Year: 1897

page_text: I, EUGÈNE FISTIÉ, of 2, rue Houdan, Sceaux, France, Engineer, do hereby
declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
This invention is applicable to gas engines in general whatever may be the gas,
vapour or sprayed liquid employed as combustible, and whether the combustion
be instantaneous or progressive, or whether expansion takes place in a single
cylinder or in compound cylinders.
I add to the engine an auxiliary cylinder which may be called an exhaust
cylinder, whose function is to receive the exhaust gases from the expansion
cylinder in order to subsequently expel them into the atmosphere. The exhaust
from the expansion cylinder thus taking place into a limited space, the size of
which depends on the effect required, expansion may be carried as far as desired
below atmospheric pressure, at the next stroke of the piston the gases suitably
compressed in the exhaust cylinder are passed out into the atmosphere.
The more the exhaust gases are cooled before passing into the exhaust cylinder
the more efficaceous the latter will be and the less the gases will be heated in
this cylinder during the compression which precedes their final expulsion.
The utility of the exhaust cylinder increases with its capacity but it is not
necessary to exaggerate this, for after a certain point the diminution in the
mechanical efficiency of the engine will more than balance the improvement in
the thermal efficiency.
To facilitate cooling in the exhaust cylinder, it may be replaced by several
smaller cylinders.
.
By making the compression pumps single acting they may be utilized as
exhaust cylinders during their return stroke. Without greatly lessening the
thermal efficiency the frequency of the strokes of the pump may be increased or
diminished relatively to that of the expansion piston, in this case the exhaust
gases from the expansion cylinder may be momentarily stored in the refrigerator.
The refrigerator placed between the expansion and exhaust cylinder may be
of any type such as a jet condenser, an ordinary steam engine condenser or a
surface condenser, any refrigerating body being employed.

page_text: The refrigerator may be of any capacity but the larger it is the longer time
the engine will take to reach its normal state after starting.
Both in order to economize the refrigerating body and to utilize waste heat for
heating the fresh gases, the latter should be made to take from the expanded
gases as much heat as possible, the refrigerator thus becomes at the same time
a heat recuperator. Any recuperator in which the gases may be at different
pressures may be used. The cooling of the expanded gases is if necessary com-
pleted in any type of refrigerator from which not so much is demanded as if
it acted alone.
As an example of the advantages gained by my invention, I may say, that
if a 4 cycle engine in which the gases are expanded to 3:3 times their original
volume (expansion equal to the compression) gives a thermal efficiency
of 25:5%; then by applying my invention and adopting the expansion of 10,
the other conditions of the engine remaining the same, the thermal efficiency is
raised to more than 36%, that is to say, an increase of 40%; if one is content
with an expansion of 7.5 the increase will still be 33%, efficiency 34%..
If the three engines run at 120 revolutions the capacity of the cylinder of the
first would be 1.40 litres per indicated horse power (2 litres if account be taken
of the clearance reserved for the explosion); the capacity of the cylinder of the
second would be 2.40 litres, and that of the thirl 1.80 litres, the two latter
engines giving one working stroke per revolution.
If by the utilization of waste heat the absolute temperature of the compressed
gases be doubled before their entry into the expansion cylinder, the thermal
efficiency is raised to 45 or 43, that is to say, an increase of 75 or 66%.
In working out the various figures the exhaust cylinder is supposed to have
the same useful capacity as the expansion cylinder; the thermal efficiency
diminishes with the capacity of the exhaust cylinder, but were the latter reduced
to 65% then with the expansion of 10 the efficiency would still be 35% (instead
of 36%) without the utilization of waste heat.
In the annexed drawings:-
Figure 1 shows an example of an engine constructed according to this inven-
tion, the usual admission and exhaust valves being of ordinary construction are
not shown. This engine is analogous to a condensing steam engine.
R is the cylinder; its piston; S is the exhaust valve which is shown open;
S₁ the automatic clack valve also shown open.
At the cylinder end at S the gases are at a temperature of 500° C. for example;
at S¹ they are at a temperature of only about 50° C.
T is a refrigerator, water being circulated in the double casing.
Figure 2 is a diagram in which A B is the expansion curve which corresponds
to the first cycle.
BC represents the fall in pressure produced by the passage of gas through
the refrigerator and their passage into the cylinder (second cycle).
C D represents the bringing of these gases in the cylinder to atmospheric
pressure and 1) O expulsion of these gases (third cycle of one side of the cylinder).
At the same time fresh gases are admitted into the working cylinder by any
means and in a quantity determined by the governor (third cycle of the other
side of the cylinder).
Fourth cycle. The gases are compressed in the working cylinder according
to E F.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed I declare that what I
claim is:
1. The addition to gas engines in general of a cylinder called an exhaust
cylinder serving as intermediary between the expansion cylinder and the atmos-
phere, this cylinder being either single or multiple and forming part or not of
the compressing apparatus.

page_text: 2. Placing a refrigerator between the expansion and exhaust cylinders.
3. The utilization of the compressed gases, entering into the expansion cylinder
of the engine, for cooling the exhaust gases in their passage from the expansion
to the exhaust cylinder, which cooling may be completed in any type of re-
frigerator.
T11111
1907