Improvements in Gaseous Fluid Pressure Motive Power Engines.
Year: 1897

page_text: Date of Application, 18th Oct., 1897
Complete Specification Left, 14th July, 1898-Accepted, 3rd Sept., 1898
PROVISIONAL SPECIFICATION.
Improvements in Gaseous Fluid Pressure Motive Power Engines.
We, LEON ABEL LETOMBE, of 56, Rue d'Isly, Lille, France, Engineer, and
FIRMAN MOLLET-FONTAINE, of Rue Gustave Testelin, Lille, France, Manufacturing
Engineer, do hereby declare the nature of this invention to be as follows;-
The present invention has for object to improve the construction and cycle of
those motors which derive their power from a fluid under pressure, such as
steam, liquefied carbonic acid gas, &c.
The main feature of the invention consists in the realization of a combined
steam or other fluid pressure and hot air engine.
The cycle adopted for the purpose of the invention is that of a hot air engine
with adiabatic compression and expansion and interchange of heat at constant
pressure. If the motor in question be a hot air engine, there would be the follow-
ing cycle of operation:-adiabatic compression; dilation by communication of
heat; adiabatic expansion; cooling at constant pressure, or equivalent exhaust
with suction to recommence the cycle.
Our researches have shown that the maximum effect of such a cycle is that
of what is known as a Carnot cycle working between the initial and final tem-
perature of compression. It follows that, for a compression which it is not
desired to exceed, the highest effect will be attained when that gas is employed
whose temperature most increases with the compression. Now this gas is the air.
Therefore according to this invention air is employed to fulfil the most important
part in the cycle, i.e. adiabatic compression.
In order to simplify explanation let us suppose that the motor is constituted
by a cylinder with a single acting piston. The cylinder is supposed to be filled
with air from the piston to the back of the cylinder. Starting from this instant,
if the system of operation is established, we have adiabatic compression of the
air. This fundamental part of the cycle being accomplished, instead of seeking
to produce dilatation of the air by heating at constant pressure, this dilatation is
replaced according to this invention by an admission of a fluid the pressure of
which is the same as that which obtains at the end of the compression. We thus
have an admission of a foreign vapour or gas: the result of which is that every-
thing occurs as if the air had actually been dilated by heating.
The mixture of fluids now expands in accordance with an adiabatic curve the
index of which will depend upon the proportion of air in the mixture. The
period of cooling, will be replaced by an equivalent period of exhaust with
fresh suction of simple air to recommence the cycle.
The advantages of this novel aerothermic cycle are numerous, whatever be
the fluid under pressure employed to complete it. We proceed to examine some
particular cases.
1. Employment of Steam. In comparing the temperatures of air adiabatically
compressed and that of steam for the same pressure, it is found that by taking
the air at the surrounding temperature, the temperature at the end of the com-

page_text: pression for the air (especially for high pressures) is generally above, sometimes
considerably above, the temperature of saturated steam. Therefore at the moment
when the admission of steam is about to be produced the cylinder is perfectly
heated. The nature of this is to attenuate condensations at the admission, but
another circumstance renders condensation at the admission practically impossible,
namely the steam on arrival in the mass of air under consideration becomes
superheated not only because the air is hotter than the steam but in particular be-
cause, in consequence of the mixture of air in large quantity and of steam, the tem-
perature of saturation is sensibly lowered; this is a consequence of the law
which governs the mixture of gases and vapors. The maximum effect will be
obtained by employing superheated steam, precisely at the temperature of com-
pression of the air; but even without superheated steam this system will be
economical, since there is no longer necessity to consider losses by condensation
at the admission or by reason of prejudicial spaces. Further in consequence of
the presence of the air, any steam which might condense during the expansion
remains in the state of mist in the mass and does not run down the sides. The
action of the sides is thus reduced to a sufficient extent to render steam jackets
and successive expansions unnecessary, we therefore do not employ a heated
jacket of any kind and we do away with compounding which becomes unnecessary,
a considerable economy in construction being thus effected.
