difficulty
about this, but it occasionally happens that water is too expensive,
or that it is unobtainable; in such cases it is usual to erect a large
cylindrical reservoir of galvanized iron holding about ten litres of
water per horse-power of the engine. This reservoir is connected by
two pipes from the top and bottom to the water jacket of the engine
cylinder, and circulation takes place by the difference of density
of hot and cold water. In the Grob motor a somewhat different device
is resorted to. The water arriving from the jacket at a temperature
of about 70° C. is divided into a number of fine streams, which pass
up through a network inside the reservoir. At the same time a small
centrifugal pump driven by the engine forces in addition a stream
of air through the water; the effect is to cool the water before it
returns to the jacket to a temperature of from 80° to 90° Fahrenheit.
The Grob motor is built in the same manner as the Capitaine engine,
which we shall describe next, but it does not work either as smoothly
or efficiently as the latter engine. It possesses, in addition,
other faults which are objectionable. The vaporizing apparatus is
particularly troublesome, for the result of gasifying petroleum at such
a high temperature is very often to decompose it, and thereby foul the
cylinder and valve mechanism.
[Illustration: FIG. 31.—Exterior View of Grob Oil Motor.]
_Capitaine petroleum motor_ (Figs. 32, 33, 34).—More than seventeen
years have elapsed since Emile Capitaine, already well known for his
experiments on gas engines, first tried his hand at oil motors. His
first patent dates from the year 1879, and since that time he has
continuously worked at the subject, expending much patience and money
in order to produce a high-speed motor capable of using ordinary
petroleum of ·88 specific gravity. The result of his labours is a
machine which is excellent in all respects, requiring no igniting or
heating apparatus. In the earlier type it was found that the motor
would not work at less than three-quarters of its full load, because
when it was doing less work the vaporizer became cooled in the
intervals which occurred between the rarer explosions. This motor
could only work under certain conditions, and after further trials and
experiments Capitaine brought out a motor which worked at small loads
as well as full loads, and which only consumed fuel in proportion to
the power developed. This machine was considered too complicated, and a
fresh type was brought out.
[Illustration: FIG. 32.—Capitaine Gas Engine.]
[Illustration: FIG. 33.—Horizontal “Balance” Motor (Capitaine).]
This third engine has a vaporizer which is in permanent communication
with the cylinder, and is so constructed that even if it became red-hot
there would be no risk of pre-ignition or the formation of tarry oils
which would foul the cylinder. The vaporizer only draws in sufficient
petroleum at a time for one explosion, and then only during the
aspirating stroke of the piston. At the end of this stroke the whole
of the petroleum in the vaporizer is gasified. The first motor on
this plan was built by Capitaine in 1889, and many of them are still
constructed at the present date by M. Louis Herlicq of Paris.
[Illustration: FIG. 34.—Capitaine Two-cylinder Gas Engine.]
Capitaine came to an agreement with Grob et Cie. in order to exploit
his inventions in a wider field. Unfortunately differences arose,
and in 1891 the agreement was cancelled. A lawsuit followed, lasting
till March 26, 1893, when it was brought to an end by Grob et Cie.
agreeing to pay Capitaine the sum of 125,000 francs in consideration
for permission to use his name and patents in connection with their
motors. After breaking up the partnership with Grob et Cie., Capitaine
continued to build engines, and has since then taken out several
patents, which have considerably enhanced the value of his previous
inventions. In the 1892–93 type a lamp is used for starting which
can afterwards be dispensed with, the heat of the compression being
sufficient to maintain the temperature of the vaporizer. This is,
however, only if the motor is developing more than three-quarters
of its full power. When it was found that the same shaped indicator
diagram could be obtained from these motors even when they were giving
only 75% of their full power, it became obvious that it was only
necessary to keep the vaporizer as warm as possible by covering it with
non-conducting jackets, in order to get the engine to run at quite a
small fraction of its full power. Capitaine has, by carefully observing
this condition, obtained a motor which will run at all loads without
any external heating apparatus.
The vaporizer forms part of the combustion chamber, and is carefully
covered with non-conducting material. Only hot gases are allowed to
pass through it. It must be started by heating for a few minutes with a
small hand-lamp, and the engine is then ready for work.
_Merlin motor._—This motor is of the vertical type, and resembles the
Capitaine motor in some respects. The oil is stored in a reservoir in
the bed-plate; this receptacle is in communication with an air-pump
driven by the motor, and also with an oil-pump. The pressure of air
generated by the former forces the petroleum up into the oil-pump,
which in its turn passes it drop by drop through a pulverizer, after
which the spray of oil enters a vaporizer and becomes gasified. The
vaporizer is heated by a special petroleum lamp. Ignition takes place
when the explosive mixture comes into contact with the heated walls of
the vaporizer, their temperature being always high enough to ensure
ignition taking place. The consumption of fuel is regulated by a
governor acting on the oil-pump, preventing it from supplying more
oil than is absolutely necessary to keep up the speed. The governor
regulates the exhaust valve as well, so that the speed, which is pretty
high, is kept quite constant.
_Hornsby-Akroyd oil engine_ (Figs. 35, 36).—This interesting machine
was invented by Messrs. Akroyd, Stuart and Binney; it works with
ordinary petroleum, and without the help of a carburator uses oils
varying greatly in specific gravity. The reservoir of fuel is situated
in the bed-plate. The ignition is automatic, and an electric spark is
unnecessary, in fact, the whole engine is of the simplest construction,
in order that there may be no inconvenience due to breakdowns.
Referring to Fig. 35, L is a special petroleum lamp situated at the
back of the cylinder A. When starting this lamp is supplied with air
from a rotary fan turned by hand; in a short space of time, by the
help of this stream of high-pressure air, the cartridge C becomes
sufficiently heated to ensure the ignition of the explosive mixture.
This cartridge C is provided on its interior with radiating ribs, which
greatly increase the surface. During the back-stroke of the piston
it becomes filled with compressed air from the cylinder, and towards
the end of this stroke a quantity of petroleum, exactly sufficient
for the explosion, is squirted into it. To do this a small pump is
provided, which is actuated by a cam driving the oil into the cartridge
and brought back by a spring. The centrifugal governor G acts on the
admission valve from this pump. The sudden injection of the oil into
the middle of the heated chamber completely vaporizes it, forming
with the air already present the necessary explosive charge, which
immediately ignites in contact with the heated walls.
[Illustration: FIG. 35.—Hornsby-Akroyd Oil Engine (section).]
When the vaporizing cartridge has been sufficiently heated a rapid
turn of the fly-wheel by hand, so as to produce the first explosion,
is sufficient to start it, after which the vaporizer keeps itself
warm. The pump which keeps up the supply of oil will be seen in the
right-hand bottom corner of Fig. 35. It is of the plunger pattern, and
at every stroke of the piston draws in the right quantity of oil and
injects it into the vaporizer through a valve. The illustration on
page 91 shows the other side of the engine with the valve-shaft, which
revolves once for every two revolutions of the crank, also driving
the centrifugal Porter governor. If the speed should happen to exceed
the normal, a steel finger moved by the governor closes the valve
admitting oil to the vaporizer, which then returns to the reservoir,
having failed to accomplish its object. As the ordinary Otto cycle is
used, a heavy fly-wheel is necessary to maintain the speed constant
between the explosions. After being once started very little attention
is necessary, everything working automatically. A water jacket W cools
the cylinder.
[Illustration: FIG. 36.—Exterior View of the Hornsby-Akroyd Oil Engine.]
The specific gravity of the oil is usually about ·854, and of this
the engine consumes about one pint per hour per B.H.-P., at a cost of
1½_d._ An additional advantage of the high speed is, that there is
less chance of the cylinder becoming fouled by tarry products.
