FR2966203A1 - Stirling type thermodynamic device for autonomous heat pump, has chambers arranged on working liquid circuits, and shifter connected to lower parts of chambers so that each chamber is entirely filled with fluid when shifter is put in motion - Google Patents

Abstract

The device has two chambers (12a, 12b) arranged on working liquid circuits (13a, 13b) at high and low temperature levels, respectively. A shifter (14c) allows simultaneous variation of volumes of the chambers to a constant cumulated volume, where lower parts (121a, 121b) of the chambers are occupied by the working liquid, and top parts (122a, 122b) of the chambers are occupied by a working gas that moves between the chambers via a duct (11). The shifter is connected to the lower parts of the chambers, so that each chamber is entirely filled with the fluid when the shifter is put in motion. An independent claim is also included for a thermal transfer method.

Description

GENERAL TECHNICAL FIELD

The present invention relates to the field of thermal machines such as external energy engines Stirling type. More specifically, it relates to an improved thermodynamic device for mechanical production and / or heat transfer from a cold environment to a hot medium.

10 STATE OF THE ART

In order to produce mechanical work from the heat provided by the combustion of a fuel, thermal engines are available. These fall into two broad categories: 15 - internal combustion engines: the inside of the engine is the seat of combustion and it is the expansion of the exhaust that produces the work. These are the most widespread engines, which equip almost all vehicles of all kinds in various forms (combustion engines, turbojet engines, gas turbines, etc.), - external combustion engines: combustion is done "in boiler" outside the engine, which transmits its heat through a heat exchanger or a sealed wall, to a gas that will transform the heat energy into work. More generally, we refer to motors with external energy (or simply "external motor") when the heat does not necessarily come from a combustion (for example from the sun).

The advantage of external motors is that they can use any type of heat source, even if it is loaded with dust or any other substance that makes it unsuitable for internal combustion engines. 1 20 25 But above all, these engines have lower fuel consumption for higher power, which makes them unsurpassed in terms of efficiency (around 40%). In this last category, the "Stirling" engines are the best known. These engines have a main gas, circulating between the two chambers that make up a Stirling engine, and subjected to a cycle comprising four phases: isochoric heating (2H43H), isothermal expansion (3H44H), isochoric cooling (4H41 H) and isothermal compression (1H42H). This cycle is represented in FIG.

Although the cycle followed is not exactly Carnot's "ideal" (two adiabatic and two isotherms), it has been shown that its yield could be equal to the "maximum" of Carnot which is worth: Heating energy To achieve this performance maximum, it is important to have what is called a "regenerator", placed between the two chambers which are the "hot" gas expansion chamber, in contact with the hot source, and the "cold" chamber, compression of the gas, in contact with the cold source. In fact, from one chamber to another, the gas reciprocates with each cycle, and carries with it heat from the hot chamber to the cold chamber, in particular during the isochoric cooling phase (4H41 H). This transported heat is directly dissipated without valorization. The regenerator aims to prevent these losses by storing the heat of the hot gas that passes through it during the cooling phase (4H41 H), and restores it by crossing it in the other direction during the heating phase (2H43H). A regenerator must fulfill several contradictory functions: it must be a good conductor of heat in the direction perpendicular to the passage of the gas, and insulating in the direction of passage (in fact, it is necessary to work produced _ Tehaude -Three the temperatures being in Kelvin It is a problem to limit the progressive heat transfer from the hot chamber to the cold by conduction in the solid structure of the regenerator), - it must have a large contact area with the gas so as to absorb / return the maximum amount of heat to each alternate passage of gas, but also have the minimum volume of gas, said volume "dead" because it does not participate in the engine cycles and degrades the mechanical power developed by the gas during its relaxation, and is thus a source of loss of efficiency , and therefore be very compact, which causes significant losses of charges during alternate passages of the gas.

The known regenerators use, for example, metal grids, for their good heat capacity, composed of wires 40 microns thick spaced by a tenth of a millimeter. Such a regenerator is typically composed of 80% gas and 20% of the solid matrix, with an efficiency of 75%, but its manufacture remains expensive.

Calculations show that to obtain the ideal yield of Carnot it is necessary on the one hand an absence of dead volumes, namely areas (regenerator, pipes, ...) interface between the rooms where the gas is not subject isothermal compressions / detents (in particular stagnant gas in the regenerator); and on the other hand a 100% efficient regenerator. In addition, the Stirling cycles often have their working pistons and / or their displacer (a piston placed between the two chambers, and whose actuation varies the volume of one chamber relative to the other without varying the volume It is used in some types of Stirling engines) driven by crankshafts in rotation, with a phase shift between them (see Figure 2, which represents two known types of Stirling engines: the "alpha" with two working pistons, and the "beta" with a working piston and a displacer). In doing so, there is a great simplification of construction, and therefore a reduction in the investment cost, but then there is no longer strictly speaking isochoric phase (the gas follows a thermodynamic cycle which "cuts" the angles of the cycle ideal) and this degrades its thermodynamic performance.

The performance of Stirling engines remains to be improved, but in addition various structural problems prevent their real commercial development.

First, the motor is heated through a wall that contains the working gas at high and cyclic pressures. The constraints are strong at this level, since one combines the functions of mechanical resistance and good thermal conductivity. The materials used are therefore expensive.

Then the ratio "external surface of the chambers" / "volume of the gas" decreases physically as the engine increases in size, and therefore in power, which limits the possibility of effectively performing detents and compressions for large powers . Both of these problems have so far restricted Stirling technology to low power applications.

