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CARBURETING AND COMBUSTION



IN



ALCOHOL ENGINES



BY

ERNEST SOREL



TRANSLATED FROM THE FRENCH
, />Vt BY
SHERMAN M. WOODWARD. M.S., M.A.

Formerly Professor of Steam Engineering, State University of Iowa

AND

JOHN PRESTON



FIRST EDITION
FIRST THOUSAND



NEW YORK

JOHN WILEY & SONS

London: CHAPMAN & HALL, Limited
1907



Copyright, 1907

BY

SHERMAN M. WOODWARD



TEH '
S

604295



TABLE OF CONTENTS.



CHAPTER I.

PAGE

Traxslator's Introduction 1

Explanation of Terms Used 2

Recent American Tests of Alcohol as an Engine Fuel .... 5



CHAPTER II.
Introduction.

General and Historical Facts 20

CHAPTER III.

Conditions Affecting Combustion of Gaseous Mixtures.

Governing and Cooling of Explosion Engines 27

Isothermal Reactions and Adiabatic Reactions 29

Velocity and Acceleration of the Reactions 29

Acceleration in Isothermal Reaction '30

Acceleration in Adiabatic Reaction 30

Apparent Equilibrium and Reaction 32

Relative Dimensions of the Cylinder 39

Influence of Pressure 43

Limits of Combustion 46

Complex Mixture Limits 49

Influence of Neutral Gases 51

Limits of Combustibility 53

iii



IV



TABLE OF CONTENTS



CHAPTER IV.

PAGE

Phenomena of Combustion of Gaseous Mixtures.

Propagation of Combustion 55

Temperature of Ignition 68

Heat of Combustion 69

Specific Heat of the Products of Combustion 74

Temperature of Combustion 77

Explosive Power 81

Maximum Pressure 82



CHAPTER V.

Actual Combustion in Engines.

Thermal Efficiency of Engines 85

Influence of the Heat of Combustion 86

Incomplete Combustion, Influence of the Proportion of Air . . 88

Influence of Cooling the Walls 97

Influence of Time of Ignition 100

The Indicator Diagram . ' 101

Acidity of the Exhaust Gases 105

Specific Consumption 105

Comparison of Alcohol with other Fuels 108



CHAPTER VI.



Carbureting.



Conditions to be Fulfilled by Carbureters
Classification of Carbureters



Ill
115



i



CHAPTER VII.

Temperature of Vaporization.

The Various Fuels to be Studied 128

Investigation of Vapor Pressures 133

Quantity of Air Theoreticafly Necessary 142

Temperature Theoretically Necessary for Vaporization .... 144

Rapidity of Evaporation 145

Influence of the Quantity of Air on the Necessary Temperature 150

Quantity of Heat Absorbed in Vaporization 150

Influence of the Temperature of the Cylinder Walls 157



TABLE OF CONTENTS V
CHAPTER VIII.

PAGE

Investigations on Carbureters.

Disadvantages of Flow through Capillary Orifices 159

Influence of Cold on Alcohol-Benzene Mixtures 169

Carbureting by Surface Evaporation 172

Carbureting by Trickling 173

The Petroleum Hydrocarbons 185

Disadvantages of Carbureters Acting by Surface Evaporation . 190

Temperature in Spray Carbureters 192

Carbureting by Bubbling 193



CHAPTER IX.

Effect of Temperatures Below the Temperature of Com-
bustion 201



CHAPTER X.

Instantaneous Action of Temperatures Relatively Mod-
erate UPON Alcohol Vapors and their Derivatives.

Method of Operation 207

Methyl Alcohol 217

Ethyl Alcohol 218

Formaldehyde 219

Alcohol and Benzene 223

Alcohols and Gasoline 225

Formaldehyde and Hydrocarbons . 225



CHAPTER XI.

The Slow Action of Temperatures Relatively Low on the
Vapors of the Alcohols or their Derivatives.

Methyl Alcohol 228

Ethyl Alcohol 229

Formaldehyde 231

Alcohols and Benzene 231

Formaldehyde and Benzene 231



VI



TABLE OF CONTENTS



CHAPTER XII.

PAGE

Simultaneous Action of Heat and Oxygen.

Method of Experimenting 233

Air and Methyl Alcohol 234

Air and Ethyl Alcohol 236

Air and Formaldehyde 236

Air and Benzene 238

Air and Gasoline 239

Air and Kerosene 240

Air and Carburated Alcohol . „ . , 241



CHAPTER XIII.
Action of Metals in the Absence of Free Oxygen.