_Vulcan motor._—This engine is in many respects a counterpart of the
Akroyd motor. The cylinder is horizontal, and projects over the end
of the bed-plate. Two fly-wheels are provided if very steady running
is required. The lamp which vaporizes the petroleum at starting is
removed when once the normal speed is attained. A water jacket prevents
the cylinder from getting too hot. The most noticeable feature is the
rather curious arrangement for governing by means of bent oscillating
levers, which control both the admission and escape valves. The
governor itself is situated inside the transmission pulley and keeps
the speed within 1% of the normal; 600 grammes of petroleum per
hour per horse-power is the usual consumption. The motor is rather
too complicated, and can scarcely be said to have justified the
expectations formed of it.
_Ragot petroleum motor_ (Figs. 37, 38).—This engine, like the preceding
ones, uses heavy petroleum and particularly schistic oil, which has a
flashing-point above 77° Fahrenheit, and which may be bought very much
more cheaply than naphtha, benzoline, or other artificial products
of petroleum. Several different patterns of the engines are on the
market, of which certain ones are of great value for electric lighting
purposes, not only because of their steady running, but also because,
by burning cheap oil, they allow the cost per horse-power to be reduced
to a minimum. One high-speed pattern has been especially designed for
coupling direct to dynamos, forming a very neat and compact plant. The
latest developments in the construction of these engines tend to the
simplification of the parts, and they are now so free from unnecessary
mechanism, that persons with little or no knowledge of mechanics are
quite capable of looking after them, and even taking them to pieces
and putting them together again if a breakdown should occur, which is
unlikely.
[Illustration: FIGS. 37, 38.—Sections of the Ragot Petroleum Engine.]
By a special arrangement in the carburator all constituents of the
petroleum which might foul the cylinder are removed before the oil
is allowed to enter the cylinder, and therefore it seldom requires
cleaning out. The carburator (Fig. 39) is very ingeniously arranged;
it consists of a cast-iron cylinder smooth on the inside, but provided
with a spiral rib on its outer surface, and heated by an oil lamp. The
spiral rib is itself enclosed by a covering, so that it forms a spiral
tube. The petroleum is allowed to enter at the top, and gradually winds
its way down, passing over a continually warmer and warmer surface
as it approaches the lamp. The more volatile portions of the oil are
therefore vaporized first, and the heavier oil passes on and is not
vaporized till near the base, where the temperature is high enough to
gasify the heavy residue. The air is heated in a jacket surrounding the
base of the spiral, and is afterwards mixed with the oil vapour.
_Root motor._—These engines work with the ordinary four-cycle, and are
interesting because of the double-ignition apparatus. A lateral chamber
is attached to the cylinder, communicating with it by an orifice
situated at the back end, which is covered when the piston is at the
beginning of its stroke. During the compression stroke a portion of
the mixture is enclosed in this chamber and separated from the rest
of the charge, which is compressed and ignited in the ordinary way.
The explosion drives forward the piston, and when it has moved forward
some distance it unmasks the above-mentioned orifice, igniting the
gas contained in the lateral chamber, and helping to maintain the
pressure behind the piston. This addition to the pressure is noticeable
in a diagram taken from the cylinder, by sudden rise of pressure. We
don’t quite see the utility of this arrangement, which seems to merely
complicate matters. The first ignition is effected by a red-hot tube.
The Root vaporizer utilizes the heat of the exhaust gases; the air
is heated in a spiral coil wound round the tube through which the
vaporized oil passes. The two become mixed in a small vessel, and the
vaporizer is supplied by a chamber placed directly round the exit of
the exhaust gases. Strictly speaking, there is no oil pump, but a
plunger in a small auxiliary cylinder serves to direct the flow of oil
into the right channels. Admission takes place through an automatic
valve. The escape valve is actuated by the same mechanism which drives
the piston governing the flow of oil.
[Illustration: FIG. 39.—Carburator of the Ragot Oil Engine.]
_Koerting-Boulet motor._—In this four-cycle engine we shall only
describe the vaporizer and spray-maker. The oil is stored in a
reservoir placed about six feet from the ground, and a pipe conducts it
into a space between two discs with a valve at the top. This circular
space, about half a millimetre in thickness, is traversed by the air
which pulverizes the oil; the spray thus formed is vaporized by the
high temperature developed by a lamp situated underneath the tube which
conducts the carburetted air to the cylinder. In addition, this lamp is
used for igniting the gases through a porcelain tube kept at red heat
by it. An auxiliary spirit-lamp is used for starting the engine, which
takes about fifteen minutes to acquire a sufficiently high temperature.
_Knight gas engine._—In his endeavour to completely drive out the
products of combustion from the cylinder, Mr. Knight has had recourse
to the Griffin cycle and to a double-acting cylinder: we have
already discussed the relative merits of this system, and think it
is sufficient to point out the greater constancy of speed obtained
by it. The vaporizer is placed behind the motor-cylinder, and is
separated from it by a steel plate, so that it is maintained at a high
temperature; this vaporizer is made of bronze, and is provided with
radiating ribs. A pump injects oil into it, and it is also supplied
with compressed air by a special pump, which furnishes in addition a
jet for producing a blow-pipe flame. This flame white-heats a platinum
wire, which ignites the gases. The wire is situated in an opening in
the ignition valve; the valve moves forward, and the white-hot wire is
brought into contact with the explosive mixture at the right moment.
The admission valve is automatic, and situated in the steel plate
separating the vaporizer from the cylinder. The other organs of the
motor are not of any special interest.
_Crossley-Holt oil engine_ (Fig. 40).—This is practically the same
engine which we described in the chapter on gas engines; a vaporizer is
added in the oil motor to enable it to work with petroleum.
It consists of a chamber divided into four channels by vertical
partitions, and heated by a lamp placed underneath. The flame traverses
these channels before reaching the chimney placed at the top. The
petroleum is converted into a spray, and drawn off by a jet of air
warmed by passing it through a spiral coil placed round the lamp
chimney. This jet of air is supplied by a small pump worked by a lever.
The oil lamp has no wick, which is rather a novel arrangement: it is
supplied by a small pump similar to that which provides the air. Since
its first appearance this engine has undergone certain changes which
have considerably improved it. Messrs. Crossley Bros. have especially
devoted themselves to shortening the length of time necessary to heat
and start the engine. Besides this they have paid great attention to
simplicity of the working parts.
[Illustration: FIG. 40.—Crossley-Holt Petroleum Engine.]
_Trusty oil engine._—This motor was devised by Mr. Knight, and is
constructed by Messrs. Weyman and Hitchcock. There is no spray-maker,
the liquid oil being directly converted into vapour. The vaporizer is
heated by the waste gas from the cylinder, and the oil falls drop by
drop on to the hot metal walls and becomes vaporized. The engine is of
the ordinary four-cycle type, the most noticeable feature being the
governing arrangement; a governor of the inertia pattern regulating
the admission valve and the oil-pump. If the speed becomes too great
the action of the governor on the valves ceases, and oil is no longer
supplied to the vaporizer from the pump and the admission valve remains
closed. Ignition is obtained by a red-hot tube heated by an oil lamp;
a layer of asbestos on the outside prevents the tube from cooling, and
keeps the tube at a high temperature. It takes twenty minutes before
the vaporizer becomes sufficiently heated to enable a start to be made,
and the cylinder is very liable to become fouled by tarry products
from the oil. These serious disadvantages are scarcely neutralized by
the variety and small quantity of oils which the engine will burn. An
engine of this type with two cylinders consumed in certain trials only
half-a-pint of oil, which speaks for itself.
_Griffin oil engine_ (Figs. 41, 42).—Yet another Otto cycle engine
provided with a pump reservoir and vaporizer. The latter is hidden in
the bed-plate, and is heated by the gases from the exhaust. The pump
is driven by an eccentric on the main shaft, and compresses the air to
about 8 lbs. on the square inch in a reservoir also situated in the
bed-plate. The compressed air passes from this chamber into a needle
pulverizer, along with a quantity of oil which it has gathered in a
small ante-chamber. This pulverized oil arrives in the vaporizer at
the same moment as the air for the explosive mixture. A portion of
the vaporized oil and air is used for the lamp, which red-heats the
ignition tube. At starting, a small quantity of air is compressed in a
hand pump, and in ten minutes the vaporizer is hot enough to gasify the
oil. The Griffin engine is very economical, and only uses about a pint
of petroleum per horse-power hour.
