Propulsion system provided with a fuel cell with regulated thermal power and aircraft comprising such a system

Abstract

Propulsion system comprising at least one turbomachine (1) and an electricity production device (3) comprising a high-temperature fuel cell connected to an electrical circuit (4);the turbomachine (1) and the electricity production device (3) being powered by a hydrocarbon via a first hydrocarbon injection member (15) and a second hydrocarbon injection member (321) respectively, the electricity production device (3) comprising a member (32) for transforming the hydrocarbon into fuel, said transformation member (32) being connected to the second hydrocarbon injection member (321), to a water injection member (322) and to an air injection member (323), the propulsion system comprising at least one electronic control unit (7) connected to the injection members (15, 321, 322, 323) to control them so as to regulate a thermal power of the electricity production device (3) as a function of an air / water ratio dependent on the hydrocarbon. FIGURE OF THE ABSTRACT: Fig. 1;

Description

Title of the invention: Propulsion system provided with a fuel cell with regulated thermal power and aircraft comprising such a system

[0001] The present invention relates to the field of vehicle propulsion, particularly 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 oxygen, and a device for removing the water and heat produced from the electrochemical cell. The electrochemical cell has two electrodes, namely an anode on which oxidation of hydrogen, which is a reducing fuel, occurs, and a cathode on which reduction of oxygen, which is an oxidant, occurs. 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 through 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] Generally speaking, a disadvantage of these fuel cells is the heat management which requires the use of thermal regulation devices whose weight and volume are detrimental to use on vehicles and in particular on aircraft.

[0014] SUBJECT OF THE INVENTION

[0015] The invention aims in particular to better manage the thermal constraints resulting from the use of a fuel cell, in particular for the supply of energy to an aircraft. Summary of the invention

[0016] To this end, the invention provides a propulsion system comprising at least one turbomachine and an electricity production device comprising a high-temperature fuel cell. The turbomachine and the electricity production device are powered by a hydrocarbon via a first hydrocarbon injection member and a second hydrocarbon injection member respectively. The electricity production device comprises a member for transforming the hydrocarbon into fuel. Said transformation member is connected to the second hydrocarbon injection member, to a water injection member and to an air injection member.The propulsion system comprises at least one electronic control unit connected to the first and second hydrocarbon injection members, to the water injection members and to the air injection members to control them so as to regulate a thermal power of the electricity production device as a function of an air / water ratio dependent on the hydrocarbon.

[0017] The invention is based on the fact that the transformation of a hydrocarbon into fuel for a fuel cell requires a supply of air and water and that the thermal power of the transformation depends on the air / water ratio. It is thus possible to control the supply of air and water in the system so as to meet the mechanical, electrical and thermal power demands, while maintaining a thermally balanced propulsion system.

[0018] It is recalled that hydrocarbons have the general formula CnH2n+2. According to a particular embodiment of the invention, the process of transforming the hydrocarbon into fuel is based on the following reaction:

[0019] CnH.M2 + x (O2 + 3.76 N.) +2 (nx)H20^n CO2 + (3« + l-2x)H2 + 3.76 x N2

[0020] In this reaction, the fuel is dihydrogen and x represents the air / water ratio. We know that: - when x=0, the transformation is an endothermic transformation (it consumes heat) called steam reforming; - when x=n, the transformation is an exothermic transformation (it produces heat) called partial oxidation; - when x is between 0 and n, the transformation involves both steam reforming and partial oxidation.

[0021] For any given hydrocarbon (n=n0), there is an air / water ratio xO such that the transformation of the hydrocarbon into dihydrogen is thermally neutral. It follows that: - when x is less than xO, the transformation is endothermic; - when x is greater than xO, the transformation is exothermic.

[0022] By also integrating the thermal balance of the fuel cell during electricity production, it is possible to determine an air / water ratio x0' for which the electricity production device as a whole is thermally neutral.

[0023] In the device of the invention, the electronic control unit is arranged to control the air flow rate and the water flow rate supplying the hydrocarbon-to-hydrogen conversion member, which amounts to adjusting the air / water ratio and therefore controlling the thermal power of the electricity production device so that it is thermally neutral, produces heat, or consumes it. It is therefore possible to regulate the temperature of the fuel cell without using a heat exchanger, or by using a smaller heat exchanger. This improves the overall energy performance of the propulsion system. In particular, the drag and mass of the cooling system are reduced.

[0024] According to optional characteristics, used individually or in whole or in part in combination: - the electronic control unit uses as inputs a thermal power setpoint from the electricity production device, an electrical power setpoint supplied by the electricity production device, and a mechanical power setpoint supplied by the turbomachine to control the first hydrocarbon injection member and the second hydrocarbon injection member; - the thermal power setpoint of the electricity production device, the electrical power setpoint supplied by the electricity production device, and the mechanical power setpoint supplied by the turbomachine correspond to operating phases of the propulsion system; - the turbomachine rotates a drive shaft connected in rotation to a propulsion member and the electricity production device is connected to an electrical circuit connected to an electrical machine having an input / output shaft mechanically connected to the drive shaft.

