‘Typical Gas Engines’

By Staff
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Fig. 320.The First Lenoir Gas Engine, 1860
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Fig. 332.Otto Gas Engine with Double Flywheels designed for extra running
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Fig. 333.Early Lenoir Engine
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Fig. 336.Hornsby Stockport Gas Engine fitted with specially heavy flywheel for direct Electric Lighting
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Fig. 322.Early Benier Gas Engine
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Fig. 321Early Bisschop Gas Engine
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Fig. 323.The Economic Gas Motor
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Fig. 324.Dugald Clerk Gas Engine
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Fig. 328__The Midland Engine
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Fig. 330.End View of Otto Valve Arrangement
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Fig. 329.Early Otto Vertical Gas Engine
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Fig. 331.Section of Ignition Slide and Admission

1772 Conrad Avenue, San Jose, California 95124-4501

The First Lenoir Engine

In external appearance this engine, illustrated in Fig. 320,
bore a marked resemblance to the ordinary type of double-acting
horizontal steam engine with flywheel and connecting rod, with
which designers were already very familiar. Gas was merely
substituted for steam, with very few alterations of the parts, and
the distribution was effected by ordinary slide valves operated by
two eccentrics. For the ignition of the mixture an electric spark
was passed between two points inside the cylinder when the piston
reached its mid-stroke position, and for the production of the
high-tension spark a Ruhmkorff coil and batteries were supplied.
During the latter portion of the forward stroke the drive took
place, and on the return stroke the exhaust gases were driven out,
while the other face of the piston was acted upon by the driving
force. Around the cylinder walls cold water was circulated to
prevent the temperature from becoming abnormal. This double-acting
arrangement, which does not permit of initial compression of the
mixture, has been abandoned by all de signers, because the
regularity of the action is obtained at the expense of the economy,
and owing to the successive actions on the two sides of the piston,
the quantity of gas burned is out of all proportion to the power
developed.

Bisschop Engine

Fig. 321 illustrates this engine, which works on the mixed
principle of the Otto and Langen atmospheric engine. Expansion of
the exploded gases raises the piston, which is then driven, during
the working stroke, by the pressure of the atmosphere. Very
successful results were obtained from the first engines, which were
well designed and constructed, but very few examples now exist. As
will be seen from the illustration, the engine, which was of small
power, was of a vertical type, with the piston crosshead guide
surmounting the cylinder. On the outside of the cylinder were cast
numerous ribs of metal, which, by providing a large air-cooling
surface, served the same purpose as a water jacket.

In 1880 the inventor was awarded a prize of 1000 francs for his
engine, which was considered the best low-power engine suited to
the requirements of small users.

Benier Engine

This simple engine was the first one made by the designers of
the Benier producer engine. As will be seen from the illustration
(Fig. 322), the cylinder A was inverted, and the crank was driven
through a connecting rod coupled to a side lever, the end B of
which received its motion from the piston rod. A cam G on the shaft
operated a single slide valve E, controlling admission and
ignition, and side springs r, r were provided to keep the cam and
slide always in contact. Air and gas in the proper proportions were
drawn in by the piston until the middle of the stroke, when the
mixture was ignited by the exposure of a flame at the admission
port, and the explosion took place. A pilot flame-was provided for
the relighting of the ignition jet after each explosion. A second
cam on the shaft opened a separate exhaust valve at the proper
moment. Water-cooling jackets kept the heat of the cylinder within
reasonable limits, and the economy obtained in actual practice was
quite satisfactory, the consumption being about 50 cubic feet per
horsepower hour. Towards the year 1880 the system received a
certain amount of attention, owing to the simplicity of the design
and the relatively small cost.

The Economic Motor

The Economic motor, which was first constructed in New York
about the year 1883, was a small type of engine rarely exceeding Vi
HP and working on the non-compression system. Its arrangement was
ingenious but somewhat complicated, as will be seen from the
illustration, Fig. 323. A is the cylinder, provided with external
air-cooling ribs, and G E is the rocking lever from which the crank
O C received its motion through the connecting rod B. Regulation of
the speed was effected by means of a centrifugal governor
throttling the gas admission, as in the other engines of the same
class. It is understood that the results obtained in practice were
satisfactory.