[Illustration: FIGS. 41, 42.—Griffin Oil Engine.]
_Niel petroleum engine._—In these motors, the general arrangement of
whose parts is similar to that of the gas engines constructed by the
same firm, the principal part is the vaporizer. It consists of a small
cast-iron chamber, provided with radiating ribs in its interior so as
to increase the surface; the petroleum, coming from a reservoir placed
at a height of about six feet, passes through a regulating valve, and
is dispersed in fine drops over the surface of the radiating ribs;
the vaporization is consequently very steady. An automatic valve
allows air to pass into this chamber from the outside, forming an
explosive mixture with the vaporized oil. A special tube coming from
the reservoir supplies a lamp with oil for heating the ignition tube
and also the vaporizer at the same time. A methylated spirit lamp is
used for warming them up to the right temperature before starting the
engine. The governor acts on both the admission and the exhaust, and
the supply of oil is indirectly regulated by the closing of the exhaust
valve. The whole mechanism is ingenious, giving excellent results;
the speed is very constant, and the consumption of oil is within wide
limits proportional to the demand for power. About a pound of oil is
consumed per horse-power hour, including that necessary for the lamp.
Two patterns of this engine are built, one vertical and the other
horizontal. In the latter, called the Atlas engine, the consumption
per hour is slightly greater. The governor is also different. The
compression in the cylinder rises to about two atmospheres, and the
quantity of water necessary for the water jacket varies from seven to
ten gallons per horse-power hour, according to the size of the motor.
CHAPTER VI
GAS GENERATING PLANT
We have so far followed, step by step, the various improvements
undergone by internal furnace engines, from their first practical
realization thirty-seven years ago by M. Lenoir. This improvement has
continually tended, as one might naturally expect, to cheapen the cost
of the motors themselves, and lessen the cost of the fuel consumption
so that they might successfully compete against the steam engine,
over which they have many advantages. As a rule, coal gas is pretty
expensive, in some particular districts ruling as high as 4_s._ or
5_s._ per 1000 cubic feet. This price would be prohibitive were it
not for the extreme economy which has been obtained in gas engines by
such devices as compression and the lengthening out of the combustion.
Inventors have sought to still further lessen the cost of power by
replacing the expensive coal gas by other gases of lower illuminating
power, produced by special gas plants attached to the engine, and
which can be used in places where there is no coal gas laid on. Other
engines have been devised, as we have already shown, which get over
the difficulty by consuming petroleum oil or distillates of same, such
as benzoline and other light hydrocarbons.
Gas companies are, as a rule, heavily taxed, and if it were not for a
vast amount of idle capital buried in the streets in the form of gas
mains, they would probably supply gas at a very low price, especially
as the sale of bye-products practically covers the cost of production.
Some companies have even reduced the price of gas if used for driving
gas engines, and have therefore slightly decreased the cost of
production of power by this means.
In France, the home of the oil motor, they are severely handicapped
by having to pay double duties on all petroleum entering, first the
country itself, afterwards the towns.
Inventors have therefore sought a method of getting round these
difficulties by producing a cheap gas, which would answer the same
purpose as coal gas. First of all many manufacturers tried to cut
down the expense by erecting their own coal gas plants, so as to
be independent of arbitrary taxation. The system, although fairly
satisfactory, had many drawbacks, and further experiments were made
with a view to simplifying the process of production. The result
has been to give us _water gas_ and also _poor gases_, whose great
practical value we shall presently demonstrate.
In order to produce what is called water gas, the process essentially
consists of placing in contact with one another red-hot carbon and
superheated steam. The result is to form a mixture of gases according
to the following chemical equation—
3 H_{2}O + 2 C = CO + CO_{2} + 3 H_{2}.
For those not understanding the above it will be as well to explain,
that on the left-hand side of the equation are placed the compounds
brought into contact, water (H_{2}O) and carbon (C), and on the right
the products of the chemical action, carbon monoxide (CO), carbonic
acid gas (CO_{2}), and hydrogen (H_{2}).
The resulting water gas contains 60% of hydrogen and 20% of carbon
monoxide, both of which are combustible gases. The proportions of the
gases evolved can be varied at will by admitting more steam or using an
excess of carbon; by this process a richer gas can be obtained—
C + H_{2}O = CO + H_{2},
and
5 H_{2}O + 3 C = 2 CO_{2} + CO + 5 H_{2}.
With 18 parts of steam and 12 parts of carbon we can obtain by the
former equation 28 parts of carbon monoxide and 2 parts of hydrogen.
This forms an extremely calorific mixture.
There are several processes for preparing water gas which give good
practical results, and the gas produced has been used in America and
Germany for lighting towns on the incandescent gas-burner system.
The Strong and Lowe processes consist of a furnace lined with
fire-bricks, and in which is placed coal or coke. When this mass of
carbon has reached a state of bright incandescence by playing upon it a
stream of air, steam is admitted at high temperature, and is decomposed
by the carbon forming oxides and liberating hydrogen. The gaseous
products pass from the furnace to a reservoir.
When the chemical action ceases, due to cooling of the carbon, the
steam is shut off and the stream of air turned on till it becomes
incandescent once more. The process of admitting steam is then repeated.
About 2½ lbs. of coke are necessary to produce 20 cubic feet of
water gas.
Analysis of the gas reveals the following parts by volume of the
constituents.
(1) Water gas produced by the Strong process:—
Hydrogen 53 volumes
Carbon monoxide 35 ”
Hydrocarbons 4 ”
Other gases 8 ”
———
100 volumes
(2) Lowe process:—
Hydrogen 30 volumes
Carbon monoxide 28 ”
Hydrocarbons 34 ”
Other gases 8 ”
———
100 volumes
It is possible to entirely get rid of the cooling effect of the steam,
by using instead a jet of air which passes up through the carbon. First
of all carbon dioxide (CO_{2}) is formed near the bottom of the mass,
but this gas passing upwards through it is reduced to carbon monoxide
(CO) by the excess of carbon, and a mixture is obtained consisting of
34 parts by volume of carbon monoxide and 65 of nitrogen. This gas has
been named after its inventor, Siemens gas.
By proceeding for ten minutes with this air process, and then stopping
it and generating water gas, two different mixtures are obtained, which
can be combined together forming a gaseous product containing 10 parts
of hydrogen, 20 of carbon monoxide, and 50 of nitrogen. One kilogramme
of coal produces 4·5 cubic metres of this mixture.
Instead of performing the operations of producing Siemens gas, or
producer gas, as it is sometimes termed, and water gas alternately and
separately, it is possible to so arrange the furnace and apparatus,
that both are generated at the same time, and continuously instead of
intermittently. The combination of the two is called poor gas.
The invention of gas-producing plant is due to two Frenchmen,
Thomas and Laurens, who studied deeply the question of the economic
generation of poor gas, and constructed the first working plant.
These two inventors stood, however, in the same position relative to
the production of poor gas that Beau de Rochas had held relative to
the gas engine, and it was not till Siemens came forward, and showed
how they might most economically be generated, that poor gases were
generally adopted. Siemens adapted them especially to metallurgy and
the manufacture of glass. We shall now describe the most interesting
processes which have been brought out since the time of the appearance
of the Siemens plant.
_Dowson gas-producer_ (Fig. 43).—This process was the first to appear
after the Siemens process, and the gas produced by it is used in a
large number of manufacturing operations. It consists of a generator,
a boiler for producing superheated steam, an hydraulic box, the
scrubbers and the gasometer. The generator is simply a gas retort lined
internally with fire-bricks, and placed vertically in position. It will
be seen in front on the left-hand side of the illustration. The fuel
is usually anthracite coal, and is supported on a grate. It is fed in
through a hopper placed at the top of the generator. By an arrangement
of valves the anthracite enters without direct communication being ever
established between the interior of the generator and the exterior
atmosphere, which would result in explosions. The steam which is to
be decomposed by the heated coal is generated in the small boiler,
seen in front on the right, at a pressure of 50 lbs. per square inch,
and superheated in a spiral coil inside. The steam passes into the
retort through an injector, drawing a quantity of air along with it
whilst passing from a nozzle across an air space. The air enters the
generator along with the steam and causes the coal to burn, and the
steam is decomposed, forming a mixture of producer gas and water gas.
