AIRCRAFT PROPULSION ASSEMBLY

Abstract

PROPULSION ASSEMBLY FOR AIRCRAFT The invention relates to a propulsion assembly (151) for an aircraft which comprises a propulsion system (150) having a core (152) enclosed in a casing (154) and having a combustion chamber (158), a supply pipe (170a-b) conveying dihydrogen to the combustion chamber (158) by passing through the casing (154) at the level of an injection zone (210), and a closed enclosure (250), delimited by a first and a second wall (251a-b) and containing a downstream pipe (170b), a dihydrogen treatment system (202, 204, 206) and the injection zone (210), where the first wall (251a) is made up of a part of the casing (154). With this arrangement, the size and weight of each enclosure are reduced because at least one wall of the enclosure is formed by the motor system housing. Fig. 2

Description

Title of the invention: PROPULSION ASSEMBLY FOR AIRCRAFT Technical field

[0001] The present invention relates to a propulsion unit for an aircraft engine operating on dihydrogen, as well as to an aircraft comprising at least one such propulsion unit. STATE OF THE PRIOR ART

[0002] In order to move, an aircraft conventionally comprises at least one propulsion unit comprising a motorization system such as a turbojet. Such a motorization system comprises a core which is enclosed in a casing and which comprises, among other things, from upstream to downstream, a compressor, a combustion chamber and a turbine.

[0003] In order to reduce carbon dioxide (CO2) emissions from aircraft engines, it is known to use dihydrogen as fuel. The aircraft then has a dihydrogen tank and the engine system is supplied with dihydrogen through pipes which run in the aircraft, between the tank and each engine system and on which treatment systems such as pumps, heaters and valves are installed.

[0004] Safety must be ensured if an incident occurs on the supply line between the tank and the engine. For this, it is known to implement different safety systems.

[0005] Although such an arrangement is efficient, it requires heavy and bulky installations and it is therefore necessary to find a new arrangement in which, among other things, the size and weight are reduced. Statement of the invention

[0006] An object of the present invention is to propose a propulsion unit supplied with dihydrogen and comprising treatment systems which are enclosed in an enclosure, one wall of which is constituted by a casing of a motorization system of the propulsion unit.

[0007] For this purpose, a propulsion unit for an aircraft is proposed comprising:

[0008] - a nacelle,

[0009] - a motorization system housed in the nacelle and comprising a core which is enclosed in a casing and which has a combustion chamber,

[0010] - a supply pipe intended to convey dihydrogen to the combustion chamber by crossing the crankcase at the level of an injection zone,

[0011] - at least one treatment system arranged on the supply pipeline and intended to treat said dihydrogen passing through the supply pipe, and

[0012] - a closed enclosure, delimited by a first wall and a second wall and containing a pipeline downstream of the supply pipeline, at least one treatment system and the injection zone, where the first wall consists of a part of the casing.

[0013] With such an arrangement, the size and weight of each enclosure are reduced due to the fact that at least one wall of the enclosure is formed by the casing of the motorization system.

[0014] According to a particular embodiment, said enclosure comprises at least one ventilation system intended to ensure the evacuation of gases present in the enclosure to the exterior of the aircraft.

[0015] Advantageously, at least one ventilation system takes the form of an air inlet passing through the second wall and through which air from outside the aircraft enters the enclosure and an air outlet passing through the second wall and through which the gases present in the enclosure escape to the outside of the aircraft.

[0016] Advantageously, at least one ventilation system takes the form of a pressure limiter mounted on the second wall and through which the gases present in the enclosure escape to the outside of the aircraft.

[0017] According to a particular embodiment, said enclosure is made up of a first sub-enclosure in which the injection zone is arranged and a second sub-enclosure separated from the first sub-enclosure by a separation wall, where the downstream pipe passes through the second sub-enclosure then the first sub-enclosure to reach the injection zone by passing through the separation wall, where each sub-enclosure is closed and delimited by a first wall, a second wall and the separation wall where the first wall delimiting each sub-enclosure is made up of a part of the casing.

