Improved efficiency electrical power generation device

Abstract

An electrical power generation device comprising: a first circulation loop of a first two-phase element having at least one first evaporation structure (2) fluidly connected to a first condensation structure (3); a second circulation loop of a second two-phase element having a second evaporation structure (4) fluidly connected to at least one second condensation structure (5), the evaporation temperature of the second two-phase element being lower than the evaporation temperature of the first two-phase element; and a set of thermoelectric elements (8) having a first face (8a) connected to the first condensation structure (3) and a second face (8b) connected to the second evaporation structure (4). Figure for the abstract: Fig 1

Description

Title of the invention: Device for producing electrical energy with improved efficiency Technical field

[0001] The present invention relates, in general, to the production of electrical energy.

[0002] More particularly, the invention relates to a device for producing electrical energy as well as an aircraft turbojet engine comprising such a device for producing electrical energy. State of the art

[0003] To date, the production of electricity on board an aircraft is carried out using structures dedicated to this task which convert mechanical energy, initially supplied by a rotational movement of the axis of the engine rotors, into electrical energy.

[0004] An aircraft incorporates at least two main electrical energy generating structures. On the one hand, the auxiliary power unit (APU), housed at the rear of the aircraft, allows the starting of the reactors during the takeoff phase. On the other hand, the generators driven by the rotation of the turbines produce the electrical energy necessary for the operation of all the components of the aircraft during the taxiing and flight phase.

[0005] The aircraft also has at least one secondary electrical generating structure. An alternator produces electrical energy intended for the computer called FADEC for the English term "Full Automatic Digital Engine Control", responsible for controlling the engine.

[0006] The use of an electrical energy generator mounted on the engine transmission shaft complicates the structure of the transmission shaft and increases the mass of the propulsion assembly in the nacelle.

[0007] Furthermore, the mechanical drive of the generator takes part of the propulsion energy from the engine and the safety of the electrical supply relies on only one generator subject to mechanical wear.

[0008] Furthermore, there are thermoelectric generators, called TEG for Ther-moElectric Generators in English, converting thermal energy into electrical energy. The thermoelectric elements that compose it make it possible to generate an electrical potential difference from a temperature gradient by Seebeck effect.

[0009] Thermoelectric elements therefore require a temperature difference between a hot side and a cold side of the portion on which they are placed.

[0010] An existing solution consists in particular of integrating thermoelectric elements on a portion of the nacelle subjected to a temperature gradient in order to transform part of the heat generated by the engine into electricity.

[0011] However, the thermal bridge caused by their installation in areas close to the engine can affect the performance of the latter.

[0012] Furthermore, the temperature range to which they are subjected is not optimal. Thermoelectric elements express maximum efficiency over a restricted temperature range. Beyond this range, the efficiency drops sharply. The temperature range of the engine during its various operating phases varies such that thermoelectric elements are rarely used over the optimum range.

[0013] The surface placement of the candidate zones also requires a large number of thermoelectric elements and induces not only an additional cost, but also an excess weight unsuitable for use in the aerospace field. Statement of the invention

[0014] The invention therefore aims to remedy these drawbacks and to propose a device making it possible to exploit the thermal energy resulting from the operation of an engine, in particular an aircraft engine, for the production of electrical energy from thermoelectric elements with improved efficiency.

[0015] There is therefore proposed a device for producing electrical energy comprising:

[0016] a first circulation loop of a first two-phase element comprising at least a first evaporation structure fluidly connected to a first condensation structure;

[0017] a second circulation loop of a second two-phase element comprising a second evaporation structure fluidly connected to at least one second condensation structure, the evaporation temperature of the second two-phase element being lower than the evaporation temperature of the first two-phase element; and

[0018] a set of thermoelectric elements comprising a first face connected to the first condensation structure and a second face connected to the second evaporation structure.

[0019] According to one embodiment, the first circulation loop is formed by a first closed enclosure or vapor chamber comprising the first evaporation and condensation structures.

[0020] According to another embodiment, the second circulation loop is formed by a second closed enclosure or vapor chamber comprising the second evaporation and condensation structures.