The quantity of gas produced is therefore regulated by the injector.
The gases generated by the combustion of the anthracite are conveyed
by a pipe into a flat hydraulic box seen behind the generator, and
divided into two parts and half filled with water. The gases are washed
by this water and then pass on to the scrubbers, where they are cooled
and washed by passing through a mass of coke moistened by fine streams
of water. To further cleanse them they are passed through saw-dust and
thence pass to the gasometer. A number of analyses made by M. Witz
show that Dowson gas consists on the average of 25% hydrogen, 16 to
25% carbon monoxide, and 50% of nitrogen. The heat of combustion of
one litre varies according to the quality of coal used, but averages
about 1400 calories. One kilogramme of anthracite will produce about
four cubic metres of Dowson gas, the cost being one-tenth of a penny
per cubic metre. It must not be forgotten that this gaseous mixture is
only a quarter as rich as coal gas, but it costs about one-tenth to
produce, and is therefore cheaper on the whole. At some future date
this type of apparatus may, to a great extent, replace the boiler of
the steam engine. That Mr. Emerson Dowson’s process has succeeded
beyond his most sanguine expectations goes without saying. His
apparatus is in use in every corner of the globe, and, to quote his own
words, “still better results can and will be obtained when an engine is
really designed to give the best effect with this gas.”
[Illustration: FIG. 43.—Dowson Gas-producing Plant.]
_Buire-Lencauchez gasogene._—The analysis of the gas produced on this
system shows that it contains 20 volumes of carbon dioxide, 115 of
carbon monoxide, 66 of hydrogen, and 178 of nitrogen; its percentage
composition is therefore the following:—
Carbon monoxide 29·4
Carbon dioxide 5·9
Hydrogen 17·6
Nitrogen 47·1
———
100
Theoretically one kilogramme of coal should develop 5·26 cubic
metres of gas, having a heat of combustion at 0° C., and atmospheric
pressure of 1360 calories. These figures enable us to calculate the
efficiency of a gas-producing plant and the value of the gas obtained.
Very good results have been obtained by gas generated by the latest
Lencauchez process, with improvements added by the firm of Buire of
Lyons, who construct the apparatus. The chief point to be noticed in
these plants is the suppression of the steam boiler, which requires
constant attention and stoking. The hearth of the generator is made of
refractory bricks surrounded by a layer of sand to keep in the heat.
The fuel enters through a hopper, which by means of a bascule and
counterpoise never allows any direct communication between the interior
of the retort and the surrounding atmosphere. The fuel is either coke
or anthracite, and is spread over a grate situated over an ash-pit.
This ash-pit forms an important part of the apparatus, for it is fed
with water which evaporates from the heat striking down on to it from
the incandescent coke. The steam generated by this novel process passes
together with air up through the heated mass of fuel, forming a mixture
of producer and water gases in the generator above. The supply of air
is regulated by a centrifugal fan driven by the gas engine which the
plant is supplying. The necessity of having to use this fan very often
more than destroys the advantage gained by the absence of a boiler.
The gases produced pass by a pipe into the scrubbers after first
surmounting the pressure of a water valve, which prevents them from
returning to the generator. The scrubbers are filled with coke, with a
continual stream of water flowing down over it. The gases in passing
up are therefore thoroughly cleansed, so much so that they are fit to
pass straight to the gasometer. When the gasometer is full and has
reached its top position, it acts on a lever connected by a wire rope
with a tap regulating the air supply of the generator. The centrifugal
fan ceases to act, and the coke in the generator soon cools down,
and the production of gas ceases. As the gasometer falls again the
process is re-started, but not before the coke or anthracite in the
generator has been re-lit automatically. The whole plant, therefore,
only produces gas in proportion to the demand made on it, which is a
necessary condition when driving gas engines. The coke is automatically
re-lit by a small jet at the side of the generator, and fed by gas from
the gasometer. A plant producing gas sufficient for 60 horse-power, or
about 200 cubic metres per hour, uses up about 100 litres of water for
vaporization, and about 500 for cooling the scrubbers. The water used
for cooling the cylinder of the engine which the plant is supplying
may be used for vaporizing purposes, and requires the addition of a
small pump. Matter et Cie. of Rouen uses the Buire-Lencauchez gasogene
for supplying their Simplex engine, which we have already described.
Altogether about 3000 horse-power have been supplied by them on this
system, and have given repeated proof of the value of this process of
generating poor gas, especially in France, where poor French coal,
which can be used, is cheaper than imported English anthracite.
_Gardie gas-producing plant._—This apparatus is characterized by the
use of high-pressure air at about 80 lbs. per square inch, mixed with
steam at the same pressure; this arrangement being more concentrated
only requires small plant. The generator is of peculiar construction,
without any grate, the coke being held up on shelves. The air and steam
enter the generator by a ring of twyers, and a small window is pierced
at the side through which the attendant can see if the proper degree
of incandescence is maintained. The fuel is poured in through a hopper
in a similar manner to other generators already described. The gas
is produced at a high temperature, and is made to heat a coil through
which the steam passes, which is thus economically superheated. After
accomplishing this duty the gases pass on to a scrubber, formed by two
concentric tubes of different heights, and travel on straight to the
gasometer. The air is compressed in a reservoir by a special pump, and
is heated by the waste gases from the cylinder of the motor. These
various heating arrangements, therefore, prevent as much as possible
any loss of waste heat.
Some of the operations described are novel and interesting, and the
gas produced is very rich, having a heat of combustion of over 1400
calories, and very little ammonia is produced. The result of this is
that only rudimentary scrubbers are required, other systems requiring
elaborate methods of cleansing the gases. The only drawback to the
apparatus is the reservoir of compressed air, which necessitates a pump
using up power.
_Taylor gas-producing plant_ (Fig. 44).—The future of gas engines,
especially large units, is intimately connected with production of poor
gases at low cost, for they would be far from economical if coal gas
were used at the price at which it is usually sold. For this reason
many inventors have attempted to devise apparatus which should produce
gases suitable for being used in a gas engine, by the decomposition
of steam by red-hot carbon. The Taylor system is one of the best of
those which have appeared in the last few years. It has been thoroughly
tested in practice. The plant consists of a generator and boiler, a
series of cleansing and washing towers, and a gasometer. The most
important feature is the automatic manner of getting rid of the coke
ash from the generator by a moving hearth, which enables it to be
cleaned out without stopping the production of gas. By this system
cheap coal can be used instead of anthracite, which is more expensive.
The steam boiler is placed on the generator, and is heated by the gases
coming from it. The steam passes first of all through a superheater
consisting of a number of tubes round which circulate the gases from
the generator. The high temperature of the mixture of steam and air
ensures a good efficiency. The gases produced in the generator pass
through vertical tubes, exposing them to a large cooling surface, where
they are chilled; they then pass through scrubbers lined with coke and
so into the gasometer.
[Illustration: FIG. 44.—Taylor Gas-producing Plant.]
The gaseous mixture, consisting of hydrogen, carbon monoxide, etc.,
produced in the generator has a heat of combustion of from 1400 to
1500 calories. The relative heating power compared with coal gas is
therefore two-sevenths. A motor consuming 700 litres of coal gas would
require 2500 litres of the poor gas produced by this system to develop
the same power, and 550 grammes of anthracite would be consumed in the
process.
The cost per horse-power hour varies according to the price of
materials. Supposing we have an eight horse-power motor consuming 25
cubic feet of coal gas per horse-power hour, at 2_s._ 6_d._ per 1000
cubic feet, and working for 10 hours, the cost per day would be
8 × 25 × 30 × 10_d._
———————————————————— = 5_s._ or ¾_d._
1000
per horse-power hour.
