FR3079877A1 - HOT AIR ENGINE WORKING PERMANENT ACCORDING TO CYCLE DERIVED FROM STIRLING CYCLE - Google Patents

Abstract

A hot air motor continuously operating according to a cycle derived from the Stirling cycle, comprising: a compression cylinder (1) in which a compression piston (2) moves which delimits two compression chambers (20, 21) held at a temperature cold, a motor cylinder (3) in which moves a motor piston (4) delimiting two working chambers held (40, 41) at a hot temperature, the compression piston and the engine piston being jointly controlled and in phase, two transfer chambers (56) maintained at a hot temperature, and a control circuit of the circulation of the working fluid between the different chambers, equipped with control members for modifying the connections between these chambers.

Description

The present invention relates to a hot air engine working continuously according to a cycle derived from the Stirling cycle comprising a compression phase, a temperature rise phase and a motor expansion phase of a working fluid.

There are different types of hot air or more generally hot working gas engines which generally use four-stroke thermodynamic cycles, among which we can cite the Carnot cycle which comprises two isothermal phases and two adiabatic phases, the Stirling which comprises two isothermal phases and two isochoric phases, the Joule cycle which comprises two isobaric phases and two adiabatic phases, or even the Beau de Rochas cycle which comprises two isobaric phases and two adiabatic phases.

In principle, using a regenerator or an energy recuperator, the efficiency of the Stirling cycle is identical to that of the Carnot cycle; in practice these yields are however difficult to obtain.

In particular, in accordance with document FR 2 966 521, a hot air engine has already been proposed using a thermodynamic cycle with essentially three phases derived from the Stirling cycle, but having an improved efficiency by eliminating one of the isochoric phases which produces no work.

According to this document, such a hot air engine whose operating cycle approaches a three-stroke cycle derived from the Stirling cycle comprises an isothermal compression phase, an isochoric temperature raising phase and a driving relaxation of a working fluid.

The object of the invention is to provide a hot air engine derived from such a known hot air engine, but which is distinguished both by a simpler configuration and by a higher efficiency.

According to the invention, such a hot air engine essentially comprises:

a compression cylinder in which a compression piston constantly moves back and forth delimiting, on either side thereof, two compression chambers maintained at a cold temperature by a cold source, a driving cylinder in which constantly moves back and forth a driving piston delimiting on either side thereof two working chambers maintained at a hot temperature by a hot source, two transfer chambers maintained at a hot temperature by a hot source and respectively associated with a first compression chamber and with a first working chamber and with a second compression chamber and with a second working chamber, and a circuit for controlling the circulation of the working fluid between the different chambers.

It is essential, in accordance with the invention, that the compression piston and the drive piston be controlled jointly by a connecting rod-crank system and are in phase.

The circuit for controlling the circulation of the working fluid between the different chambers is equipped with control members making it possible to modify the connections between these chambers during a rotation of the crank so that:

that during a compression phase, the cold working fluid contained in a first of the two compression chambers of the compression cylinder is compressed by the compression piston until it has reached a predefined pressure, than during '' a temperature rise phase, the cold working fluid having reached the predefined pressure contained in the first compression chamber is transferred into the transfer chamber associated with this first chamber or first transfer chamber, and only during a motor relaxation phase the working fluid contained in the first transfer chamber, having been compressed and high in temperature, is transferred to the working cylinder working chamber associated with this first transfer chamber or first working chamber so as to relax and push the working piston while the working fluid contained in the second working chamber is disposed together.

During this phase of motor relaxation, the cold working fluid contained in the second compression chamber is parallel compressed by the compression piston until it has reached the predefined pressure during another compression phase, then is transferred to the transfer chamber associated with this second chamber or second transfer chamber during another temperature rise phase, before being transferred to the working cylinder working chamber associated with this second transfer chamber or second working chamber during another phase of motor relaxation during which the working fluid contained in the first working chamber is discharged, and so on.

The succession of these different phases makes it possible to guarantee that the driving piston is constantly driving.

