IMPROVEMENTS IN OBTAINING MOTIVE POWER. AND IN APPARATUS TO BE USED FOR THIS PURPOSE
Year: 1874

page_text: LETTERS PATENT to Flceming Jenkin, of 3, Great Stuart Street, in the
City of Edinburgh, for the Invention of "IMPROVEMENTS IN OBTAINING
MOTIVE POWER. AND IN APPARATUS TO BE USED FOR THIS PURPOSE."
Sealed the 15th December 1874, and dated the 11th July 1874.
PROVISIONAL SPECIFICATION left by the said Fleeming Jenkin at the
Office of the Commissioners of Patents, with his Petition, on the
11th July 1874.
:
I, FLEEMING JENKIN, of 3, Great Stuart Street, in the City of
Edinburgh; do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN OBTAINING MOTIVE POWER, AND IN APPARATUS TO BE USED
FOR THIS PURPOSE," to be as follows:-
The object of my Invention is to diminish the quantity of fuel
required in the production of motive. power. I effect this object by a.
thermodynamic engine, which approximates to what is known as a
perfect heat engine, and which is free from those defects that have
"
}

page_text: prevented the general adoption or other engines, the design or which nas
been based on similar principles.
My engine, which I call, to distinguish it from others, a "fuel engine,"
works with a very great range of temperatures, and belongs to that class
of heat engines in which the pressure of the fluid undergoes a great
change while its volume remains constant, or nearly so. The primitive.
type of this engine is Stirling's air engine.
The fuel engine contains the following parts:-Combustion chamber
or chambers; displacer or displacers; regenerator or regenerators;
cooling chamber or chambers; working cylinder or cylinders; com-
pressing air cylinder or cylinders; and, finally, apparatus for introducing
fuel into the combustion chamber in such manner that as much fuel as
is introduced into the combustion chamber during one cycle of
operations, as for instance, during one revolution of the crank shaft
shall be consumed during that cycle.
I have, named working cylinders and compressing cylinders as the
simplest form of parts intended to produce the desired effect, but any
analogous contrivance may be employed.
In all forms of my Invention I use as the fluid driving the engine the
gaseous products of combustion. In the simplest form of fuel engine I
employ combustible gas as my fuel. The ordinary purified illuminating
gas may be used, or the complex and unpurified products of the distilla-
tion of coal or other fuel; these unpurified products being cheaper are so
far preferable.
The following is the action and construction of the gas fuel engine:-
The combustion chamber is lined with fire-brick or a similar substance,
which during the working of the engine becomes and remains white
hot. When the engine is to be started it must be heated by allowing
the combustion of a sufficient quantity of fuel, which must at this period
be, lighted independently in any of the ways now employed to ignite.
gas and air in ordinary gas engines. When the combustion chamber
has once been heated it will itself fire the gas and air introduced into it.
The air required for combustion is forced into the cooling chamber by
the compressing cylinder; it is cooled while being compressed. The
gas is also forced into part of the cooling chamber and is cooled while a
being compressed. When the required charge of gas and air have been