To correct them, we tend to work at high pressures and with a gas such as helium that delivers more mechanical power to equivalent engine volume. But then, one increases the difficulties of sealing through the joints of the working piston. Document EP0722073 proposes to circumvent the problem of lowering the ratio "external exchange surface" / "gas working volume", by spraying a liquid fluid in the working chambers. By heating (and cooling) by external exchangers a liquid (usually a mineral oil), and by spraying it in the working chambers, one manages to have a very large surface of heat transfer with the gas, which makes it possible to easily enlarge the motor. However, this does not solve the problem of loss of efficiency due to dead volumes, and poses a new difficulty which is the risk of progressive fouling of the regenerator due to evaporation of the fluid which is recondenser in the regenerator, colder.

As a result, the current Stirling engines are still to be improved.

PRESENTATION OF THE INVENTION The present invention aims at obtaining a thermodynamic device of the Stirling type presenting superior performance to all that has already been proposed. An ancillary purpose of this device is to separate the constraints of mechanical strength and thermal conductivity, and thus allow high power applications at reasonable cost. This device can also operate not only in motor but also in production of heat or cold. For this purpose, the present invention relates in a first aspect to a thermodynamic device comprising two chambers of variable volume, a chamber being disposed on a liquid working fluid circuit at a high temperature level (NT), and a chamber being disposed on a liquid working fluid circuit 20 at a low temperature level (BT), the chambers being further in communication via a conduit; at least two pistons including - at least one working piston allowing the variation of the volume of the HT chamber or the volume of the BT chamber, and 25 - at least one displacer allowing the simultaneous variation of the volumes of the two chambers with cumulated volume of the chambers constant, the pistons being mechanically connected so as to cyclically vary said volumes; Characterized in that - the lower part of the HT chamber and the lower part of the BT chamber are occupied by the liquid working fluid, - the upper part of the HT chamber and / or the upper part of the BT chamber are occupied. by a working gas moving alternately between the chambers via the pipe, - the displacer is connected to the lower parts of the chambers, the liquid working fluid acting as a liquid piston when the displacer is set in motion, so that at least one Once per cycle each chamber is fully filled with fluid.

According to other advantageous and nonlimiting features: the device comprises a second displacer, the second displacer sweeping a volume equal to the maximum volume of gas minus the minimum volume of gas on a cycle; - The device comprising two working pistons, including an expansion piston for varying the volume of the HT chamber, and a compression piston for varying the volume of the BT chamber; - At least one working piston for varying the volume of a chamber is located in the upper part of said chamber, said pistons being in contact with the working gas; and a solid structure is suspended under said working piston, said solid structure extending towards the lower part of said chamber. - At least one working piston for varying the volume of a chamber is located in the lower part of said chamber, said pistons being in contact with the liquid working fluid; and a solid structure is fixed in the upper part of said chamber, said solid structure extending towards the lower part of said chamber. - The device further comprises a regenerator disposed on the pipe; the displacer sweeps a volume equal to the minimum volume of gas on one cycle, plus the gaseous volume of the regenerator; - A liquid working fluid circuit successively connects a first side of the displacer, the regenerator, and a second side of the displacer; the regenerator comprises in its upper part a plurality of successive chambers separated by porous walls limiting the passage of a liquid but not a gas, said chambers comprising a solid matrix of thermal storage, the pipe being connected to the upper part regenerator, and the circuit being connected to the lower part of the regenerator; the regenerator comprises an upper wall, said upper wall substantially coinciding with the maximum level of the working fluid on a cycle; the expansion and / or compression pistons are connected by a crankshaft performing two turns per cycle; - The expansion piston and / or the expansion piston are integral with the crankshaft for only part of the cycle; - The device is adapted to a production of mechanical work, further comprises mechanical work recovery means, heat sensing means, heat dissipation means, characterized in that: - the mechanical work recovery means are connected with the pistons; - The heat sensing means are engaged with the HT circuit; and the heat dissipation means are in engagement with the LV circuit. - The device is adapted to cold production, further comprises means for supplying mechanical work, cold recovery means, heat dissipation means, characterized in that: - the means of supply of work mechanical are connected with the pistons; - The cold recovery means are engaged with the HT circuit; and the heat dissipation means are in engagement with the LV circuit. - The device is adapted to heat production, further comprises means for supplying mechanical work, heat recovery means, heat sensing means, characterized in that: - the means of supply of work mechanical are connected with the pistons; - The heat sensing means are engaged with the HT circuit; and the heat recovery means are in engagement with the LV circuit.

According to a second aspect, the invention proposes an autonomous heat pump, comprising a first thermodynamic device according to the first aspect of the invention adapted to a production of mechanical work, and a second thermodynamic device according to the first aspect of the invention to a production of cold or heat, characterized in that the mechanical work necessary for the second thermodynamic device is provided by the first thermodynamic device.

According to a third aspect, the invention proposes a thermal transfer method according to a thermodynamic cycle called "Stirling", implemented by a device according to the first aspect of the invention, comprising successive phases of: - first complete isochoric transfer of the working gas, from the HT chamber to the BT chamber; - Isothermal compression of the working gas occupying the BT chamber; second complete isochoric transfer of the working gas, from the BT chamber to the HT chamber; - Isothermal expansion of the working gas occupying the HT chamber.

According to other advantageous and non-limiting characteristics: the four phases of the cycle have the same duration; - The expansion piston and / or compression are separated from the crankshaft and immobilized in the low position during the isochoric transfer phase following the isothermal compression phase of the gas; the regenerator is filled with liquid fluid during the isothermal expansion and isothermal compression phases; - The displacer changes position at the beginning of each isochoric transfer phase to empty the liquid fluid contained in the regenerator via the circuit; - A liquid pumping system for moving the liquid working fluid in the circuits is activated during each isochoric transfer phase.