Introductory 242

Action of Soft Iron Filings 245

Soft Iron Filings and Alcohol 246

Soft Iron Filings and Formaldehyde 247

Soft Iron Filings and Carburated Alcohol 248

Turnings of Gray Cast-Iron 249

Turnings of Tool Cast-Steel 251

Aluminum 252

Zinc 254

Nickel 256

Summary 258

CHAPTER XIV. ^■1

Summary of the Chemical Studies on Industrial Alcohol 260



4



CARBURETING AND COMBUSTION
IN ALCOHOL ENGINES.



CHAPTER I.
TRANSLATOR'S INTRODUCTION.

The recent action of the United States Congress, by
which the use of alcohol for industrial purposes is per-
mitted without the payment of the internal revenue tax
levied upon the alcohol in spirituous liquors, has devel-
oped a wide-spread interest in the possible uses to which
alcohol may now be put. The internal revenue tax of two
dollars and twenty cents per gallon on 100 per cent alcohol
— a tax which has been maintained at this figure for many
years — has prevented the extensive use of alcohol in the
various arts and industries for which its properties naturally
fit it.

As a fuel any extensive use was prohibited by the high
cost, due to the internal revenue tax. While the cost of
manufacture of a gallon of strong alcohol has probably not
much exceeded thirty cents, until the recent congressional
action the market price has been about two dollars and
fifty cents. Under the new law alcohol, which has been
properly denatured by the addition of a definite proportion
of poisonous and repulsive ingredients to render it unfit for
drinking, is exempt from the payment of any internal
revenue tax and hence may be sold at the cost of manu-
facture.

1



ALCOHOL ENGINES.



The physical properties of alcohol are such as to make
it an admirable fuel in many ways; but it differs sufficiently
from the other familiar liquid fuels so that special forms
of apparatus are necessary for its use. So little has been
done in this country in experimenting upon suitable appa-
ratus that we naturally look for information to the continen-
tal European countries, where during the last ten years the
use of denatured alcohol has been rapidly expanding.

Many tests of alcohol engines have been made in both
Germany and France, but the most extensive study of the
subject which has yet been printed is the work, recently
published in France, a translation of which is here presented.
The original researches of which this book is largely an
account were made under a commission from the French
minister of agriculture. The book deals but slightly, and
then only in a general way, with what might be called the
structural details of the alcohol engine. As a matter of
fact the only important essential difference between an
alcohol engine and an internal combustion engine for using
any other fuel, lies in the apparatus for properly preparing
and proportioning the explosive mixture composed of the
vaporized fuel and air.

This work takes up and treats exhaustively the physical
and chemical principles upon which the design of all satis-
factory alcohol engines must depend. Most of the data
herein given had never been investigated before M. Sorel
began his researches. A thorough comprehension of the
results of these researches will serve to prevent many
useless and expensive experiments in inventing alcohol
engines; and, in fact, it does not seem too much to say, that
an adequate understanding of these results will prove indis-
pensable to the design of a satisfactory alcohol engine.

Explanation of terms used The extensive use of

internal combustion engines is still so recent that no univer-



TRANSLATOR'S INTRODUCTION. 3

sally accepted system of nomenclature is in use, and it may
tend toward ease in understanding the work to explain
here some of the terms and methods used in translating.

The word carbureter is used for the mechanism which
converts the liquid alcohol into vapor and mixes it with
air; and the process of so preparing the explosive mixture
is called carbureting. When alcohol is used as an engine
fuel, it is a common practice abroad to mix with it some
hydrocarbon having a higher heat of combustion per
pound than has alcohol. Such a mixture of fuels is men-
tioned many times in the book and, after much hesitation,
has been called carburated alcohol for lack of a better
term.

Gasoline has been uniformly used to represent any light
petroleum distillate, while benzene has been used to repre-
sent the substance whose chemical symbol is CeHg, whether
in the pure or commercial state. While largely similar
to gasoline in its properties, this substance is relatively
more abundant abroad on account of its occurrence as a
gas house by-product.

Whenever the strength of alcohol is mentioned as a per
cent, the proportion of alcohol by volume, in the mixture
with water or other ingredients, is signified unless the per
cent by weight is expressly stated. This is in accordance
with the customary usage in the United States, and is the
method followed in France. To avoid confusion, it is well
to know, however, that in Germany the universal practice
is to state the strength of alcohol by giving the amount
present as a per cent by weight.

In general, the French text has been closely followed in
the translation. In a few places a slight condensation has
been adopted.