Dugald Clerk Engine

In the design of a gas engine the ideal arrangement is to have
an explosion, that is, an impulse, every stroke, and for many
purposes the very usual Otto cycle having one impulse every four
strokes is not sufficiently good. Many attempts have been made to
devise a satisfactory two-cycle engine, but the experimenters have,
in general, found that the problem is more difficult in practice
than in theory. Dugald Clerk’s engine, which first appeared in
1881, was the earliest of the two-cycle types, and his name is
generally associated with such engines. It was of the simplest
possible design, the use of gear wheels being avoided, and in
actual use the working was very regular and noiseless (see Fig.
324). Two cylinders were arranged side by side on the overhanging
end of the bed plate; the one serving as a single-acting engine,
and the other as a compressor for the explosive mixture; that is,
the mixture was compressed in a separate cylinder instead of in the
working cylinder, as in engines of the four cycle type. After the
transfer of the compressed charge into the working cylinder, the
compressor was arranged to entrap and compress a quantity of air,
which was later used for sweeping out of the cylinder the exhaust
gases resulting from the previous explosion. By the use of the
second cylinder it is possible to dispense with half the strokes of
the Beau de Rochas cycle, and to have one impulse for each
revolution of the crank. Combustion which takes place at constant
volume is more complete and instantaneous, but the expansion is
greater, notwithstanding that the out put is increased. It should
be mentioned that the ignition is effected by the carriage of a
flame from the ignition jet to the combustion chamber by means of a
slide valve provided with suitable pas sages. A water jacket round
the cylinder keeps the temperature from becoming excessive, and by
a special arrangement the two cylinders could be made to work on
the compound principle by allowing the gases, after their expansion
in the working cylinder, to act on the forward face of the second
(compressor) piston. Exhaust then took place in the ordinary way,
but from the compressor instead of from the working cylinder. In
spite of its many excellent features the engine never competed
successfully with the somewhat more economical engines of the Otto
type, and at the present time the system has been almost wholly
abandoned.

The Midland Engine

As will be seen from Fig. 328, this double-acting engine
comprised two equal cylinders arranged side by side, with a pair of
connecting rods driving two cranks set at an angle of 65 degrees to
one another. One of the cylinders acted solely as a compressor for
the ex plosive mixture, which was transferred at the proper moment
to the other cylinder, in which the exploded mixture exerted its
driving force.

There are many other types of two-cycle engines, but space
forbids further reference to them here. Description of these
engines are given in considerable detail in the treatise by M. Witz
on The Theory and Practice of Gas and Oil Engines, already referred
to. The Benier two-cycle producer-gas engine will, however, be
dealt with later, when treating of engines driven with poor gases,
as certain novel and interesting features are involved in it. The
following section deals with four-cycle engines introduced by Beau
de Rochas, but first practically realized by Dr. Otto in 1887.

The Otto Engine

A general description now of the principles upon which the Otto
engine is based will save further repetition when dealing with the
engines built by other makers, which work on the Otto cycle, or on
some very analogous system. From the first introduction of the Otto
engine the successful results obtained ensured its very general
adoption, and on the expiry of the patents many imitations and
improvements of more or less value were introduced by other
manufacturers.

A partial section through the cylinder, compression chamber, and
slide valve of a vertical engine of the Otto type is given in Fig.
329. An enlargement I of the cylinder bottom serves as a chamber
for the compression of the explosive mixture of gas and air, which
is sucked in during the upward stroke of the piston and compressed
on the return to a pressure of from three to four atmospheres. At
this pressure, when the piston has reached the end of its stroke,
the gas jet b is exposed to the explosive charge in the cylinder by
the movement of the slide valve operated by the connecting rod t.
Explosion then takes place, and the temperature rises to about 1500
C, the driving pressure being about 185 lb. per square inch of the
piston area. On the return of the piston to the bottom of the
cylinder, that is, during the fourth stroke corresponding to the
final half of the second revolution of the crank, the burnt gases
are expelled to the atmosphere under a pressure of from 2 lb. to 4
lb. Water jackets are fitted around all portions of the engine that
are subjected to the high temperature of the exploded gases.
Attention was particularly directed by the designer to the question
of the reduction of the gas consumption, and good results were
obtained by diluting the mixture with a proportion of the waste
gases resulting from the previous explosion. By diluting the
mixture in this way the charge was consumed more gradually instead
of explosively. It was found that the low consumption was not
wholly due, as claimed, to the super posed arrangement of layers of
gas and air in the cylinder, but to a certain action of the
walls.

