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 equipped with an optimized integrated high-temperature fuel cell.

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

[0002] BACKGROUND OF THE INVENTION

[0003] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0004] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. With the aim of improving the energy efficiency of aircraft, the Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and 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 in order to reduce the environmental footprint of its activity.

[0006] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter onboard equipment, and the development of the use of electrical technologies for propulsion...

[0007] For this purpose, it has been envisaged, in aircraft, to supply the on-board electrical network by a fuel cell powered by 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 removing water and heat is produced. The electrochemical cell has two electrodes: an anode, where hydrogen (a reducing fuel) is oxidized, and a cathode, where oxygen (an oxidizing agent) is reduced. The two electrodes are separated by an electrolyte which: - allows the passage of ions between the electrodes, - blocks electrons to force them to pass between the two electrodes through an external electrical circuit which is connected to the two electrodes and to which are connected the equipment that the electrochemical cell must supply with electricity, - acts as a membrane by opposing 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 approximately 200°C) to operate. These fuel cells are called high-temperature fuel cells.

[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 about 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 about 100°C.

[0013] SUBJECT OF THE INVENTION

[0014] The invention is notably aimed at increasing the contribution of the fuel cell to the energy supply of an aircraft. Summary of the invention

[0015] To this end, the invention provides a propulsion system comprising at least one turbomachine and a high-temperature fuel cell connected to an electrical circuit. The turbomachine includes at least one compressor and one combustion chamber. The fuel cell includes at least one electrochemical cell, a fuel supply circuit for the electrochemical cell, and a circuit The air supply circuit for the electrochemical cell includes an air and water vapor exhaust circuit. The air supply circuit comprises a valve device having a first inlet connected to an outside air intake and a second inlet connected to a turbomachine compressor port to selectively connect the air supply circuit to the outside air intake and 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 aircraft's energy architecture. In particular, supplying the fuel cell with pressurized air improves its efficiency and increases its maximum power output. It is also possible to assist the operation of the turbomachine, especially during startup, and / or utilize the heat from the products expelled from the fuel cell to provide energy to equipment in the vehicle fitted with the propulsion system according to the invention.

[0017] According to optional features, 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 drives in rotation a drive shaft linked in rotation to a propulsion unit and the electrical circuit is connected to an electric machine having an input / output shaft mechanically connected to the drive shaft; - the evacuation circuit is connected to a heat exchanger integrated into a channel arranged to generate additional thrust by Meredith effect; - the drainage circuit is connected to a defrosting fluid circuit; - the exhaust circuit is connected to a hot inlet of a heat exchanger thermal conductivity of the defrosting fluid circuit; - the exhaust 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 driving in rotation an electric generator connected to the electrical network; - the exhaust 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: - to couple the fuel cell and the turbomachine during the takeoff and cruise phases; - 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 turbomachine's start-up and / or for electric taxiing (turbomachine stopped or idling). In the event of a turbomachine failure in flight, the electronic control unit commands decoupling so that the fuel cell assists the turbomachine's restart.

[0020] Coupling 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 turbomachine's combustion chamber to reduce nitrogen oxides (NOx) and reduce fuel consumption; - injecting torque onto the electric machine of the turbomachine (internal hybridization gains); - improving the efficiency of the fuel cell by drawing air from the turbomachine; - reducing 1s transients of the fuel cell by injecting torque towards the air compressor (electrical power taken from the turbomachine).

[0021] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings

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

[0023] [Fig.1] [Fig.1] 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 method of implementing 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 method of implementing 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 herein described 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 per se, schematically comprises a compressor 11, a combustion chamber 12, a turbine 13 driving a shaft 14 which is rotationally connected 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 to avoid complicating the description. The electrical machine 6 is arranged and controlled in a manner known per se to selectively drive the shaft 14 (motor mode: for example, for starting assistance) or to drive the input / output shaft 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 per se and will not be further detailed 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 hydrogen supply device 32 for the electrochemical cells 31, an oxygen supply device 33 for 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 as they are not particularly related to the invention.

[0032] Each electrochemical cell 31 comprises two electrodes, namely an anode for producing the oxidation of dihydrogen and a cathode for producing the 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, which ensures ionic conductivity between the electrodes and blocks the passage of electrons between them, forcing them to pass through the external electrical circuit 34 that supplies the electrical network 4 (and more specifically the part of the electrical network 4 supplying non-propulsive equipment such as onboard computers and calculators, air conditioning, signaling, lighting, etc.). The electrolyte also blocks the passage of gases between the electrodes. Each The electrochemical cell 31 comprises, in a manner known to itself, a dihydrogen inlet, an excess dihydrogen outlet, an air inlet, and an outlet for oxygen-depleted air and water vapor. The electrochemical cells 31 are connected to each other in series from an electrical point of view and in parallel from a fluidic point of view.

[0033] The hydrogen supply device 32 comprises, in a manner known per se, a hydrogen circuit connected to a pressurized hydrogen reservoir that supplies the electrochemical cells 31 on the anode side, and a pump positioned within the hydrogen circuit and driven by an auxiliary electric motor to circulate the hydrogen through the electrochemical cells 31 via the hydrogen inlet and outlet. The pump thus circulates the hydrogen within the hydrogen circuit. The hydrogen circuit is known per se and may also include 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 located in the air circuit and driven by an auxiliary electric motor. The first auxiliary compressor allows adjustment of the pressure and flow rate of the air introduced into the electrochemical cells 31, this pressure and flow rate determining the performance of the electrochemical cells 31. The air circuit is known per se and may also include a filter, a heater, a humidifier, a separator, valves, sensors...

