Propulsion system equipped with a high-temperature fuel cell with optimized integration.

Abstract

Propulsion system comprising at least one turbomachine (1) and a high-temperature fuel cell (3) connected to an electrical circuit (4); the turbomachine (1) comprising at least one compressor (11) and one combustion chamber (12); the fuel cell comprising at least one electrochemical cell (31), a fuel supply circuit (32) for the electrochemical cell, an air supply circuit (33) for the electrochemical cell, and an exhaust circuit (35) for air and water vapor from the electrochemical cell. The air supply circuit comprises a valve device (36) having a first inlet connected to an outside air intake and a second inlet connected to a port of the turbomachine compressor for selectively connecting the air supply circuit to the outside air intake and the compressor port. FIGURE IN ABBREVIATION: [Fig. 1]

Description

Title of the invention: Propulsion system provided with a high-temperature fuel cell with optimized integration.

[0001] The present invention relates to the field of vehicle propulsion, in particular aeronautical vehicles, and more particularly the management of energy in propulsion systems.

[0002] BACKGROUND OF THE INVENTION

[0003] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft, but also to those already in circulation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0004] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. With the aim of improving the energy efficiency of aircraft, the Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences.

[0005] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to reduce the environmental footprint of its activity.

[0006] This sustained research and development work focuses on new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, etc.

[0007] For this purpose, it has been considered, in aircraft, to power the on-board electrical network by a fuel cell supplied with dihydrogen.

[0008] It is recalled that a fuel cell comprises at least one electrochemical cell, a first device for supplying the electrochemical cell with dihydrogen, a second device for supplying the electrochemical cell with dioxygen, and a device for discharging, outside the electrochemical cell, water and the heat produced. The electrochemical cell has two electrodes, namely an anode on which oxidation of dihydrogen, which is a reducing fuel, takes place, and a cathode on which reduction of dioxygen, which is an oxidant, takes place. The two electrodes are separated by an electrolyte which: - allows the passage of ions between the electrodes, - blocks the electrons to force them to pass between the two electrodes by an external electrical circuit which is connected to the two electrodes and to which the equipment that the electrochemical cell must supply with electricity is connected, - acts as a membrane by preventing the passage of gases from one electrode to the other.

[0009] Several fuel cell technologies exist, some of which require a relatively high temperature (over 200°C approximately) to operate. These fuel cells are called high-temperature.

[0010] Among these are solid oxide fuel cells (or SOFCs) in which the electrolyte is a solid oxide, generally a ceramic such as zirconium oxide, and requires a temperature between 400° and 1000°C to have sufficient ionic conductivity for the operation of the electrochemical cell.

[0011] There are also molten carbonate fuel cells (or MCFCs), in which the electrolyte comprises molten carbonate salts dispersed in a porous ceramic matrix, which operate from around 650°C.

[0012] There are also high-temperature proton exchange membrane fuel cells (or HT-PEM or HT-PEMFC from the English High Temperature Proton Exchange Membrane Fuel Cell, or High Temperature Polymer Electrolyte Membrane Fuel Cell, or PEMHT) whose electrolyte is a polymer membrane and which operates from around 100°C.

[0013] SUBJECT OF THE INVENTION

[0014] The invention aims in particular to increase the contribution of the fuel cell in the energy supply of an aircraft. Summary of the invention

[0015] To this end, according to the invention, a propulsion system is provided comprising at least one turbomachine and a high-temperature fuel cell connected to an electrical circuit. The turbomachine comprises at least one compressor and a combustion chamber. The fuel cell comprises at least one electrochemical cell, a circuit for supplying fuel to the electrochemical cell, a circuit air supply circuit for the electrochemical cell, a circuit for discharging air and water vapor from the electrochemical cell. The air supply circuit comprises a valve device having a first inlet connected to an external air intake and a second inlet connected to a port of the compressor of the turbomachine for selectively connecting the air supply circuit to the external air intake and to the compressor port.

[0016] Thus, it is possible to exploit this relatively high operating temperature of the fuel cell to better integrate the fuel cell into the energy architecture of the aircraft. In particular, supplying the fuel cell with pressurized air makes it possible to improve the efficiency of the fuel cell and to increase its maximum power. It will also be possible to assist the operation of the turbomachine, in particular at start-up, and / or to exploit the heat of the products evacuated from the fuel cell to supply energy to equipment of the vehicle provided with the propulsion system according to the invention.

