Aircraft propulsion system comprising an electric propulsion machine powered by a fuel cell

Abstract

An aircraft propulsion system comprising at least one electric propulsion machine (M); a fuel cell (9) for powering the electric propulsion machine (M); and a gas turbomachine (2) comprising: a gas generator (3) including a main drive shaft (4) connected to at least one main compression stage (31) configured to accelerate a main airflow (A1) from a main air inlet (33), and an auxiliary compression stage (5) mounted on an auxiliary drive shaft (6) mechanically connected to the main drive shaft (4), the auxiliary compression stage (5) being configured to accelerate an auxiliary airflow (A2) between an auxiliary air inlet (51) and an auxiliary air outlet (52), the auxiliary air outlet (52) being connected to the air inlet (91) of the fuel cell (9) so as to supply it with a pressurized airflow. Abstract figure: Figure 1

Description

Description Title of the invention: Propulsion assembly for aircraft comprising an electric propulsion machine powered by a fuel cell combustible Technical field

[0001] = The present invention relates to the field of propulsion units used for the propulsion of an aircraft and relates in particular to a propulsion unit comprising an electric propulsion machine powered by a fuel cell.

[0002] Climate change is a major concern for many bodies legislative and regulatory measures across the world. Indeed, various restrictions on carbon emissions have been, are or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft but also those in circulation requiring the implementation of technological solutions in order to make them comply with current regulations. Civil aviation sc has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] — Technological research efforts have already made it possible to significantly improve significantly improve the environmental performance of aircraft. The Applicant takes into account consideration of impacting factors in all phases of design and development development to obtain less expensive aeronautical components and products energy-intensive, more environmentally friendly and whose integration and use in civil aviation have moderate environmental consequences for the purpose improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact through the use of methods and the operation of processes virtuous development and manufacturing and minimizing greenhouse gas emissions greenhouse gases to the minimum possible to reduce the environmental footprint of its activity.

[0005] — This sustained research and development work covers both new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and the lighter on-board equipment, the development of the use of electric machines to provide propulsion, in particular, powered by a fuel cell.