According to the invention, the control members equipping the circuit for controlling the circulation of the working fluid can advantageously be constituted by drawers or by taps, the actuation of which is preferably controlled by cams.

According to a first variant of the invention, the two compression chambers of the compression cylinder are in communication with the outside air and maintained at a cold temperature by this outside air which constitutes the cold source.

According to a second variant of the invention, the hot air engine further comprises two cooling chambers maintained at a cold temperature by a cold source and respectively associated with one of the compression chambers of the compression cylinder to maintain this chamber at a cold temperature.

According to a first embodiment of the invention, the hot air engine comprises a heat exchanger in which circulates the hot working fluid discharged from one of the working chambers of the engine cylinder during a drive expansion phase in the other working chamber of this engine cylinder to allow the heating of the cold working fluid transferred from one of the compression chambers of the compression cylinder into the transfer chamber associated with this compression chamber during a phase of rise in temperature, which also circulates in this heat exchanger against the current.

This first embodiment of the hot air engine according to the invention which requires the use of an exchanger making it possible to minimize the heat losses has the advantage of being particularly simple and inexpensive; however, it should be noted that such a heat exchanger is not fully efficient.

According to a second embodiment of the hot air engine according to the invention which has the advantage of making it possible to avoid heat transfers between the cold sources and the hot sources, this hot air engine comprises two intermediate cylinders in which constantly moves back and forth respectively a double section insulating piston essentially in the shape of a T defining on either side of it an intermediate chamber of large section associated with one of the compression chambers of the cylinder compression, an intermediate chamber of small section associated with one of the transfer chambers as well as a neutral chamber in communication with the outside air.

Each intermediate chamber of large section is advantageously connected to the compression chamber which is associated with it by a pipe for circulation of the working fluid equipped with a calibrated non-return valve.

It should be noted that instead of using a calibrated non-return valve, a connection can be created by a set of drawers controlled by a cam.

According to a variant of this second embodiment of the hot air engine according to the invention, the two intermediate cylinders are combined into a single double intermediate cylinder enclosing an insulating piston with a single double section defining on either side thereof. ci two intermediate chambers of large section and two intermediate chambers of small section and no neutral chamber.

It should be noted that, in accordance with the invention, the transfer chambers and, where appropriate, the cooling chambers may have a volume significantly greater than the volume necessary, not to improve the efficiency of the hot air engine, but to increase the inertia and obtain better stability of this engine.

The characteristics of the hot air engine which is the subject of the invention will be described in more detail with reference to the accompanying non-limiting drawings in which:

Figures la to ld are diagrams illustrating different phases of the operating cycle of a hot air engine corresponding to the first variant of the first embodiment, Figures 2a, 2b, 2c and 2d are diagrams respectively similar to Figures la , lb, le and ld but corresponding to the second variant of the first embodiment of the hot air engine, FIGS. 3a and 3b are diagrams illustrating two phases of the operating cycle of a hot air engine corresponding to the second mode of embodiment, Figures 4a and 4b are diagrams respectively similar to Figures 3a and 3b corresponding to a variant of the second embodiment.

According to Figures la to ld, the hot air engine comprises a compression cylinder 1 in which constantly moves back and forth a compression piston 2, a drive cylinder 3 in which constantly moves back and forth a piston motor 4 as well as two transfer chambers 5, 6 which are maintained at a hot temperature by a hot source.

The compression piston 2 and the driving piston 4 are controlled jointly by a connecting rod-crank system not shown and are in phase.

The compression piston 2 defines, on either side of it, two compression chambers 20, 21 which are maintained at a cold temperature by a cold source constituted by the outside air which is introduced into these chambers as shown diagrammatically by the arrows I.

The driving piston 4 delimits, on the other hand, two working chambers 40, 41 which are maintained at a hot temperature by a hot source.

The two transfer chambers 5, 6 which are maintained in temperature by a hot source are respectively associated with a first compression chamber 20 and with a first working chamber 40 and with a second compression chamber 21 and with a second working chamber 41.