Since most of the numerical data refer to chemical and
physical laws in connection with which the metric units




4 ALCOHOL ENGINES.

are in common use in this country, the metric units are
retained throughout. Probably the greatest objection to
this usage is in connection with temperature values. On
this account in some places temperatures are given in
their Fahrenheit equivalents as well as in their Centigrade
values. I

As the reader may desire to compare some of the numer- |
ical results with data from other sources expressed in
English units, the following conversion factors are given
which may be easily applied, and which will suffice to
transform most of the numerical quantities given in the
book :

1 kilogram = 1000 grams = 2.205 pounds. '

1 meter = 100 centimeters = 1000 miUimeters =39.37

inches = 3.281 feet. J

1 cubic meter = 35.31 cubic feet. fli

1 liter = 1.057 quarts = .2642 gallon = .03531 cubic

foot.
1 Centigrade temperature degree = | Fahrenheit de-
grees.
To change a temperature in Centigrade degrees to a
Fahrenheit temperature, let F be the Fahrenheit temper-
ature and C be the Centigrade temperature. Then,
F = I C + 32.

1 calory = 3.968 British thermal units.
1 calory per kilogram = f British thermal units per

pound.
1 calory per cubic meter = .1124 British thermal

units per cubic foot.
1 metric horsepower = 75 kilogram meters per second

= .9863 British horsepower.
A fuel consumption of 1 kilogram per metric horse-
power per hour = 2.235 pounds per British horse-
power per hour.



i



i



TRANSLATOR'S INTRODUCTION. 5

Recent American tests of alcohol as an engine fuel. —

During 1906 the United States Department of Agriculture
conducted a series of experiments in the mechanical
engineering laboratories of Columbia University with
alcohol as a fuel in various types of internal com-
bustion engines in extensive use throughout the United
States.

The object of these experiments was: to determine what
difficulties would be encountered in using alcohol as a fuel
for the types of engines already in general use; to ascer-
tain whether the engines could be made to operate satisfac-
torily on alcohol fuel, and what the consumption of alcohol
would be as compared with the fuels for which the engines
were originally designed; and finally, to throw light upon
the action of alcohol as an engine fuel so that some infor-
mation might be obtained as to the nature and extent of
the modifications necessary in the engine mechanisms, in
order that the most economical consumption of alcohol
fuel might be obtained.

The following engines were used in these tests :

A 15-horsepower, 2-cylinder, vertical, 4-cycle Nash

gasoline engine.
A 6-horsepower, horizontal, 4-cycle, International

Harvester Co. gasoline engine.
A 6-horsepower, horizontal, 4-cycle, Weber gasoline

engine.
A 6-horsepower, vertical, 4-cycle, Fairbanks, Morse

& Co. gasoline engine.
A 6-horsepower, horizontal, 2-cycle, Mietz & Weiss

kerosene engine.
A 40-horsepower, 4-cylinder, American Mercedes

automobile gasoline engine.
A 40-horsepower, 4-cylinder, Pope-Toledo automobile

gasoline engine.
A 2-horsepower, vertical, 2-cycle Mianus marine

gasoline engine.



6



ALCOHOL ENGINES.



All the above engines were operated successfully on
commercial 94 per cent grain alcohol. The changes neces-
sary in the adjustments of the fuel supptying mechanism
were in most cases simple and easily made, although a
large amount of experimentation was necessary to deter-
mine the best arrangements and adjustments in order to
secure the most economical fuel consumption.

The results obtained will be briefly summarized for each
of the engines.

The Nash engine had a spray carbureter. The air supply
after passing the spray orifice entered a mixing chamber
through a fuel mixture valve. An auxiliary air valve
admitted fresh air from the outside directly to the mixing
chamber, and between the mixing chamber and the engine
was the regular cam operated admission valve. The
amount of air passing the spray orifice and hence the
suction operating on this orifice, was controlled by the
setting of the auxiliary air valve. The greater the open-
ing of this auxiliary valve the larger the proportion
of air entering the mixing chamber directly, and the
smaller the amount which passed the spray orifice, and
hence also the smaller the amount of fuel which entered
the fuel mixture.

The hit-and-miss governor acted by preventing the fuel
mixture valve between the spray orifice and the mixing
chamber from opening. But on a miss stroke the regular
admission and exhaust valves were operated by the cams
as usual. Hence, on a miss stroke the engine cylinder
receives a supply of fresh air which has entered the mixing
chamber through the auxiliary air valve. The pure air on
a miss stroke scavenges the cylinder of the products of
combustion remaining from the previous explosion. If
the auxiliary air valve is not much open its throttling action
on a miss stroke produces a vacuum in the cylinder on the



TRANSLATOR'S INTRODUCTION. 7

suction stroke sufficient to reduce materially the weight
of the air charge drawn into the cylinder. In such a case
an indicator diagram shows for a miss stroke a compres-
sion line distinctly lower than the usual compression
line.