[0006] To this end, the invention is the result of technological research aimed at significantly improve aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. To this end, The invention relates to the field of aircraft comprising a hybrid propulsion unit comprising an electric propulsion machine powered by a fuel cell. As is known, an aircraft comprises a propulsion unit to enable its movement from the acceleration of an air flow. As part of the decarbonization of aircraft, a so-called "hybrid" architecture is known, in which the propulsion system includes an electric propulsion machine powered by a fuel cell. The fuel cell is powered by hydrogen and reduces kerosene consumption. A fuel cell is a device for carrying out an electrochemical reaction to generate electrical energy from a redox reaction. To achieve this, the fuel cell is powered by an oxidizing fluid and a reducing fluid, for example dihydrogen and dioxygen, which circulate in a plurality of cells and react by means of a catalyst to form the electrochemical reaction and produce electrical energy. As is known, the fuel cell must be supplied with a pressurized flow of oxygen. Also, it is known to provide a compressor to supply a pressurized flow of air to the fuel cell and supply it with oxygen. However, such a compressor is heavy and bulky, which presents a significant disadvantage in an aeronautical context which aims to limit the mass of aircraft to limit their energy consumption and thus their environmental impact. In addition, the compressor needs to be supplied with energy to operate. Such energy is generally provided by the fuel cell itself, which limits its efficiency since it provides less energy to the other equipment of the aircraft. The autonomy of the fuel cell is also affected since it must provide more energy to power the compressor in parallel. The invention thus aims to eliminate at least some of these drawbacks by proposing a propulsion unit which is efficient and whose autonomy is increased, while ensuring that both its mass and its size are limited. The propulsion unit according to the invention also makes it possible to maintain an optimal level of operational safety while limiting greenhouse gas emissions. PRESENTATION OF THE INVENTION The invention relates to a propulsion assembly for aircraft comprising: at least one electric propulsion machine, at least one fuel cell configured to generate energy electric to power the electric propulsion machine, the fuel cell fuel comprising an air inlet, and a gas turbomachine comprising: a gas generator comprising a main propulsion shaft connected to at least one main compression stage and at least one turbine stage, the main compression stage being configured to accelerate a main airflow from an air inlet main, an auxiliary compression stage mounted on a propulsion shaft auxiliary mechanically connected to the main propulsion shaft, the auxiliary compression stage being configured to accelerate a auxiliary air flow between an auxiliary air inlet and an air outlet auxiliary, the auxiliary air outlet being connected to the air inlet of the fuel cell so as to feed it with an air flow under pressure. The propulsion unit according to the invention makes it possible to supply the gas generator and the fuel cell in parallel with two separate air flows accelerated by two separate compression stages integrated into the gas turbomachine. Thanks to the invention, the fuel cell is supplied with a pressurized air flow without the addition of an external compressor, which makes it possible to limit the mass and size of the propulsion unit. Thanks to the electric propulsion machine in addition to the gas turbomachine, the propulsion unit also has increased autonomy, which makes it possible to optimize its performance. The hydrogen-powered fuel cell supplies the electric propulsion machine with electrical energy, resulting in a propulsion system with significantly reduced greenhouse gas emissions. In one embodiment, the auxiliary air inlet is merged with the main air inlet. The gas turbomachine thus comprises a single common air inlet for the main compression stage and the auxiliary compression stage, which makes it possible to simplify the architecture of the gas turbomachine. In one embodiment, the gas turbomachine comprises a declutching system mechanically connecting the main propulsion shaft and the auxiliary propulsion shaft, the declutching system being configured to move between an engaged position, in which the main propulsion shaft is secured to the auxiliary propulsion shaft, and a declutched position, in which the main propulsion shaft is detached from the auxiliary propulsion shaft. Such a declutching system advantageously makes it possible to decouple the two propulsion shafts in rotation, allowing each compression stage to operate independently. An optimal level of operational safety is thus guaranteed. The declutching system allows the fuel cell to be supplied with the auxiliary airflow even when the gas generator is not operating, for example in the event of a gas generator failure. In this case, the auxiliary compression stage is preferably driven by an electric motor. In one embodiment, the propulsion assembly comprises a monitoring system configured to detect when the gas generator is operating, thereby enabling the disengagement system to be placed in the disengaged position automatically. Continuity of power supply to the electric propulsion machine is thus guaranteed. In one