[0021] According to another embodiment, the first circulation loop is formed by a first closed enclosure or vapor chamber comprising the first evaporation and condensation structures and the second circulation loop is formed by a second closed enclosure or vapor chamber comprising the second evaporation and condensation structures.

[0022] In one embodiment, the first evaporation structure and the first condensation structure are connected by one or more heat pipes.

[0023] In another embodiment, the second evaporation structure and the second condensation structure are connected by one or more heat pipes.

[0024] In another embodiment, the first evaporation structure and the first condensation structure are connected by one or more heat pipes and the second evaporation structure and the second condensation structure are also connected by one or more heat pipes.

[0025] Advantageously, at least one of the heat pipes may comprise graphene carbon.

[0026] In one embodiment, the first circulation loop comprises at least one pump for circulating the first two-phase element between the first evaporation structure and the first condensation structure.

[0027] In another embodiment, the second circulation loop comprises at least one pump for circulating the second two-phase element between the second evaporation structure and the second condensation structure.

[0028] In another embodiment, the first circulation loop comprises at least one pump for circulating the first two-phase element between the first evaporation structure and the first condensation structure, and the second circulation loop also comprises at least one pump for circulating the second two-phase element between the second evaporation structure and the second condensation structure.

[0029] Preferably, the second condensation structure is rotatable.

[0030] More preferably, the internal walls of the second condensation structure comprise a capillary sheet.

[0031] The invention also relates to a turbojet engine for an aircraft comprising at least one device for producing electrical energy as previously described, the first evaporation structure being connected to a first heat source formed by a first zone of the turbojet engine and the second condensation structure being connected to a second heat source formed by a second zone of the turbojet engine with a temperature lower than the temperature of the first heat source of the turbojet engine.

[0032] According to one embodiment, the first evaporation structure may be an air deflector of a first stage of the low pressure compressor comprising a plurality of fins each comprising a passage for the circulation of the first two-phase element.

[0033] According to one embodiment, the first condensation structure and / or the second evaporation structure may comprise one or more cells, each cell comprising a plurality of fins.

[0034] According to one embodiment, the second condensation structure may be an air deflector downstream of a fan of the turbojet, and may comprise a plurality of fins each comprising a passage for the circulation of the second two-phase element.

[0035] The invention also relates to an aircraft comprising at least one turbojet engine as described above. Brief description of the drawings

[0036] Other aims, advantages and characteristics will emerge from the description which follows, given purely for illustrative purposes and with reference to the appended drawings in which:

[0037] [Fig-1] schematically illustrates a device for producing electrical energy according to one embodiment of the invention.

[0038] [Fig.2] illustrates a device for producing electrical energy for an aircraft turbojet engine according to one embodiment of the invention.

[0039] [Fig.3A] schematically illustrates a hybridized electrical energy production device using a vapor chamber on a hot source according to one embodiment of the invention.

[0040] [Fig.3B] schematically illustrates a hybridized electrical energy production device using a vapor chamber on a cold source according to one embodiment of the invention.

[0041] [Fig.3C] schematically illustrates a device for producing electrical energy using a steam chamber on a cold source and a steam chamber on a hot source according to one embodiment of the invention.

[0042] [Fig.4] schematically illustrates a hybridized electrical energy production device comprising a pump according to one embodiment of the invention.

[0043] Furthermore, the expression “at least one” used in the present description is equivalent to the expression “one or more”. Detailed description of an embodiment

[0044] [Fig.l] schematically illustrates an electrical energy production device 1 for converting thermal energy into electrical energy.

[0045] According to one embodiment, the thermal energy converted into electrical energy by the electrical energy production device 1 can be produced by a turbo- aircraft reactor.

[0046] The electrical energy production device 1 comprises a first circulation loop for the circulation of a first two-phase element and a second circulation loop for the circulation of a second two-phase element.

[0047] By two-phase element is meant in the present invention a heat transfer element, for example a two-phase fluid.

[0048] In the example illustrated, the two-phase element is a two-phase heat transfer fluid, present in vapor phase and in liquid phase.