PRESENTATION OF THE FIGURES Other features and advantages of the present invention will appear on reading the description which follows of a preferred embodiment. This description will be given with reference to the appended drawings in which: FIG. 1 previously described is a representation of a Stirling cycle; - Figure 2 previously described is a diagram of two known types of Stirling engine; FIG. 3 is a diagram of one embodiment of the thermodynamic device according to the invention; FIG. 4 is a diagram of another embodiment of the thermodynamic device according to the invention; FIGS. 5a-h are diagrams of the successive states according to a Stirling cycle of a particularly preferred embodiment of the thermodynamic device according to the invention; FIGS. 6a-b are diagrams of a regenerator used in an advantageous embodiment of the thermodynamic device according to the invention.

DETAILED DESCRIPTION

General architecture With reference to FIG. 3, a thermodynamic device according to the invention comprises two chambers 12. These two chambers 12 have a variable volume, that is to say that one of their walls is a movable element, In particular, the head of a piston 14. The volume of each chamber 12 may vary from a minimum volume to a maximum volume, these volumes being adapted to the intended uses of the pump, and preferred volumes will be described later. The two chambers are connected by a pipe 11. This pipe is a characteristic element of the Stirling engines, and is visible on the motors of FIG. 2. The two chambers may optionally be contiguous, as in the device represented in FIG. and in this case the pipe 11 is reduced to an orifice connecting the chambers 12. These two chambers 12 are at different energy levels. The first, identified under the reference 12a and said High Temperature (HT) is intended to recover the energy of a hot source, via a circuit 13a of liquid working fluid at a high temperature level. This circuit 13a allows the effective transfer of heat from a hot source to the inside, the heat exchange with a fluid being indeed much more efficient than with a gas. This liquid working fluid 25 is for example water or a mineral oil, and preferably any coolant known to those skilled in the art for its good thermal properties. It should be noted that submerged burners (ie for example "u" tubes immersed in the hot liquid fluid and in which the hot fumes produced by the external combustion to the engine of natural gas, wood, coal ...) as a hot spring. In this case, the circuit 13a is entirely inside the chamber 12a. The second chamber 12b, called low temperature (BT) allows the heat dissipation to a cold source, via a second circuit 13b, this time a liquid working fluid circuit at a low temperature level. The liquid working fluid circulating in this circuit 13b is advantageously the same as that flowing in the circuit 13a, but it is quite possible to use two different fluids. It should be noted that the HV level is not necessarily a temperature level higher than the LV level, although this is generally the case. In particular, in a use of the device according to the invention in a heat pump (production of heat or cold), the hot source is colder than the cold source, and thus the chamber 12a HT is colder than the chamber 12b BT . This use will be described in detail later. However, even in these cases of inverted temperature levels, the chamber 12a HT will still be heated by the hot source, and the chamber 12b BT cooled by the cold source.

Solid pistons

The device 10 comprises at least two pistons 14, each allowing the variation of the volume Va of the chamber 12a HT and / or the volume Vb of the chamber 12b BT. Vtota defines the cumulative volume of the chambers 12a HT and 12b BT, Vtotai = Va + Vb. Knowing that a piston 14 can vary only two volumes among Va, Vb and Vtotab one will choose at least two different pistons 14 so as to vary the three volumes.

In particular, it will take at least one displacer 14c, that is to say as explained above a piston for the simultaneous variation of the volumes Va, Vb of the two chambers 12a, 12b constant volume Vtota, and at least one piston 14a or 14b said "work", that is to say a piston interface between one of the chambers 12 and outside, and thus allowing a transfer of mechanical energy with the outside, this working piston can in particular be: - either a trigger piston 14a, that is to say a piston adapted to recover mechanical energy when Va increases. Such a piston 14a has no influence on Vb and thus allows the variation of Vtota, simultaneous with the variation of Va. - Or a compression piston 14b, that is to say a piston adapted to reduce Vb by consuming mechanical energy. Such a piston 14b has no influence on Va and thus allows the variation of Vtota, simultaneous with the variation of Vb. Advantageously, the device 10 will comprise each of the two types of working piston 14a and 14b.

For example, in the device 10 shown in Figure 3 there is a displacer 14c, and a working piston 14b which acts as a compression piston when used alone, but which also plays the role of piston 14a when it is used in a coordinated manner with the displacer 14c (the mechanical power of the expansion of the gas in the chamber 12a is then transmitted via the displacer 14c and the liquid working fluid of the chamber 12b BT, but without variation volume Vb of the chamber 12b BT).

The device represented in FIG. 4 advantageously comprises a second displacer 14d, which plays the full role of the expansion piston 14a (in cooperation with the compression piston 14b), the first displacer 14c having no need to intervene in compression or relaxation phases of the cycle. For this, advantageously the displacer 14d scans a volume Vdepl (d) equal to the maximum gas volume Vmax minus the minimum volume of gas Vmin on a cycle, that is to say the volume corresponding to a relaxation or a complete compression. In a particularly preferred embodiment, shown in Figure 5a, the device 10 comprises an expansion piston 14a, a trigger piston 14b, and a displacer 14c. It is not excluded to add more pistons 14.

The pistons 14 are mechanically connected so as to vary each of these volumes cyclically, for example via one or more crankshafts 18 and various mechanical links, as can be seen in FIG. 4.

Liquid pistons

The device 10 is a Stirling type device. As previously explained, it therefore contains a working gas, which will be subjected to the mentioned four-phase cycle. However, in the case of the device 10 according to the invention, the working gas never occupies all of one of the chambers 12a and 12b, but at best the upper part 122a or 122b respectively of the chamber 12a HT or the chamber 12b BT, moving alternately from one to the other via the pipe 11. Indeed the rest of the rooms, in this case the lower part 121a of the chamber 12a HT and the lower part 121b of the chamber 12b BT are occupied by the liquid working fluid, as can be seen in one of FIGS. 3, 4 or 5. It will be noted that the notion of low and high parts is defined with respect to a vertical axis, the gravity being that the fluid is below the gas. It is recalled that the liquid working fluids are incompressible, and that the volume variations of the chambers are related to variations in the volume of the gases that compress or relax.

