IM- PROVEMENTS IN GAS MOTOR ENGINES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Matthew Piers Watt Boulton at the
Office of the Commissioners of Patents on the 25th June 1878.
MATTHEW PIERS WATT BOULTON, of Tew Park, in the County of Oxford. "IM-
PROVEMENTS IN GAS MOTOR ENGINES."
This Invention relates to engines worked by the combustion of an inflammable
mixture of elastic fluids, the products of combustion being used in the engine.
In the following descriptions I shall speak of gas and air as the ingredients used,
it being understood that what is said of these is applicable when other elastic fluids
are employed.
In engines constructed according to this Invention, the heat abstracted from the
cylinders or vessels employed may be used to generate steam which assists in
working the engine, or otherwise, the abstracted heat may pass away as waste.
I shall first describe a mode of introducing the charge of inflammable mixture
and causing conibustion.
The combustible charge is contained in two cylinders, one filled with air, the
other with a mixture of gas and air, mixed in such proportion as not to be liable to
ignite within the cylinder. I call these cylinders the charging cylinders.
The cylinder in which the piston which drives the engine works, which is of
larger size than the charging cylinders, is called by me the main cylinder, and its
piston the main piston. Communicating with this cylinder is a space or receptacle
iuto which fluid to be heated is introduced.
At the commencement of the working stroke the fluid in the receptacle may be
at atmospheric pressure, or it may be at high pressure, its pressure having been
raised by compression or otherwise. At this period the charges in the charging
cylinders have the same pressure as the fluid in the receptacle.
At the commencement of the working stroke, the charging pistons are caused
to move, driving their charges into the receptacle. As they enter this they are
mixed and undergo combustion; this combustion occupying a sensible time takes
place quietly. As the charges are expelled from the charging cylinders, fluid from
the receptacle enters behind their pistons, so that these move with nearly equal

page_text: pressure on both sides. Otherwise, the charging pistons may force their charges
into the receptacle without being thus put in equilibrium.
The combustion caused as above described raises the pressure of the fluid in the
receptacle, and the heated fluid expands, driving the piston.
In some of the combustions which I shall describe, the receptacle into which
the charges are expelled is a cylinder.
In operating in the manner above described, the pressure outside the charging
cylinders would rise owing to the combustion sooner than the pressure within
them, and this would tend to cause some backward flow of fluid into the cylinders.
This. may be prevented by causing the pistons of the charging cylinders to move
with a varying velocity, and by varying the areas of their discharging apertures.
The movement of the charging pistons is timed so that their stroke takes place
while the piston in the main cylinder is performing a small portion of its stroke.
This may be done by means of a cam, or by any known suitable contrivance.
In the descriptions which I proceed to give of constructions and modes of
operation, I shall suppose this method of causing the combustion to be employed.
But the constructions are also applicable when other modes of effecting the com-
bustion are employed, concerning which I shall speak subsequently.
In ordinary constructions of gas engine the cylinder is cooled externally by
water, so that heat is abstracted from the inetal and fluid while it is performing
work. It is desirable to work in such a way as to lessen the need of such external
cooling agency.
I proceed to describe a construction for this purpose, which is applicable both
when steam is generated and when it is not so; I provide two cylinders in which
the fluid works, a smaller and a larger one. In the working stroke the fluid passes
from the smaller to the larger cylinder, expanding therein, and in virtue of the
'difference of the areas the pistons performing work; I provide also a refrigerator or
chamber kept cool by pipes or surfaces cooled by water or liquid, or by any known
suitable method of refrigeration, and passages governed by valves are provided,
so that the fluid can pass from one of the cylinders to the other, either through the
refrigerator or through another passage.
The operation is as follows:-The smaller cylinder is full of cool incombustible
fluid; its piston moves, driving out fluid into the larger cylinder. At the same
time the pistons of the charging cylinders move, driving their contents into the
smaller cylinder, which ungergo combustion therein in the manner previously
explained. Or these contents might be driven into the fluid in some other part of
the space occupied thereby. The combustion as previously explained is caused to
take place before the working pistons perform much of their strokes. The heat of
the combustion raises the pressure of the fluid in the working cylinders, and it
expands, performing work. During this stroke, the fluid in passing from the smaller
to the larger cylinder does not pass through the refrigerator.