If, on the other hand, it were supplied with poor gas generated from
anthracite costing 25_s._ a ton, it would burn about 1¼ lbs. per
horse-power hour, costing 16_d._, which is about one-fifth the cost,
and using cheap coal this cost can be still further reduced. These
figures clearly show how much cheaper it is to burn poor gases than
coal gas.
_Bénier gasogene._—Since the 1889 Exhibition, where a Simplex engine
was to be seen working with poor gas generated on the Dowson system,
engineers and others have fully recognized the advantages of this cheap
motive power. In the last few years a very large number of these plants
have been erected, and the experience gained by practice has shown,
that in spite of the extreme cheapness there are serious faults to be
found with this class of apparatus.
The gases are produced under pressure and are of an exceedingly
poisonous nature, carbon monoxide being the same gas which is
principally evolved from burning charcoal. Great care has therefore to
be taken that there are no leaks, which might have fatal results if
inhaled by the persons attending to the plant. The chemical operation
of the production of the gas is a very delicate one, and requires
skilled attendants if constancy in the quality of the gas is required.
The Bénier gasogene has been designed to eradicate or circumvent these
grave drawbacks. It presents many novel features, the most interesting
of which is the device for absolutely ensuring no leaks. This is done
by generating the gas below the pressure of the atmosphere. This low
pressure is maintained throughout the plant right up to the valve
which admits the explosive mixture to the motor cylinder. The only
places in which the pressure is raised are surrounded by vacuum jackets
leading to the gas reservoir. The gas-producing plant can therefore be
installed anywhere, even in dwelling-houses or cellars, without running
any risk of poisoning the inmates.
The irregularity of the qualities of the gas produced by other
generators is due to the difficulty of always admitting the air and
steam in the same proportions to the generator. This difficulty is
got over in the Bénier gasogene, indirectly as the result of the low
pressure in the interior: the air and steam enter under atmospheric and
therefore constant pressure, and their proportions can be regulated to
a fine degree of accuracy by varying the size of the orifices through
which they are admitted. So regular is the production of the gas in
quality that diagrams taken from an engine at intervals of several
hours showed no appreciable difference. The functions of attendant can
be thoroughly fulfilled by an unskilled labourer or boy, the operation
of emptying a quantity of coke once every half-hour being sufficient
to keep the plant working steadily. This apparatus is also an economic
one, partly because of the invariable qualities of the gas produced,
but chiefly owing to air and steam being heated before entering the
hearth. A rotating grate is also provided, so that the generation
of gas is in no way interfered with by the clearing out of ash and
clinkers. A special engine is constructed for use with this plant,
which we shall describe in the next chapter.
_Taylor gas-producing plant modified by Wimand._—There exist a number
of systems of gas-producers which are not so well known as those which
we have already described, but which are none the less interesting.
The most important of these is a modification by Wimand of the Taylor
system, in which the boiler is discarded, and replaced by a jacket or
vessel surrounding the generating plant and heated by the waste gases.
The hot water trickles down over a column of coke, and meets at the
base the current of air passing towards the generator; the air is
therefore heated, and becomes saturated with water vapour. This device
can be applied to any generator.
_Kitson gas-producer._—A rotating hearth is provided, as in other
systems already described. The air is driven by a steam injector
through holes in it, and the steam is supplied from a spiral coil
situated in the fire-brick lining of the generator. A second tube
through which the steam passes acts as a superheater. The steam enters
a reservoir chamber at the side of the generator, from which it passes
out again to fulfil its functions. There is therefore no fan needful,
and the generating furnace is not liable to become fouled. The price of
the plant is moderate.
_Loomis gasogene._—This apparatus aspirates its air and draws it
completely through a layer of carbon from top to bottom. The generator
is open at the top, and instead of the usual grate at the bottom it is
provided with a cone-shaped base instead. The air drawn in combines
with the carbon during its downward journey, and then passes through
a cooling tower surrounded by a water jacket which acts as a boiler.
The heat extracted from the gas is therefore used to produce steam,
which drives an engine working the pump which aspirates the air. The
exhaust steam from this engine passes into the incandescent fuel and
is decomposed, forming hydrogen and carbon monoxide. The valves which
govern the supplies of air and steam are so arranged that producer gas
or water gas, or both at once, may be generated at will. One particular
plant is known to have worked unceasingly for two years without
stopping, but in this case it did not supply a gas engine, in fact, we
believe that this system has not been applied for driving motors at all
as yet.
_Wilson gas-producer._—The generator is broader than it is high, and it
is possible to use in it all sorts of cheap coal and coke. A window is
provided, so that the attendant can see if the fuel is sticking and not
settling down properly. The air is blown into the centre of the hearth
by a steam injector at a low pressure of about two inches of water or
less. Stoking is effected by turning spiral grate bars which rid the
fire of clinkers and ashes. The air is heated by waste gases from the
motor, a process which gives a slight gain in economy.
_Longsden process._—We have mentioned that water gas generated by
various processes has been used for lighting towns in America on the
incandescent system. The drawback of the system is the exceedingly
poisonous nature of carbon monoxide even when very dilute, and it is
all the more dangerous because it is odourless. Many accidents have in
consequence occurred, some of them terminating fatally. Mr. Longsden
has attempted to produce a gas entirely free from carbon monoxide, so
as to avoid this difficulty. He first attempted to rid water gas of the
monoxide, but not being able to find a cheap enough solvent for it he
tried other means. His present process consists of adding a sodium salt
to the carbon in the generator. The gas produced has then the following
composition:—
Hydrogen 62·2 volumes
Carbonic acid gas 26·4 ”
Carbon monoxide 1·2 ”
Hydrocarbons 6·5 ”
Nitrogen 2·2 ”
Oxygen 1·5 ”
—————
100 ”
This very rich gas, which might easily be ridded of its carbonic acid
by passing it through lime, is very suitable for supplying motive power
through the medium of the gas engine.
_Gayon and Métais process._—This process, which, as far as we know, has
not been put into practice, was intended by its inventors to diminish
the price of coal gas. Instead of allowing coke to be deposited in the
gas retorts, as it usually is, and selling it as a bye-product, their
intention was to use it there and then for the production of water
gas, which was to be mixed with the coal gas and increase its heat of
combustion, while diminishing its cost of production. One ton of coal
would produce 450 cubic metres of gas instead of 300; the idea has,
however, never been put into practical shape.
CHAPTER VII
ENGINES FOR USE WITH POOR GASES
_Simplex motor_ (Fig. 45).—Although this motor works equally well with
coal gas and oil, we have put off the description of it until now
because it has become associated particularly with the production of
poor gases, and by their help forms one of the most formidable rivals
of the steam engine.
The Simplex was invented in 1884 by MM. Edouard Delamare-Deboutteville
and Léon Malandin. In appearance it is of the usual four-cycle type.
A lateral shaft transmits the rotation of the crank-shaft to a small
crank which actuates the sliding valve. This sliding valve forms one of
the principal features of the engine, and consists of a sliding iron
plate pierced with two holes, one oblique regulating the ignition,
and the other straight forming the admission valve. The piston
having completed its first forward stroke comes back to compress the
explosive mixture, and the sliding valve having advanced puts it in
communication with a chamber containing two metallic points, between
which a continuous stream of electric sparks is made to flow. After
the explosion this cavity and the passage leading to it are filled with
burnt gas, which must be driven out to prevent a miss-fire at the next
stroke. This is effected by a small purging hole, through which they
are driven by a fresh charge entering the cylinder.
In earlier patterns of this engine an ingenious air governor was used,
but it has now been replaced by a fresh arrangement of a different
pattern. This governor (Figs. 46 and 47) consists of a double pendulum,
which takes up a vertical position because of the lower ball, seen in
the illustration, being the heaviest. The whole pendulum is pivoted on
a fixed bearing. The variation in the speed is obtained by a weighted
knife blade acting on the gas-valve. The sliding valve is provided with
a knife blade square at one end and pointed at the other, which catches
in a notch on the pendulum, and is held by it in position so that the
square end hits the end of the gas-valve and admits gas. If, however,
the speed of the engine be too great the sliding valve carries its
knife blade forward too soon and it does not catch in the notch, with
the result that no gas is admitted as the square end is too low. The
speed of the engine, therefore, tends to remain adjusted to the rate of
vibration of the pendulum, which is a fixed quantity. A self-starting
arrangement is provided by stopping the engine half-way back along the
compression stroke, so that it is only necessary to pass an electric
spark across for an explosion to occur and give it the necessary
starting impetus.