This liquid working fluid, in addition to playing the role of good thermal conductor, will play the role of liquid piston.

For this purpose, the displacer 14c is connected to the lower parts 121a, 121b of the two chambers 12a and 12b. It is therefore in contact with the working fluid (that is why it advantageously has good thermal insulation characteristics in order to prevent heat transfer by conduction between the two chambers 12a, 12b), and causes the displacement of the columns of fluid when set in motion. For example, with reference to FIG. 3, the displacement of the displacer 14c to the left from the position at which it is represented causes the level of fluid to rise in the chamber 12a HT and its decrease in the chamber 12b BT, and the transfer subsequent gas from the chamber 12a HT to the chamber 12b BT. Like a working piston 14a or 14b, a liquid piston can compress or relax the gas, and has the additional advantage of not being limited by geometry issues, in the manner of a piston which would deform while progressing in the chamber then the pipework: when the liquid piston has completely expelled the gas from a chamber (the chamber 12a HT in our example), the fluid enters the pipe 11 and continues its role of liquid piston . By continuing this transfer until purge completely the pipe 11, it is possible to transfer almost all the gas in the second chamber (12b BT in our example). Thus, at least once per cycle, and even advantageously several times (in particular twice: at the end of each isochoric phase, that is to say at the points 1H and 3H), each chamber 12a, 12b is filled with fluid, that is to say that at least once per cycle the fluid completely fills a chamber and the pipe 11, and thus the gas is contained in a single chamber. This is particularly the case for example for the device in the state where it is shown in Figure 5e. The gas is therefore forced to make a complete round trip from one chamber to another during a cycle, and can not stagnate in the pipe 11: the problem of dead volume, which is seen particularly on the devices Prior art shown in Figure 2, is thus solved, even though the pipe 11 would include a regenerator 15: at least once per cycle the regenerator is filled with liquid fluid. This embodiment will be described below.

The working pistons 14a, 14b can be placed anywhere in their chamber 12, the liquid piston accommodating any geometry. For example, in the device 10 shown in Figure 3, the compression piston 14b is disposed in the lower part 121b of the chamber 12b BT, opposite the displacer 14c with which it will cooperate easily. But to advantageously improve the efficiency and complementarity of the solid and liquid pistons in the case of a device with three types of pistons 14 (as shown in Figure 5a), the expansion piston 14a is located in the upper part 122a of the chamber 12a HT and the compression piston 14b is located in the upper part 122b of the chamber 12b BT, the pistons 14a, 14b being in contact with the working gas. This architecture allows the application of mechanical stresses to the gas and the gas both from above (solid piston) and below (liquid piston), for maximum mechanical efficiency since the working pistons do not need to first transmit their energy to the liquid piston to transmit it to the gas, and vice versa. This is particularly interesting during the isothermal relaxation phase (3H44H), which is the driving phase of the cycle.

The heat transfer between the gas and the liquid fluid of each chamber 12a, 12b can be done according to various known principles, the invention being not limited to any of them. For example, the streaming of the liquid on a fixed lining inside each chamber 12a, 12b, or the spraying of the liquid into fine droplets in the chambers 12a and 12b. More advantageously, one or more solid structures 140a, 140b, which are advantageously good heat conductors, are suspended under the working piston or pistons 14a, 14b, as can be seen for example in FIG. 5a, said solid structures 140a, 140b being extend towards the lower parts 121a, 121b of the chambers 12a and / or 12b in which the piston or pistons 14a, 14b are respectively located. These are for example metal bars, which pass through the upper portions 122a, 122b of the chambers 12a, 12b, and dive into the fluid each time the gas of the chamber is compressed and / or that the liquid piston rises. These structures 140a, 140b substantially increase the contact area between the gas and the liquid fluid. In the case where a chamber does not have a working piston (for example the chamber 12b of the device 10 shown in FIG. 4), it is still possible to use these structures 140, which are fixed to the sky of the chamber and perform the same functions .

Innovative regenerator Advantageously, as mentioned above, the device 10 according to the invention further comprises a regenerator 15 disposed on the pipe 11, which limits the heat transfer from the chamber 12a HT to the chamber 12b BT during the displacements of the gas in the pipe 11. This regenerator 15 may be the subject of all the known embodiments, in particular the use of a metal matrix with a high thermal inertia as shown in FIG. 3. While traversing this matrix, the hot gas coming from the room 12a HT transfers its heat. If it is chosen with a sufficiently high thermal inertia, this exchange lowers the temperature of the gas, and slightly increase that of the matrix. During the return from the chamber 12b BT to the chamber 12a HT, the now compressed gas recovers this heat stored in the matrix and heats up. The presence of a regenerator 15 is here made compatible with the liquid pistons. The liquid fluid can pass through it as well as the gas, the stroke of the displacer 14c must simply be adapted so that at least once per cycle the regenerator 15 is filled with liquid fluid. Advantageously, the displacer 14c scans in this case a volume Vdepi (c) equal to the minimum volume of gas Vmin on a cycle, plus the gas volume of the regenerator Vregen (this volume being equal to the internal volume of the regenerator 15, minus the volume of the solid matrix). Thus a stroke of the displacer 14c allows exactly an integral transfer of the compressed gas from one chamber to the other during the isochoric heating step (2H43H), the regenerator 15 being successively filled with liquid fluid, then with gas, then with fluid fluid during this transfer. Note also that if the use of a liquid piston to expel gas from the regenerator 15 is very effective, the use of a "gaseous piston" to expel the fluid during the return of the gas (for example at the beginning of the isochore cooling 4H41 H) is less. To counter this problem, advantageously an additional circuit 16 of liquid working fluid successively connects a first side of the displacer 14c, the regenerator 15, and a second side of the displacer 14c. With this circuit 16, the displacement of the displacer 14c firstly causes the suction of the liquid fluid filling the regenerator and its replacement by the gas. The two branches of this circuit 16, starting on either side of the regenerator 15, can be equipped with valves configured to not be open simultaneously to prevent fluid from passing from one chamber to another bypassing the displacer 14c.