The engine was started with alcohol in the fuel chamber
by injecting a few drops of gasoline into the air suction.
After the first explosion was obtained the engine would
run perfectly on the alcohol, provided the fuel and air
valves were properly set. It was found that the opening
of the fuel admission valve needed to be nearly twice as
large for alcohol as for gasoline in order to secure a
sufficient supply of the fuel. The operation of the engine
on the alcohol fuel was regular, smooth, and noiseless.
As compared with gasoline the rate of propagation of
combustion with the alcohol seemed to be smaller, and it
appeared less explosive. This is shown by the reproduc-
tions of indicator cards shown in Plate I. Cards 1 and 2
were obtained with ignition taking place when the piston
was 13 per cent of its stroke before reaching the dead
centre. Cards 3 and 4 were taken with the ignition 3 per
cent before dead center. Nos. 1 and 3 are gasoline cards,
and 2 and 4 alcohol cards. The former show the more
rapid combustion with the resulting production of large
waves on the cards.

Card No. 5, Plate I, is a gasoline card showing the large
cycle produced on the first explosion after a miss during
which the cylinder had been cleared of burned gases by the
charge of pure air which entered the cylinder during the
miss stroke. When this card was taken, a considerable
excess of gasoline fuel was being supplied to the engine.
This excess was sufficient to make the fuel mixture for
the ordinary explosions rather slow burning as shown by
the indicator cards, but with the increased amount of



8



ALCOHOL ENGINES.



I



air present in the cylinder after the miss, the excess of
fuel became useful, increasing the charge of available
combustible mixture and forming a highly explosive
mixture.

Card No. 6, Plate I, shows the effect of introducing a
considerable excess of alcohol fuel. Apparently the
alcohol was not entirely vaporized as fast as supplied, but
some of the alcohol supplied collected in the mixing cham-
ber or in the engine cylinder in the liquid state. When the
fuel valve remained closed on a miss stroke, the fresh air
admitted vaporized the liquid alcohol remaining from
the previous fuel admissions. Thus was formed a feebly
combustible mixture which gave an explosion on what
would ordinarily be a miss stroke. That this explosion
took place when the fuel admission valve remained closed
is shown on the indicator card by the lowered compression
line. The fact was also verified by careful observation of
the engine while running.

The ordinary compression on the Nash engine was about
70 pounds per square inch. After the comparative con-
sumptions of alcohol and gasoline were obtained, plates
were attached to the inner faces of the cylinder heads,
raising the compression to nearly 90 pounds. The engine
was again run on both alcohol and gasoline, although with
the latter fuel it was difficult to make a satisfactory test
on account of the tendency to pre-ignition, producing
objectionable hammering. Next still thicker plates were
put on the cylinder heads raising the compression to 110
pounds, and the alcohol consumption determined. With
the lowest compression the best fuel consumptions obtained
were 0.72 pound with gasoline, and 1.17 pounds with
alcohol per brake horsepower hour. For the intermediate
compressions the best consumptions were, respectively,
0.71 and 1.12 pounds. For the highest compression the



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ALCOHOL ENGINES,



best alcohol consumption obtained was 1.12 pounds per
brake horsepower hour.

With the highest compression using alcohol and with
the ignition set very early, maximum pressures of over
400 pounds were shown by the indicator without there
being any perceptible knocking or hammering.

During the tests it was observed that the maximum
power obtainable from the engine when using alcohol fuel
was plainly greater than when gasoline was used.

At the most economical fuel consumptions the mean
effective pressure as shown by the indicator cards, with
both gasoline and alcohol, was between 80 and 85 pounds
per square inch, but the mean effective pressure could be
raised to 90 pounds by using a considerable excess of fuel.

The International Harvester Co. engine. — This engine
had a hit-and-miss governor and used a spray carbureter.
Its initial compression was about 73 pounds per square
inch. Many tests were made on this engine with both
alcohol and gasoline as fuel to determine the effect upon
fuel consumption of change in the brake load and in the
fuel needle valve setting.

This engine could be started as easily in the laboratory on
alcohol as on gasoline w^hen the proper adjustments had
been determined. The maximum horsepower obtainable
with alcohol was greater than with gasoline, and in every
way the running of the engine was as smooth and satis-
factory on alcohol as on gasoline.