When the pressure of the working fluid is reduced by expansion to the pressure
of the fluid in tho refrigerator, a valve opens, and, as the stroke proceeds, fluid issues
from the refrigerator into the working fluid, in some portion of the space which it
occupies becomes heated therein, and as it expands assists in performing work. At
the end of the stroke the pressure of the working fluid may be reduced considerably
below the atmospheric. On the return stroke the fluid is driven back from the
larger to the smaller cylinder, being made in doing this to pass through the
refrigerator, wherein heat is abstracted from it. When the pressure of the fluid has
risen to the atmospheric, an escape or eduction valve is opened, and a certain
portion of the fluid is expolled. The rest of the fluid in the larger cylinder is
driven into the refrigerator and the smaller cylinder, and at the end of the stroke
occupies these at such a pressure as is desired.
When this construction is used, the principal portion of the necessary cooling may
be effected by the refrigerator, external cooling of the cylinder by water being
reduced or in some cases entirely dispensed with.
The construction last described is also applicable when steam is generated. In

page_text: tliis case the refrigerator which cools the hot gases or fluid acts as a boiler which
generates steam. The steam used is admitted into the smaller cylinder, or into
some portion of the space occupied by the working fluid during the first part of the
working stroke.
In operating according to the principle of action above explained, instead of two
cylinders of different sizes one cylinder may be provided fitted with a differential
piston, the fluid in passing alternately from one end of this cylinder to the other
being treated as previously described.
The following is another construction for effecting generally the same object:―
A receptacle is provided in connection with the main cylinder, into which receptacle
the fluid to be heated by the combustion is introduced. Passages governed by
valves are provided so that at certain times circulation can be made to take place
through the refrigerator and receptacle, and space in the main cylinder occupied by.
the fluid which has performed work.
In order that circulation may take place through the space in the main cylinder,
I provide two passages or sets of passages opening into it, connected with the
refrigerator. Through one of these the fluid from the refrigerator issues into the
main cylinder, thence it flows up to the piston and sweeps back to the other passage
or passages, through which it flows out again in its course to the refrigerator. Ŏr
otherwise, I attach to the piston of the main cylinder a pipe arranged to work in a
tube external to the cylinder, the pipe and tube being of such length as to con-
stitute a channel, through which at every stage of the piston's movement the
passage of fluid previously described can take place; a fan or rotary instrument is
provided for causing the movement of the fluid through the refrigerator and-
passages or otherwise this may be done by a piston in a cylinder.
I proceed to describe the operations:-It will be understood that several of the
details may be varied. The charging cylinders drive their charges into the
receptacle; and combustion is caused to take place as previously explained. The
heated fluid expands in the main cylinder the performing work. When its pressure
is reduced to that in the refrigerator a valve opens, and as the stroke proceeds, fluid
issues from the refrigerator, passing through the receptacle, receiving heat, and as it
expands, performing work as previously explained.
When the piston of the main cylinder has nearly reached the end of its working
stroke, the valve which governs the passage for circulation through the refrigerator
is opened, and circulation is caused to take place through the refrigerator, the
receptacle, and the space in the main cylinder occupied by the fluid which has
performed work. The cool current thus sweeping through the vessels abstracts a
further portion of heat from them, and also abstracts a portion of heat from the
fluid which has performed work, so that the temperature of the latter becomes
nearly as low as that of the refrigerator. On the return stroke the circulation
through the refrigerator continues, and a large portion of the heat due to com-
pression is abstracted by it. At atmospheric pressure a portion of fluid is expelled,
and at the end of the stroke the receptacle is occupied by fluid at such pressure as
is desired. The operation is then ready to be repeated.
The construction above described may also be employed when steam is generated,
the refrigerator acting as a boiler as previously mentioned. In this and in
preceding constructions the eduction valve is arranged so that the time during
which it is open can be adjusted at pleasure. And in this way the degree of.
compression given to the fluid can be varied.
Again in cases where compression is used, the engine at first starting may work
without compression, afterwards the compressing action is brought into play to such
a degree as is desired.
The time of opening the eduction valve may be regulated by a governor, so as to
vary it according to the speed of the engine.
The constructions which I have described remain applicable when modes of
introducing the inflammable mixture and effecting the combustion are employed,
different from that which I have above explained. For instance, the whole fluid

page_text: occupying the cylinder and receptacle in the latter part of the stroke might be
mixed, so as to be rendered combustible before ignition, and then ignited.
This part of the operation would then be timed as follows:-In the return stroke
of the main piston it would at a certain period expel a portion of fluid through the
escape or eduction valve. This valve having been closed the inflammable charge
would be introduced and be mixed with the other fluid still remaining in the main
cylinder, so that at the end of the stroke the receptacle would contain combustible
fluid at such pressure as desired. At the commencement of the next stroke this
would be ignited. But it is possible and in some cases desirable to operate other-
wise, so that at the end of the stroke and moment of ignition part of the fluid shall
be combustible and part incombustible.
