IMPROVEMENTS IN CALORIC ENGINES, WHEREIN THE WORKING FLUID IS HEATED BY INTERNAL COMBUSTION OF GAS OR OTHER FUEL
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Matthew Piers Watt Boulton at the
Office of the Commissioners of Patents on the 18th March 1881.
MATTHEW PIERS WATT BOULTON, of Tew Park, in the County of Oxford.
"IMPROVEMENTS IN CALORIC ENGINES, WHEREIN THE WORKING FLUID IS HEATED
BY INTERNAL COMBUSTION OF GAS OR OTHER FUEL."
In the Specification to Letters Patent granted to me on the 7th February, 1879,
No. 495, and in a Provisional Specification filed by me on the 17th December
1880, No. 5270, I described. the construction and operation of a caloric engine,
in which successive charges of cold air or elastic fluid received in a charging vessel
were by the movements therein of a displacer. passed through a separate heating
vessel back to the charging vessel, whence they expanded in a cylinder performing
work.
•
My present Invention relates to a construction and arrangement in which the
separate heating vessel is dispensed with, by employing the internal combustion of
gaseous or liquid fuel. The following main parts of the engine remain the same,
that is to say :-
(1.) A cylinder fitted with a piston which drives the engine, which piston is
furnished with a shield, or may be so.
(2.) A chamber within which works a shielded piston, which by its movements
takes in charges of cold air, transfers them from the cold to the hot end of the
chamber, and expels a portion of the exhaust. I term this chamber the air charging
chamber, and its piston the displacer or the main displacer.
(3.) A regenerator.
In addition to these I provide means for introducing charges of the gas or other
fuel.
When gas is employed, it may be introduced by means of a pump.
I also provide two eduction valves, one opening from the regenerator, which I
call the main eduction valve, and one opening from the cylinder, which I call the
secondary eduction valve.
The combustion takes place within the air charging chamber, or a space connected
with it.
I use these parts to a certain extent in the way which I described in my previous
Specifications above referred to, that is 'to say, I cause the displacer to make two

page_text: :
strokes for preparing the charge of hot air which is to expand in the cylinder and
perform work therein, which two strokes take place while the piston which
drives the engine is making its discharge stroke. While the hot air is expanding
in the cylinder urging the piston on its working stroke, the displacer is stationary
or nearly so.
But though my present mode of operating so far resembles my former one, it
differs in several respects owing to the difference in the manner of effecting the
combustion.
In describing the course of operations, I shall first take the case where gas is the
fuel employed; I may observe that in my description I shall frequently use the
term "air" to signify elastic fluid generally.
The air taken into the air charging chamber is not all intended for combustion.
A portion of it only is burnt with the gas, the remainder is heated by the
combustion.
By suitably proportioning the capacities of the air charging chamber and the gas:
pump.or gas charge, the temperature of the hot working air is made such as is
desired.. If this is made high, then the piston which drives the engine is furnished
with a shield; but a temperature may be used so moderate that a shield is not
necessary. And this is convenient if it is desired that the engine should be double
acting.
For convenience of description, I shall suppose that the upper end of the air
charging chamber is the cool end, the lower one the hot end. And I shall suppose
that the working stroke of the piston is upward, its discharge stroke downward.
I shall take for starting point the time when the piston is ready to begin
its discharge stroke. At this time the displacer is at the upper or cool end of its
chamber, the space beneath it being full of exhaust air, still retaining considerable
'heat.
The piston is at the top of its cylinder; the space beneath it similarly full of
exhaust air.
Communication is open between all the spaces filled with exhaust air.
I may observe that by exhaust air I mean generally air which has discharged its
office of performing work in the cylinder as described. It may in some cases pass
off to perform work elsewhere.
The displacer moves downwards. Above, it draws in or is followed by the supply
of atmospheric air. Below, it expels exhaust through the regenerator, and out by
the main eduction valve.
The piston also moves downwards, expelling exhaust in like manner, through
the regenerator and main eduction valve. This state of things continues till the
displacer has completed its downstroke, at which time the piston is about mid-way
in its discharge stroke.
Communication is now closed between the cylinder and the other parts of
the engine. The secondary eduction valve, connected directly with the cylinder, is
opened.
The displacer now ascends, displacing the atmospheric air above it. It causes
this to pass through the regenerator into the hot space beneath the displacer.
While this is taking place the gas pump makes its stroke, injecting gas which
mingles with a portion of the air entering the hot space as previously described, is
ignited and undergoes combustion, which takes place gradually. This combustion
heats the other portion of the entering air.
While the displacer is making its upstroke as previously described, the piston
completes its discharge stroke, expelling exhaust through the secondary eduction
valve.
When the strokes above described are completed, the space beneath the displacer
is filled with hot air, ready for performance of work.
The proper changes of valves having been made, communication is now opened
between the cylinder and the other parts of the engine, and the hot air expands in
the cylinder, urging the piston which performs its working stroke.