embodiment, the turbine stage of the gas generator being configured to rotate around the main propulsion shaft at a rotational speed, the declutching system is configured to move between the engaged position and the disengaged position automatically depending on the rotational speed of the turbine stage of the gas generator, making it possible to ensure the operation of the propulsion assembly. In one embodiment, the clutch system is configured to move from the disengaged position to the engaged position when the rotational speed of the turbine stage of the gas generator is greater than a threshold speed, in particular, when the speed of the main propulsion shaft is greater than that of the auxiliary propulsion shaft. Preferably, the clutch system is a freewheel, allowing the use of a simple system, easily integrated into the enclosure of the gas turbomachine. When the gas generator turbine stage is operating at too low a speed, for example when it is shutting down, the disengagement system can automatically move to the disengaged position to advantageously allow the fuel cell to operate. Preferably, the main propulsion shaft and the auxiliary propulsion shaft are coaxial, allowing simple integration into the gas turbomachine. In a preferred embodiment, the main compression stage and the auxiliary compression stage are oriented in opposite directions, making it possible to accelerate two air flows simultaneously in the main compression stage towards the turbine stage of the gas generator and in the auxiliary compression stage towards the auxiliary air outlet to supply the fuel cell. The two air flows are thus distinct and can supply the compression stages independently without the architecture of the gas turbomachine being too complex. In one embodiment, the propulsion assembly comprises an auxiliary electric machine connected to the auxiliary propulsion shaft, the electric machine auxiliary being configured to rotate the auxiliary propulsion shaft and generate electrical energy from the rotation of the auxiliary propulsion shaft. The auxiliary electrical machine advantageously makes it possible to power the fuel cell with the auxiliary air flow even when the gas generator is not operating. Preferably, the gas turbomachine and the fuel cell are powered by the same fuel, making it possible to simplify the architecture of the propulsion system, which saves space and weight in the aircraft. In one embodiment, the fuel supplying the gas turbomachine and the fuel supplying the fuel cell are stored in the same tank, in particular dihydrogen, making it possible to further limit the greenhouse gas emissions of the propulsion system. Alternatively, the turbomachine is powered by kerosene and the fuel cell by dihydrogen. In a preferred embodiment, the gas generator and the auxiliary compression stage are mounted in the same enclosure. In other words, the gas turbomachine comprises a single casing in which all the elements are mounted, which makes it possible to significantly limit the size of the gas turbomachine. In one embodiment, the main propulsion shaft is connected to a propulsion member. The invention also relates to an aircraft comprising at least one propulsion unit as described previously. Finally, the invention relates to a method for supplying air to a fuel cell of a propulsion unit as described previously, the method comprising the steps of: accelerate an auxiliary airflow in the mounted auxiliary compression stage in the gas turbomachine, and route the auxiliary airflow through the auxiliary air outlet of the tur- gas engine to the fuel cell air inlet to power it. In one embodiment, the main propulsion shaft being rotationally integral with the auxiliary propulsion shaft, the method comprises the steps of: drive the auxiliary propulsion shaft by the main propulsion shaft to accelerate the auxiliary airflow, separate the main propulsion shaft and the propulsion shaft auxiliary, and drive the auxiliary propulsion shaft by an auxiliary electric machine to accelerate the auxiliary airflow. In one embodiment, the method of supplying air to the fuel cell is integrated into a method of supplying energy to an electric propulsion machine. The supply method then comprises a step of generating electrical energy in the fuel cell from the auxiliary air flow and a fuel flow to supply the electric propulsion machine. In one embodiment, the method comprises a step of rotating the auxiliary propulsion shaft from the auxiliary electrical machine. In such a configuration, the fuel cell advantageously generates electrical energy to power the auxiliary electrical machine which then makes it possible to actuate the auxiliary compression stage and therefore to provide a flow of pressurized air to the fuel cell. PRESENTATION OF FIGURES The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects. [Fig. 1] is a schematic representation of a propulsion assembly according to a first embodiment of the invention. [Fig.2] is a schematic representation of a propulsion assembly according to a second embodiment of the invention. [Fig. 3] is a schematic representation of a propulsion assembly according to a third embodiment of the invention. It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION With reference to [Fig. 1], there is shown a propulsion unit 1 for an aircraft according to one embodiment of the invention. The propulsion unit 1 extends longitudinally along an axis X and comprises a propulsion member (not shown), configured to