[0025] The invention also relates to an aircraft equipped with such a propulsion system.

[0026] It is understood that the transformation member can be controlled to be thermally neutral, produce heat or consume heat. It is possible to exploit the exothermic nature of the transformation to heat aircraft equipment or, on the contrary, to exploit the endothermic nature of the transformation to cool aircraft equipment. The production of heat can, for example, be used for de-icing wings or nacelles, heating fuel, etc. The consumption of heat can be used to keep a liquefied natural gas circuit cold.

[0027] Preferably, the electronic control unit is arranged to:

[0028] - coupling the fuel cell and the turbomachine during the take-off phase and in cruise ;

[0029] - decouple the fuel cell and the turbomachine when the turbomachine is at idling or cruising when the fuel cell fails.

[0030] Advantageously, the electronic control unit is arranged to control the injection members as a function of flight phases of the aircraft.

[0031] Advantageously, the electrical production device is associated with one or more pieces of equipment via at least one means of heat exchange.

[0032] 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

[0033] Reference will be made to the accompanying drawings, among which:

[0034] [Fig-1] [Fig.l] is a schematic representation of an aircraft according to a first embodiment of the invention;

[0035] [Fig.2] [Fig.2] is a schematic representation of a device for producing dihydrogen according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] With reference to [Fig.l], the invention is described here in application to an aircraft A comprising a turbomachine 1 associated with a propeller 2, an electricity production device 3 and an on-board electrical network 4.

[0037] 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 on the one hand to the propeller 2 by a gearbox 5 and on the other hand to an input / output shaft of an electric machine 6 connected to the electrical network 4. The combustion chamber 12 is supplied with hydrocarbon by an injection member 15, here represented by a pump, connected to a hydrocarbon tank 16. The hydrocarbon is here kerosene. There are intermediate shafts and other components which have not been described here.The electrical machine 6 is arranged and controlled in a manner known per se to selectively drive the shaft 14 in rotation (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 certain flight phases requiring less mechanical power). The structure and operation of the turbomachine 1 are known per se and will not be detailed further here.

[0038] The electricity production device 3 comprises a fuel cell, here of the SOFC type, which comprises a plurality of electrochemical cells 31 (also called electrolytic cells), a device 32 for supplying hydrogen to the electrochemical cells 31, a circuit 33 for supplying oxygen to the electrochemical cells 31, an external electrical circuit 34 connected to the electrochemical cells 31 and on the other hand to the electrical machine 6, and a fluid evacuation circuit 35 also connected to the electrochemical cells 31. The fuel cell also comprises, in a manner known per se, other components which are not mentioned here because they have no particular connection with the invention. Alternatively, the fuel cell may correspond to any high-temperature cell (preferably greater than or equal to 150°C) consuming hydrogen.

[0039] 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 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.

[0040] The dihydrogen supply device 32 comprises a member 320 for transforming hydrocarbon into dihydrogen which supplies dihydrogen to the electrochemical cells 31 (on the anode side), a hydrocarbon injection member 321 (incorporating for example a pump) connecting the transformation member 320 to the hydrocarbon reservoir 16; a water injection member 322 (incorporating for example a pump) connecting the transformation member 320 to a water reservoir not shown, and an air injection member 323 (incorporating for example a pump) connecting the transformation member 320 to an outside air inlet. The transformation member 320 successively comprises a desulfurization unit 324, a vaporizer 325, a steam reformer 326, a conversion reactor 327, and a gas separator 328. The hydrocarbon injection member 321 is connected to an inlet of the desulfurization unit 324.The water injection member 322 is connected to an inlet of a heat exchanger which is arranged to transform water into steam and which has an outlet connected to the vaporizer 325. The air injection member 323 is connected to an inlet. of the gas separator 328. The gas separator 328 operates for example by pressure swing adsorption. The production of dihydrogen from a hydrocarbon by a steam reforming transformation process is known in itself and will not be detailed here except as directly related to the invention. The dihydrogen supply device 32 may also comprise a filter, a heater, a humidifier, a separator, valves, sensors, etc.

[0041] 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. 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. Preferably, the air 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 11 of the turbomachine 1 for selectively connecting the air supply circuit to the external air intake and to a sampling port of the compressor 11.

[0042] The depleted air and water vapor outlets of the electrochemical cells 31 are connected in parallel to the evacuation circuit 35. More preferably, the evacuation circuit 35 supplies a second auxiliary compressor 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 having a first outlet connected to the auxiliary compressor and a second outlet connected to a vent in communication with the outside air.