page_text: forced into the cooling chamber they are displaced by the displacer,
they pass through the regenerator, and enter the combustion chamber
where they take fire. The air and gas are heated and expanded by the
regenerator, and are still further heated by their combustion: In this
condition of high pressure they are admitted to the working cylinder
and drive the piston through its working stroke. At or near the end of
this stroke the displacer removes the products of combustion to the
cooling chamber. The exhaust or return stroke of the piston in the
working cylinder now begins; the products of combustion which have
entered the cylinder are now driven out into the chimney. During the
exhaust stroke a fresh charge of air and gas are forced into the cooling
chamber and the cycle of operations is repeated.
The above description refers to the single-acting cylinder engine; the
double-acting single-cylinder engine requires two cooling chambers,
two regenerators, two combustion chambers, and two pairs of com-
pressing cylinders for air and gas.
Engines to some extent analogous to these fuel engines have been
constructed, in which the charge of coal for some hours' work was
introduced at once into the combustion chamber, this fuel being in the
heated state.
In my fuel engine, as above described, the gaseous form of the fuel
forms one distinction, but a second distinction arises from the fact that
the fuel is only introduced in such quantities as are required for each
stroke:
.
Although I prefer gas, other forms of fuel, such as petroleum, or even
comminuted coal may be employed, but I do not pass these through the
regenerator. I sometimes introduce the gas itself directly into the
combustion chamber instead of into the cooling chamber; this plan
avoids all risk of combustion or explosion in the cooling chamber or
regenerator. At each stroke the products of combustion must be let out
from the exhaust equal in weight to the fuel and air introduced by the
compressing cylinders so long as I do not wish to alter the initial
pressure at the beginning of each working stroke, but this pressure can
bé raised or lowered at any time by altering the relative quantities of
fluids introduced and expelled. The horse power can be regulated by
increasing or diminishing the quantities of fuel and air introduced at
each stroke. _

page_text: (
The working cylinder may, as in the case of the steam engine, be in
connection with the, high-pressure fluid during the whole or during only
part of the stroke of the engine. The engine will work although the
regenerator is omitted, but it will use more fuel for a given horse power.
The displacer is essential.
The following advantages are possessed by fuel engines, and these
advantages have never yet been combined in any one engine:-The
working fluid may be at high pressure, and the working parts may con-
sequently be small; the range of temperatures is great, being the
difference between the heat of combustion and that of the cooling
chamber; this gives economy of fuel; the heat is communicated directly
to the fluid, instead of being transmitted from them across-metal plates;
this allows durability and strength to be secured notwithstanding the
high temperature of the fluid; the fuel in the working cylinder is cool;
this allows of proper lubrication and prevents undue corrosion; the fuel
is introduced as required and in quantities which can be adjusted with
nicety, so that the power can be increased or diminished from stroke to
stroke; this renders the engine as available as the steam engine for all
things where the power developed must be under control; the fuel
engine can continue at work for an indefinite time; this is not the case
where fresh charges of coal require to be introduced after some hours'
work, as in the air engine above alluded to; the heat is produced at one
part of the cycle where it can be advantageously used, and is not pro-
duced whilst the fluid is being cooled; the fuel engine can be set at
work in a shorter time than the steam engine, and there is less risk of
explosion; the fuel engine is more economical than the ordinary gas
engines, and it avoids the shock produced by the explosion of gas.
•
14
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Fleeming Jenkin. in the Great Seal Patent Office
on the 11th January 1875..
'
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FLEEMING
JENKIN, of 3, Great Stuart Street, in the City of Edinburgh, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eleventh day of July, in the year of

page_text: our Lord One thousand eight hundred and seventy-four, in the thirty-.
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Fleeming Jenkin, Her special license
that I, the said Fleeming Jenkin, my executors, administrators, and
assigns, or such others as I, the said Fleeming Jenkin, my executors,
administrators, and assigns, should at any time agree with, and no others,.
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN OBTAINING
MOTIVE POWER, AND IN APPARATUS TO BE USED FOR THIS PURPOSE," upon the
condition (amongst others) that I, the said Fleeming Jenkin, my
executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe
and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the
Great Seal Patent Office within six calendar months next and imme-.
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Fleeming Jenkin, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement thereof, that is to say:
The object of my Invention is to diminish the quantity of fuel required
in the production of motive power. I effect this object by a thermo-
dynamic engine, which approximates to what is known as a perfect heat
engine, and which is free from those defects that have prevented the
general adoption of other engines, the design of which has been. based
on similar principles.
My engine, which I call, to distinguish it from others, a "fuel
engine," works with a very great range of temperatures and belongs to
that class of heat engines in which the pressure of the fluid undergoes
a great change while its volume remains constant or nearly so; the
primitive type of this engine is Stirling's air engine.
The fuel engine contains the following parts -Combustion chamber
or, chambers, displacer or displacers, regenerator or regenerators, cooling
chamber or chambers, working cylinder or cylinders, compressing air
cylinder or cylinders, and finally apparatus for introducing fuel into the
:

page_text: combustion chamber in such manner that as much fuel as is introduced
into the combustion chamber during one cycle of operations, as for
instance during one revolution of the crank shaft, shall be consumed
during that cycle.
I have named working cylinders and compressing cylinders as the
simplest form of parts intended to produce the desired effect, but any
analogous contrivance may be employed.
In all forms of my Invention I use as the fluid driving the engine the
gaseous products of combustion. In the simplest form of fuel engine I
employ combustible gas as my fuel. The ordinary purified illuminating
gas may be used, or the complex and unpurified products of the
distillation of coal or other fuel; these unpurified products being cheaper
are so far preferable.
.
The following is the action and construction of the gas fuel engine :-
The combustion chamber is lined with fire-brick, or a similar substance,
which during the working of the engine becomes and remains white hot.
When the engine is to be started it must be heated by allowing the
combustion of a sufficient quantity of fuel, which must at this period be
lighted independently in any of the ways now employed to ignite gas
and air in ordinary gas engines. When the combustion chamber has
once been heated it will itself fire the gas and air introduced into it.
The air required for combustion is forced into the cooling chamber by
the compressing cylinder, it is cooled while being compressed. The gas
is also forced into part of the cooling chamber, and is cooled while being
compressed. When the required charge of gas and air have been forced
into the cooling chamber they are displaced by the displacer, they pass
through the regenerator and enter the combustion chamber, where they
take fire. The air and gas are heated and expanded by the regenerator,
and are still further heated by their combustion. In this condition of
high pressure they are admitted to the working cylinder and drive the
piston through its working stroke, at or near the end of this stroke the
displacer removes the products of combustion to the cooling chamber.
The exhaust or return stroke of the piston in the working cylinder now
begins; the products of combustion which have entered the cylinder are
now driven out into the chimney. During the exhaust stroke a fresh
charge of air and gas are forced into the cooling chamber and the cycle
of operations is repeated.

page_text: double acting single cylinder engine requires two cooling chambers, two
regenerators, two combustion chambers, and two pairs of compressing
cylinders for air and gas.
Engines to some extent analogous to these fuel engines have been
constructed, in which the charge of coal for some hours work was
introduced at once into the combustion chamber, this fuel being in the
heated state.
In my fuel engine, as above described, the gaseous form of the fuel
forms one distinction, but a second distinction arises from the fact that
the fuel is only introduced in such quantities as are required for each
stroke.
Although I prefer gas, other forms of fuel, such as petroleum, or even
comminuted coal may be employed, but I do not pass these through
the regenerator. I sometimes introduce the gas itself directly into the
combustion chamber instead of into the cooling chamber. This plan
avoids all risk of combustion or explosion in the cooling chamber or
regenerator. At each stroke the products of combustion must be let out
from the exhaust equal in weight to the fuel and air introduced by the
compressing cylinders so long as I do not wish to alter the initial
pressure at the beginning of each working stroke, but this pressure can
be raised or lowered at any time by altering the relative quantities of
fluids introduced and expelled. The horse power can be regulated by
increasing or diminishing the quantities of fuel and air introduced at
cach stroke.
The working cylinder may as in the case of the steam engine be in
connection with the high-pressure fluid during the whole or during only
part of the stroke of the engine. The engine will work although the
regenerator is omitted, but it will use more fuel for a given horse power.
The displacer is essential.
-
The following advantages are possessed by fuel engines, and these
advantages have never yet been combined in any one engine. The
working fluid may be at high pressure, and the working parts may
consequently be small. The range of temperatures is great, being the
difference between the heat of combustion and that of the cooling
chamber; this gives cconomy of fuel. The heat is communicated
directly to the fluid instead of being transmitted from them across metal