The operation may also be performed as follows:-The charge is introduced into
a separate cylinder and ignited therein, whereupon a large portion of it rushes into
the receptacle heating the fluid in it. The piston of the charging cylinder moves,
expelling into the receptacle the hot gases still remaining in the charging cylinder,
while fluid from the receptacle enters behind it.
When the combustible charge is introduced by means of two separate cylinders in
the manner I have above described, the supply of gas and air can be diminished as
desired, in combustible fluid being supplied to such an extent as may be desired in
their stead to the cylinder, which is charged with gas and air. Such alteration of
supply can be regulated by a governor, so as to vary the strength of the com-
bustible mixture according to the speed of the engine.
The construction of engine last described may be modified as follows:-The
receptacle is provided with a displacing piston, so that the fluid in the receptacle
can be displaced therein when desired, and passages governed by valves are
provided so that the displaced fluid can be made to travel either directly from one
end of the receptacle to the other, or through the refrigerator.
The main cylinder is also provided with a displacing piston; to this piston is
attached a tube working in a passage which communicates with the refrigerator
and is governed by a valve. The fluid between the displacing piston and main
piston can pass through this tube into the refrigerator when the valve is open. The
space on the other side of this displacing piston also communicates with the
refrigerator through a passage governed by a valve, so that when the valves are
open, circulation can take place through the refrigerator from one side of the
displacing piston to the other.
Passages governed by valves are also provided between the receptacle and main
cylinder, so that the fluid can pass from the one to the other, either through the
refrigerator or not through it.
In the working stroke the fluid passes from the receptacle to the main cylinder
without passing through the refrigerator; in the return stroke it passes back
through the refrigerator.
"
During the working stroke the displacing piston in the receptacle displaces the
fluid within it, so as to travel by the direct course. In thus moving, the fluid
abstracts heat from the metal of the receptacle.
When it is desired to bring the cooling action into play, the displacing piston in
the main cylinder is caused to move so as to approach the main piston, while the
communications between the main cylinder and refrigerator are opened. In con-
sequence the fluid in the main cylinder is caused to pass through the refrigerator
and is cooled. The fluid in the receptacle is also cooled by the movement of the
displacing piston, which causes it to pass through the refrigerator, and the fluid
which is compressed by the main piston on the return stroke passes through the
refrigerator to the receptacle.
Most of the operations above described may be performed by means of one.
displacing piston working in the main cylinder.
For the purpose of effecting the ignition of the inflammable mixture I employ the
following construction :-I provide a chamber within which a gas flame is made to
burn at certain times at the ordinary or atmospheric pressure. The gas and air

page_text: which feed this flame are governed, by valves which may be self-acting, and the
chimney or tube by which the products of combustion pass away is governed by a
valve in like manner. A passage is provided governed by a valve worked by tho
engine, so that communication between this chamber and the chamber or vessel
containing the inflammable mixture, which it is desired to ignite is opened and
closed at certain times. Outside the mouth of the chimney of the flame chamber
previously mentioned, and near to it, a gas flame is kept constantly burning at the
ordinary or atmospheric pressure.
When the time arrives at which it is desired to ignite the mixture, the slide or
valve opens the passage previously mentioned, so as to make communication
between the flame chamber and the chamber containing the inflammable mixture
The mixture in this chamber has a higher pressure than the pressure in the flame
chamber. In virtue of this higher pressure it rushes or flows into the flame
chamber, and is ignited by the flame there, and the ignition strikes back into
the chamber containing the inflammable mixture. Just at this moment the valves
which govern the communications of the flame chamber with the outer air and
gas supply are closed. The supply of the flame being cut off it is extinguished.
The valve now closes the communication between the flame chamber and the
chamber in which the mixture was ignited, and the communications of the flame
chamber with the outer air and the gas supply are opened.
The gas and air supplied to the chamber rise through the chimney, and issuing
from its mouth como in contact with the flame there kept constantly burning. In
consequence of this they are ignited, and the ignition striking back lights the flame
in the chamber. The operation is then ready to be repeated.
I prefer that the jet in the flame chamber should be fed with a mixture of gas
and air, so that the flame may burn smokelessly.
In the descriptions of engines which I have above given, I have for the sake of
simplicity described them as single-acting, but it is to be understood that in all.
cases except that where the differential piston is employed, they may be made
double-acting by suitable duplication of the parts.