participate in the propulsion of the aircraft by accelerating an air flow circulating from upstream to downstream. The terms “upstream” and “downstream” refer to the axis X which extends from upstream to downstream of the propulsion unit 1, as shown in [Fig. 1]. With reference to [Fig. 1], the propulsion assembly 1 according to the invention comprises a gas turbomachine 2, an electric propulsion machine M and a fuel cell 9 for powering the electric propulsion machine M. The electric propulsion machine M is configured to participate in the propulsion of the aircraft by transferring energy to the propulsion member so as to drive it in rotation. The fuel cell 9 is configured to generate electrical energy Elec to power the electric propulsion machine M. As is known, the fuel cell 9 is a device for carrying out an electrochemical reaction to generate electrical energy Elec from a redox reaction. For this, the fuel cell 9 is supplied with an oxidizing fluid and a reducing fluid, for example dihydrogen (H2) and dioxygen (O2), which circulate in a plurality of cells and react by means of a catalyst to form the electrochemical reaction and produce electrical energy Elec. To enable the implementation of the oxidation-reduction reaction, the fuel cell 9 is configured to be powered by a flow of fuel Q, preferably dihydrogen (H2). In this example, the fuel Q is stored in a cryogenic tank R (shown in [Fig. 3]) which makes it possible to store the dihydrogen in the liquid state, making it possible to carry a greater mass of fuel Q in the aircraft. The fuel cell 9 is also configured to be supplied with a pressurized oxygen flow. For this, the fuel cell 9 comprises an air inlet 91. Still referring to [Fig. 1], the gas turbomachine 2 according to the invention comprises a gas generator 3 comprising a main propulsion shaft 4 connected to the propulsion member, for example, via a gearbox. The gas generator 3 also comprises a main compression stage 31 and a turbine stage 32 connected to the main propulsion shaft 4 to drive it in rotation and thus drive the propulsion member. The gas generator 3 comprises a main air inlet 33 for supplying the main compression stage 31 with a main air flow A1, in particular, from the outside. The main compression stage 31 is configured to accelerate the main air flow A1 so as to drive the rotation of the turbine stage 32 and thus of the main propulsion shaft 4. The main air flow A1 preferably circulates from upstream to downstream in the gas generator 3, that is to say along the longitudinal axis X. The turbine stage 32 drives the main propulsion shaft 4 at a predetermined rotational speed. The gas generator 3 also comprises an exhaust nozzle 34 through which an exhaust air flow from the combustion between a fuel and the main air flow A1 compressed in the main compression stage escapes. 31. The operation of such a gas generator 3 is known to those skilled in the art and will not be described in further detail in this document. According to the invention, the gas turbomachine 2 comprises an auxiliary compression stage 5 mounted on an auxiliary propulsion shaft 6. The auxiliary propulsion shaft 6 is mechanically connected to the main propulsion shaft 4. In a preferred embodiment, the main propulsion shaft 4 and the auxiliary propulsion shaft 6 are coaxial and are adjacent along the longitudinal axis X, allowing a simple architecture. In this embodiment, the main propulsion shaft 4 and the auxiliary propulsion shaft 6 are integral in rotation, preferably, together form a single propulsion shaft. The auxiliary compression stage 5 comprises an auxiliary air inlet 51 and an auxiliary air outlet 52 and is configured to accelerate an auxiliary air flow A2 flowing from the auxiliary air inlet 51 to the auxiliary air outlet 52. The auxiliary air outlet 52 is connected to the air inlet 91 of the fuel cell 9 so as to supply it with a pressurized air flow. In other words, the auxiliary compression stage 5 mounted in the gas turbomachine 2 makes it possible to generate a pressurized air flow intended for the fuel cell 9. Preferably, the auxiliary air inlet 51 takes air from the external environment. In this example, the main compression stage 31, mounted on the main propulsion shaft 4, and the auxiliary compression stage 5, mounted on the auxiliary propulsion shaft 6, each comprise a centrifugal wheel for accelerating the main air flow A1 and the auxiliary air flow A2 respectively. The centrifugal wheels are preferably mounted axially successively along the longitudinal axis X. The air flows A1, A2 are thus sucked in longitudinally and discharged radially. It goes without saying, however, that the invention also applies to axial wheels. Preferably, the auxiliary air inlet 51 is positioned longitudinally between the main compression stage 31 and the auxiliary compression stage 5. More precisely, in this example, the gas turbomachine 2 successively comprises from upstream to downstream the auxiliary air outlet 52, the auxiliary compression stage 5 and the auxiliary air inlet 51. In other words, in this example, the main compression stage 31 and the auxiliary compression stage 5 extend in opposite directions so as to allow optimal mechanical integration. The air flows A1, A2 are conducted respectively from upstream to downstream and from the main air inlet 33 and from downstream to upstream from the auxiliary air inlet 51. In a preferred embodiment, as shown in [Fig.2], the auxiliary air inlet 51 is merged with the main air