[0049] Alternatively, it may be provided that the two-phase element is present in the solid phase or even in the sublimation phase.

[0050] The first circulation loop comprises a first evaporation structure 2 and a first condensation structure 3 fluidly connected.

[0051] According to another embodiment, it may be provided that the first condensation structure 3 is fluidically connected to a plurality of first evaporation structures 2.

[0052] In addition, the second circulation loop comprises a second evaporation structure 4 and a second condensation structure 5 fluidically connected.

[0053] According to another embodiment, it may be provided that the second evaporation structure 4 is fluidically connected to a plurality of second condensation structures 5.

[0054] The first circulation loop is connected to at least one first heat source called hot source 6 and the second circulation loop is connected to at least one second heat source of temperature, lower than the temperature of the hot source 6, called cold source 7.

[0055] The location of the hot source 6 and the cold source 7 may vary.

[0056] According to one embodiment, the first evaporation structure 2 can be connected to a first zone of an aircraft turbojet engine forming the hot source 6 and the second condensation structure 5 can be connected to a second zone of the aircraft turbojet engine, subjected to a temperature lower than the first zone, forming the cold source 7.

[0057] Furthermore, the electrical energy production device 1 comprises a set of thermoelectric elements 8, also called ThermoElectric Generators (TEG) in English.

[0058] In the illustrated example, the set of thermoelectric elements 8 are in the form of a matrix comprising a plurality of TEG cells housed by a parallelepiped structure.

[0059] A first face 8a of the set of thermoelectric elements 8 is connected to the first condensation structure 3 of the first circulation loop.

[0060] A second face 8b opposite the first face 8a, called the cold face 8b, is connected to the second evaporation structure 4 of the second circulation loop.

[0061] The evaporation temperature of the second two-phase element is lower than the evaporation temperature of the first two-phase element so that a temperature gradient can be formed between the first and second faces 8a and 8b of the set of thermoelectric elements 8. The first face 8a is called the hot face 8a and the second face 8b, subjected to a lower temperature, is called the cold face 8b.

[0062] Advantageously, the first and second two-phase elements can be chosen according to their evaporation temperature so that the difference between the evaporation temperatures of the first and second two-phase elements is equal to the temperature difference between the hot face 8a and the cold face 8b for optimal operation of the thermoelectric elements 8.

[0063] By choosing the first and second two-phase elements, it is possible to maintain a thermal gradient across the set of thermoelectric elements 1 that is adequate for optimal operation of the set of thermoelectric elements 1 and improved resulting efficiency.

[0064] Preferably, the first evaporation structure 2 can be connected to the first condensation structure 3 in a sealed manner by at least one first heat pipe 9.

[0065] Similarly, the second evaporation structure 4 can be connected to the second condensation structure 5 in a sealed manner by at least one second heat pipe 10.

[0066] In the example illustrated, each first or second heat pipe 9, 10 is an adiabatic pipe within which the vapor and liquid phases of the two-phase element that it conveys remain in equilibrium.

[0067] The first and second heat pipes 9, 10 make it possible to transmit a significant heat flux with a low temperature gradient. In addition, the use of heat pipes makes it possible to exploit the heat sources of the most favorable zones arranged at a distance from the set of thermoelectric elements 8.

[0068] According to one embodiment, the first evaporation structure 2 can be connected to the first condensation structure 3 by a plurality of first heat pipes 9 so as to maximize the heat exchange between the first evaporation structure 2 and the first condensation structure 3. This maximizes the heat flux transmitted to the set of thermoelectric elements 8 which can be concentrated on a small surface, significantly reducing the number and weight of the electrical energy production device 1.

[0069] Similarly, the second evaporation structure 4 can be connected to the second condensation structure 5 by a plurality of second heat pipes 10 so as to maximize the heat exchange between the second evaporation structure 4 and the second condensation structure 5.

[0070] A plurality of first evaporation structures 2 can be connected to the first condensation structure 3 by a plurality of first heat pipes 9 so as to be able to exploit a plurality of heat sources 6 located in different zones, for example, of an aircraft turbojet.