[0017] According to optional characteristics, used individually or in whole or in part in combination: - the exhaust circuit supplies an auxiliary compressor having an outlet connected to the combustion chamber of the turbomachine; - the turbomachine rotates a drive shaft connected in rotation to a propulsion member and the electrical circuit is connected to an electrical machine having an input / output shaft mechanically connected to the drive shaft; - the evacuation circuit is connected to a heat exchanger integrated in a channel designed to generate additional thrust by the Meredith effect; - the evacuation circuit is connected to a defrosting fluid circuit; - the exhaust circuit is connected to a hot inlet of a heat exchanger of the defrost fluid circuit; - the evacuation circuit is connected to an inlet of a condenser having a gas outlet in communication with the defrosting fluid circuit and a liquid outlet connected to an injection port opening into the combustion chamber; - the evacuation circuit is connected to an inlet of a turbine rotating an electric generator connected to the electrical network; - the evacuation circuit is connected to a hot inlet of a heat exchanger of an organic Rankine cycle machine comprising a turbine driving a generator connected to the electrical network; - the fuel supply circuit is connected to a cold inlet of a condenser of the organic Rankine cycle machine.

[0018] Preferably, the system comprises an electronic control unit arranged to: - couple the fuel cell and the turbomachine during the take-off phase and during cruise; - decouple the fuel cell and the turbomachine when the turbomachine is idling or cruising when the turbomachine is faulty.

[0019] In the case of an aircraft, with decoupling when the aircraft is on the ground, the fuel cell provides energy to assist the start-up of the turbomachine and / or for electric taxiing (turbomachine stopped or idling). In the event of a failure of the turbomachine in flight, the electronic control unit controls decoupling so that the fuel cell assists the restart of the turbomachine.

[0020] The coupling of the fuel cell and the turbomachine makes it possible to optimize the energy efficiency of the propulsion system, for example by: - injecting steam into the combustion chamber of the turbomachine in order to reduce nitrogen oxides (NOx) and reduce fuel consumption; - injecting torque into the turbomachine's electric machine (internal hybridization gains); - improving the efficiency of the fuel cell by taking air from the turbomachine; - reducing 1 s transients of the fuel cell by injecting torque into the air compressor (electrical power taken from the turbomachine).

[0021] Other characteristics and advantages of the invention will emerge from reading the following description of particular and non-limiting embodiments of the invention. Brief description of the drawings

[0022] Reference will be made to the accompanying drawings, among which:

[0023] [Fig.l] [Fig.l] is a schematic representation of an aircraft according to a first embodiment of the invention;

[0024] [Fig.2] [Fig.2] is a schematic representation of an aircraft according to a second embodiment of the invention;

[0025] [Fig.3] [Fig.3] is a schematic representation of an aircraft according to a third embodiment of the invention;

[0026] [Fig.4] [Fig.4] is a schematic representation of an aircraft according to a fourth embodiment of the invention;

[0027] [Fig.5] [Fig.5] is a schematic representation of an aircraft according to a fifth embodiment of the invention;

[0028] [Fig.6] [Fig.6] is a schematic representation of an aircraft according to a variant of the first embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] With reference to [Fig. 1], the invention is described here in application to an aircraft A comprising a turbomachine 1 associated with a propeller 2, a fuel cell 3 and an on-board electrical network 4.

[0030] The turbomachine 1, known in itself, schematically comprises a compressor 11, a combustion chamber 12, a turbine 13 driving in rotation a shaft 14 linked in rotation to the propeller 2 by a gearbox 5 and to an input / output shaft of an electrical machine 6 connected to the electrical network 4. There are intermediate shafts and other components which have not been described here so as not to complicate the description. The electrical machine 6 is arranged and controlled in a manner known in itself to selectively drive in rotation the shaft 14 (motor mode: for example for start-up assistance) or so that the input / output shaft is driven in rotation by the shaft 14 to supply the electrical network 4 (generator mode: for example during flight phases). The structure and operation of the turbomachine 1 are known in themselves and will not be detailed further here.

[0031] The fuel cell 3 is here of the SOFC type and comprises a plurality of electrochemical cells 31 (also called electrolytic cells), a device 32 for supplying dihydrogen to the electrochemical cells 31, a device 33 for supplying dioxygen to the electrochemical generators 31, an external electrical circuit 34 connected to the electrochemical cells 31 and a fluid evacuation circuit 35 also connected to the electrochemical cells 31. The fuel cell 3 also comprises, in a manner known per se, other components which are not mentioned here because they have no particular connection with the invention.

