By C.W. SIEMENS, London.
The cylinder of the engine--assuming that it has only a single-acting
one, placed with its axis vertical--consists of two parts; the upper hot
part being lined with plumbago, fire-clay, or other refractory material,
and the lower part kept cool by a water casing. The cylinder has a trunk
piston working in the lower part, and on its upper side a shield that
almost fills the hot part of the cylinder when the piston is at the
extreme of its upstroke. The trunk-rod of the piston passes through a
stuffing-box in the cylinder bottom, and is connected to a crank on the
engine-shaft; and this (unless multiple cylinders are employed) carries
a heavy fly-wheel. From the lower end of the cylinder there is a passage
which, by means of a rotating or reciprocating slide, is alternately
put in communication with inlets for gas and air (regulated by suitable
cocks or valves) and with a strong receptacle. As the piston, makes its
upstroke, air and gas are drawn into the annular space surrounding its
trunk, and the mixed air and gas are compressed by the downstroke of
the piston, and delivered into the receptacle, in which considerable
pressure is maintained. The receptacle is made of cylindrical form, with
a domed cover of thin sheet metal; so that in case of excessive internal
pressure it can operate as a safety-valve to save the body of the
receptacle from damage. From the upper end of the cylinder there is
a passage that, by means of a rotating or reciprocating slide, is
alternately put in communication with the receptacle and with a
discharge outlet. In this passage are fixed a number of wire gauze
screens or pieces of metal with interstices. These constitute a
regenerator of heat, and also prevent a communication of flame from the
cylinder to the receptacle. In the upper end of the cylinder or of the
piston shield are provided electrodes which give an electric spark, or
a platinum wire which is rendered incandescent by a current from an
inductor or other source of electricity to ignite the combustible charge
of the cylinder. After the engine has been for some time at work,
the heat at the upper part of the cylinder may suffice for effecting
ignition without provision of other means for this purpose.
In combining such an engine with means for generating the combustible
gas, a gas producer is employed. In this producer a current of heated
air is introduced into the heart of a body of kindled fuel, and
the gases produced--partly by distillation and partly by imperfect
combustion of the fuel--are conveyed to the gas inlet of the cylinder
or pump of the engine. As the gas in leaving the producer is hot, it is
caused to pass through regenerating apparatus, to which it delivers a
large portion of its heat before it reaches the engine, and the air
which supplies the producer is made to pass through this regenerating
apparatus so as to take up the heat abstracted from the gas.
In the accompanying engravings, Fig. 1 shows a front elevation (partly
in section) of a pair of engines constructed according to this
invention. The lower part, A, of each cylinder is cooled by water
circulating through its casing. The upper part, B, is lined with
refractory material, such as fire-clay. The trunk piston, C, is made
hollow, and formed with a shield covered by refractory material to
protect the packing of the piston and the surface of the lower part of
the cylinder from heat. The pistons of the two cylinders are connected
by rods, D, to opposite cranks on the shaft, E. This shaft, by means of
bevel gear, F, works a revolving cylindrical valve, G, situated in a
casing between the two cylinders. The lowest part of this casing is
supplied with combustible gas and with air, in proportions capable of
being regulated by stopcocks or valves. The highest part of the casing
communicates with a discharge-pipe; and the middle part of it with a
reservoir which can be cut off from communication by a stopcock, so that
the charge in the reservoir may be retained when the engine is stopped.
The middle space of the hollow valve, G, communicates, by a number of
holes, with the middle space of the slide casing. It also, by means of a
port at its lower part, communicates alternately with the annular spaces
of the two cylinders; this communication in each case being made when
the piston is performing the latter part of its downstroke. The interior
of the slide also, by means of a second port at its upper part,
communicates alternately with the tops of the two cylinders; this
communication being in each case made while the piston is performing the
first portion of its downstroke. During the upstroke of each piston the
slide, by means of another port, makes communication alternately to each
cylinder from the bottom of the slide casing, and by means of a fourth
port make communication alternately from each cylinder to the top of the
slide casing. In the passage connecting the top of the slide casing
to each cylinder is placed a regenerator, consisting of a number of
perforated metal plates or sheets of wire gauze.