2. Employment of Liquefied Gases. These gases employed as above indicated
for steam may be employed without being previously heated either before their
admission to the cylinder, or during their expansion. Suppose that one of these
gases is carbonic acid for example, and that it is caused to act in identically the
same way as steam as above described, we have the following working;-
1st period: Suction of air.
2nd period: Adiabatic compression of air.
3rd period:-Arrival of carbonic acid in an atmosphere of hot air which heats
it in its turn.
4th period: Exhaustion of everything.
It is thus possible to prolong the expansion without risk of too greatly reducing
the temperature. The same reasoning applies if compressed air be employed
instead of a liquefied gas.
In carrying the invention into effect, it is preferable as the adiabatic compres-
sion of the air has to produce high temperatures, to have recourse not to ordinary
arrangements of steam engines, but to arrangements similar to those adopted in
certain simple or double effect four period gas motors, in which distribution
is effected by means of valves with a single seating.
For the sake of simplicity we will take, the case of a single-acting motor.
The distribution is effected by three valves. These valves are so disposed as
respectively to automatically effect the admission of the air to the cylinder, the
admission of the steam or other fluid under pressure to produce the mixture
before described and the exhaust of the expended fluid.
The steam admission and the exhaust valves are actuated by cams mounted on a
shaft driven by any suitable gearing from the driving shaft of the motor and
making one revolution for two revolutions of that shaft. It is preferred to
operate the steam admission valve from the said cam shaft through the inter-
mediation of a suitable arrangement of cam, links and levers.
In the motor under consideration the operation is as follows:-
First Stroke. The piston moves forward; the air admission valve rises under
the action of the suction of the piston and allows the cylinder to fill with air at
the ordinary temperature. There would be no advantage from the theoretical
point of view in heating the air to a temperature above that of the exhaust before
its arrival in the cylinder.
Second Stroke. The piston returns, the air admission valve closes and the
exhaust valve is slightly opened during a portion of the stroke by a cam, in
order to effectively clear the cylinder of steam. At a suitable point of the stroke

page_text: the exhaust valve closes and compression commences in order to attain the pres-
sure of the steam or other pressure fluid; this amongst other advantages has the
effect of equilibrating the steam admission valve.
Third Stroke. The steam admission valve being subject to two equal pressures,
then opens very easily under the action of jointed levers as before described,
the lever which transmits the motion to the valve spindle being situated in the
steam or other fluid in order to preserve perfect equilibrium. The piston again
moves forward under the impulse of the fluid under pressure which mixes with
the air and at the end of a specified time the steam admission valve closes and
expansion commences.
Fourth Stroke. The piston arriving at the end of its stroke the exhaust valve
opens to allow of the exhaust, which takes place during the entire stroke. As
the steam admission valve opens without effort, a condition indispensable to effect
variable admissions automatically, there may be applied thereto actuation by
means of a stepped cam under the control of the governor, as in certain gas motors.
For this purpose the lever which transmits the motion to the spindle of the steam
admission valve may carry two rollers the larger of which actuates the valve
and the other, the smaller, regulates the fall. The latter roller slides on its
spindle under the action of a fork actuated by the governor; it is obvious that
any convenient pawl arrangement or valve or other arrangement employed in
the governing of steam engines may be employed for the purpose above described.
Dated this 18th day of October 1807
Improvements in Gaseous Fluid Pressure Motive Power Engines.
We, LEON ABEL LETOMBE, of 56, Rue d'Isly, Lille, France, Engineer, and
FIRMAN MOLLET-FONTAINE, of Rue Gustave Testelin, Lille, France, Manufacturing
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:-
The present invention has for object to improve the construction and cycle of
those motors which derive their power from a fluid under pressure, such as
steam, liquefied carbonic acid gas, &c.
The main feature of the invention consists in the realization of a combined
steam or other fluid pressure and hot air engine.