[0032] Each electrochemical cell 31 comprises two electrodes, namely an anode to produce an oxidation of dihydrogen and a cathode to produce a reduction of dioxygen. These electrodes are electrically connected in series to the external electrical circuit 34. The electrodes are positioned on either side of a solid electrolyte, formed of a ceramic based on an oxide such as zirconium oxide, responsible for ensuring ionic conductivity between the electrodes and blocking the passage of electrons between the electrodes to force them to pass through the external electrical circuit 34 which supplies the electrical network 4 (and more particularly the part of the electrical network 4 supplying non-propulsion equipment such as on-board computers and calculators, air conditioning, signaling, lighting, etc.). The electrolyte also blocks the passage of gases between the electrodes.Each electrochemical cell 31 comprises, in a manner known per se, a dihydrogen inlet, an outlet for excess dihydrogen, an air inlet and an outlet for depleted air. oxygen and water vapor. The electrochemical cells 31 are connected together in series from an electrical point of view and in parallel from a fluidic point of view.

[0033] The dihydrogen supply device 32 comprises, in a manner known per se, a dihydrogen circuit which is connected to a pressurized dihydrogen tank and supplies the electrochemical cells 31 on the anode side, and a pump positioned in the dihydrogen circuit and driven by an auxiliary electric motor to circulate the dihydrogen in the electrochemical cells 31 via the dihydrogen inlet and the dihydrogen outlet. The pump thus makes it possible to circulate the dihydrogen in the dihydrogen circuit. The dihydrogen circuit is known per se and may also comprise a filter, a heater, a humidifier, a separator, valves, sensors, etc.

[0034] The oxygen supply device 33 comprises, in a manner known per se, an air circuit supplying the electrochemical cells 31 on the cathode side via the air inlet, and a first auxiliary compressor placed in the air circuit and driven by an auxiliary electric motor. The first auxiliary compressor allows adjustment of the pressure and flow rate of air introduced into the electrochemical cells 31, this pressure and this flow rate conditioning the performance of the electrochemical cells 31. The air circuit is known per se and may also comprise a filter, a heater, a humidifier, a separator, valves, sensors, etc.

[0035] The depleted air and water vapor outlets of the electrochemical cells 31 are connected in parallel to the evacuation circuit 35.

[0036] According to a first characteristic of the invention, the air circuit comprises a valve device 36 having a first inlet connected to an external air intake 37 and a second inlet connected to a port of the compressor 11 of the turbomachine 1 to selectively connect the air supply circuit to the external air intake 37 and to a sampling port of the compressor 11.

[0037] According to a second characteristic of the invention, the evacuation circuit 35 supplies a second auxiliary compressor 38 having an outlet connected by an injector to the combustion chamber 12 of the turbomachine 1. More precisely, the evacuation circuit 35 is connected to an inlet of a valve device 39 having a first outlet connected to the auxiliary compressor 38 and a second outlet connected to a vent 40 in communication with the outside air. The auxiliary compressor 38 is actuated by an auxiliary electric motor preferably supplied by the external electrical circuit 34.

[0038] According to a third characteristic of the invention, the external electrical circuit 34 is connected to the electrical machine 6.

[0039] The fuel cell 3, and more particularly the controllable members of the fuel cell 3, including the valve devices 36, 39 and the electrical switches of the external electrical circuit 34, are connected to an electronic control unit 7 which comprises at least one processor and a memory containing at least one computer program executable by the processor. This program comprises instructions arranged to control said members according to the flight phases, control instructions from the pilot of the aircraft A, setpoint values ​​developed from said control instructions, internal operating parameters of the turbomachine 1 (in particular provided by sensors equipping the turbomachine 1), external operating parameters of the aircraft A (in particular provided by sensors equipping the aircraft A)...

[0040] The electronic control unit 7 is thus programmed to control the valve device 36 to connect the air supply circuit either to the external air intake 37 or to the compressor port 11 of the turbomachine 1. Thus, the fuel cell 3 can be supplied with air, depending on the flight phase considered, either by taking air from the turbomachine 1 (the operation of the fuel cell 3 is then coupled to that of the turbomachine 1; for example to provide additional power at takeoff or to optimize energy consumption during cruising), or by the external air intake (the operation of the fuel cell 3 is then decoupled from that of the turbomachine 1; for example when the aircraft is on the ground and the turbomachine is idling, or in the event of a breakdown).For example, the autonomous operation of the fuel cell 3 requires that the electrochemical cells 31 be at a temperature between 400°C and 1000°C: it is understood that, when the turbomachine 1 is operating, the air coming from the compressor 11 is hotter than that coming from the outside air intake 37. The injection of pressurized and hot air into the fuel cell 3 makes it possible to increase the energy efficiency and the maximum power of the fuel cell 3. It is therefore more advantageous to start the fuel cell 3 to control the valve device 36 to connect the air supply circuit 33 to the port of the compressor 11 when the turbomachine 1 is operating. On the other hand, when the turbomachine 1 is not in operation, the valve device 36 is controlled to connect the air supply circuit 33 to the outside air intake 37.