[0018] According to a particular embodiment, the propulsion unit comprises a ventilation system taking the form of an air inlet passing through the second wall of the first sub-enclosure and through which air from outside the aircraft enters the first sub-enclosure, an air outlet passing through the second wall of the second sub-enclosure and through which the gases present in the second sub-enclosure escape to the outside of the aircraft and an air passage passing through the separation wall and opening on one side into the first sub-enclosure and on the other side into the second sub-enclosure (350b).

[0019] According to a particular embodiment, the propulsion unit comprises a ventilation system taking the form of an air inlet passing through the second wall of the first sub-enclosure and through which air from outside the aircraft enters the first sub-enclosure, an air outlet passing through the second wall of the first sub-enclosure and through which the gases present in the first sub-enclosure escape to the outside of the aircraft.

[0020] Advantageously, the passage of the downstream pipe through the separation wall is carried out in a sealed manner.

[0021] Advantageously, at least one sub-enclosure has a ventilation system taking the form of a pressure limiter mounted on the second wall of said sub-enclosure and through which the gases present in said sub-enclosure escape to the outside of the aircraft.

[0022] Advantageously, at least one treatment system comprises a treatment part in which the dihydrogen is treated and a non-treatment part in which the dihydrogen is absent, the treatment part and the non-treatment part are sealed relative to each other, the treatment system is arranged through an opening in the second wall and fixed in a sealed manner to said second wall and the treatment part is arranged in the corresponding enclosure or sub-enclosure and the non-treatment part is arranged outside the corresponding enclosure or sub-enclosure.

[0023] The invention also proposes an aircraft comprising a dihydrogen tank and at least one propulsion unit according to one of the preceding variants where the supply pipe is fluidically connected to the dihydrogen tank.

[0024] The invention also proposes an aircraft comprising a dihydrogen tank and at least one propulsion unit according to one of the preceding variants where the supply pipe is fluidically connected to the dihydrogen tank. Brief description of the drawings

[0025] The above-mentioned features of the invention, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being made in relation to the attached drawings, among which:

[0026] [Fig-1] is a side view of an aircraft comprising a propulsion unit according to the invention,

[0027] [Fig.2] is a schematic representation in side view of the propulsion unit according to a first embodiment of the invention,

[0028] [Fig.3] is a schematic representation in side view of the propulsion unit according to a second embodiment of the invention,

[0029] [Fig.4] is a schematic and perspective representation of a propulsion unit according to a third embodiment of the invention,

[0030] [Fig.5] is a schematic representation of a detail of an embodiment of a variant of the invention, and

[0031] [Fig.6] schematically illustrates an example of a control unit implemented in the invention.

[0032] DETAILED DESCRIPTION OF EMBODIMENTS

[0033] In the following description, the terms relating to a position are taken with reference to an aircraft in a forward position, that is to say as shown in [Fig.l] where the arrow F shows the direction of forward movement of the aircraft.

[0034] In the following description, and by convention, X is the longitudinal axis of the motorization system which is parallel to the longitudinal axis of the aircraft oriented positively forward in the direction of advancement of the aircraft, Y is the transverse axis which is horizontal when the aircraft is on the ground, and Z is the vertical axis or vertical height when the aircraft is on the ground, these three axes X, Y and Z being orthogonal to each other.

[0035] [Fig.l] shows an aircraft 100 which has a fuselage 102 on either side of which a wing 104 is fixed. Under each wing 104 is fixed at least one propulsion unit 151 which comprises a nacelle 149 made up of cowls 147 forming an aerodynamic exterior surface.

[0036] [Fig.2] shows the propulsion assembly 151 according to a first embodiment of the invention which also comprises a motorization system 150 which is shown schematically and which is housed inside the nacelle 149.

[0037] In the embodiment of the invention presented in [Fig. 2], the engine system 150 is a turbojet which comprises a core 152 which is enclosed in a casing 154 which is generally cylindrical around the longitudinal axis X.