It was found that the fuel consumption depended
largely upon the setting of the needle valve, and for any
given load was approximately proportional to the needle
valve opening. The best consumption was obtained with
the smallest needle valve setting under which the engine
could carry the load. The consumption of fuel could be
increased to nearly double the minimum by opening the




TRANSLATOR'S INTRODUCTION. 11

needle valve, before the excess of fuel would prevent the
engine from carrying tlie load. At all settings between
the two extremes the operation of the engine was perfectly
satisfactory so far as external appearances would indicate,
and the excessive consumption of fuel could be determined
only by measurement. Plate II, based upon the results
of these tests, shows the consumption of alcohol and gasoline
for different loads and needle valve settings. The fuel
consumption per brake horsepower hour naturally increases
as the brake load is diminished. With the extreme mix-
tures the fuel is slow burning in the engine cylinder and
the consumption is improved by using a very early
ignition.

Plate III shows representative indicator cards taken
during different tests with gasoline fuel, and Plate IV
cards with alcohol fuel. When all these cards were
taken the load on the engine was approximately five
horsepower. Each card is marked with the needle valve
setting used during the test, the mean effective pressure
determined from the average of all the cards taken during
each test, and the fuel consumption in pounds per brake
horsepower hour. The time of ignition was the same for
all these cards except Nos. 1 and 7, Plate IV, which were
taken with a much earlier ignition than the other cards.

The cards show that the highest rate of propagation of
combustion and the highest mean effective pressure corre-
spond to a fuel consumption much in excess of the lowest
possible.

The best consumptions obtained with this engine were
0.69 pound of gasoline or 1.23 pounds of alcohol per brake
horsepower hour. The mean effective pressure at best
consumption was about 90 pounds per square inch for
either fuel, and considerably higher values were obtained
with an excess of fuel.




12 3 4 5 6

Brake Horse Power

Plate II. Diagram showing for the International Harvester Co. Engine,
THE Relative Consumption of Alcohol and Gasoline in Pounds per
Brake Horse Power Hour, for Various Brake Horse Powers and
Needle Valve Settings.





Plate III. Representative Indicator Cards Obtained When Usino
Gasoline as Fuel.



14 "^^^ ALCOHOL ENGINES. ^^^^^^

With a small load on the engine and a large excess of
alcohol fuel supplied, very curious effects were observed.
On the first fuel admission after a miss no explosion would
occur. On the next fuel admission an explosion would
occur, producing a mean effective pressure of 126 pounds
per square inch as shown by the indicator card. The odor
of alcohol could be perceived in the exhaust at the end of
a long exhaust pipe, and the exhaust gases could be
ignited.

The Weber engine. — This engine is similar to the last
engine mentioned, and tests showed the same general
variations of fuel consumption with changes in needle
valve settings and brake loads. Successive explosions
varied greatly in the maximum and average pressures pro-
duced. With alcohol fuel slow speeds gave a better con-
sumption than high speeds. Plate V shows this engine j
fitted up for testing with friction brake, fuel measuring |
device, and indicator attached. The other engines were 4
tested in a similar manner. ^H

Fairbanks, Morse & Co. engine. — This was a throttle
governed engine with the compression raised to 128 pounds
per square inch. As before it was found that the fuel con-
sumption for any given load depended chiefly upon the 1
settings of the air and fuel admission valves. This engine j
had a spray carbureter, and the effect of heating the air \
supply before it entered the carbureter was tried. No ^
improvement in fuel consumption was obtained with the
heated air. It was found that when the air was heated to
about 125° F. the charge would self-ignite and the engine
would run steadily and satisfactorily under full load with
the battery current cut off. When the temperature of the
entering air was raised to 150° F., self -ignition took place
so early as to reduce materially the maximum load which
the engine could carry. Still there was no hammering or





Plate IV. Representative Indicator Cards Obtained When Usino
Alcohol as Fuel.



16



ALCOHOL ENGINES.



knocking in the engine cylinder. The best fuel con-
sumption obtained with alcohol was 1.13 pounds per
brake horsepower hour.

Mietz & Weiss kerosene engine. — This hot bulb engine
was made to run satisfactorily on alcohol fuel by increas-
ing the size of the fuel injection orifice and increasing the
amount of the fuel pump stroke. The maximum power
obtained from the engine on alcohol was greater than
could be obtained with kerosene. The best consumption
obtained with kerosene was 0.98 pound, and with alcohol
1.60 pounds per brake horsepower hour.