We will now proceed to describe our invention with reference to the accom-
panying illustrative drawings.
The cycle adopted for the purpose of the invention is that of a hot air engine
with adiabatic compression and expansion and interchange of heat at constant
pressure such as that indicated in diagram in Figure 1, in which y represents
the line of atmospheric pressure. If the motor in question be a hot air engine,
there would be the following cycle of operation;-Adiabatic compression
from a-b; expansion by communication of heat from 6 to c; adiabatic expan-
sion from e to d; and cooling at constant pressure, or equivalent exhaust from
to f with suction from f to a to recommence the cycle.
Our researches have shown that the maximum effect of such a cycle is that
of what is known as a Carnot cycle working between the initial and final fem-
peratures of compression. It follows that, for a compression which it is not
desired to exceed, the highest effect will be attained when that gas is employed

page_text: whose temperature most increases with the compression. Now this gas is the air.
Therefore according to this invention air is employed to fulfil the most important
part in the cycle, i.e. adiabatic compression.
In order to simplify explanation let us suppose that the motor is constituted
by a cylinder with a single acting piston, (Figure 1). The piston having reached
the position corresponding to the point a. The cylinder is supposed to be filled
with air from the piston (at the point a) to the back (9) of the cylinder. Start-
ing from this instant, if the system of operation is established, we have adiabatic
compression of air from a to b. This fundamental part of the cycle being, accom-
plished, instead of seeking to produce expansion of the air by heating at constant
pressure, this expansion is replaced according to this invention by an admission
of a fluid the pressure of which is the same as that which obtains at the end of
the compression. We thus have from 6 to c an admission of a foreign vapour
or gas; the result of which is that everything occurs as if the air had actually
been expanded by heat.
The mixture of fluids now expands from c to d in accordance with an adiabatic
curve the index of which will depend upon the proportion of air in the mixture.
The period of cooling from d to a will be replaced by an equivalent period of
exhaust from d to f with fresh suction of simple air from f to a to recommence
the cycle.
The advantage of this novel aerothermic cycle are numerous, whatever be the
· fluid under pressure employed to complete it. We will now proceed to examine
some particular cases.
1. Employment of Steam. In comparing the temperatures of air adiabatically
compressed and that of steam for the same pressure, it is found that by taking
the air at the surrounding temperature, the temperature at the end of the com-
pression for the air (especially for high pressures) is generally above sometimes
considerably above, the temperature of saturated steam. Therefore at the moment
when the admission of steam is about to be produced the cylinder is perfectly
heated. The nature of this is to diminish condensation at the admission, but
another circumstance renders condensation at the admission practically impossible,
namely the steam on arrival in the mass of air under consideration becomes
superheated not only because the air is hotter than the steam but in particular be-
cause, in consequence of the mixture of air in large quantity and of steam, the tem-
perature of saturation is appreciably lowered; this is a consequence of the law
which governs the mixture of gases and vapors. The maximum effect will be
obtained by employing superheated steam, at the exact temperature of com-
pression of the air. But even without superheated steam this system will be
economical, since there is no longer any necessity to consider losses by condensation
at the admission or by reason of "dead" spaces. Further, in consequence of
the presence of the air, any steam which might condense during the expansion
remains in the state of mist in the mass and does not run down the sides. The
action of the sides is thus reduced to a sufficient extent to render steam jackets
and successive expansions unnecessary. We therefore do not employ a heated
jacket of any kind and we do away with compounding which becomes unnecessary,
a considerable economy in construction being thus effected.
2. Employment of Liquefied Gases. These gases employed in the manner above
indicated for steam, may be employed without being previously heated either
before their admission to the cylinder, or during their expansion. Supposing that
one of these gases is carbonic acid for example, and that it is caused to act in
identically the same way as above described in the case of steam, we have the
following working:
1st period: Insuction of air;
2nd period:-Adiabatic compression of the air;
3rd period: Arrival of the carbonic acid in an atmosphere of hot air which
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page_text: It is thus possible to prolong the expansion without risk of too greatly reducing
the temperature. The same reasoning applies if compressed air be employed
instead of a liquefied gas.