[Illustration: SIEMENS' GAS PRODUCER AND GAS MOTOR. Fig 1.]
In order that gas of poor quality or gas diluted with a large proportion
of air may be utilized, an igniting arrangement is employed which
operates as follows: I is a vessel containing a supply of hydrocarbon
oil, preferably of volatile character. From this vessel pipes lead to
two cocks, one for each cylinder; these corks being caused to revolve in
time with the engine-shaft by a chain, M, communicating motion from a
wheel on the engine shaft to a chain-wheel of equal size on the spindle
of the two cocks. The plug of each cock has on its side a small hollow,
which during one part of its revolution presents itself under the
oil-pipe, and receives a charge of oil. During another part of its
revolution, which is timed to correspond with the flow of gaseous
mixture to the cylinder, the hollow of the plug presents itself to the
bend of a pipe leading from the top of the cylinder to a port opening
into the cylinder below the regenerator, in which port are situated
two wires of platinum. These wires are connected with the brushes of a
commutator, K, on the engine-shaft, which commutator is in electrical
connection with the poles of a battery, dynamo-electric machine, or
other source of electricity. Instead of two wires to produce a spark, a
single wire may be arranged to become incandescent at the proper time
for ignition.
The operation of the engine is as follows: Each piston as it ascends
draws into the annular space under it a supply of gas and air in
proportion regulated by the cocks or valves, and as it descends it
forces this charge into the interior of the revolving valve and its
casing, and into the reservoir which communicates therewith. When either
piston is at the top of its stroke, the revolving valve admits to the
upper part of the cylinder a supply of the gaseous mixture from the
reservoir and valve casing, and this passes through the generator. At
the same time a portion of the charge passes by the pipe, and becomes
enriched by admixture of the hydrocarbon oil delivered to it by the
cock. The enriched mixture, in passing the platinum wires, which at that
time give an electrical spark, is ignited, and ignites the charge that
is passing through the regenerator into the cylinder. The mixture thus
ignited expands, and acting on the full area of the piston propels it
downward, the under side of the piston being at that time subject to
pressure only on its annular area. When the piston has completed its
down-stroke the passage is opened to the discharge-pipe, and the
expanded products of combustion then pass from the cylinder through the
regenerator, and are discharged. In their passage they give out to the
regenerator a large portion of their heat, which the charge entering
the cylinder for the next stroke receives in passing through the
regenerator.
[Illustration: SIEMENS' GAS PRODUCER AND GAS MOTOR. Fig 2.]
Fig. 2 is a vertical section of a gas producer and scrubber, which, as
stated above, may be employed in combination with engines such as have
been described for supplying them with combustible gas. The producer
is a vessel lined with refractory material. At the top it has a supply
opening covered by a cap, U, having a flange dipping into a sand joint.
At the bottom it has an opening surrounded by inclined bars, V, which
rest upon a water-pipe perforated with small holes, by which water
issues to cool the bars and generate vapor. This vapor rises along
with a limited supply of air through the incandescent fuel above, and
combustible gas is produced, which collects in the annular space, and
is led thence by a pipe to the scrubber. The scrubber is a vessel
containing in its lower part water, W, supplied by a pipe, and having an
overflow. By means of a perforated deflecting plate the gas is caused
to bubble through the water, whereby it is cleansed and cooled, and it
passes by a pipe, X, to supply the engine. The upper end of the vertical
pipe of the scrubber is made open and covered by a cap sealed in water
while the producer is at work. In starting the producer this cap is
removed and a chimney pipe put in its place, so as to give a draught for
kindling the fuel in the producer. When the fuel is kindled the chimney
is removed and the cap substituted, whereupon the suction of the engine
continues the draught as required.
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