American Mercedes, Pope-Toledo, and Mianus engines. —
These high-speed engines were all run successfully and
satisfactorily on alcohol fuel. The consumption of alcohol
bore in general about the same ratio to the consumption of
gasoline for each engine as had been obtained in the other



5^

engines



4

4



The following general conclusions are drawn as a result
of the' investigations conducted by the United States j
Department of Agriculture: j

1 . Any gasoline engine of the ordinary types can be run \
on alcohol fuel without any material change in the con-
struction of the engine. The only difficulties likely to be
encountered are in starting and in supplying a sufficient
quantity of fuel, a quantity which must be considerably
greater than the quantity of gasoline required. ^■Jj

2. When an engine is run on alcohol its operation is more^^'
noiseless than when run on gasoline, its maximum power
is usually materially higher than it is on gasoline, and
there is no danger of any injurious hammering with alcohol
such as may occur with gasoline.

3. For automobile air-cooled engines alcohol seems to be
especially adapted as a fuel, since the temperature of the
engine cylinder may rise much higher before auto-ignition




18



ALCOHOL ENGINES.



takes place than is possible with gasoline fuel ; and if auto-
ignition of the alcohol fuel does occur no injurious hammer-
ing can result.

4. The consumption of fuel in pounds per brake horse-
power, whether the fuel is gasoline or alcohol, depends
chiefly upon the horsepower at which the engine is being
run and upon the setting of the fuel supply valve. It is
easily possible for the fuel consumption per horsepower
hour to be increased to double the best value, either by
running the engine on a load below its full power or by a
poor setting of the fuel supply valve.

5. These investigations also showed that the fuel con-
sumption was affected by the time of ignition, by the
speed, and by the initial compression of the fuel charge.
No tests were made to determine the maximum possible
change in fuel consumption that could be produced by
changing the time of ignition, but when near the best fuel
consumption it was shown to be important to have an early
ignition. So far as tested, the alcohol fuel consumption
was better at low than at high speeds. So far as investi-
gated, increasing the initial compression from 70 to 125
pounds produced only a very slight improvement in the
consumption of alcohol.

6. It is probable that for any given engine the fuel con-
sumption is also affected by the quantity and temperature
of cooling water used, and the nature of the cooling system
by the type of ignition apparatus, by the quantity and
quality of lubricating oil, by the temperature and humidity
of the atmosphere, and by the temperature of the
fuel.

7. It seems probable that all well-constructed engines
of the same size will have approximately the same fuel con-
sumption when working under the most advantageous
conditions.




TRANSLATOR'S INTRODUCTION. 19

8. With any good small stationary engine as small a
fuel consumption as .70 pound of gasoline, or 1.16 pounds
of alcohol per brake horsepower hour may reasonably be
expected under favorable conditions. These values corre-
spond to .118 and .170 gallon, respectively, or .95 pint of
gasoline and 1.36 pints of alcohol. Based on the high
calorific values of 21,120 British thermal units per pound
of gasoline, and 11,880 per pound of alcohol, these con-
sumptions represent thermal efficiencies of 17.2 per cent
for gasoline and 18.5 per cent for alcohol.

But calculated on the basis of the low calorific values of

19,660 British thermal units per pound for gasoline and

10,620 for alcohol, the thermal efficiencies become 18.5 for

the former fuel and 20.7 for alcohol. The ratio of the high

calorific values used above is, gasoline to alcohol, 1.78.

The corresponding ratio of the low calorific values is 1.85.

The ratio of the consumptions mentioned above is, alcohol

to gasoline, 1.66 by weight, or 1.44 by volume.

S. M. W.
July, 1907



CHAPTER II.



INTRODUCTION.



General and historical facts. — The idea of utilizing the
expansive force of gases produced by the explosion of a
combustible mixture is doubtless as old as the invention
of gunpowder. But the question remained largely one of
speculation until it became known how cheaply to manu-
facture and store the combustible gases, and how to mix
them in suitable proportions with air.

As knowledge concerning the mutual equivalence of
mechanical work and heat became general, these vague
ideas took form, and instead of burning the fuel at a very
low efficiency in the furnace of a steam boiler, attempts
were made to develop in engines, without the use of any
intermediary substance, the potential energy contained in
such combustibles as are suitable for the utilization,
although somewhat imperfectly, of that part of the energy
retained by steam in driving a steam engine.

It was to the use of illuminating gas, produced from the
distillation of coal, that the first efforts were directed.
Lebon described, in 1801, a mechanical apparatus in
which illuminating gas and air, compressed in separate
chambers, were mixed at the bottom of a double-acting
cylinder and lighted, and in which the gases formed by
combustion forced the piston to move backward and
forward.