In carrying the invention into effect, it is preferable as the adiabatic compres-
sion of the air has to produce high temperatures, to have recourse not to ordinary
arrangements of steam engines, but to arrangements similar to those adopted in
certain single-action or double-action four period gas motors, in which distribution
is effected by means of valves with a single seating.
For the sake of simplicity we will take the case of a single-acting motor
(Figure 2). The distribution is effected by means of three valves A B C. The
valve A is arranged to automatically effect the admission of the air to the cylinder;
the valve B controls the admission of the steam or other fluid under pressure to
produce the mixture before described, and the valve C controls the exhaust of
the spent fluid.
The steam admission valve B and the exhaust valve C are actuated by cams
mounted on a shaft O driven by any suitable gearing from the driving shaft of
the motor and making one revolution for two revolutions of that shait. It is
preferred to operate the steam admission valve from the said cam shaft through
the intermediation of a suitable arrangement of cam, links and levers.
In the motor under consideration the operation is as follows:-
First Stroke. The piston moves forward; the air admission valve A rises under
the action of the suction of the piston and allows the cylinder to fill with air at
the ordinary temperature. There would be no advantage from the theoretical
point of view in heating the air to a temperature above that of the exhaust before
its arrival in the cylinder.
Second Stroke. The piston returns, the air admission valve A closes and the
exhaust valve C is slightly opened during a portion of the stroke by a cam, in order
to effectively clear the cylinder of steam. At a suitable point of the stroke the
exhaust valve C closes and compression commences in order to attain the pressure
of the steam or other pressure fluid; this amongst other advantages has the
effect of balancing the steam admission valve B.
Third Stroke. The steam admission valve B being subject to two equal pres-
sures, then opens very easily under the action of the jointed levers b and b¹, the
lever b which transmits the motion to the valve spindle being situated in the
steam or other fluid in order to preserve perfect equilibrium. The piston again
moves forward under the impulse of the Huid under pressure which mixes with
the air, and at the end of a specified time the steam admission valve B closes and
expansion commences.
Fourth Stroke. The piston arriving at the end of its stroke the exhaust valve C
opens to allow of the exhaust, which takes place during the entire stroke. As
the steam admission valve B opens without effort, a condition indispensable to
effect variable admissions automatically, it may be actuated by means of a stepped
cam under the control of the governor, as in certain gas motors. For this purpose
the lever 6' which transmits the motion to the spindle of the steam admission
valve may carry two rollers m and n the wider one (m) of which produces the
opening movement of the valve and the other or narrower one (n) regulates the
fall of the valve back upon its seat as shown more clearly in Figure 3 which is
an elevation partly in section of the lever and rollers. The roller n is adapted to
slide on its spindle under the action of a fork actuated by the governor. It is
obvious that any convenient pawl arrangement or valve or other arrangement
employed in the governing of steam engines may be employed for the purpose
above described.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:
-
1. A combined steam or other fluid pressure and hot air engine working on

page_text: a cycle based on a total adiabatic compression (as hereinbefore described) of air
admitted into the engine cylinder at ordinary atmospheric temperature, the said
cycle being completed by an admission of a fluid under pressure which mixes
with the air and acts as if the air had actually been expanded by heat, constructed,
arranged and operating substantially as described.
2. In a combined steam or other fluid pressure and hot air engine, the com-
bination of the four-period working of single-action or double-action gas motors
with distribution by means of cams keyed on a shaft revolving at half the speed
of the main or driving shaft, substantially as described.
3. A combined steam or other fluid pressure and hot air engine constructed,
arranged and operating substantially as herein before described and illustrated
by the accompanying drawings.
Dated this 14th day of Tul, 1000
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.