inlet 33, which allows a single air inlet A to supply both the main compression stage 31 with the main airflow A1 and the auxiliary compression stage 5 with the auxiliary airflow A2. This improves compactness and equips the single air inlet with an anti-icing debris collection grille. Preferably, the gas generator 3 and the auxiliary compression stage 5 are mounted in the same closed enclosure. In other words, the auxiliary compression stage 5 is integrated into the gas turbomachine 2 and the latter comprises a single casing, allowing significant space savings. The gas turbomachine 2 thus makes it possible to dispense with the addition of an external compressor to supply the fuel cell 9 with air, which makes it possible to limit the mass and size of the propulsion assembly 1. This is all the more advantageous since the main propulsion shaft 4 and the auxiliary propulsion shaft 6 are mechanically connected. The lubrication is advantageously common within the casing. In other words, the gas turbomachine 2 according to the invention makes it possible to supply the gas generator 3 and the fuel cell 9 in parallel with two separate air flows A1, A2 accelerated by two separate compression stages 31, 5 mounted in the same enclosure. In this example, the main air flow A1 and the auxiliary air flow A2 come from the same air flow A entering the gas turbomachine 2. In a preferred embodiment, with reference to [Fig. 2], the gas turbomachine 2 comprises a declutching system 7 which mechanically connects the main propulsion shaft 4 and the auxiliary propulsion shaft 6. In other words, the declutching system 7 is at the interface between the two main propulsion shafts 4 and auxiliary propulsion shafts 6. Advantageously, this makes it possible to drive the auxiliary propulsion shaft 6 independently of the main propulsion shaft 4. This is particularly advantageous when the auxiliary propulsion shaft 6 is connected to an independent auxiliary electrical machine as will be presented later. The declutching system 7 is configured to move between an engaged position in which the main propulsion shaft 4 is rotationally secured to the auxiliary propulsion shaft 6, and a declutched position in which the main propulsion shaft 4 is detached from the auxiliary propulsion shaft 6. In other words, the declutching system 7 is configured to detach the main propulsion shaft A and the auxiliary propulsion shaft 6, which makes it possible to supply the fuel cell 9 with the auxiliary air flow A2 even when the gas generator 3 is not in operation. In particular, in this example, the declutching system 7 is configured to move between the engaged position and the disengaged position automatically depending on the rotation speed of the turbine stage 32 of the gas generator 3. In one embodiment, the declutching system 7 is configured to be automatically in the engaged position when the rotational speed of the turbine stage 32 is greater than a predetermined speed threshold. Similarly, the declutching system 7 is configured to be in the disengaged position when the rotational speed of the turbine stage 32 is lower than the predetermined speed threshold. In this example, the engaged position is activated when the speed of the main propulsion shaft 4 is greater than that of the auxiliary propulsion shaft 6. Conversely, the disengaged position is activated when the speed of the main propulsion shaft 4 is lower than that of the auxiliary propulsion shaft 6. In summary, in this example, when the gas generator 3 is operating at too low a speed, for example when it is being stopped, the disengagement system 7 is configured to automatically switch to the disengaged position, allowing the fuel cell 9 to continue operating. In this example, the clutch system 7 is in the form of a freewheel, allowing a simple system with limited space requirements for mounting in the gas turbomachine 2. In one embodiment, the propulsion assembly 1 comprises a supervision system (not shown) configured to detect when the gas generator 3 is operating and when it is not operating. The supervision system is configured to automatically place the disengagement system in the disengaged position in the event of detection of non-operation of the gas generator 3, which makes it possible to guarantee the supply of electrical energy Elec to the electric propulsion machine M and thus to guarantee the operation of the propulsion member. In one embodiment, with reference to [Fig. 2], the gas turbomachine 2 comprises an auxiliary electrical machine 8 connected to the auxiliary propulsion shaft 6. The auxiliary electrical machine 8 is configured to rotate the auxiliary propulsion shaft 6, for example when the clutch system 7 is in the disengaged position. In other words, when the clutch system 7 is in the disengaged position, for example in the event of a failure of the gas generator 3, the fuel cell 9 is configured to supply electrical energy Elec to the auxiliary electrical machine 8, which can thus drive the auxiliary compression stage 5. Preferably, the auxiliary electrical machine 8 is mounted externally to the casing of the gas turbomachine 2. The auxiliary electric machine & is also configured to generate electrical energy Elec from the rotation of the auxiliary propulsion shaft 6, so as to power, for example, the propulsion electric machine M in addition to the fuel cell 9. In one embodiment, the gas generator 3 and the fuel cell 9 are powered by the same fuel Q, making it possible to simplify