The hot air engine is also equipped with a circuit for controlling the circulation of the working fluid between the various chambers 20, 21, 5, 6, 40, 41 which is equipped with non-represented control members making it possible to modify the connections between these chambers during a rotation of the crank, this in a manner which will be described in more detail in the remainder of this description.

According to FIG. 1 a, during a compression phase, the cold working fluid contained in a first 20 of the two compression chambers 20, 21 of the compression cylinder 1 is compressed by the compression piston 2 until it has reached a predefined pressure.

According to FIG. 1b, during a temperature rise phase, the cold working fluid having reached the predefined pressure contained in the first compression chamber 20 is transferred into the transfer chamber 5 associated with this first chamber 20 or first transfer chamber due to a connection established between these chambers 20, 5, this passing through a heat exchanger 7 in which it recovers heat, in a manner which will be described in more detail in the remainder of this description .

According to FIG. 1 a, during a drive relaxation phase, the working fluid contained in the first transfer chamber 5 which has been compressed and raised in temperature is transferred into the working chamber 40 of the engine cylinder 3 associated with this first transfer chamber 5 or first working chamber due to an established connection between these chambers 5, 40, so as to relax and push the driving piston 4 while the working fluid contained in the second working chamber 41 is discharged to the outside as shown by the arrow IL

During this evacuation, the working fluid 41 which is hot passes through the heat exchanger 7.

In view of the phase control of the compression piston 2 and of the driving piston 4, during this drive expansion phase, the cold working fluid contained in the second compression chamber 21 of the compression cylinder 1 is simultaneously compressed by the compression piston 2 during another compression phase until it has reached the predefined pressure.

According to FIG. 1d when it has reached this predefined pressure, the cold working fluid contained in the second compression chamber 21 of the compression cylinder 1 is transferred into the transfer chamber 6 associated with this second chamber 21 or second transfer chamber during another phase of temperature rise due to a connection established between these chambers 21.6, passing beforehand through the heat exchanger 7 or it is heated by the hot working fluid discharged to the outside according to the arrow II of the second chamber 41 of the engine cylinder 3.

According to Figure la, the working fluid contained in the second transfer chamber 6 having been compressed and raised in temperature is then transferred into the working chamber 41 of the engine cylinder 3 associated with this second transfer chamber 6 or second working chamber due to a connection established between these chambers 6, 41, this, during another phase of motor relaxation during which the working fluid contained in the first working chamber 40 of the engine cylinder 3 is discharged towards the outside according to arrow II passing previously through the heat exchanger 7 and so on so that the engine cylinder 4 is constantly engine.

According to FIGS. 2a, 2b, 2c and 2d, the hot air engine further comprises two cooling chambers 8, 9 maintained at a cold temperature by a cold source and respectively associated with one of the compression chambers 20, 21 of the compression cylinder 1 to maintain this chamber at a cold temperature.

These cooling chambers 8, 9 replace the outside air penetrating according to the arrows I into the compression chambers 20, 21 of the compression cylinder 1 in accordance with the first variant of the first embodiment of the hot air engine, illustrated by Figures la to ld.

Consequently, the different phases of an operating cycle of the hot air engine corresponding to the second variant of the first embodiment of the hot air engine according to the invention illustrated by FIGS. 2a to 2d are similar to those described here. -above with reference to Figures la, lb, le and ld with the only difference that the hot working fluid discharged from the working chambers 40, 41 of the engine cylinder 3 during a drive expansion phase and cooled in the exchanger heat 7 is evacuated not to the outside, according to arrows II, but to one of the cooling chambers 8, 9 to then be transferred to one of the compression chambers 20, 21 of the compression cylinder 1.

According to Figures 3a and 3b, the hot air engine according to the second embodiment of the invention is distinguished from the hot air engine according to the first embodiment of the invention illustrated by Figures 2a, 2b, 2c and 2d by replacing the heat exchanger 7 with two intermediate cylinders 10, 10 ′ in which a substantially T-shaped double-section insulating piston 11, 11 ′ moves constantly back and forth respectively, making it possible to prevent transfer of heat between hot springs and cold springs.