Mechanically, the Otto was an excellent example of good design
and simplicity of arrangement. Admission and exhaust were
controlled by means of cams, and ignition of the charge was
effected by the transport of a flame under pressure. When the speed
exceeded a certain fixed limit, a governor acting on the ‘hit
&. miss’, or, as it is called by French engineers, ‘the
all or nothing’, system, suppressed the admission until the
speed again became normal. Motion was transmitted to the crank in
the usual way by means of a connecting rod, and a specially heavy
flywheel was employed for the storage of sufficient energy during
the working stroke to ensure some regularity of running during the
three remaining idle strokes of the cycle. The consumption was
about 28 cu. ft. of gas per horsepower hour.

Fig 330 is an end view in partial section showing the
arrangement of the valves adopted by Dr. Otto in his early engines
and the arrangement of the levers for operating them. A section
through the mixture admission valve M and the ignition slide and
port I is also given in Fig. 331.

Gas enters through the valve G, which is opened at the correct
moment by a system of levers operated from a cam on the half-speed
shaft at the right side of the engine, and the mixture of gas and
air is sucked as shown by the arrows into the chamber M and thence
through the valve M’ into the cylinder. An external view of an
Otto engine is given in Fig. 332.

To Dr. Otto belongs the credit of having first introduced the
gas engine in a really practical form, and of indicating the
direction of future developments. Other engineers, following the
lead of Otto, have improved the details of construction, and the
consumption of gas, to a very considerable extent by reducing heat
losses and increasing the expansion until at the present time the
gas engine is able to compete with steam under most industrial
conditions.

A few of the more remarkable types introduced during the last
twenty-five years will be now briefly described, in order to
illustrate the development of four-cycle engines that has taken
place.

Lenoir Engine

In this engine, which first appeared in 1883, the inventor
introduced the experience of twenty-five years of continuous
experiment and work. The cylinder which overhung the base was
provided externally with air-cooling vanes, as illustrated in Fig.
333, and the crosshead was guided in a bored out trunk in line with
the cylinder. Electric ignition was adopted, the spark being
produced by a battery in conjunction with a Ruhmkorff coil. About
28 cu. ft. of gas were consumed per horse-power hour. Two other
Lenoir engines burning petroleum vapor have been introduced, one of
them being specially arranged for motor-car work. These will be
described later when dealing with oil engines.

The Hornsby-Stockport

These engines were originally made by Andrew & Company, and
were known in France as the Triomphe engine. Two modern examples of
Hornsby-Stockport engines are given in Figs. 335 [not shown here]
and 336. The latter has a specially heavy flywheel for direct
electric lighting, and the outer ‘ end of the shaft is
supported on an extra bearing. Governors of a special vibrating
weight type are fitted to the small engines of about 6 HP, Fig.
335, but centrifugal-ball governors are used for all larger sizes,
which are also provided with self-starters of a compressed-air
type. Small engines may be readily started by hand, and for the
intermediate sizes a simple pump arrangement is recommended. Either
tube or electric ignition may be provided, but magneto-electric
ignition is supplied in all cases where suction gas is used.

To start an engine provided with a self-starting gear, care must
be taken to stop the engine with the connecting rod just above the
centre and with the piston near the end of its stroke at the
position of ignition. Gas is then admitted to the cylinder through
a small valve held open by a light spring, and entering as it does,
under some pressure, a portion of the air in the cylinder is driven
through another small spring controlled valve into a chamber
communicating directly with the incandescent ignition tube. After a
few moments some of the entering gas also passes through the up per
valve into the ignition space, and when sufficient has passed to
make an explosive mixture, ignition of the small charge takes place
in contact with the tube or the electric spark. The flame of the
small charge in turn explodes the mixture in the cylinder, and the
piston moves forward, driven by the force of the expanding gases.
After the first stroke the working of the engine be comes
automatic, the gas and air valves being controlled in the usual way
from the cam shaft driven from the engine itself. Producer gas may
also be used, in which case the consumption of anthracite is about
1 to 1 lb. per horse power hour.         
                 
       

Editor’s Note: We’ll be continuing
with more ‘Typical Gas Engines’ in a future issue.

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