[0038] Outside air enters the nacelle 149 through an opening provided in the cowls 147 at the front of the nacelle 149.

[0039] Inside the nacelle 149, the air flow is divided into a primary flow 10 and a secondary flow 20. The primary flow 10 enters the core 152 to supply a combustion chamber 158 with oxygen and the secondary flow 20 flows around the core 152 to be evacuated at the rear of the nacelle 149.

[0040] The casing 154 is thus open at the front to allow the introduction of the primary flow 10 into the core 152 and open at the rear to allow the exhaust of the gases resulting from the combustion through a nozzle. The core 152 here comprises, from upstream to downstream, a compressor 156, the combustion chamber 158 and a turbine 160. The compressor 156 and the turbine 160 are provided with blades rotating around the longitudinal axis X.

[0041] The primary flow 10 thus passes successively through the compressor 156 where it is compressed before being injected into the combustion chamber 158 where it is mixed with the fuel. The gases resulting from the combustion then pass through the turbine 160 and drive it in rotation. The turbine 160 then in turn drives the compressor 156 in rotation and the gases are then ejected to the rear.

[0042] The propulsion assembly 151 also comprises a supply pipe 170a-b which allows dihydrogen to be conveyed from a dihydrogen tank 172 of the aircraft 100 to the combustion chamber 158. The supply pipe 170a-b is fluidically connected to the dihydrogen tank 172 and it winds here outside the casing 154 to the combustion chamber 158 which it reaches by crossing the casing 154 at an injection zone 210.

[0043] The pipeline 170a-b is divided into an upstream pipeline 170a and a downstream pipeline 170b.

[0044] In the embodiment of the invention presented in [Fig. 2], the downstream pipe 170b is equipped at the injection zone 210, with an injector ramp 184 equipped with injectors 185 which plunge into the combustion chamber 158 through the casing 154.

[0045] To prepare the dihydrogen upstream of the combustion chamber 158, the propulsion unit 151 comprises at least one treatment system 202, 204, 206 such as heaters, pumps, etc. and which are intended to treat the dihydrogen circulating in the supply pipe 170a-b.

[0046] Each treatment system 202, 204, 206, which here number three, are arranged along the supply pipe 170a-b, and more particularly on the supply pipe 170a-b to interact directly with the dihydrogen which circulates therein.

[0047] The propulsion unit 151 comprises an enclosure 250 delimited by walls 25la-b, namely a first wall 25la and a second wall 251b. The first wall 251a may consist of several sub-walls secured to each other.

[0048] The supply pipe 170a-b is divided into the upstream pipe 170a which is between the tank 172 and the enclosure 250 and the downstream pipe 170b inside the enclosure 250 up to the combustion chamber 158.

[0049] The enclosure 250 contains the downstream pipe 170b, at least one treatment system 202, 204, 206 and the injection zone 210. Thus, if dihydrogen leaks at the level of a treatment system 202, 204, 206 present in the enclosure 250, the dihydrogen remains confined in the enclosure 250 which is closed relative to the rest of the propulsion assembly 151.

[0050] The enclosure 250 thus forms around the downstream pipe 170b and the treatment systems 202, 204, 206, a containment tank for the dihydrogen.

[0051] To save material and therefore space and weight, the first wall 251a of the enclosure 250 is made up of a part of the casing 154. Thus, a part of the weight of the enclosure 250 is already included in the weight of the casing 154 and the treatment systems 202, 204, 206 are as close as possible to the casing 154 to save space around it.

[0052] The second wall 251b of the enclosure 250 is fixed in a sealed manner to the casing 154 by any suitable means such as welding, rivets with seals, etc.

[0053] In the embodiment of the invention presented in [Fig.2], the upstream pipe 170a is a double-skin pipe comprising an inner pipe in which the dihydrogen flows and an outer pipe around the inner pipe and which is evacuated or filled with a gas that is neutral with respect to dihydrogen such as nitrogen.