Later there appeared the system called the atmospheric
system, that is still in use in some places. Within a cylin-
der equipped with a large air-cooling surface or surrounded

20




INTRODUCTION. 21

with a water jacket, and open at the top, a piston can
move back and forth. A gas pipe is connected with the
bottom of the cyhnder. The proper amount of air is let
in at the same time as the gas, then the mixture is lighted
by contact with a flame constantly burning on the outside
of the cylinder, and which penetrates it at the proper
instant. An explosion is produced, and immediately the
opening by which the flame enters is closed, while the piston
is raised by the explosion. When the piston has reached
its highest point, the burned gas escapes through a valve
that at once closes. As the gases remaining in the cylinder
cool, the pressure of the atmosphere forces the piston to
descend. When equilibrium has been reestablished, a
valve set in the piston opens, and the piston continues to
descend under the force of a powerful fly wheel and drives
out the remnant of the burned gases. The fly wheel con-
tinues to draw the piston in an upward movement, air and
combustible gas enter, and the cycle of operations continues
so long as the gas supply is open.

Such are the two prototypes of explosion engines.
These engines attracted the attention of engineers because
they showed great practical advantages over the steam
engines of that time.

Always ready to work, they required no expense in
starting and no loss of time, a thing of the greatest impor-
tance to small plants requiring work of variable duration
and at irregular intervals. Nevertheless, the presence of
high temperatures, incompatible with the methods of lubri-
cation then available, and the very rapid fluctuations in
turning moment of the engine, made for a long time grave
practical diflficulties that delayed the hoped for progress.
It was not till 1860 that the problem seemed to be solved
by Lenoir, who invented a type of double-acting horizon-
tal engine with a water jacket, but its consumption of gas



22



ALCOHOL ENGINES.



was excessive. Gradually it was seen that it is not advan-
tageous to introduce the gas, as was done by Lenoir, dur-
ing the time that the piston in its movement is increasing
the capacity of the explosion chamber. So it was decided
to introduce the mixture of previously proportioned and
compressed air and gas into an extra clearance space, and
explode it when the piston was at its lowest point. Next,
in order to obviate the difficulties of keeping the packing
in order, the cylinder was left open at one end and only
one face of the piston was used.

Beau de Rochas made an important change in engines
and greatly simplified them when he invented the four-
cycle engine, which did away with the separate com-
pressor. In this engine the piston during its initial rise
draws in a combustible mixture properly prepared outside;
then on its return stroke it compresses this mixture in a
clearance space at the bottom of the cylinder. When the
piston is at the end of its stroke the explosion of the mix-
ture is produced, either by an electric spark or by the
contact of the combustible mixture with an incandescent
surface. There results a considerable increase of pressure
that forces up the piston, against which the expanding hot
gases continue to maintain an effective pressure; then the
piston reverses its motion under the action of the fly wheel.
A valve operated by the engine is opened, the still very
hot burned gases are driven out, and the cycle is
repeated.

It is seen that only a single impulse is produced to two
complete revolutions of the shaft; that, moreover, the
turning moment fluctuates very rapidly during the stroke.
If then we wish to obtain a regular movement, even with
small engines, we must use very heavy fly wheels unless high
speeds are used. Finally, in order to avoid too rapid
wearing of the engine, very long bearings must be used, as




INTRODUCTION. 23

much for the piston as for the piston rod and the main
shaft.

The more explosive the mixture is, the more necessary-
are these conditions.

If rich mixtures are used in large engines, to secure regu-
larity of motion and to avoid too rapid wear of the moving
parts and possible danger of sudden breakdown, the use
of single engines is commonly abandoned, in spite of the
disadvantage of increased friction.

To begin with, for moderate sizes two cylinders are used,
whose pistons move two cranks mounted at 180^^ on the
main shaft, yielding an impulse for each revolution of the
fly wheel. Similarly, even four cylinders may be attached
to the shaft. In the latter case, in order not to complicate
the valve-operating mechanism, generally the four cylin-
ders are so connected to the shaft as to act like two separate
two-cylinder engines.

In spite of the disadvantage of furnishing only one
impulse to every four strokes of the piston, the Beau de
Rochas four-cycle engine is most frequently used, although
attempts are made to return to the two-cycle engine. It
is still found in modern kerosene engines in which there is
substituted for the explosion a continuous combustion at
constant pressure or at constant temperature instead of at
constant volume.

The use of illuminating gas is too expensive for large
engines, even when the owner makes his own gas. Hence
the use of explosion motors would not have developed
extensively if illuminating gas were the only fuel avail-
able.