[Illustration: FIG. 45.—Simplex Gas Engine (Delamare-Deboutteville).]
[Illustration: FIGS. 46, 47.—Governor of the Simplex Engine.]
MM. Delamare-Deboutteville and Malandin were the first to construct
units of very great power. At the Havre Exhibition in 1889 they
exhibited a Simplex engine using Dowson gas, and in 1889 they exhibited
at the Paris Exhibition a 100 horse-power single-cylinder motor.
Their latest achievement in this direction is the erection of a 320
horse-power engine supplied by two Buire-Lencauchez gasogenes with poor
gas. This is the largest single-cylinder gas engine in the world. The
Simplex engine was the pioneer of motors using poor gas. The machine we
described was for use with coal gas, and some modification has to be
made in the parts when the motor is required to use gases of the Dowson
type. The economy is very good, only 580 litres of coal gas or 550
grammes of anthracite being used per horse-power hour.
[Illustration: FIG. 48.—Combined Simplex Engine and Buire-Lencauchez
Gas-Producer.]
_Gardie motor._—We have shown how poor gases are, beyond a shadow of a
doubt, cheaper than coal gas for the production of power. Many makers
have therefore attempted to use it by simply adding a gas-producing
plant to existing engines. Sometimes these motors were totally unsuited
for these cheaply produced gases, and the result has been failure from
miss-fire or irregular speed. The Crossley, Niel, and Andrews motors
are exceptions, and a few others have also given fairly good results.
We described in the previous chapter the ingenious gasogene devised by
M. Gardie of Nantes; the motor which is constructed for use with it is
rather novel. It has two cylinders placed side by side, a compressing
pump and reservoir for compressed air. The gaseous mixture arriving at
a high temperature from the gasogene passes into the cylinders, and
is mixed with a volume of air coming from the reservoir; these gases
are compressed to about 100 lbs. on the square inch. At the entrance
to the cylinders are placed two igniters of platinum heated to a
white heat by an electric current at starting, but the temperature
is afterwards maintained by the combustion. During the admission the
gaseous mixture burns without any explosion and without raising the
pressure, but considerably increasing in volume. At the commencement
of the stroke the pressure in the cylinder is therefore the same as in
the compressor, but it soon decreases by virtue of the expansion and
driving forward of the piston.
After having exhausted themselves in doing work the gases pass out
into a regenerator, which communicates their heat to the air for
admission. The valves are actuated by a horizontal shaft placed above
the cylinders; the cams are three in number corresponding to three
valves, of which two regulate the admission of gas and air to a
chamber in which they are mixed. The third valve opens the exhaust.
This arrangement is not unlike that adopted by MM. Forest and Gallice
for their marine oil engines.
The cylinders are surrounded by water jackets for cooling purposes,
aided by air which can enter the front end when the piston is moving
in its backward stroke. The hottest portion is therefore that situated
at the valve end, and in which the explosion takes place. This portion
is surrounded by a closed chamber forming a boiler, where steam is
formed for use in the gas plant; the steam is superheated in a spiral
coil placed on the top of the gasogene. As we have already stated,
this system of gas production avoids the ammoniacal products, which
are a constant source of trouble in other engines. The drawback lies
in the compressor, which uses up about one-third of the indicated
power, but the speed is exceedingly constant, and averages about 175
revolutions per minute. The consumption of gas is not very high,
probably owing to the amount of heat which is absorbed from the waste
gases, usually lost. A number of other engines exist of a similar type
to the Gardie motor, such as the Shaw, Woodburg, Crowe, Buchett, and
others, which cannot, however, consume poor gases, and which have not
any distinguishing features worth mentioning.
_Bénier motor gasogene_ (Figs. 49 and 50).—We have described the Bénier
gasogene, and we will now complete the description by a short notice
of the motor associated with it. This motor works on the Dugald-Clerk
cycle, and in general arrangement is not unlike the Dugald-Clerk
motors. A special compressing cylinder is provided cast in one with
the motor cylinder, and the cranks are set at 90° degrees apart from
one another. The pump is double, with two pistons coupled tandem-wise
in the same cylinder. One of these draws in the air and the other
forces the gas into the gasogene. The air and gas thus conducted by
different paths reach the mixing chamber placed behind the motor
cylinder and provided with a valve. The motor cylinder has exhaust
ports perforating the walls, and which are uncovered by the piston when
it has moved through five-sixths of the forward stroke. It remains open
during the remaining sixth and the first sixth of the return stroke.
At this moment the two piston pumps have forced into the cylinder the
air and gas which they contain. The mixture enters through a valve
and a perforated plate, which thoroughly mixes them in the cylinder.
During the return stroke the piston, having closed the exhaust ports,
compresses the explosive mixture till the end of the stroke. Ignition
then takes place, and the explosion drives the piston forward, and the
products of combustion escape to the air directly the exhaust ports are
uncovered by the piston.
[Illustration: FIGS. 49, 50.—Bénier Engine and Gas Plant (sectional
plan and elevation).]
By this arrangement it might happen that the explosive mixture
introduced into the cylinder might escape by the open exhaust valves.
M. Bénier has obviated this difficulty by a novel device. Pure air is
first admitted, driving out the products of combustion; the explosive
mixture which follows is only admitted when the ports are closed. This
result is obtained by properly regulating the supply of air and gas
from the pump. One explosion therefore occurs in every revolution.
The Bénier engine is constructed in sizes up to 100 horse-power, and
also smaller ones of a few horse-power. A 5 horse-power motor consumes
800 grammes of anthracite per horse-power hour: this result is very
remarkable, because great difficulty has been found in working these
small engines at all with poor gas; the gas generator seems to work
badly when its dimensions are so small. A 15 horse-power motor only
consumes 600 grammes per horse-power hour. The Bénier combined plant
shown in Figs. 49 and 50 has received a most flattering reception on
the Continent, and there is good reason to believe that it will be very
much more widely used in the future. We close this chapter with a table
setting forth the relative merits and economy of a number of motors.