[0043] The electrical production device 3, and more particularly the controllable members of the electrical production device 3 (injection members, valves, electrical switches of the external electrical circuit 34, etc.), and the turbomachine 1 and more particularly the controllable members of the turbomachine 1 (injection member, servomotors, etc.) 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 includes instructions arranged to control said organs 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), internal operating parameters of the electricity production device 3 (in particular provided by sensors. equipping the electricity production device 3), internal operating parameters of aircraft A (notably provided by sensors equipping aircraft A)...

[0044] The electronic control unit 7 is arranged to control the air flow rate and the water flow rate supplying the member for transforming the hydrocarbon into dihydrogen, which amounts to adjusting the air / water ratio and therefore controlling the thermal power of the electricity production device 3.

[0045] It is recalled that the process of transforming hydrocarbon into fuel is based on the following reaction:

[0046] CnH2lM + x (O2 + 3.76 N2) +2 (nx)H20^n CO2 + (3n + \-2x)H2 + 3.16 x N2

[0047] In this reaction, the fuel is dihydrogen and x represents the air / water ratio. We know that: when x=0, the transformation is an endothermic transformation called steam reforming; when x=n, the transformation is an exothermic transformation called partial oxidation; when x is between 0 and n, the transformation involves steam reforming and partial oxidation.

[0048] For any given hydrocarbon (n=n0), there is an air / water ratio xO such that the transformation of the hydrocarbon into dihydrogen is thermally neutral. It follows that: when x is less than xO, the transformation is endothermic; when x is greater than xO, the transformation is exothermic.

[0049] By also integrating the thermal balance of the fuel cell during electricity production, it is possible to determine an air / water ratio xO' for which the electricity production device as a whole is thermally neutral.

[0050] In practice, the electronic control unit 7 uses as inputs a Pthreq setpoint for thermal power of the electricity production device 3, a PeieCreq setpoint for electrical power supplied by the electricity production device 3, and a Pmecareq setpoint for mechanical power supplied by the turbomachine 1 to control the hydrocarbon injection members 15 and 321, the water injection member 322 and the air injection member 323.

[0051] The control principle implemented by the electronic control unit is therefore as follows:

[0052]

[0053] ^fuel,TàG> ^fueLSOFc} f^threq1 req> Pmecareq^ With: x the air / water ratio, ^fuel,TàG the hydrocarbon flow rate for turbomachine 1, ^fueljsoFC the hydrocarbon flow rate for the power generation device.

[0054] Of course, this control principle depends on the efficiencies of the turbomachine 1 and the electricity production device 3.

[0055] An example is provided below considering that the turbomachine 1 has an efficiency qtag and the electricity production device 3 has an efficiency qsofc. These efficiencies represent the ratio of the useful output power (respectively of the turbomachine 1 and of the electricity production device 3) to the chemical power of the injected fuel flow (respectively in the turbomachine 1 and in the electricity production device 3).

[0056] Thus, in the case where the electrical power Peiec is supplied by the electricity production device 3 and the mechanical power Pmeca is supplied by the turbomachine 1, we have the following equations:

[0057] Pelec = î]SOfc* mfueLsoFC

[0058] Pmeca ~ ^à^mfuATAG

[0059] The thermal equation of the electrical production device 3 is then as follows:

[0060] PthSOFC Preforming P oxidation — ^-P 'AF

[0061] In which: - PthsoFC is the thermal power of the fuel cell itself, namely the heat produced by the reaction of air and dihydrogen; — P reforming is the thermal power of the reforming reaction during the transformation of hydrocarbon into dihydrogen; — Oxidation is the thermal power of the oxidation reaction during the transformation of hydrocarbon into dihydrogen; - Cp is the heat capacity of the electricity production device 3; - AT is the temperature difference of the electricity production device 3.

[0062] For reasons of simplicity, we assume that what is not transformed into electricity is lost in the form of heat (which is a rough approximation), we obtain:

[0063]

[0064]

[0065] PthSOFC = (l - Psofc)* mfueisOFc P reforming ^^waterSOFC^ reforming P oxidation ^airPOFC'^ ^-^oxidation

[0066] Hm is the mass enthalpy of reaction (in kW / kg).

[0067] The electronic control unit 7 is programmed to adapt the hydrocarbon flow rates in the turbomachine 1 and in the electricity production device 3 and the water and air flow rates (the ratio of which is x) in the electricity production device 3 so as to: - obtain the target electrical and mechanical powers which depend on the needs of aircraft A (propulsion + aircraft electrical equipment), - maintain the fuel cell in an optimal operating range.

[0068] As power requirements are constantly changing during flight (high power at takeoff, medium power at cruise and low power at descent), all flow rates are continuously adjusted to ensure proper system operation in all phases of operation.