Particularly preferably, a regenerator 15 is used which comprises at its upper part a plurality of successive chambers 150, for example three chambers as shown in FIG. 6, in order to maintain a mean thermal profile which improves the efficiency of the regenerator. Each chamber 150 is then at an almost constant temperature during the cycles, and with a decreasing profile from the high temperature chamber to the low temperature chamber. For this purpose, the chambers 150 are separated by porous walls 151 limiting the passage of a liquid but not a gas, said chambers 150 comprising a solid matrix 152 of thermal storage, the pipe 11 being connected to the upper part of the regenerator, and the circuit 16 being connected to the lower part of the regenerator 15. Its main advantage is to allow the use of oils as liquid fluid with high temperatures for the hot source, without fear of progressive fouling. regenerator 15 by condensates. Indeed, while conventional regenerators aim to be very small in order to minimize dead space, this type of innovative regenerator can be designed much larger. Thus the problems of progressive fouling of the solid matrix by the liquid fluid are eliminated because of larger gas flow dimensions in the solid matrix of the regenerator. Without this advantageous regenerator, the maximum temperature of the chamber 12a HT should in practice remain below 200-250 ° C. (very low saturation pressure of the oils), whereas with it is possible to consider increasing to 300-400 ° C. without fearing the condensation of oils. Each chamber 150 is separated from its neighbor by a wall 151 which allows the gas to pass easily, but prevents the liquid from circulating easily (in order to avoid convection movements between the chambers because of the temperature differences between them) without block it completely. A non-limiting embodiment of these walls 151 will consist of a gate whose pores will be of the order of one tenth of a millimeter, or even anti-particle filters that are commonly encountered in hydraulic circuits. This arrangement allows excess liquid (condensation of vapors, or liquid carried by the gas leaving one of the two chambers) to rebalance naturally between the working chambers.

The regenerator comprises an upper wall 153, this upper wall advantageously being either substantially flat or forming a slight arch (see below the interest of such a shape), and in both cases advantageously coinciding with the maximum level of liquid fluid. working on a cycle so that in the phases where one of the pistons is fixed, the liquid level is flat between the regenerator 15 and the chamber 12a or 12b filled with fluid. It is then relevant (but other arrangements are possible) that the lower surface of the working pistons 14a, 14b (in the case where they are placed in the upper part 122a, 122b of a chamber 12a, 12b) when they are in the lowest position is located at the top wall 153. The solid matrix 152 of each chamber 150 which performs the function of energy transfer with the gas during its passage is non-exclusively composed of small (internal diameter from 0.1 to 0.5 mm) metal tubes, or a "porous" structure of the "packing" type, technology used in particular for direct counter-current exchanges between a gas and a liquid (scrubbers, distillation columns, ..) Under each of these chambers 150, is advantageously a pocket 154 of liquid fluid. At the end of each isochoric phase (FIGS. 6a and 6b respectively correspond to the state of the regenerator during and at the end of the 4H41H phase), liquid fluid (here hot) is introduced by the movement of the displacer 14c (via the circuit 16) in the regenerator 15. Its introduction will push the liquid contained in each pocket 154 which will rise (the other branch of the circuit 16 being closed), and drive the gas contained in the regenerator 15 through the pipe 11, reducing to zero the dead volume of the regenerator 15 as seen in Figure 6b. The fluid of each chamber 150 acts as a liquid piston. This architecture guarantees a controlled evacuation of the gas towards an upper corner of the regenerator (the right corner in our case) without risk of trapping bubbles. However, even if the innovative regenerator 15 completely eliminates the dead volume, it is in some cases advantageous to keep a light gas at the top wall 153 of the regenerator 15 (vault shape) or working chambers 12a, 12b for safety reasons, in order to absorb if necessary "water hammer", that is to say shock waves that propagate in the fluid if a working piston 14a, 14b was to hit an incompressible liquid. This "safe" dead volume, however, has no common measure with the dead volumes observed in known devices, and is small enough to have an insignificant impact on the overall yield.

In a nonlimiting manner, a membrane 155 of silicone type will contain the liquid fluid of each pocket 154 and provide a thermal seal with the neighboring pockets 154, the fluid located below that pushes it, and the neighboring chambers 150. It will be noted that the thermal capacities of the liquid of each pocket 154 plus that of the solid matrix 152 are much greater than that of the gas passing through the regenerator. Thus, each pocket, as well as the solid matrix 152 of the pocket located above, will be at almost constant temperature, decreasing from the hot chamber to the cold room. The liquid of each pocket 153 can be seen as an "extension" of the solid matrix 152 in that it further increases its thermal inertia. On the other hand, the displacer chamber 14c is alternately filled with hot and cold liquid according to the allers and return of the displacer 14c, it is therefore necessary to avoid any mass transfer, or heat between it and the regenerator 15 that is why they will not advantageously be placed side by side. As explained above, liquid fluid aspiration preferably occurs at the beginning of the isochoric phase, and is triggered by the movement of the displacer 14c at the beginning of the stroke, whereas the introduction of liquid fluid occurs at the end of each isochoric phase. , and is triggered by the movement of the displacer 14c at the end of the stroke. The regenerator 15 is thus filled with liquid fluid during the isothermal expansion and isothermal compression phases.