[0041] The electronic control unit 7 is programmed to control the valve device 36 to connect the exhaust circuit 35 either to the vent 40 (in particular when the turbomachine 1 is not started) or to the injection port of the combustion chamber 12 (when the turbomachine 1 is operating). It is recalled that the products evacuated by the exhaust circuit 35 comprise oxygen-depleted air and water essentially in the form of steam. The injection of the evacuated products into the combustion chamber 12 makes it possible to increase the specific power of the turbomachine 1 and to improve its thermal efficiency, as well as to reduce the oxides nitrogen at the outlet of the combustion chamber 12. The auxiliary compressor 38 is arranged and controlled to bring the evacuated products to a pressure compatible with their injection into the combustion chamber 12.

[0042] As has been seen, the external electrical circuit 34 is arranged to supply the electrical network 4 and more particularly the non-propulsive part of the electrical network 4. The electronic control unit 7 can control the switching members of the external electrical circuit 34 to connect it to the electrical machine 6 to control the latter as a motor so that the electrical machine 6 provides torque to the turbomachine 1 so as to assist the starting of the turbomachine 1 (generally on the ground but such assistance can be used for restarting the turbomachine 1 in flight) or provide it with additional power, if the turbomachine 1 is already in operation, for example to provide temporary acceleration (in particular during the takeoff and / or TOP climb phase).Taking into account this power input, it is possible to reduce the dimensions of the compressor 11 and / or to optimize the operation of the turbomachine and for example reduce its fuel consumption and / or the temperature of the exhaust gases.

[0043] Alternatively, an e-taxiing device (or electric taxiing device) powered by the external electrical circuit 34 and capable of moving the aircraft A on the ground may be provided. The e-taxiing device may comprise one or more motorized wheels fitted to the landing gear of the aircraft A or an electric motor which may be coupled via a clutch or dog clutches to an input shaft of the gearbox 5 so as to drive the propeller 2 in rotation even when the turbomachine 1 is not in operation.

[0044] Elements identical or analogous to those previously described will bear a numerical reference identical to these in the following description of the other embodiments of the invention.

[0045] With reference to [Fig. 2] and according to the second embodiment, the exhaust circuit 35 is connected via the valve device 39 to a hot inlet of a heat exchanger 100 integrated in a channel arranged on the aircraft A to generate additional thrust by Meredith effect. Preferably, the channel in question is arranged in the lower part of the fuselage of the aircraft A downstream of the propeller 2 and close to the engine flow outlet of the turbomachine 1. Preferably, a variable section channel will be used to adapt the additional flow to the flight conditions. This phenomenon and its use on an aircraft are known in themselves and will not be detailed further here.

[0046] With reference to [Fig. 3] and according to the third embodiment, the evacuation circuit 35 is connected via the valve device 39 to a de-icing circuit 110 arranged to allow de-icing of parts of the aircraft A such as the wing, the propeller 2, and / or the inlet of the turbomachine 1. It is understood that the temperature of the evacuated products is largely sufficient for this defrosting function. The evacuated products can be directly injected into the defrosting circuit 110 to form the defrosting fluid or be introduced into the hot inlet of a heat exchanger heating the defrosting fluid circulating in the defrosting circuit 110. In the first case, there is a risk that the water vapor of the evacuated products condenses near the surfaces to be defrosted. To avoid this, the outlet of the evacuated products is connected to an inlet of a condenser 111 having a gas outlet connected to the defrosting circuit and a liquid outlet connected to the injection port of the combustion chamber 12.

[0047] With reference to [Fig. 4] and according to the fourth embodiment, the aircraft A comprises an organic Rankine cycle machine generally designated 120 which comprises a heat transfer fluid circuit comprising a condenser 121, a pump 122, a heat exchanger 123 and a turbine 124 driving a generator 125 connected to the electrical network 4. The evacuation circuit 35 is connected via the valve device 39 to a hot inlet of the heat exchanger 123.

[0048] Preferably then, the dihydrogen supply circuit 32 is connected to a cold inlet of the condenser 121 of the organic Rankine cycle machine 120.