page_text: plates; this allows durability and strength to be secured notwithstanding
the high temperature of the fluid. The fuel in the working cylinder is
cool; this allows of proper lubrication, and prevents undue corrosion:
The fuel is introduced as required, and in quantities which can be
adjusted with nicety so that the power can be increased or diminished
from stroke to stroke; this renders the engine as available as the steam
engine for all things where the power developed must be under control.
The fuel engine can continue at work for an indefinite time; this is
not the case where fresh charges of coal require to be introduced after
some hours' work as in the air engine above alluded to. The heat is
produced at one part of the cycle where it can be advantageously used,
and is not produced whilst the fluid is being cooled. The fuel engine
can be set to work in a shorter time than the steam engine, and there is
less risk of explosion. The fuel engine is more economical than the
ordinary gas engines, and it avoids the shock produced by the explosion
of gas.
Figure 1 is a sectional front clevation, Figure 2° a side elevation, and
Figure 3° a plan of a simple formi of my Invention, in which one single
acting working cylinder is used.
A is an air pump, drawing air from the surrounding atmosphere, and
cómpressing it into the cool end C of the displacer cylinder by the
pipe B; the air does not enter C until it has been considerably com-
pressed. The Drawing shews the pipe passing direct from the com-
pressing pump to the displacer cylinder, but the air may with some
advantage pass through a refrigerator to the displacer; or the upper end
of the displacer cylinder might be made to act as a refrigérator. The
.displacer D containing a regenerator is well protected at its lower end
by a covering of fire-brick which separates the wire gauze or similar
material from the combustion chamber E, which is also lined with fire-
brick or similar material; F is a pump by which gas, petroleum, or
similar material is injected into the combustion chamber by a pipe G.
The gas might be supplied to the upper part of the displacer cylinder C
with advantage so far as economy of heat is concerned, but to avoid risk
of combustion at C I now prefer to supply it at E. In case petroleum
were used the pump and pipes would be very much smaller than those a
shewn. His the working cylinder, communicating by an ordinary slide
valve with the cool upper part of the displacer cylinder. The exhaust
allows the products of combustion to escape into the air. The regenerator

page_text: and displacer D are driven by an eccentric on the main shaft, so fixed
that the displacer is near the bottom of its stroke when the piston of H
is near the top. The pump F is driven by another eccentric on the
main shaft, so placed as to inject fuel when the piston on H is near the
bottom of its stroke.
The action of the engine is as follows:-When the engine is to be
started an opening K on the displacer cylinder is uncovered and: gas
injected by the pump, which may be disconnected for the purpose by
well-known means. This gas is ignited from outside of the displacer
through an aperture made for the purpose at K; until the sides of the
combustion chamber or a portion of them, or a piece of asbestos
introduced for the purpose, becomes hot enough to ignite gas; the
opening K is then closed. As the engine turns the gas or petroleum
burn in the chamber E, producing heat when the piston of H is rising.
Communication is at this time open between C and H through the slide
valve ports; air is being sucked in by the pump A. When the piston F
is descending the burnt gas and air will have been displaced througli
the regenerator at C; and cooled by the process. Communication
between C and H is cut off during the descending stroke of F, the
previous charge of cold gas and air is expelled through the exhaust, and
a new charge of air compressed into C, either through a refrigerator or
directly. At the next stroke this cold air cools the regenerator, and is
heated when displaced by the rise of D. A refrigerator is not essential
in my engine. The cold chamber C will only receive the waste heat of
the regenerator, and even without a refrigerator need be little hotter
than the air when first compressed by the pump A... The fluid in the
displacer cylinder is never allowed to fall to atmospheric pressure. The
slide valve cuts off communication, so that at the end of the upward.
stroke the pressure in C is still much above the pressure of the
atmosphere.