Disengageable Pistons It has been mentioned previously that known Stirling engines tended to "cut corners" of the Stirling cycle for simplicity of construction. This degrades performance, and in particular makes that there is no real isochoric phase. The device 10 30 according to the invention, for which the isochoric transfers are the strong point, advantageously solves the problem by including the possibility of disengaging the working pistons 14a, 14b, that is to say that the working pistons 14a 14b are secured to the crankshaft 18 only during part of the cycle. This is made possible in particular when the expansion piston 14a and 14b compression are connected by a crankshaft 18 performing two turns per cycle. The connection with the piston is indeed in this case there by a rod, which is extended by a feeder 19, chosen for example cylindrical to be threaded on the piston rod, and blocked by a stop of the rod of piston. At each impact of the weight 19 on the stop, one goes from an engaged mode to a disengaged mode, and vice versa.

Thus, on two turns of crankshaft 18 per cycle, each working piston 14a, 14b advantageously passes one being secured to the crankshaft, and another in the low position. The two pistons 14a, 14b being advantageously phase-shifted by a half-turn on the crankshaft 18, there is successively at the end: the cycle with the two pistons engaged; the cycle with only the compression piston 14b engaged; - the cycle with no piston engaged; - Of the cycle with only the trigger piston 14a engaged.

We find the four phases of the perfect Stirling cycle. Stirling process

The device 10 according to the invention therefore advantageously implements a thermal transfer process according to a thermodynamic cycle called "Stirling", comprising successive phases of: - first isochoric transfer (4H41 H) integral of the working gas, the chamber 12a HT at room 12b BT; - Isothermal compression (1 H42H) of the working gas occupying the chamber 12b BT; second complete isochoric transfer (2H43H) of the working gas, from the chamber 12b BT to the chamber 12a HT; - Isothermal expansion (3H44H) of the working gas occupying the chamber 12a HT. As shown above, the four phases of the cycle advantageously have the same duration: to respect the isochores, the expansion piston 14a is integral with the crankshaft 18 only during the isothermal expansion and first isochoric transfer phases, and the compression piston 14b is secured to the crankshaft 18 only during the phases of first isochoric transfer and isothermal compression, the expansion piston 14a and 14b compression being immobile during the second isochoric transfer phase. In addition, the device 10 may comprise a liquid pumping system 17, this system 17 for moving the liquid working fluid in the circuits 13a, 13b on command, as shown in Figure 5a where it consists of two pistons separated by a waterproof membrane and very little conductivity of heat. The advantage of this system 17 is to be able to activate it only during the isochoric transfer phases, in particular by moving this double piston at the beginning of each phase: in a first direction at the beginning of the isochoric phases to fill the piston with heated fluid / cooled according to the circuit 13a or 13b, and in a second direction at the beginning of the isochoric phases to send this fluid respectively into the chambers 12a and 12b. This allows, in addition to real isochoric phases, to have isothermal phases, during which there is no temperature variation. The system 17 makes it possible to concentrate these heat transfers on only one half of the cycle, without dividing by half the energy exchanged. It is possible to couple it mechanically to the displacer 14c.

To detail a complete cycle in a particularly preferred embodiment of the device 10 according to the invention (here configured as a motor), starting with the point 1H (end of the first isochoric transfer), the device 10 is in the state represented by Figure 5a.

The chamber 12a HT is completely filled with liquid fluid. Its expansion piston 14a is disengaged from its weight 19 connected to the crankshaft 18 at the low point thereof. The regenerator 15 is filled with liquid pushed by the hot fluid expelled from the displacer chamber 14c, at the end of stroke thereof. In the isothermal compression phase (1 H42H) represented by FIG. 5b, the crankshaft 18 is thus disengaged from the expansion piston 14a which remains locked. The compression piston 14b compresses the gas of the chamber 12b BT, the isothermal character of this compression being here provided by the absorption of the compression energy by the solid structure 140b hooked to the piston 14b. The displacer 14c is stationary in this phase. At the position 2H, represented by FIG. 5c, the compression piston 14b, in the low position, disengages from the crankshaft 18 and remains locked. During the phase 2H43H (Figure 5d), the two working pistons 14a and 14b are thus locked in the low position, the gas volume is at least (Vmin), the pressure is maximum. This is the second phase of isochoric transfer. The displacement of gas from the chamber 12b BT to the chamber 12a HT is caused by the single movement of the displacer 14c which moves here to the right, by first sucking the hot liquid of the regenerator 15 and then imposing the crossing of the regenerator 15 to the gas. The system 17 is simultaneously activated to renew the chambers 12a and 12b respectively liquid fluid heated and cooled.

At point 3H (FIG. 5e), the chamber 12a HT contains all of the gas, compressed to the maximum, and is at the warmest: It has been reheated by the regenerator feedthrough, and by the liquid fluid of this chamber 12a, in which are dipped structures 140a. The energy level is maximum, and all conditions are met for the isothermal expansion phase 3H44H (Figure 5f). This is the motor phase of the cycle. The piston 14a, violently pushed by the expanding gas, resolidarise with the crankshaft 18 and transmits mechanical work. The droplets, possibly condensed in the regenerator 15 because of the pressure, or carried by the gas to the chamber 12b BT, are directly returned to the chamber 12a HT, by gravity, level of liquid level between the chamber 12b BT and the wall top of the regenerator. The displacer 14c is stationary (The regenerator is filled since the end of the previous phase with cold fluid coming from the chamber 12b) At the point 4H shown in FIG. 5g (end of isochoric expansion), the expansion piston 14a is at its point high. The chamber 12a HT still contains all the working gas. The compression piston 14b, which was previously disconnected from the crankshaft 18, clings to the weight 19 when it reaches its low point. When the isochoric movement (4H41 H) begins, the expansion piston 14a descends as the compression piston rises. The movements are equal, the volume Vtota, is therefore constant (Figure 5h). The displacer 14a moves here to the left, starting by sucking the cold liquid from the regenerator 15, then the cold liquid from the chamber 12b BT. The gas passes from the chamber 12a HT to the chamber 12b BT by yielding its heat to the regenerator 15. The hot liquid left of the displacer 14c is in turn injected into the regenerator 15 in order to empty its gas to the chamber 12b BT at the end of the phase. A condensation phenomenon of the vapors of the hot liquid will occur during this phase. Droplets will be deposited on the walls of the chambers 150 of the regenerator 15, and a portion may be carried by the gas to the chamber 12a HT. Point 1H is reached again (Figure 5a) and the cycle is complete.