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

[0036] According to a first feature of the invention, the air circuit comprises a valve device 36 having a first inlet connected to an outside 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 outside air intake 37 and to a sampling port of the compressor 11.

[0037] According to a second feature of the invention, the exhaust circuit 35 supplies a second auxiliary compressor 38 having an outlet connected via an injector to the combustion chamber 12 of the turbomachine 1. More specifically, the exhaust 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 driven by an auxiliary electric motor preferably powered by the external electrical circuit 34.

[0038] According to a third feature 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 components 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 includes at least one processor and a memory containing at least one computer program executable by the processor. This program includes instructions arranged to control said components according to the flight phases, pilot command instructions for aircraft A, setpoint values ​​derived from said command instructions, internal operating parameters of the turbomachine 1 (in particular provided by sensors equipping the turbomachine 1), external operating parameters of aircraft A (in particular provided by sensors equipping 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 outside 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 phase of flight 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 an extra boost of power at takeoff or to optimize energy consumption in cruise), or by the outside 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 case of failure).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 from the compressor 11 is hotter than that from the outside air intake 37. Injecting pressurized and hot air into the fuel cell 3 increases the energy efficiency and maximum power of the fuel cell 3. It is therefore more advantageous to start the fuel cell 3 by controlling the valve device 36 to connect the air supply circuit 33 to the port of the compressor 11 when the turbomachine 1 is operating. Conversely, when the turbomachine 1 is not operating, 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 should be noted that the products The exhaust gases discharged by the exhaust system 35 consist of oxygen-depleted air and water, primarily in vapor form. Injecting these exhaust gases into the combustion chamber 12 increases the specific power of the turbomachine 1 and improves its thermal efficiency, while also reducing nitrogen oxides at the combustion chamber 12 outlet. The auxiliary compressor 38 is arranged and controlled to bring the exhaust gases to a pressure suitable for injection into the combustion chamber 12.

[0042] As we have 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 elements of the external electrical circuit 34 to connect it to the electric machine 6 to control it as a motor so that the electric machine 6 provides torque to the turbomachine 1 in order to assist the start-up of the turbomachine 1 (generally on the ground but such assistance can be used for restarting the turbomachine 1 in flight) or to provide it with an additional power, if the turbomachine 1 is already in operation, for example to provide temporary acceleration (particularly during take-off and / or TOP climb).Taking this power input into account, it is possible to reduce the dimensions of the compressor 11 and / or optimize the operation of the turbomachine and, for example, reduce its fuel consumption and / or the exhaust gas temperature.

[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 can 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 shall bear a numerical reference identical to those in the following description of 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 into a channel arranged on the aircraft A to generate additional thrust by the Meredith effect. Preferably, the channel in question is located in the lower part of the fuselage of the aircraft A downstream of the propeller 2 and near the engine flow outlet of the turbomachine 1. Preferably, a channel with a variable cross-section is used to adapt the additional flow to the flight conditions. This The phenomenon and its use on an aircraft are known in themselves and will not be further detailed here.

[0046] With reference to [Fig. 3] and according to the third embodiment, the drain 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 drained products is more than sufficient for this de-icing function. The drained products can be directly injected into the de-icing circuit 110 to form the de-icing fluid or introduced into the hot inlet of a heat exchanger that heats the de-icing fluid circulating in the de-icing circuit 110. In the first case, there is a risk that the water vapor from the drained products will condense near the surfaces to be de-iced.To avoid this, the outlet of the evacuated products is connected to an inlet of a condenser 111 which has 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 includes an organic Rankine cycle machine generally designated as 120 which includes 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 exhaust 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 to ensure the best possible integration of the fuel cell 3 into the energy architecture of aircraft A; or - the first embodiment is combined with the second and third embodiments, and with either of the fourth and fifth embodiments; or - the first embodiment is combined with the second embodiment and any one 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 different structure than that described.

[0053] It should be noted that the invention is described in relation to a simplified aircraft structure to better illustrate the invention. It goes without saying that in reality the aircraft structure is much more complex.

[0054] For example, a turbomachine generally comprises several shafts and several compressors. Moreover, if the turbomachine includes 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 the high-pressure compressor. Preferably, for a two-stage turbomachine, one machine is considered on the shaft of the high-pressure compressor and another on the shaft of the low-pressure compressor, the machines being connected to a control unit arranged to operate the machines independently of each other according to the desired turbomachine assistance effect.

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

[0056] It should 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 reservoir. The dihydrogen supply device 32 then includes a reformer to convert the methane into dihydrogen.

[0057] The fuel cell may be of a different type than SOFC and, for example, MCFC or PEMHT. It should 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 given off by the latter, or even be integrated into the turbomachine 1, preferably between the high-pressure compressor and the combustion chamber.

Claims

Demands

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 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, an exhaust circuit (35) for air and water vapor from the electrochemical cell, the air supply circuit comprising 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;characterized in that the system comprises an electronic control unit (7) arranged to: - couple the fuel cell and the turbomachine during the takeoff 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.

2. System according to claim 1, wherein 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, wherein the turbomachine (1) drives in rotation a drive shaft (14) which is rotationally linked 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, wherein the evacuation circuit (35) is connected to a heat exchanger (100) integrated in a channel arranged to generate additional thrust by Meredith effect.

5. System according to any one of the preceding claims, wherein the evacuation circuit (35) is connected to a defrosting fluid circuit (110).

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

7. System according to claim 6, wherein the exhaust 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, wherein the discharge circuit (35) is connected to an inlet of a turbine (130) driving in rotation an electric generator (131) connected to the electrical network (4).

9. System according to any one of the preceding claims, wherein the exhaust 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).

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