But Dowson changed the situation by the invention of
his generator in which a current of steam and air is passed
over red hot coal. Under these conditions from 2 kilo-
grams of coal, 1.5 kilograms of steam, and 4.56 cubic



24 ALCOHOL ENGINES.

meters of air, there is formed a gas having the following
general composition:

Carbon monoxide, CO ... . 41 per cent

Hydrogen, H 21

Nitrogen, N 38 "

Total 100

This gas has a calorific power of 1710 calories per cubic
meter, or 192 British thermal units per cubic foot.

The use of high compressions, which have been generally
adopted to-day, permits the employment of still poorer
combustible gases, such as blast furnace gas. The pro-
duction of a ton of iron yields on the average 4500 cubic
meters (160,000 cubic feet) having a calorific value of 800
to 1000 calories per cubic meter (90 to 110 British thermal
units per cubic foot). Scarcely more than sixty per cent
of the gas is used to warm the blast. There then remains
1800 cubic meters (64,000 cubic feet) for the production of
power. While a steam engine requires 7.5 cubic meters
(265 cubic feet) of gas per hour per horsepower, a gas
engine consumes for the same work only 3 cubic meters
(105 cubic feet). The favor gas engines have found with
the owners of blast furnaces is therefore easily understood.

But gas pipes are not available everywhere; and even if
they were at hand, there would still be great practical
difficulties in utilizing the gas for engines destined for
traffic.

The production of the explosive gas, either in the engine
itself or just before its use, has been proposed. Carbide
of calcium is the only known solid which can be used in
this way to furnish a combustible gas; but the acetylene
produced would be too expensive and probably too dan-
gerous. The only things remaining then for use are the
combustible liquids, which are besides very easy to store.




INTRODUCTION. 25

The combustible liquids easiest to use are alcohol and
the various mineral hydrocarbons such as gasoline, kerosene,
crude petroleum, and benzene. Gasoline is a fuel very
easy to use. The same is true of benzene, but up to the
present time its consumption is not very great. Kero-
sene and crude petroleum require special devices for their
use. If suitable engines are employed, alcohol makes a
good fuel provided its cost is not too great.

For several years a great effort has been made in Ger-
many to develop the use of alcohol as a source of light,
heat, and power, in order to increase the demand for
agricultural products.

In France the government has attempted a like move-
ment, in anticipation of the threatened injury the new
sugar legislation is likely to have on the beet root industry
in many sections of the country.

Two competitions, one national, in 1901, the other inter-
national, in 1902, organized by the French Minister of
Agriculture, provided an opportunity for manufacturers to
meet their competitors, and compare results. Unfortu-
nately a great and sudden increase in the price of alcohol
delayed the promised development in use of this combus-
tible. It is clear that alcohol as an illuminant will be
superior to kerosene, as long as we have not the means to
use kerosene in incandescent lamps.

As a source of heat, from a physical point of view, it is
comparable with its rival; for even if its calorific power is
much weaker, it requires less air. In many cases its
slight inferiority is offset by the fact that the products of
its combustion are odorless, while gasoline and kerosene
never completely burn, but yield products with a dis-
agreeable odor.

As regards its use in engines, it appears from experiments
made at the international competition in 1902, that the



26



ALCOHOL ENGINES.



thermal efficiency of alcohol may be increased until it very
much exceeds that of its hydrocarbon rivals. Much has
been said for and against the use of alcohol in motors.
Its partisans declare it can be substituted, instantly and
without any modification, for gasoline in any engine; that
it does not leave any disagreeable odor or smoke. On the
other hand, its opponents claim that it forms acid pro-
ducts that corrode the cylinders and suction valves so
strongly as to make them adhere to their seats after cool-
ing. Generally speaking, the praises and objections are
not well founded; all depends on the circumstances of the
use, and the manner of production of the mixture of air
and explosive. In the following chapters we shall try to
show the conditions necessary for its use; they have already
been complied with by certain types of engines. ^H

Although the title of this book is ''Alcohol Engines," it^^
seems fitting to include a comparison, as complete as pos-
sible, of alcohol and the various hydrocarbons as fuels, in
order that the difficulties in the use of each may be under-
stood.

In order to understand their effect, we must also study
briefly certain parts of the engines, especially carbureters.

Finally, it will not be useless to review the laws, gen-
erally little understood by nianufacturers, which relate to
the phenomena of combustion.



CHAPTER III.

CONDITIONS AFFECTING COMBUSTION OF GASEOUS

MIXTURES.

Governing and cooling of explosion engines. — The
internal combustion engines that we are to study do not
have any such reserve supply of energy as steam engines
possess in the hot water of their boilers. Each explosion
of the gaseous mixture introduced during the
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