[0071] Similarly, a plurality of second condensation structures 5 can be connected to the second evaporation structure 4 by a plurality of second heat pipes 10 so as to be able to exploit a plurality of cold sources 7.

[0072] Preferably, the first and second heat pipes 9 and 10 are formed from carbon graphene, allowing a gain in weight and efficiency.

[0073] The thermal energy of the hot source 6 increases the temperature of the first two-phase element in the liquid phase up to its boiling point.

[0074] The vapor of the first two-phase element produced during boiling is conveyed by the first heat pipe 9 to the first condensation structure 3 where the vapor comes into contact with the hot face 8a of the set of thermoelectric elements 8.

[0075] In contact with the hot face 8a, the vapor condenses, generating a heat transfer from the first two-phase element to the hot face 8a of the set of thermoelectric elements 8, then returns by capillarity following the reverse path along the first heat pipe 9 to the first evaporation structure 2.

[0076] Opposite the hot face 8a, the thermal energy supplied by the cold face 8b of the set of thermoelectric elements 8 increases the temperature of the second two-phase element in liquid phase up to its boiling point.

[0077] The vapor of the second two-phase element produced during boiling is conveyed by the second heat pipe 10 from the second evaporation structure 4 to the second condensation structure 5 where the vapor condenses in contact with the cold source 7.

[0078] The difference between the boiling temperature of the first two-phase element present in the first evaporation structure 2 and the boiling temperature of the second two-phase element present in the second evaporation structure 4 ensures a fixed temperature at the terminals of the hot and cold faces 8a, 8b of the set of thermoelectric elements 8 thus positioned at its optimal operating point. This results in optimal thermodynamic efficiency.

[0079] In an embodiment where the electrical energy production device 1 is integrated into an aircraft turbojet, the temperature at the terminals of the set of thermoelectric elements 8 remains stable, and this during all phases of flight. of the aircraft, regardless of its engine speed.

[0080] Preferably, the second condensation structure 5 is rotatable. The progression of the liquid phase of the second two-phase element may be slowed down or hindered if the arrangement of the second condensation structure 5 and the second evaporation structure 4 relative to each other or if the structure of the second heat pipes 10 connecting them does not allow gravity or capillarity to fully exert their action. The rotation then makes it possible to disperse, under the action of centrifugal force, the liquid phase of the second two-phase element continuously condensing on the internal walls of the second condensation structure 5 in order to make it take an exclusive return path towards the second evaporation structure 4.

[0081] More preferably, the internal walls of the second condensation structure 5 comprise a capillary layer so as to facilitate the passage of the liquid phase of the second two-phase element along an exclusive return path.

[0082] In an embodiment where the electrical energy production device 1 is integrated into an aircraft turbojet engine, the mechanical energy ensuring the rotation of the second condensation structure 5 can be taken from a turbine of the turbojet engine.

[0083] Figures 3A, 3B and 3C illustrate variants of the electrical energy production device 1.

[0084] [Fig.3A] illustrates a hybridized electrical energy production device 1 in which the first circulation loop is formed by a first closed enclosure 11 comprising the first evaporation and condensation structures 2 and 3. The first closed enclosure 11 is a vapor chamber, arranged in contact with the heat source 6, and within which the passage between the vapor and liquid phases of the first two-phase element takes place. In this example, the second evaporation and condensation structures 4 and 5 of the second circulation loop are two independent structures connected for example by one or more heat pipes 10.

[0085] [Fig.3B] illustrates a hybridized electrical energy production device 1 in which the second circulation loop is formed by a second closed enclosure 12 comprising the second evaporation and condensation structures 4 and 5. The second closed enclosure 12 is a vapor chamber, arranged in contact with the cold source 7, and within which the passage between the vapor and liquid phases of the second two-phase element takes place. In this example, the first evaporation and condensation structures 2 and 3 of the first circulation loop are two independent structures connected for example by one or more heat pipes 9.