the gas turbine engine 2 and limit its size in the aircraft. Preferably, the fuel Q is di-hydrogen, allowing a clean fuel which limits greenhouse gas emissions. It goes without saying that the fuel could be different, for example a sustainable fuel known by its English abbreviation SAF for "sustainable aviation fuel". Similarly, it goes without saying that the fuel cell 9 could, for example, be powered by di-hydrogen and the gas generator 3 by kerosene. With reference to [Fig. 3], in this example, the fuel Q, configured to supply the gas generator 3 and the fuel cell 9, is stored in a single tank R, preferably a cryogenic tank R, which makes it possible to carry a greater mass of fuel Q while limiting the mass of the aircraft. In such an embodiment, the propulsion assembly 1 comprises a fuel circuit for jointly supplying the gas generator 3 and the fuel cell 9. The fuel circuit then preferably comprises a heat exchanger Ec configured to heat the fuel flow Q and change it to the gaseous state, so that it does not frost the air entering the combustion chamber of the gas generator 3 or in the fuel cell 9. In a complementary or alternative manner, the fuel circuit comprises a portion mounted around the nozzle 34 so as to exchange calories between the exhaust flow which circulates in the nozzle 34 and the fuel flow Q which circulates around the nozzle 34. In an exemplary embodiment, the nozzle 34 comprises a peripheral vein for circulating the fuel flow Q.The latter is thus configured to be heated directly by the air flow circulating in the gas generator 3, which allows efficient heating by limiting the addition of additional heat exchangers. In one embodiment, the propulsion assembly | comprises a cooling system S configured to cool the engine oil circulating in the gas turbomachine 2 from the cryogenic fuel flow Q leaving the tank R. A method for supplying energy to an electric propulsion machine M of a propulsion unit 1 as described above will now be described, with reference to [Fig. 3]. The supply method comprises a method for supplying air to a fuel cell 9 of the propulsion unit 1. In this example, with reference to [Fig. 3], the gas generator 3 and the fuel cell 9 are supplied in parallel by the same fuel Q from the same tank R, in this example dihydrogen. In addition, in this example, the declutching system 7 is initially in the engaged position. In other words, the main propulsion shaft 4 and the auxiliary propulsion shaft 6 are initially secured and rotate at the same rotational speed. The method comprises a first step E1 of introducing an auxiliary air flow A2 in the gas turbomachine 2, via the auxiliary air inlet 51 mounted, in this example, between the main compression stage 31 and the auxiliary compression stage 5. The auxiliary air flow A2 is then accelerated, in a step E2 in the auxiliary compression stage 5 mounted in the enclosure of the gas turbomachine 2. The main air flow A1 is accelerated in the gas generator 3 which rotates the main propulsion shaft 4 and the auxiliary propulsion shaft 6. At the outlet of the auxiliary compression stage 5, the pressurized auxiliary air flow A2 is conveyed, in a step E3, via the auxiliary air outlet 52 to the air inlet 91 of the fuel cell 9 so as to supply it. If the mechanical energy generated is greater than the compression requirements of the auxiliary air flow A2, this mechanical energy can be supplied to a propulsion member (not shown) or converted into electrical energy by the auxiliary electrical machine 8. In parallel with the auxiliary air flow A2, in a step E4, a fuel flow Q from the tank R is heated, in this example in a heat exchanger Ec, then conveyed to the fuel cell 9. Following the oxidation-reduction reaction, the fuel cell 9 generates electrical energy Elec, in a step ES, to power the electric propulsion machine M. In one embodiment, when the turbine stage 32 of the gas generator 3 rotates at a rotational speed lower than that of the auxiliary propulsion shaft 6, the declutching system 7 is placed in the declutched position, so as to detach the auxiliary propulsion shaft 6 from the main propulsion shaft 4. Preferably, the declutching is carried out automatically. The auxiliary electrical machine 8, powered by the fuel cell 9 or a battery, rotates the auxiliary propulsion shaft 6, so as to power the fuel cell 9 with a pressurized auxiliary air flow A2. The gas turbine engine 2 is thus advantageously self-powered by allowing the rotation of the auxiliary propulsion shaft 6 thanks to the electrical energy Elec provided by the fuel cell 9 while powering the fuel cell 9 with a pressurized air flow.Advantageously, the main propulsion shaft 4 is not driven, which makes it possible to reduce the power of the auxiliary electrical machine 8. It nevertheless goes without saying that the main propulsion shaft 4 could be driven, in particular, when the latter participates in the propulsion. Thanks to the invention, the electric propulsion machine is powered by a fuel cell that operates with a fuel whose environmental impact is limited. The addition of an auxiliary compression stage in the enclosure of the gas turbomachine makes it possible to power the fuel cell with a pressurized air flow without adding an external compressor, for example, as was the case in the prior art. The gas turbomachine thus makes it possible to supply the gas generator and the fuel cell in parallel with two separate air flows under pressure without increasing its size or mass.