page_text: times place a reservoir between the compressing pump A and the end of
the displacer cylinder, even when this reservoir is not used as a
refrigerator. I always maintain the pressure in the displacer cylinder C
considerably above the pressure of the atmosphere, and cut off com-
munication between C and H by a valve, so that the latter part of stroke
of the piston in H is performed by the expansion of the fluid in the
cylinder H. The chief object of so doing is that the regenerator D may
act more effectively, as will be the case when the fluid is comparatively
dense. A minor object is that the arrangement allows me when I desire
to do so to cool the air during compression more conveniently than I
could were I to begin to introduce air into C at the atmospheric
pressure.
Another advantage gained by the slide valve is that it prevents any
portion of the products of combustion from being further heated by
compression, as is the case in some forms of air or gas engines, in which
the displacer and working cylinder either communicate directly or form
part of the same cylinder. This valve therefore allows me to keep the
working piston cooler than can be done in the forms alluded to. A
reservoir of air between A and C enables me to control easily the initial
pressure at which the air enters C. It may also be used to help to start
the engine by its simple expansive force. I sometimes allow the valve.
admitting air to C from the reservoir to be self-acting, and sometimes
I work the valve from the engine, using means to vary the amount of
air admitted. The products of combustion' are intended to be expelled
at each stroke equal in amount to air and fuel admitted, and it is also
intended that the space in the end C of the displacer shall be only a
moderate fraction of the space swept through by the piston H, as for
instance, when the minimum pressure in C is about 50 lbs. absolute
pressure the space in C may be made about %, th of the volume swept
through by the piston, and the piston of the compfessing pump may
sweep through th of the volume swept through by the working
piston. This arrangement. helps to secure coolness of the working
cylinder, a point of great importance, for at the beginning of each
downward stroke of the piston H the weight of air in the end C of the
displacer cylinder is not great compared with the air introduced during
the downward stroke of A; then the pad of air and gas between C'and
H will be cool during the upward stroke of the latter, but if C contains
at the beginning of the downward stroke of H a large quantity of fluid

page_text: heated by repeated passage through the regenerator the mixture after
the introduction of cold air from A will still be hot, and the pad of air
between C and H will be hot during the upward stroke of the latter..
Moreover the action of the regencrator is improved by the low tempe-
rature which I secure in C before D begins to rise.
Moreover the action of the regenerator is improved by the low tempe-
rature which I secure in C before D begins to rise.
Figure 4 shews a plan, Figure 5 a side elevation, and Figures 6, 7, 8,
details of another arrangement of my engine more suitable for large
engines.
In order to secure efficient working it is necessary to expand from
high pressures, such as 250 lbs. per square inch, to low pressures
approaching that of the atmosphere, and the piston of the working
cylinder must, as arranged in the previous design, sweep through a large
number of cubic feet, involving a large working cylinder and great
strain on the working parts. I avoid this evil by adopting Wolff's or
the compound principle of a high and low pressure cylinder with the
addition that the low-pressure cylinder and compressing. pump are of
equal or nearly equal contents, and may be so arranged that the pressure
in one is partly balanced by the pressure in the other; the work done
in the low-pressure cylinder being very nearly equivalent to the work
required to compress the air up to that pressure at which it enters the
displacer and leaves the high-pressure cylinder. It will be observed
that in this form, as in the previous one, I only admit the air into the
displacer cylinder at a pressure which is already great compared with
that of the atmosphere. This arrangement enables me to reduce greatly
the size of the working cylinder.
→
A is the air compressing pump; this pump delivers the air into the
refrigerator B; G and H are the inlet and outlet used for the water of
the refrigerator. From the refrigerator the air passes by the pipe band.
the flap valves I to the two displacer cylinders C and C. From these
the products of combustion are admitted by suitable slide valves working
from the eccentric J to the cylinder D; the products of combustion are
cut off by the valves so as to leave the fluid in C and C' at high pressure.
The admission takes place while the displacer communicating with
the required end of the cylinder D is raised, and while the fluid is
mainly in the hot part of the displacer cylinder. The gas or petroleum