Thermodynamic Applications The device 10 has the advantage of being able to operate according to three different operating modes (Stirling engine, production of cold and production of heat) according to the sources to which it is connected. These three configurations are the subject of three advantageous embodiments. Firstly, when it is configured as a motor, that is to say adapted to a production of mechanical work as is the case for the device 10 shown in FIG. 5a, it must comprise means 30 for the recovery of mechanical work connected with the pistons 14. For example, in Figure 5a these means are coincident with the crankshaft 18, in the form of a rotary shaft that transmits the movement to any other means that could use it, such as wheels if the device 10 configured as a motor is installed in a car. In addition, it must include heat sensing means 21 and heat dissipating means 22, which will respectively be the cold source and the hot source respectively engaged with the circuit 13a HT and the circuit 13b BT. The means 21 of heat capture include any way to recover heat, usually at more than 300 ° C. This may for example be an exchanger with burners of any fuel, such as gasoline in the case of a car, or a recuperator of solar energy, geothermal, etc. The means 22 for heat dissipation include radiators (in the case of the vehicle), but also any exchanger with air, water or any cooler medium. The application of a device 10 configured Stirling engine is particularly suitable for any vehicle that could be described as hybrid: the Stirling engine is only poorly adapted to abrupt changes in regime (urban driving for example), but is perfect for recharging a battery permanently via a generator, which will power an electric motor that will provide the motive power to the vehicle. We think of cars, trucks or buses, but also conventional submarines, which operate on batteries for reasons of discretion, or even air vehicles and fixed electric generators.

In the other two configurations, the device 10 according to the invention is a consumer of mechanical work. It is equivalent to a heat pump. The pistons 14 are this time connected to means 31 of mechanical input supply, as can be seen for example in Figure 3, where the device 10 is configured for cold production. The relaxation phase 3H44H is no longer driving, but is instead forced by the means 31. Thus, instead of allowing hot gas to cool in the chamber 12a HT, it forces already cold gas to cool again more. This is the configuration where the chamber 12a HT is at a temperature level lower than that of the chamber 12b BT. The circuit 13a HT is thus engaged with cold recovery means 20, these means 21 still playing the role of heat source, but this time at temperatures of a few degrees Celsius, or even below. These cold recovery means 21 consist for example of an air conditioning circuit, an exchanger with a cold room, or any other way of extracting heat from a medium that it is desired to cool. The device 10 configured in cold production further comprises means 22 for heat dissipation engaged with the other circuit 13b BT as engine application. The device 10 configured in heat production (not shown) operates on the same principle, but with energy levels shifted upwards (for example, conventional source temperatures are mentioned in parentheses), replacing the means for heat dissipation (T = 40 ° C) by heat recovery means (T ...-, 80 ° C), and the cold recovery means (T = -30 ° C) by means 21 heat capture (T = o ° C). The heat recovery means 20 may be a heating network, comprising a plurality of convectors, or any other way of transmitting heat to a medium that it is desired to heat. In addition, the system being reversible, the heat recovery means can quite be transformed into cold recovery means according to the seasons: in an office building, the device 10 can heat the winter, and cool the summer .

Independent heat pump According to a last aspect, the invention relates to a stand-alone heat pump, said autonomous heat pump comprising two devices 10 according to the invention: one configured as a motor, and the other configured in cold production or hot. Thus one produces mechanical work, and the other consumes it. This combination makes it possible to no longer have to use a noble energy such as electricity to operate the second device 10, but to develop heat sources called "at medium temperature" such as water heated by the sun, industrial waste , fumes from a factory, etc. sources often free and unlimited: the heat pump can be autonomous. Those skilled in the art can refer to the patent application FR1053418 in which are described many autonomous heat pump configurations that can be adapted to the use of two devices 10 according to the invention placed upside down.

Claims (22)