[0086] [Fig.3C] illustrates an electrical energy production device 1 in which the first circulation loop is formed by a first closed enclosure 11 comprising the first evaporation and condensation structures 2 and 3, and the second circulation loop is formed by a second closed enclosure 12 comprising the second evaporation and condensation structures 4 and 5. The first and second closed enclosures 11 and 12 are steam chambers, arranged respectively in contact with the hot source 6 and the cold source 7. Such an electrical energy production device can be used on an oil or water and exhaust gas circuit.

[0087] It may be provided that the first evaporation structure 2 and the first condensation structure 3 are formed by a first closed enclosure 11 or a steam chamber including engine casings.

[0088] It may also be provided that the second evaporation structure 4 and the second condensation structure 5 are formed by a second closed enclosure 12 or steam chamber placed at the leading edge of the wing or engine pylon.

[0089] Furthermore, [Fig.4] illustrates an electrical energy production device 1 in which the first evaporation structure 2 and the first condensation structure 3 are connected by at least one first heat pipe 9.

[0090] Furthermore, the first circulation loop of the electrical energy production device 1 illustrated in [Fig.4] comprises at least one pump 13 for the circulation of the first two-phase element between the first evaporation structure 2 and the first condensation structure 3.

[0091] An active recirculation mode of the first and second two-phase heat-transfer elements in liquid phase using a pump makes it possible to overcome the usual distance limits encountered in heat pipes.

[0092] An active recirculation mode of the first and second two-phase heat-transfer elements in vapor phase using a pump can also be used in order to overcome the usual distance limits encountered in heat pipes.

[0093] In another embodiment, it may be provided that the second circulation loop comprises at least one pump for the circulation of the second two-phase element between the second evaporation structure 4 and the second condensation structure 5.

[0094] It may also be provided that the first and second circulation loops comprise at least one pump.

[0095] In the case where a strong thermal gradient resides between the hot source 6 and the cold source 7, exceeding by several orders of magnitude that of the set of thermoelectric elements 8, a plurality of electrical energy production devices can be connected in series.

[0096] In a series arrangement, two successive electrical power generation devices 1 may be connected by connecting the second structure of condensation 5 of one with the first evaporation structure 2 of the next. The first and second two-phase elements differ according to the electrical energy production device 1 of the series and are chosen so as to form a temperature gradient between the first and last electrical energy production devices 1 and maintain an optimal thermal gradient for each set of thermoelectric elements 1.

[0097] [Fig.2] illustrates a turbojet electrical energy production device 1 aircraft.

[0098] The first evaporation structure 2 is connected to the first heat source 6 formed by a first zone of the turbojet engine. The second condensation structure 5 is connected to the second heat source 7 formed by a second zone of the turbojet engine with a temperature lower than the temperature of the first heat source 6 of the turbojet engine.

[0099] In the example illustrated, the first evaporation structure 2 is formed by an air deflector of a first stage of the low-pressure compressor carried by the turbojet engine. This makes it possible to lower the temperature as well as the density of the air on the stage of the low-pressure compressor. This compression gain results in a propulsive gain of the turbojet engine.

[0100] The illustrated low pressure compressor first stage air deflector comprises a plurality of hollow fins whose internal structure forms a passage 14 for the circulation of the first two-phase element.

[0101] According to another embodiment, it may be provided that the first evaporation structure 2 is formed by a nozzle for discharging hot gases from the turbojet.

[0102] In the illustrated example, the first condensation structure 3 and the second evaporation structure 4 comprise one or more cells, the internal structure of each cell comprising a plurality of fins. The cells, located in contact with the hot face 8a of the set of thermoelectric elements 8, are sealed against each other. The plurality of fins of each cell makes it possible to increase the heat exchange surface.

[0103] Preferably, each cell is connected by a first heat pipe 9 specific to a fin of the air deflector of the first stage of the low pressure compressor.

[0104] In the example illustrated, the second condensation structure 5 is formed by an air deflector arranged downstream of a fan of the turbojet engine. This makes it possible to increase the volume of air leaving the fan. The resulting gain in volume translates into a propulsive gain.

[0105] The air deflector arranged downstream of the blower illustrated comprises a plurality of hollow fins whose internal structure forms a passage 15 for the circulation of the second two-phase element.