page_text: is introduced to the bottom of C by a pump at M, and two small pipes
dotted, as lines in the plan, Figure 4. From the cylinder D the products
of combustion enter the receiver E formed in the bed plate according to
this design. The low pressure cylinder F is driven by this burnt gas, as
it may be called, as any ordinary steam engine might be driven by com-
pressed air. The burnt gas is ejected from D at the pressure or nearly
the pressure at which air is forced into C or C¹. This pressure may be
made very considerable in cases where it is desirable to reduce the size
of the working cylinder, and the pistons of F and A being directly con-
nected the pressure which drives F is in considerable part balanced by
the pressure required to compress the air in A. The cylinder D then
plays precisely the part of the cylinder in Stirling's engine, giving the
advantage of small working parts, dense fluid in the displacer, and cool
working cylinder.
.
.
In the form of my engine just shewn, Figures 1 to 3, the lower part
of the working cylinder H into which the fluid is admitted by the slide
valve fulfils the functions of cylinder D in the second form, the upper
part of the cylinder F in which the fluid expands fulfils the functions of
the low-pressure cylinder F, but without the special advantage of the
small strain on the working parts given by the second arrangement.
The construction of the displacers and manner of working the engine is
the same in the two forms, but in the second form I have the additional
advantage of being able to use a variable expansion in cylinder F to
regulate the working of the engine, and the receiver D enables me when
left charged to start the engine before pressure is got up in C or C¹.
This form of engine may be worked with or without the refrigerator B,
but in any case I prefer to use a receiver at B which contains air at the
minimum pressure used in C or 'C'. This minimum pressure can be
increased by altering the quantity withdrawn by the valves J, J¹
relatively to the quantity delivered by the compressing pump A. It is
very advantageous to be able to control the power of the engine in this
way as well as by regulating the admission of fuel.
:
. Instead of gas or petroleum or other liquid fuel comminuted coal dust
may be mixed with air and introduced as fuel in the same manner as
gas is introduced, or a minute quantity of comminuted coal may at each
stroke be dropped by a hopper from a closed chamber into the com-
bustion chamber.

page_text: I do not claim the use of air, gas, or petroleum engines generally
having any combination of working cylinders, displacers, and regene- -
rators with internal combustion, neither do I claim the use of petroleum
or gas or similar fuel burnt inside a combustion chamber to produce the
working fluid of a hot air or gas engine. These elements have been
variously combined, especially by C. W. Siemens, but I claim the
following special combinations, from which the advantages of my engine
1. The complete engine consisting of the following parts combined, as
shewn in the Drawings:-a, high and low pressure cylinders ejecting at
each stroke all the fluid they receive, and receiving the fluid through
slide valves or analogous arrangements; b, a compressing pump or
pumps, introducing at each stroke a weight of air equal to that expelled
from the working cylinders; c, a refrigerator or refrigerators between
the compressing pumps and displacer cylinders, this refrigerator being
capable of acting as a reservoir of compressed air. d, a displacer
cylinder or analogous reservoir, part of which forms an internal com-
bustion chamber or chambers lined with refractory material, this
cylinder or reservoir being cut off from direct communication with the
working cylinder by a slide valve or analogous contrivance. e, a re-
generator between the hot combustion chamber and the cool part of the
displacer cylinder; f, a displacer used to transfer the fluid from one end
to the other end of the displacer cylinder; 9, slide valves used, as
shewn, to admit the fluid to the cylinders; h, a burnt gas receiver
between the two cylinders which may be used to start the engine; i, a
pump or analogous contrivance introducing at each stroke fuel in the
gaseous or liquid form sufficient for one stroke.
2. The same engine from which any or all of the following parts have
been omitted. a, one of the two working cylinders so reducing the
engine to a simple instead of a compound engine; c, the refrigerator
cometimos nood without a refricanston

page_text: duce gas, or by a hopper feed from a close vessel, the hopper being
arranged to drop in only. fuel enough at each stroke for that stroke:
In witness whereof, I, the said Fleeming Jenkin, have hereunto set
my hand and seal; this Seventh day of January, in the year of
our Lord One thousand eight hundred and seventy-five.