Each of the insulating pistons 11, 11 'respectively defines on either side thereof an intermediate chamber of large section 12, 12' an intermediate chamber of small section 13, 13 'as well as a neutral chamber 14, 14' which is in communication with the outside air.

The intermediate chambers of large section 12, 12 'are respectively associated with one of the compression chambers 20, 21 of the compression cylinder 1 while the intermediate chambers of small section 13, 13' are respectively associated with one of the chambers transfer 5, 6 and consequently to one of the transfer chambers 5, 6 and consequently to one of the working chambers 40, 40 'of the engine cylinder 4.

Each intermediate chamber of large section 12, 12 'is connected to the compression chamber 20, 21 which is associated with it by a pipe for circulation of the working fluid equipped with a non-return valve 15, 15' calibrated for s' open when the pressure in this compression chamber 20, 21a reaches the predefined pressure.

According to FIG. 3a, during a compression phase, the cold working fluid contained in the compression chamber 20 is compressed by the compression piston 2 until it has reached the predefined pressure.

When this predefined pressure has been reached, the calibrated valve 15 opens so that the working fluid contained in the compression chamber 20 is transferred into the intermediate section of large section 12 of the intermediate cylinder 10 and pushes the insulating piston double section 11 to compress the working fluid contained in the intermediate chamber of small section 13 which is transferred into the transfer chamber 5 when its pressure is higher than that prevailing in this chamber 5.

According to FIG. 3b, when the pressure of the hot working fluid contained in the transfer chamber 5 is maximum, this transfer chamber 5 is connected to the working chamber 40 of the engine cylinder 3 to push the engine piston 4 during a motor relaxation phase.

Simultaneously, the hot working fluid contained in the working chamber 41 of the engine cylinder 3 is compressed and transferred into the small section chamber 13 of the intermediate cylinder 10 to push the insulating piston 11 and compress the cold working fluid contained in the chamber. large section 12.

This cold working fluid is then transferred into the compression chamber 20 of the compression cylinder 1 via the cooling chamber 8 at which it is cooled.

The compression piston 2 then compresses the working fluid contained in the compression chamber 21 until it has reached the predefined pressure.

When this predefined pressure has been reached, the calibrated valve 15 'opens so that the working fluid contained in the compression chamber 21 is transferred into the intermediate chamber 12' of the intermediate cylinder 10 'and pushes the insulating piston double section 11 'to compress the hot working fluid contained in the intermediate chamber of small section 13' which is transferred into the transfer chamber 6 when its pressure is higher than that prevailing in this chamber 6.

According to FIG. 3a, when the pressure of the hot working fluid contained in the transfer chamber 6 is maximum, this transfer chamber is connected to the working chamber 41 of the engine cylinder 3 to push the engine piston 4 during a phase motor relaxation, and so on.

The operating mode of the hot air engine according to the second embodiment of the invention is thus largely comparable to that of the hot air engine according to the first embodiment of the invention.

According to Figures 4a and 4b, the two intermediate cylinders 10, 10 'shown in Figures 3a and 3b are combined into a double intermediate cylinder 101 containing an insulating piston with a double single section 111 defining on either side thereof two intermediate chambers of large section 12, 12 'and two intermediate chambers of small section 13, 13' and no neutral chamber.

The mode of operation of this engine is in every way similar to that of the engine according to the second embodiment of the invention illustrated in FIGS. 3a and 3b.