[0049] With reference to [Fig.5] and according to the fifth embodiment, the evacuation circuit 35 is connected to an inlet of a turbine 130 driving in rotation an electric generator 131 connected to the electrical network 4.

[0050] Several of the embodiments can be combined with each other in whole or in part. For example: - preferably, the five embodiments are combined with each other to ensure the best possible integration of the fuel cell 3 into the energy architecture of the aircraft A; or - the first embodiment is combined with the second embodiment and the third embodiment, and with either of the fourth and fifth embodiments; or - the first embodiment is combined with the second embodiment and one or other of the third, fourth and fifth embodiments; or - the first embodiment is combined with the second embodiment and either of the fourth and fifth embodiments.

[0051] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0052] In particular, the aircraft may have a structure other than that described.

[0053] It will be noted that the invention is described in relation to a simplified aircraft structure to better understand the invention. It goes without saying that in reality the structure of the aircraft is much more complicated.

[0054] For example, a turbomachine generally comprises several shafts and several compressors. Moreover, if the turbomachine comprises an intermediate compressor and a high-pressure compressor, the air supply circuit for the electrochemical cells can be connected to the intermediate compressor and / or to the high-pressure compressor. Preferably, for a two-stage turbomachine, one envisages a machine on the shaft of the high-pressure compressor and a machine on the shaft of the low-pressure compressor, the machines being connected to a control unit arranged to control the machines independently of one another according to the desired turbomachine assistance effect.

[0055] For example, the fuel cell comprises a control circuit which has not been detailed here.

[0056] It will be noted that the fuel may be different from dihydrogen. Thus, in the variant of [Fig.6], the fuel cell 3 is supplied via a methane tank. The dihydrogen supply device 32 then comprises a reformer for transforming the methane into dihydrogen.

[0057] The fuel cell may be of a type other than SOFC and for example MCFC or PEMHT. It will be noted that an MCFC fuel cell assembly can operate with fuels other than dihydrogen without an external reformer.

[0058] The fuel cell can be placed as close as possible to the turbomachine 1 to benefit from the heat released by it, or even be integrated into the turbomachine 1, preferably between the high-pressure compressor and the combustion chamber.

Claims

Claims

1. Propulsion system comprising at least one turbomachine (1) and a high-temperature fuel cell (3) connected to an electrical circuit (4); the turbomachine (1) comprising at least one compressor (11) and a combustion chamber (12); the fuel cell comprising at least one electrochemical cell (31), a fuel supply circuit (32) for the electrochemical cell, an air supply circuit (33) for the electrochemical cell, a circuit (35) for discharging air and water vapor from the electrochemical cell; characterized in that the air supply circuit comprises a valve device (36) having a first inlet connected to an external air intake and a second inlet connected to a port of the compressor of the turbomachine for selectively connecting the air supply circuit to the external air intake and to the port of the compressor.

2. System according to claim 1, in which the exhaust circuit (35) supplies an auxiliary compressor (38) having an outlet connected to the combustion chamber (12) of the turbomachine (1).

3. System according to claim 1 or 2, in which the turbomachine (1) rotates a drive shaft (14) linked in rotation to a propulsion member (2) and the electrical circuit (4) is connected to an electrical machine (6) having an input / output shaft mechanically connected to the drive shaft (14).

4. System according to any one of the preceding claims, in which the evacuation circuit (35) is connected to a heat exchanger (100) integrated in a channel arranged to generate additional thrust by Meredith effect.

5. A system according to any preceding claim, wherein the exhaust circuit (35) is connected to a defrosting fluid circuit (110).

6. System according to claim 5, in which the discharge circuit (35) is connected to a hot inlet of a heat exchanger of the defrosting fluid circuit (110).

7. System according to claim 6, in which the evacuation circuit (35) is connected to an inlet of a condenser (111) having a gas outlet in communication with the defrosting fluid circuit (110) and a liquid outlet connected to an injection port opening into the combustion chamber (12).

8. System according to any one of the preceding claims, in which the evacuation circuit (35) is connected to an inlet of a turbine (130) rotating an electric generator (131) connected to the electrical network (4).

9. System according to any one of the preceding claims, in which the evacuation circuit (35) is connected to a hot inlet of a heat exchanger (123) of an organic Rankine cycle machine (120) comprising a turbine (124) driving a generator (125) connected to the electrical network (4).

10. System according to any one of the preceding claims, comprising an electronic control unit (7) arranged to: - couple the fuel cell and the turbomachine during the take-off phase and in cruise; - decouple the fuel cell and the turbomachine when the turbomachine is idling or in cruise when the fuel cell is faulty.

Images