REVENDICATIONS1. Thermodynamic device (10) comprising two chambers (12) of variable volume, - a chamber (12a) being disposed on a circuit (13a) of liquid working fluid at a high temperature level (HT), and - a chamber (12b) ) being arranged on a circuit (13b) of liquid working fluid at a low temperature level (BT), the chambers (12a, 12b) being further in communication via a pipe (11); at least two pistons (14) of which - at least one working piston (14a, 14b) for varying the volume (Va) of the chamber (12a) HT or the volume (Vb) of the chamber (12b) BT, and at least one displacer (14c) allowing the simultaneous variation of the volumes (Va, Vb) of the two chambers (12a, 12b) with constant volume (Vtotai) of the chambers (12a, 12b) constant, - the pistons (14) being connected mechanically so as to cyclically vary said volumes; characterized in that - the lower part (121a) of the chamber (12a) HT and the lower part (121b) of the chamber (12b) BT are occupied by the liquid working fluid, - the upper part (122a) of the chamber (12a) HT and / or the upper part (122b) of the chamber (12b) BT are occupied by a working gas moving alternately between the chambers (12) via the pipe (11), - the displacer (14c) is connected to the lower parts (121a, 121b) of the chambers (12a, 12b), the liquid working fluid acting as a liquid piston when the displacer (14c) is set in motion, so that at least once per cycle each chamber ( 12a, 12b) is completely filled with fluid. 2. Device according to claim 1 comprising a second displacer (14d), the second displacer (14d) sweeping a volume (Vdepl (d) equal to the maximum volume of gas (Vmax) minus the minimum volume of gas (Vmin) on a cycle . 3. Device according to one of claims 1 to 2, comprising two working pistons (14a, 14b), including an expansion piston (14a) for varying the volume (Va) of the chamber (12a) HT, and a compression piston (14b) for varying the volume (Vb) of the chamber (12a) BT. 4. Device according to one of claims 1 to 3, wherein at least one working piston (14a, 14b) for varying the volume of a chamber (12a, 12b) is located at the top (122a, 122b). said chamber (12a, 12b), said pistons (14a, 14b) being in contact with the working gas; and a solid structure (140a, 140b) is suspended under said working piston (14a, 14b), said solid structure (140a, 140b) extending towards the lower portion (121a, 121b) of said chamber (12a, 12b). 5. Device according to one of claims 1 to 4, wherein at least one working piston (14a, 14b) for varying the volume of a chamber (12a, 12b) is located at the bottom (121a, 121b). said chamber (12a, 12b), said pistons (14a, 14b) being in contact with the working fluid; and a solid structure (140a, 140b) is fixed in the upper portion (122a, 122b) of said chamber (12a, 12b), said solid structure (140a, 140b) extending toward the lower portion (121a, 121b). ) of said chamber (12a, 12b). 6. Device according to one of claims 1 to 5, further comprising a regenerator (15) disposed on the pipe (11). 7. Device according to claim 6, wherein the displacer (14c) scans a volume (Vdep, (c) equal to the minimum volume of gas (Vmin) on a cycle, plus the gas volume of the regenerator (Vregen). 8. Device according to one of claims 6 to 7, wherein a circuit (16) of liquid working fluid successively connects a first side of the displacer (14c), the regenerator (15), and a second side of the displacer (14c ). 9. Device according to claim 8, wherein the regenerator (15) comprises in its upper part a plurality of successive chambers (150) separated by porous walls (151) limiting the passage of a liquid but not a gas, said chambers (150) comprising a solid thermal storage matrix (152), the conduit (11) being connected to the upper portion of the regenerator, and the circuit (16) being connected to the lower portion of the regenerator (15). The device of claim 9, wherein the regenerator (15) comprises an upper wall (153), said upper wall (153) substantially coinciding with the maximum level of the working fluid on a cycle. 11. Device according to one of claims 1 to 10, wherein the expansion piston (14a) and / or compression (14b) are connected by a crankshaft (18) performing two turns per cycle. 30 12. Device according to claim 11, wherein the expansion piston (14a) and / or the expansion piston (14b) are integral with the crankshaft (18) during only part of the cycle. 13. Device according to one of claims 1 to 12, adapted to a production of mechanical work, further comprising means (30) for the recovery of mechanical work, means (21) for collecting heat, means (22). heat dissipation device, characterized in that: - the mechanical work recovery means (30) are connected with the pistons (14); the means (21) for collecting heat are in contact with the circuit (13a) HT; and - the means (22) of heat dissipation are in engagement with the circuit (13b) BT. 14. Device according to one of claims 1 to 12, adapted to a production of cold, further comprising means (31) for supplying mechanical work, means (20) for recovering cold, means (22). heat dissipation, characterized in that: - the means (31) for mechanical work input are connected with the pistons (14); the cold recovery means (20) are engaged with the circuit (13a) HT; and - the means (22) of heat dissipation are in engagement with the circuit (13b) BT. 15. Device according to one of claims 1 to 12, adapted to a production of heat, further comprising means (31) for supplying mechanical work, means (20) for heat recovery, means (21). heat sensing system, characterized in that: the mechanical working supply means (31) are connected with the pistons (14); the means (21) for collecting heat are in contact with the circuit (13a) HT; and the heat recovery means (20) are engaged with the circuit (13b) BT. 16. Autonomous heat pump, comprising a first thermodynamic device according to claim 13 and a second thermodynamic device according to one of claims 14 to 15, characterized in that the mechanical work necessary for the second thermodynamic device is provided by the first thermodynamic device. . 17. Heat transfer process according to a thermodynamic cycle called "Stirling", implemented by a device according to one of claims 1 to 15 comprising successive phases of: - first isochoric transfer of the entire working gas, the chamber ( 12a) HT to the chamber (12b) BT; - Isothermal compression of the working gas occupying the chamber (12b) BT; second complete isochoric transfer of the working gas, from the chamber (12b) BT to the chamber (12a) HT; - Isothermal expansion of the working gas occupying the chamber (12a) HT. 18. The method of claim 17, wherein the four phases of the cycle have the same duration. 19. The method of claim 18, implemented by a device according to claim 12, wherein the expansion piston (14a) and / or compression (14b) are disengaged from the crankshaft (18) and immobilized in the low position during the isochore transfer phase following the isothermal compression phase of the gas. 20. Method according to one of claims 17 to 19, implemented by a device according to claim 6, wherein the regenerator (15) is filled with liquid fluid during the isothermal expansion and isothermal compression phases. 21. The method of claim 20, implemented by a device according to claim 8, wherein the displacer (14c) changes position at the beginning of each isochoric transfer phase to empty the liquid fluid contained in the regenerator (15) via the circuit (16). 22. Method according to one of claims 17 to 21, wherein a liquid pumping system (17) for moving the liquid working fluid in the circuits (13a, 13b) is activated during each isochoric transfer phase.