[0069] It will be noted that the electronic control unit 7 performs other functions here.

[0070] The electronic control unit 7 is thus also programmed to control the valve devices for connecting the air supply circuit either to the external air intake 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. 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 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 air supply circuit 33 is connected to the outside air intake 37.In addition, the electronic control unit 7 is programmed to control the valve device to connect the exhaust circuit 35 either to the vent (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 discharged by the exhaust circuit 35 comprise oxygen-depleted air and water essentially in the form of steam. The injection of the discharged 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 nitrogen oxides at the outlet of the combustion chamber 12. The auxiliary compressor is arranged and controlled to bring the discharged products to a pressure compatible with their injection into the combustion chamber. combustion 12.

[0071] 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 phase and / or the end of the TOP climb).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.

[0072] 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.

[0073] 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.

[0074] In particular, the aircraft may have a structure other than that described.

[0075] 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.

[0076] 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.

[0077] For example, the fuel cell comprises a control circuit which has not been detailed here.

[0078] The fuel cell may be of a type other than SOFC and for example MCFC or PEMHT. Alternatively, the fuel cell may correspond to any high-temperature cell (preferably greater than or equal to 150°C) consuming dihydrogen. It will be noted that an MCFC fuel cell assembly can operate with fuels other than dihydrogen without an external reformer.

[0079] 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.

[0080] The turbomachine and the electricity production device may use the same hydrocarbon, or two different hydrocarbons. The hydrocarbon may be kerosene, methane or any other hydrocarbon whose physicochemical properties allow its use in the application considered.

[0081] The transformation of the hydrocarbon into fuel can be internal or external to the fuel cell.

[0082] The electrical production device may be associated with one or more pieces of equipment via at least one means of heat exchange. For example: - a heat guide made of thermally conductive material extends between the electrical production device and the equipment(s) by touching them so as to allow heat transfer by conduction between the electrical production device and the equipment(s); - a heat exchanger has a first circuit of heat transfer fluid passing through the electrical production device and a second circuit of heat transfer fluid passing through the equipment(s) to allow heat transfer by convection between the electrical production device and the equipment(s).

[0083] The electrical production device and the accessory(ies) are provided with temperature sensors to be able to regulate it finely.

[0084] The fluid injection members mentioned above may comprise pumps or piloted valves arranged in a circuit of said pressurized fluid.

Claims

Claims

1. Propulsion system comprising at least one turbomachine (1) and an electricity production device (3) comprising a high-temperature fuel cell;the turbomachine (1) and the electricity production device (3) being supplied with a hydrocarbon via a first hydrocarbon injection member (15) and a second hydrocarbon injection member (321) respectively, the electricity production device (3) comprising a member (32) for transforming the hydrocarbon into fuel, said transformation member (32) being connected to the second hydrocarbon injection member (321), to a water injection member (322) and to an air injection member (323), the propulsion system comprising at least one electronic control unit (7) connected to the first and second hydrocarbon injection members (15, 321), to the water injection member (322) and to the air injection member (323) to control them so as to regulate a thermal power of the electricity production device (3) according to a ratio air / water dependent on hydrocarbon.;

2. System according to claim 1, in which the transformation member (32) is arranged to transform the hydrocarbon into dihydrogen by implementing the following reaction: + x (O2 + 3.76 N2) + 2 (nx)H2On CO2 + (3n + 1 - 2x)H2 + 3.76 x N2 where x represents the air / water ratio.

3. System according to claim 1 or 2, in which the electronic control unit (7) uses as inputs a thermal power setpoint of the electricity production device (3), an electrical power setpoint supplied by the electricity production device (3), and a mechanical power setpoint supplied by the turbomachine (1) to control the first hydrocarbon injection member (15) and the second hydrocarbon injection member (321).

4. System according to any one of the preceding claims, in which the thermal power setpoint of the electricity production device (3), the electrical power setpoint supplied by the electricity production device (3), and the mechanical power setpoint supplied by the turbomachine (1) correspond to operating phases of the propulsion system.

5. A system according to any preceding claim, in wherein the turbomachine (1) rotates a drive shaft (14) connected in rotation to a propulsion member (2) and the electricity production device (3) is connected to an electrical circuit (4) connected to an electrical machine (6) having an input / output shaft mechanically connected to the drive shaft (14).

6. An aircraft comprising a system according to any one of the preceding claims.

7. Aircraft according to claim 6, wherein the electronic control unit (7) is 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.

8. Aircraft according to claim 6 or 7, in which the electronic control unit (7) is arranged to control the injection members as a function of flight phases of the aircraft.

9. Aircraft according to any one of claims 6 to 8, in which the electrical production device (3) is associated with one or more pieces of equipment via at least one heat exchange means.

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