----------------+----------+-------+-------------+------------+------+----------
| | | | | Cost |
| Nature | Power | |Consumption | per | Trials
Type of Engine. | of |of the | Consumption | per |horse-|conducted
| Fuel. |Engine.| of Fuel. |horse-power |power | by
| | | | hour. |hour, |
| | | | |pence.|
----------------+----------+-------+-------------+------------+------+----------
Lenoir (1860) | Coal gas | ·9 | 2400 litres| 2700 litres| 9 |Tresca
Hugon (1866) | ” | 2·07 | 5400 ” | 2600 ” | 8·5 | ”
Langen and Otto | ” | ·46 | 660 ” | 1380 ” | 4·5 | ”
(1867) | | | | | |
Wittig and Hees | ” | 4 | 4960 ” | 1240 ” | 3·5 |Brauer
(1881) | | | | | |
Koerting- | ” | 2·18 | 2700 ” | 1275 ” | 3·7 |Schettler
Lieckfeld | | | | | |
Otto | ” | 8·34 | 9500 ” | 915 ” | 2·8 |Allard and
| | | | | | Potier
Dugald-Clerk | ” | 11·6 | 9700 ” | 877 ” | 2·5 |Sterne
(1884) | | | | | |
Lenoir (1885) | ” | 2 | 1320 ” | 655 ” | 1·9 |Tresca
Simplex (1885) | ” | 9·41 | 5580 ” | 593 ” | 1·1 |Witz
” ” | Dowson | 3·66 | 6040 ” | 3300 ” | ·7 | ”
| gas | | | | |
Lenoir (1885) |Carburet- | 4·15 | 2·7 ” | ·65 ” | 4·5 |Tresca
| ted air | | (petroleum) | | |
Benz (1885) | Coal gas | 5·1 | 3600 litres| 707 ” | 1·4 | ”
Atkinson (1888) | ” | 9·48 | 6000 ” | 618 ” | 1·3 |Society
| | | | | | of Arts
Crossley(1888) | ” | 14·74 |10,800 ” | 765 ” | 1·5 | ” ”
Griffin (1888) | ” | 12·51 | 9500 ” | 786 ” | 1·5 | ” ”
Charon (1889) | ” | 4·17 | 2210 ” | 530 ” | 1·1 |Witz
Forest (1890) |Petroleum | 16·67 | 7 kilg. 400 | 458 grms. | 3 |Martin
| spirit | | | | |
Niel (1891) | Coal gas | 3·75 | 1250 ” | 402 litres| ·8 |Witz
Simplex (1889) | Poor gas | 75 |191 cub. met.| 2370 ” | ·7 | ”
” (1893) | ” |220 |110 kilg. | 500 grms. | ·3 |Leblan
| | |(anthracite) | | |
Lenoir (1891) | Coal gas | 6 | 4260 | 710 litres| 1·5 |Lencauchez
Charon (1892) | ” | 7·5 | 4380 | 586 ” | 1·2 |Chauveau
Priestman (1890)| Daylight | 7·7 | 3 kilg. | 385 grms. | 1·7 |Unwin
| oil | | | | |
” (1891)|Russoline | 6·7 | 2 kilg. 700 | 428 ” | 1·9 | ”
Crossley (1892) | Dowson |148 | 415 kilg. | 280 ” | ·2 |Dowson
| gas | |(anthracite) | | |
Atkinson (1892) | ” | 16·7 | 6·6 kilg. | 455 ” | ·3 |Tomlinson
Schleicher-Schum| Poor gas | 92 | 55 ” | 596 ” | ·32 |Spanglon
Trusty |Petroleum | 4·3 | 1·83 ” | 440 ” | 2·2 |Beaumont
|(ordinary)| | | | |
Delamare- |Lencauchez| 62 | 37 ” | 603 ” | ·2 |Bourdon
Deboutteville | gas | | |(cheap coal)| |
(1894) | | | | | |
Campbell (1895) |Petroleum | 6 | 2·4 ” | 400 grms. | 2·5 | ”
|(ordinary)| | | | |
----------------+----------+-------+-------------+------------+------+----------
The price of fuel has been calculated from prices current at the dates given.
CHAPTER VIII
MAINTENANCE OF GAS AND OIL ENGINES
Gas engines are in most cases mounted on a metal bed-plate, and for
small engines the weight of the machine is very often sufficient to
keep it in place; it is more satisfactory, however, to bolt it firmly
down to a bed of concrete or stone. Plenty of room must be allowed
round about to enable cleaning and repairs to be executed; space is
also necessary for turning the fly-wheel round if no self-starting
mechanism is provided.
Above two or three horse-power water must be used for cooling
the cylinder, mere cooling by air circulation being insufficient
for carrying off the waste heat except in very small motors. It
occasionally happens that water is laid on, which can be used for the
water jacket, the heated water being simply allowed to run to waste.
Unless the water is exceedingly cheap this arrangement is far too
expensive, and it becomes necessary to erect a separate circulating
system, in which the water is used over and over again. Makers provide
for this purpose galvanized iron tanks, which are connected by two
pipes to the water jacket. The tank being filled with water, and the
engines started, circulation takes place in a manner similar to the
ordinary household hot-water systems. The lower opening of the water
jacket is connected to the lower pipe from the tank, and the second
pipe, starting from a point near the top of the tank, is connected to
the upper opening of the cooling jacket. The difference of density
between hot and cold water causes the former to rise and flow back to
the reservoir along the upper pipe, and cold water rushes in to take
its place.
About 400 to 500 litres of cold water are required per horse-power, but
it largely depends on the rate at which the tank cools; in some cases
only 200 litres being found quite sufficient. The temperature of the
water leaving the jacket should be about 60° C. It is more economical
to let it rise to 80° C., but in this case very good lubricating oil is
required for the cylinder. A tap in the lower pipe, and a thermometer
placed against the upper one, will enable the attendant to adjust this
temperature.
_Starting and stopping._—Starting is an operation requiring a little
practice. First of all the igniting burner must be lit, and time
allowed for it to red-heat the ignition-tube; if electricity is used
this wait of a few minutes is obviated. The lubricating arrangements
are then attended to, so as to make sure of them being in satisfactory
working order. If no self-starting arrangement is provided, the supply
of gas to the cylinder is partly turned on, and a few quick turns of
the fly-wheel by hand are sufficient to set the engine in motion.
Having attained the normal speed the gas can be turned full on. If
the motor refuses to start, the tap regulating the gas supply should
be examined as it may be too full on; the ignition apparatus must then
be inspected. Sometimes the reason of the refusal to start lies in the
exhaust-valve which leaks; in this case no compression takes place.
This can easily be verified by turning the fly-wheel backwards, and
seeing whether the piston tends to resist the motion, which it would
do if the compression was taking place properly. When running it is
a mistake to flood the engine with oil; a barely sufficient quantity
of good mineral oil is all that is required. If the valves require
cleaning, then of course plenty of oil should be used to wash away the
deposit, but they should be well wiped before starting. Many persons
have become erroneously imbued with the idea that a gas engine requires
a skilled mechanic to attend to it. As a matter of fact any person
without previous knowledge is, with a few days’ practice, competent to
take charge of a motor provided that he is intelligent and careful.
Under these conditions a gas engine will last as long as a steam
engine, and will be generally found much more satisfactory.
To stop the machine, the self-starting mechanism must first be allowed
to operate, and then the supply of gas is shut off. After this the
burner or electric ignition must be cut off, and the cooling water too,
if it is not a circulating system. If the machine is to remain stopped
for some considerable period, turn the fly-wheel round till the piston
is in its most forward position; this will prevent dust and grit from
getting into the cylinder, and scoring the inside when the engine is
re-started. These are the general rules which must be obeyed in the
maintenance of the gas engine. The attention they require is therefore
small, and this quality has contributed not a little to their success.
No stoker or engine-driver is required; any person can, with very
little instruction, take charge of them. If the engine is properly
erected by skilled workmen, and has been running sufficiently long to
have arrived at a condition of regular lubrication, etc., a person in
constant attendance can be dispensed with, and it is sufficient to look
in occasionally and see that everything is all right, that there is a
sufficient supply of oil, and that the cylinder is cool, because if it
became overheated it might bind and destroy the interior.
Every month a complete cleaning should be undertaken, the valve
mechanism and cylinder being washed with mineral oil to dissolve the
deposit of carbon and tarry substances in them. Every six months the
valves should be re-adjusted, and if necessary re-ground into their
seatings. The time and trouble necessary for these periodical cleanings
will be amply repaid by the satisfactory working of the engine; nothing
is more annoying than a breakdown due to accumulation of dirt, and to
the continual postponement of the cleaning out.
_Maintenance of oil engines._—These machines require the same careful
treatment as gas engines, but they have in addition a carburator or
a vaporizer which require special attention, and render the cylinder
particularly liable to become fouled by the heavier products of the
vaporized oil. We have already described the principal systems of
vaporizers and carburators, and we shall only return to them to state,
that for efficient working they should be cleaned out once a week.
At the very outside not more than a month should elapse between the
removals of incrustations and deposits of carbon. The lamps used for
supplying heat to the vaporizer should also be attended to from time to
time, and occasionally thoroughly cleaned out.
_Ignition of the explosive mixture._—As we have already seen, several
different methods exist of setting fire to the explosive gases,
and each of them has its advantages and drawbacks. Ignition by an
incandescent tube of iron or porcelain seems to be the most simple, and
works as well as any other system; the sliding valve containing the
igniting jet is somewhat more complicated.
Electric ignition, if effected by a magneto generator driven by the
engine, is certain in its operation, but it is awkward at starting.
For petroleum and carburetted air motors batteries both primary
and secondary are better, especially when the motors are used for
propelling vehicles.