Claims

Claims

1. Propulsion assembly (1) for aircraft comprising: at least one electric propulsion machine (M), at least one fuel cell (9) configured to generate electrical energy (Elec) to power the machine electric propulsion (M), fuel cell (9) comprising an air inlet (91), and a gas turbomachine (2) comprising: a gas generator (3) comprising a shaft of main propulsion (4) connected to at least one stage of main compression (31) and at least one stage of turbine (32), main compression stage (31) being configured to accelerate a main airflow (A1) from a main air inlet (33), an auxiliary compression stage (5) mounted on a auxiliary propulsion shaft (6) mechanically connected only to the main propulsion shaft (4), the auxiliary compression stage (5) being configured to accelerate an auxiliary air flow (A2) between a auxiliary air inlet (51) and one air outlet auxiliary (52), the auxiliary air outlet (52) being connected to the air inlet (91) of the fuel cell (9) so as to supply it with a flow of air under pressure.

2. Propulsion assembly (1) according to claim 1, in which the tur- gas engine (2) comprises a clutch system (7) connecting me- mechanically the main propulsion shaft (4) and the propulsion shaft auxiliary (6), the clutch system (7) being configured to evolve between an engaged position, in which the drive shaft main (4) is integral with the auxiliary propulsion shaft (6), and a disengaged position, in which the main propulsion shaft (4) is detached from the auxiliary propulsion shaft (6).

3. Propulsion assembly (1) according to claim 2, in which the stage of turbine (32) of the gas generator (3) being configured to rotate around of the main propulsion shaft (4) according to a rotation speed, the clutch system (7) is configured to move between the position engaged and disengaged position automatically depending on the rotational speed of the turbine stage (32) of the gas generator (3).

4. Propulsion assembly (1) according to claim 3, in which the system clutch release (7) is configured to move from the disengaged position to the engaged position when the turbine stage rotation speed (32) of the gas generator (3) is greater than a threshold speed, of preferably, when the speed of the main propulsion shaft (4) is greater than that of the auxiliary propulsion shaft (6).

5. Propulsion assembly (1) according to one of claims | to 4, in which the main propulsion shaft (4) and the auxiliary propulsion shaft (6) are coaxial.

6. Propulsion assembly (1) according to one of claims | to 5, comprising an auxiliary electrical machine (8) connected to the propulsion shaft auxiliary (6), the auxiliary electrical machine (8) being configured to drive the auxiliary propulsion shaft (6) in rotation and generate electrical energy (Elec) from the rotation of the propulsion shaft auxiliary (6).

7. Propulsion assembly (1) according to one of claims | to 6, in which the gas turbomachine (2) and the fuel cell (9) are powered by the same fuel. |Claim 8] Propulsion assembly (1) according to one of claims 1 to 7, in which the gas generator (3) and the auxiliary compression stage (5) are mounted in the same enclosure.

9. Aircraft comprising at least one propulsion unit (1) according to one of the claims 1 to 8.

10. Method for supplying air to a fuel cell (9) of a propulsion unit (1) according to one of claims | to 8, the method comprising the steps of: accelerate an auxiliary air flow (A2) in the com- auxiliary pressure (5) mounted in the gas turbomachine (2), And route the auxiliary airflow (A2) via the air outlet auxiliary (52) of the gas turbomachine (2) to the air inlet (91) of the fuel cell (9) to power it.

11. A feeding method according to claim 10, wherein the shaft of main propulsion (4) being rotationally integral with the auxiliary propulsion shaft (6), the method comprises the steps of: drive the auxiliary propulsion shaft (6) by the shaft of main propulsion (4) to accelerate the auxiliary airflow (A2), separate the main propulsion shaft (4) and the drive shaft auxiliary propulsion (6), and drive the auxiliary propulsion shaft (6) by a machine auxiliary electric (8) to accelerate the auxiliary air flow (A2).