[0106] According to another embodiment, it may be provided that the second condensation structure 5 is formed by a fuel inlet structure of the turbojet.

[0107] In an aircraft, the electrical energy produced by the electrical energy production device 1 can be used to power equipment on board, replacing the mechanical source of electrical energy production such as an electric alternator, which is less reliable and subject to mechanical breakdowns.

[0108] The electrical energy production device 1 converts the thermal energy lost during the operation of the turbojet engine into useful electrical energy.

[0109] It may be provided that the electrical energy production device 1 is integrated into a different structure of an aircraft.

[0110] For example, in the aerospace field, the electrical energy production device 1 may be used to power certain devices on board a rocket launcher.

[0111] The first evaporation structure may be, for example, connected to a hot point formed by a nozzle of the rocket and the second condensation structure 5 may be a fuel or an oxidizer in the cryogenic state.

[0112] In a nuclear power plant, the electrical energy production device 1 can replace emergency generators in order to provide electrical energy also in the event of flooding of the installations.

[0113] According to other examples, the electrical energy production device 1 can be used in the field of geothermal energy or even operated on industrial chimneys, on a boiler room, an incinerator, a blast furnace, a flare, etc., to convert the residual heat from a chimney flue into electrical energy.

Claims

Claims

1. Turbojet for aircraft comprising at least one electrical energy production device (1) comprising: a first circulation loop of a first two-phase element comprising at least one first evaporation structure (2) fluidly connected to a first condensation structure (3); a second circulation loop of a second two-phase element comprising a second evaporation structure (4) fluidly connected to at least one second condensation structure (5), the evaporation temperature of the second two-phase element being lower than the evaporation temperature of the first two-phase element;and a set of thermoelectric elements (8) comprising a first face (8a) connected to the first condensation structure (3) and a second face (8b) connected to the second evaporation structure (4), the first evaporation structure (2) being connected to a first heat source (6) formed by a first zone of the turbojet engine and the second condensation structure (5) being connected to a second heat source (7) formed by a second zone of the turbojet engine with a temperature lower than the temperature of the first heat source (6) of the turbojet engine.;

2. Turbojet according to claim 1, in which the first circulation loop is formed by a first closed enclosure (11) comprising the first evaporation and condensation structures (2, 3) and / or the second circulation loop is formed by a second closed enclosure (12) comprising the second evaporation and condensation structures (4, 5).

3. A turbojet engine according to claim 1 or 2, wherein the first evaporation structure (2) and the first condensation structure (3) are connected by one or more heat pipes (9) and / or the second evaporation structure and the second condensation structure are connected by one or more heat pipes (10).

4. A turbojet engine according to claim 3, wherein at least one of the heat pipes (9, 10) comprises graphene carbon.

5. Turbojet according to any one of claims 1 to 3, in which the first circulation loop comprises at least one pump (13) for the circulation of the first two-phase element between the first evaporation structure (2) and the first condensation structure (3) and / or the second circulation loop comprises at least one pump for circulating the second two-phase element between the second evaporation structure (4) and the second condensation structure (5).

6. A turbojet engine according to any one of claims 1 to 5, wherein the second condensation structure (5) is rotary.

7. Turbojet according to claim 6, in which the internal walls of the second condensation structure (5) comprise a capillary layer.

8. Turbojet according to any one of claims 1 to 7, in which the first evaporation structure (2) is an air deflector of a first stage of the low pressure compressor comprising a plurality of fins each comprising a passage (14) for the circulation of the first two-phase element.

9. Turbojet according to any one of claims 1 to 8, in which the first condensation structure (3) and / or the second evaporation structure (4) comprises one or more cells, each cell comprising a plurality of fins.

10. A turbojet engine according to any one of claims 1 to 9, wherein the second condensation structure (5) is an air deflector downstream of a fan of the turbojet engine, and comprises a plurality of fins each comprising a passage (15) for the circulation of the second two-phase element.

11. Aircraft comprising at least one turbojet engine according to any one of claims 1 to 10.

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