Looked at from the economy point of view, it is very hard to decide
which is the best system of ignition: red-hot tubes require gas,
accumulators require electric energy to be put into them, magneto
machines are expensive and use up power, in fact, they are all about
the same as far as cost is concerned. In France electric ignition is in
much greater vogue than in this country, where hot tubes reign supreme.
The electric system requires a few words concerning batteries and
induction coil.
If primary batteries are used the chromic acid type is the best.
These are manufactured in a large number of varieties; some of the
French makers, Trouvé, Guérot, Radiguet, and others, have paid special
attention to their application to gas and petroleum engines. The
induction coil should have a rather thicker secondary winding than
usual; it is necessary to have as hot a spark as possible to ignite the
gas, and this is not obtained if the spark is of exaggerated length.
[Illustration: FIG. 51.—Section of the Simplex Gas-producing Plant.]
The spark-gap also requires occasional attending to. It consists
usually of a porcelain rod with two points between which the sparks
pass, either intermittently or governed by an automatic switch, or
else continuously. In either case the points often become coated with
a deposit of carbon, which decreases their efficiency. They must
therefore be wiped clean about once a week.
_Maintenance of engines using poor gas._—These engines differ very
little from the ordinary coal-gas engine. The arrangement of valves
which will do for the one is also suitable for the other. We shall
therefore only give a few hints on the management of the gas-producing
plants which forms their only point of difference; to do this we shall
consider a “Simplex” plant.
The firm of Matter et Cie. have received many letters from other firms
to whom they have supplied their apparatus, replacing existing steam
engines, in which they state that the whole management and maintenance
of their new source of power is much more simple than the old. This is
not to be wondered at, because the whole plant is perfectly automatic.
There are no pressure or water gauges to attend to, because no more gas
is ever produced than is absolutely wanted. A steam boiler may require
to be stoked once every quarter of an hour, whilst a poor gas generator
only requires charging about once every six hours, according to demand
for power. The Simplex motor itself requires very little attention, and
all bearing surfaces are made as large as possible to avoid the risk of
heating.
Fig. 51 shows a complete plant in section. A is the generator filled
with coke or anthracite; the opening of the hopper, N, and the door, D,
of the hearth are closed. Air arrives from the centrifugal pump through
a stop-valve, I, and water through W. The air passes through the mass
of incandescent carbon forming carbonic acid gas, which is again
reduced by the excess of carbon to carbon monoxide. The water becomes
vaporized, and is dissociated by the action of the heated carbon
forming hydrogen and oxygen, which combines with the carbon forming
more carbon monoxide. The gas produced consists therefore of carbon
monoxide, hydrogen, nitrogen, and a small proportion of hydrocarbons
and carbonic acid gas.
Passing by the pipe S to the base of the washing-tower the gases meet
in their ascent water from the pipe Z, which cleanses them of all
impurities, after which they pass by the pipe Y to the gasometer, and
from there to the engine. We close this description of gas and oil
engines, hoping that we have said enough to put before electrical
engineers who are thinking of making use of this economic form of
motive power, the exact state of affairs, what results have been
obtained, and especially the considerations which govern the choice of
an engine.
[Illustration: FIG. 52.—Agricultural Oil Locomotive.]
We further hope that this systematic examination of all engines which
have received the sanction of practical experience, will prove of some
service to those who wish to become better acquainted with the numerous
existing types, and to understand their relative advantages and faults,
in order that they may select a gas engine which is suitable to the
particular requirements of each individual case.
INDEX
Buire-Lencauchez Gas, 110
Carburator, Schrab, 69
” Delamare, 70
” Lothhammer, 70
” Meyer, 69
Carburetted Air Engine, Brouhot, 74
” Daimler, 73
” De Dion-Bouton (Tricycle), 75
” Durand, 71
” Lenoir, 68
” Tenting, 71
Carburetted Gas, Faignot, 68
” Mille, 67
De Dion-Bouton Motor Tricycle, 75
Dowson Gas, 107
Efficiency of Heat Engines, 15
Gas Engine, Andrews, 41
” Atkinson, 57
” Baldwin, 33
” Bénier, 26
” Benz, 31
” Bisschop, 24
” Cadiot, 63
” Campbell, 34
” Charon, 59
” Compagnie Parisienne, 61
” Crossley, 47
” Cuinat, 55
” Dugald-Clerk, 29
” Economic, 28
” Fielding, 42
” Forest, 27, 53
” François, 25
” Griffin, 65
” H. C., 63
” Koerting-Lieckfeld, 39
” Lablin, 45
” Lenoir, 23, 38
” Lentz, 28
” Letombe, 62
” Martini, 45
” Midland, 34
” National, 51
” Niel, 44
” Noël, 56
” Otto, 35
” Pygmée, 49
” Richardson and Norris, 63
” Robuste, 62
” Roger, 61
” Rollason, 65
” Simplex, 121
” Stockport, 31
” Tenting, 57, 71
Gas-producer, Bénier, 115, 126
” Gardie, 112
” Kitson, 118
” Loomis, 118
” Taylor, 113
” Taylor-Wimand, 117
” Wilson, 119
History of Gas Engine, 1
Longsden process, 119
Lowe ” 105
Maintenance of Gas Engines, 131
Otto Cycle, 8
Oil Engine, Brayton, 77
” Campbell, 82
” Capitaine, 85
” Crossley-Holt, 98
” Griffin, 100
” Grob, 82
” Hornsby-Akroyd, 90
” Knight, 98
” Koerting-Boulet, 97
” Merlin, 89
” Niel, 101
” Priestman, 79
” Ragot, 94
” Root, 95
” Sécurité, 79
” Trusty, 99
” Vulcan, 93
Siemens Gas, 107
Strong process, 105
Working Principles of Gas Engine, 13
_Richard Clay & Sons, Limited, London & Bungay._
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+--------------------------------------------------------------+
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| WHITTAKER’S ELECTRO-MECHANICAL SERIES |
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has been written.’—_Electrical Review._
By J. GRAY, B.Sc.
=ELECTRICAL INFLUENCE MACHINES=: containing a Full Account of
their Historical Development, their Modern Forms, and their
Practical Construction. 4_s._ 6_d._
‘This excellent book.’—_Electrical Review._
By EDWIN J. HOUSTON, A.M., Professor of Natural Philosophy
and Physical Geography in the Central High School of Philadelphia,
Professor of Physics in the Franklin Institute of Pennsylvania, etc.
=ADVANCED PRIMERS OF ELECTRICITY.=
Vol. I.—ELECTRICITY AND MAGNETISM. 3_s._ 6_d._
Vol. II.—ELECTRICAL TRANSMISSION OF INTELLIGENCE. 5_s._
Vol. III.—ELECTRICAL MEASUREMENTS. 5_s._
=THE METRIC SYSTEM OF WEIGHTS AND MEASURES COMPARED WITH THE
IMPERIAL SYSTEM.= By W. H. WAGSTAFF, M.A., Professor
of Geometry at Gresham College. Crown 8vo, cloth. 1_s._ 6_d._
=ENGINEER DRAUGHTSMEN’S WORK.= Hints for Beginners. By a
PRACTICAL DRAUGHTSMAN. With 80 Illustrations. Small cr.
8vo, cloth. 1_s._ 6_d._
‘Will be found of practical value to the beginner in the drawing
office.’—_Engineer._
=PRACTICAL ELECTRICAL MEASUREMENTS.= An Introductory Manual
in Practical Physics for Students and Engineers. By E. H.
CRAPPER, Lecturer in Electrical Engineering at the Sheffield
Technical School. With 56 Illustrations. Crown 8vo, 2_s._ 6_d._
London: WHITTAKER & CO., 2 White Hart Street, Paternoster Sq.
Transcriber’s Notes:
- Text enclosed by underscores is in italics (_italics_).
- Text enclosed by equals is in bold (=bold=).
- Blank pages have been removed.
- Silently corrected typographical errors.
- Spelling and hyphenation variations made consistent.
- Front advertisements moved to the back.
- “_{}” is used to enclose a subscripted number, such as “H_{2}”.
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