IMPROVEMENTS IN CALORIC ENGINES
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by John Imray at the Office of the
Commissioners of Patents, with his Petition, on the 6th May
-
1878. A communication from abroad, by Nicol Auguste Otto, of
the Gas-Motoren Fabrik-Deutz, at Deutz, in the German Empire.
I, JOHN IMRAY, of No. 20, Southampton Buildings, Chancery Lane, in
the County of Middlesex, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN CALORIC ENGINES," to be as follows:-
In applying heated air gas or gaseous products of combustion to the
working of a piston in a cylinder for the purpose of obtaining motive
power in caloric engines, it is usual to admit the heated fluid to the
cylinder at a pressure exceeding that of the atmosphere, and to employ
this excess of pressure for the propulsion of the piston.
In the Specification of a Patent obtained on the 12th February 1866,
No. 484, by C. D. Abel, (being a communication from the said A. N.
Otto, and E. Langen,) was described a caloric engine in which a piston
was propelled by the pressure of products of combustion or gaseous
explosion without doing work, the work of the engine being performed
by the return stroke of the piston subjected on the one side to

page_text: atmospheric pressure, and on the other side to the less pressure of the
fluid which had propelled it when such fluid was contracted by cooling.
In the said engine the piston during its return stroke was connected to
and worked the crank, while it made its stroke freely under the
propulsive action of the fluid.
The present Invention relates to a method of, and apparatus for
obtaining motive power from heated air, gas, or gaseous products of
combustion admitted to a cylinder at the pressure of the atmosphere, and
cooled therein, so that their pressure on one side of the piston being
reduced below that of the atmosphere, the excess of atmospheric ]
pressure on the other side of the piston shall effect its propulsion, the
pistion in this case being always connected to the crank. For this
purpose a piston fitted to work in a cylinder is connected to a crank on a
shaft provided with a heavy flywheel, and with an eccentric or cam for
working a slide or valve whereby heated air, gas, or gaseous products of 1
combustion can be admitted at the proper moment, and for the proper
time to one end of the cylinder the other end of which is open. The
cylinder has a casing or jacket supplied with water for the purpose of
cooling the cylinder, and has at its closed end, besides the supply port
and slide, a discharge port fitted with a valve opening outwards.
The action is as follows:-When the piston is at the closed end of the
cylinder, the supply port is opened by the movement of the slide, and
heated fluid is admitted at the pressure of the atmosphere.
The piston
being thus subjected to equal pressure on both sides, is moved by the
momentum of the flywheel until it has performed a certain portion of
its stroke, which may be from four to seven tenths of the whole stroke.
At this point the slide is made to close the supply port, and the rest of
the stroke of the piston is effected by the momentum of the flywheel,
the fluid within the cylinder being dilated in volume, and having its
pressure reduced and temperature lowered partly by absorption of
latent heat, and partly by cooling. When the piston has reached the
end of the stroke, the fluid behind it having its pressure reduced not only
by the dilatation which it has undergone but also by the absorption of
latent heat, and by the cooling influence of the cylinder, below that of
the atmosphere; a portion of the return stroke of the piston is effected
by the excess of the atmospheric pressure on its one side above that of
the fluid on its other side, and when by the movement of the piston, the
pressure of the fluid behind it has been raised to that of the atmosphere

page_text: partly by compression and partly by the liberation of the heat which
had become latent, it is discharged from the cylinder by the escape
valve.
In order to operate more efficiently with this apparatus, it is preferred
to make the engine work quickly, also to have the one stroke, namely,
that during which heated fluid is supplied, effected more rapidly than
the return stroke, during which chiefly the contraction of the fluid by
cooling should take place. This difference of speed in the two strokes
may be obtained by any known arrangements of mechanism for effecting
an alternately quick and slow reciprocating movement, such as are in
use in planing, and other machines. By this arrangement the heated
fluid while undergoing dilatation, has little time to lose heat by
conduction, but while the piston is changing its direction, and during its
return stroke, a large portion of the heat is absorbed by the cooled
cylinder. Thus the power which had been absorbed in effecting the
dilatation of the fluid is regained along with the additonal power
obtained from the contraction of the fluid by cooling.
It will be readily understood that the heat is more fully utilised by
admitting the heated fluid to the cylinder only during a portion of the
stroke, and causing the contents to expand therein. The effective power
thus obtained is that due to the difference between the pressure of the
fluid in the cylinder at each point of the forward stroke, and its reduced
pressure at corresponding points in the return stroke.