Claims (7)

1 °) hot air engine working continuously according to a cycle derived from the Stirling cycle comprising a compression phase, a temperature rise phase and a drive expansion phase of a working fluid, hot air engine characterized in that it comprises a compression cylinder (1) in which constantly moves back and forth a compression piston (2) delimiting, on either side of it, two compression chambers (20, 21) maintained at a cold temperature by a cold source, a driving cylinder (3) in which constantly moves back and forth a driving piston (4) delimiting from the latter two working chambers (40, 41) maintained at a hot temperature by a hot source, the compression piston (2) and the driving piston (4) being controlled jointly by a crank rod system and being in phase, two transfer chambers (5, 6) maintained at a hot temperature by a hot spring and respectively associated with a first compression chamber (20) and a first working chamber (40) and a second compression chamber (21) and a second working chamber (41), and a circuit for controlling the circulation of the working fluid between the different chambers (20, 21, 5, 6, 40, 41), equipped with control members making it possible to modify the connections between these chambers during a rotation of the crank so that: that during a compression phase the cold working fluid contained in a first of the two compression chambers (20) of the compression cylinder (1) is compressed by the compression piston (2) until it has reaches a predefined pressure, during a temperature rise phase, the cold working fluid having reached the predefined pressure contained in the first compression chamber (20) is transferred to the transfer chamber (5) associated with this first chamber or first transfer chamber, and that during a motor expansion phase, the working fluid contained in the first transfer chamber (5), having been compressed and high in temperature, is transferred into the working chamber (40 ) of the engine cylinder (3) associated with this first transfer chamber or first working chamber so as to relax and push the engine piston (4) while the working fluid contains d in the second working chamber (41) is discharged, the cold working fluid contained in the second compression chamber (21) being compressed in parallel by the compression piston (2) until it has reached the predefined pressure during another compression phase and then being transferred into the transfer chamber (6) associated with this second compression chamber or second transfer chamber during another temperature rise phase, before being transferred into the working chamber (41) of the engine cylinder (3) associated with this second transfer chamber (6) or second working chamber, during another drive expansion phase during which the working fluid contained in the first chamber working (40) is evacuated, and so on. 2) hot air engine according to claim 1, characterized in that the control members equipping the circuit for controlling the circulation of the working fluid are constituted by drawers or by valves whose actuation is preferably controlled by cams. 3) hot air engine according to any one of claims 1 and 2, characterized in that the two compression chambers (20, 21) of the compression cylinder (1) are in communication with the outside air and maintained at a cold temperature by this outside air which constitutes the cold source. 4 °) hot air engine according to any one of claims 1 and 2, characterized in that it comprises two cooling chambers (8, 9) maintained at a cold temperature by a cold source and respectively associated with the one of the compression chambers (20, 21) of the compression cylinder (1) to maintain this chamber at a cold temperature. 5 °) hot air engine according to any one of claims 1 to 4, characterized in that it comprises a heat exchanger (7) in which circulates the hot working fluid discharged from one of the working chambers (40, 41) of the engine cylinder (3) during a drive expansion phase in the other working chamber (41, 40) of this engine cylinder to heat the cold working fluid transferred from one of the compression (20, 21) of the compression cylinder (1) in the transfer chamber (5, 6) associated with this compression chamber during a temperature rise phase, which also circulates in this heat exchanger (7 ), against the current. 6 °) hot air engine according to any one of claims 1 to 4, characterized in that it comprises two intermediate cylinders (10, 10 ') in which respectively move constantly back and forth an insulating piston with essentially T-shaped double section (11, 11 ') making it possible to prevent heat transfer between the cold sources and the hot sources and delimiting on either side thereof an intermediate chamber of large section (12 , 12 ') associated with one of the compression chambers (20, 21) of the compression cylinder (1), an intermediate chamber of small section (13, 13') associated with one of the transfer chambers (5, 6) as well as a neutral chamber (14, 14 ') in communication with the outside air. 7 °) hot air engine according to claim 6, characterized in that each intermediate chamber of large section (12, 12 j is connected to the compression chamber (20, 21) associated by a pipe for circulation of the working fluid fitted with a calibrated non-return valve (15, 15d. 5 8) hot air engine according to any one of claims 6 and 7, characterized in that the two intermediate cylinders are combined into a single double intermediate cylinder (10) enclosing an insulating piston with a single double section 10 (11) delimiting on either side of it two intermediate chambers of large section (12, 12d and two intermediate chambers of small section (13, 13d and no neutral chamber.