page_text: While it is making this, the displacer remains at the upper or cool end of its
chamber, stationary or nearly so. The working stroke having been completed, and
the proper changes of valves made, the point previously taken as starting point is
reached.
In the above described manner of operating, the gas pump injects its charge of
gas against the pressure in the displacing chamber, which rises as the displacer
ascends. But as the quantity of gas relatively to the total quantity of working
fluid is small, the power needed to work the gas pump is not very considerable.
Instead however of using a gas pump, a gas charging chamber and displacer,
with regenerator or passage may be employed for the purpose of introducing the
gas supply and sending it to mix with the air in the hot space. In this case, when
the gas displacer displaces the gas above it, or on its cool side, it sends the gas
through the gas regenerator or passage into the space where combustion is effected,
as previously described, while air or fluid from the hot space beneath the main
displacer enters below the gas displacer, or on its hot side.
Such a second charging chamber instead of taking in gas alone, may take in gas
and air mixed in incombustible proportion.
For the mixing of the gas and air for the purpose of combustion, any known
suitable form of mixer or burner may be employed, in any convenient position
between the regenerator and the hot end of the air charging chamber.
In the method of operating above described, the combustion takes place gradually,
but another method may be employed. The gas is introduced into the hot space
only during the first portion of the main displacer's stroke. It is not ignited as it
enters, but it mixes with the air which enters the hot space, as it is displaced by
the main displacer, so as to form a combustible mixture beneath the main displacer.
The proper quantity of this having beon introduced, the stroke of the gas pump or
gas displacer finishes, and at the same time ignition is effected. The main displacer
in the meanwhile is continuing its upward movement, and in doing so it transfers
air from the cool space above it to the hot space below, through the regenerator,
this air taking up the heat which the expansion of the ignited mixture through the
regenerator had previously imparted to it.
The general construction above described remaining the same, one eduction valve
only may be employed, and the exhaust be discharged through this, and not through
the regenerator.
In the above account I have supposed gas to be the fuel employed, but the matter
employed as fuel may be varied. A liquid whose vapour is inflammable, such as
various hydrocarbons and many other liquids, may be employed to generate
inflammable vapour in any known suitable apparatus at regulated pressure, and a
definite quantity of this vapour may be supplied to the engine, and act like gas, as
above explained. Or a certain portion of the vapour may be admitted by means
of a valve allowing it to flow for a certain time from a vessel of regulated pressure,
as in the case of the gas.
Again, liquid such as above mentioned may be injected directly into the hot
chamber, so as to be vaporised by the heat within it, and undergo combustion along
with the air.
In such a case the liquid may be injected in numerous fine streams, or in such a
manner as to form fine spray, which is dispersed by the air, and undergoes
combustion.
When gas is employed as the material for combustion, it may be supplied to
the engine in regulated quantity from a reservoir in which it is stored at any
pressure and in any quantity desired. Such a mode of supplying gas to the engine
is more specially applicable for purposes of locomotion.
Also both the gas and air supplied to the engine may be compressed in vessels
at high pressure, and may work within the engine at high pressure. This method
again is applicable for purposes of locomotion. Compressed air is now employed in
some cases to work locomotive engines; if the same amount of elastic fluid is

page_text: compressed as gas and air it would effect locomotion to much greater distances on
account of the generation of heat. The gas and air issuing from the reservoirs
should be delivered to the engine at regulated pressure, as previously noticed.
When the gas and air thus work at high pressure, the elastic fluid which is
discharged from the apparatus above described, after performance of work in it, is 5
discharged at high pressure, and is still capable of performing work. For this
purpose it is employed in a second cylinder, or in successive cylinders, as steam is
in a compound steam-engine.
In carrying out the operations above described, ignition may be effected by
means of any suitable known apparatus. One which may be employed is that 1
which I described in the Specification of a Patent granted to me on the 19th June
1868, No. 1988, where ignition is effected by the movement of a lamp. But I
improve this form by making the upper part or the terminal part which enters
the vessel where the mixture is to be ignited to seat itself as a valve when the lamp
is withdrawn.
The following is another construction which may be employed:-
A flame as of a gas jet or lamp burns within or partially within a passage close
to the igniting port. This passage has two apertures, one for ingress of air, and the
other for egress of the flame or the products of combustion. Outside the latter
aperture a flame is kept constantly burning. Within the passage is fitted a slide
which at the moment of ignition is moved by the engine so as to cover both the
apertures. The stem of this slide when it is moved raises in the last part of its
stroke a check valve, which covers the igniting port, thus opening the igniting
passage to the chamber containing the inflammable mixture.
In cases where this mixture is at a pressure higher than that of the atmosphere, 2
a small secondary check valve may be fitted on the main check valve. This
secondary valve being first opened by the stem of the slide, permits passage of fluid
along a groove or cavity in the stem, so as to establish equilibrium in the ignition
passage; immediately after which the larger check valve opens.
After the ignition, the slide is retracted, permitting the check valve or valves to
close, and reopening the apertures of the ignition passage, and the igniting flame if
it should have been extinguished, is re-lighted by the external flame. Things are
then ready for repeating the operation.
The movement of the slide may also, immediately before opening the check
valve, open a valve in the gas pipe, so as to give a momentary increase to the lighting
flame.
The movement of the slide may also change the direction of the igniting jet, so
as to direct it against or towards the igniting port.