[0054] Due to the installation of the enclosure 250, the downstream pipe 170b is a single-skin pipe which extends the internal pipe because the enclosure 250 acts as a double skin, hence also a simplification.

[0055] The passage of the pipe 170a-b through the second wall 251b is carried out in a sealed manner at the level of a crossing system 258 ensuring here only the passage of the internal pipe. Such a crossing system 258 is known to those skilled in the art and is not described more precisely because it is not directly part of the invention.

[0056] To assist in the evacuation of dihydrogen from the enclosure 250, the latter comprises, in particular at the level of the second wall 251b, at least one ventilation system 252a-b which ensures the evacuation of the gases, in particular, the air and the dihydrogen present in the enclosure 250 towards the outside of the aircraft 100.

[0057] In the embodiment of the invention presented in [Fig. 2], a ventilation system 252a-b takes the form of an air inlet 252a and an air outlet 252b which both pass through the second wall 251b. The air inlet ensures the entry of air from outside the aircraft 100 into the enclosure 250, and more particularly here the air coming from the secondary flow 20 when the propulsion unit 151 is in operation. The air outlet 252b ensures the evacuation of the gases present in the enclosure 250 which thus escape to the outside of the aircraft 100.

[0058] The gases which escape through the air outlet 252b are ejected directly towards the outside of the nacelle 149 via a dedicated pipe which opens outside by passing through a cover 147, or directly into the secondary flow 20.

[0059] As a replacement or in addition, a ventilation system 254 takes the form of a pressure limiter 254 mounted on the second wall 251b and through which the gases present in the enclosure 250 escape to the outside of the aircraft 100.

[0060] As for the air outlet 252b, the gases which escape through the pressure limiter 254 are ejected directly towards the outside of the nacelle 149 via a dedicated pipe which opens outside by passing through a cover 147, or directly into the secondary flow 20.

[0061] The installation of the pressure limiter 254 makes it possible to supplement the air inlet 2542a and the air outlet 252b, in particular, when there is a sudden increase in the pressure in the enclosure 250 and the air outlet 252b is not sufficient to evacuate this excess pressure.

[0062] [Fig. 3] shows a propulsion unit 151 according to a second embodiment of the invention, in which the enclosure 350 is made up of a first sub-enclosure 350a and a second sub-enclosure 350b which is separated from the first sub-enclosure 350a by a common separation wall 351.

[0063] In the first sub-enclosure 350a is arranged the injection zone 210 and the downstream pipe 170b passes from the upstream pipe 170a and in the direction of flow of the dihydrogen, the second sub-enclosure 350b then the first sub-enclosure 350a to reach the injection zone 210 by passing through the separation wall 351.

[0064] Each sub-enclosure 350a-b is closed and delimited by a first wall 251a, a second wall 251b and the separation wall 351 and as previously, the first wall 251a delimiting each sub-enclosure 350a-b is made up of a part of the casing 154.

[0065] Of course, there can be more than two sub-enclosures in a row.

[0066] According to a particular embodiment, each sub-enclosure 350a-b contains at least at least one treatment system 202, 204, 206. In the embodiment of the invention shown in [Fig.3], the first sub-enclosure 350a contains the treatment systems 204 and 206, such as heaters and the second sub-enclosure 350b contains the treatment system 202 such as a pump.

[0067] According to a particular embodiment, the propulsion assembly 151 of [Fig. 3] comprises a ventilation system 352 which takes the form of an air inlet 352a passing through the second wall 251b of the first sub-enclosure 350a, an air outlet 352b passing through the second wall 251b of the second sub-enclosure 350b and an air passage 352c passing through the separation wall 351 and opening on one side into the first sub-enclosure 350a and on the other side into the second sub-enclosure 350b.

[0068] Thus, an external air flow coming for example from the secondary flow 20 enters the first sub-enclosure 350a through the air inlet 352a. The air flow then passes through the first sub-enclosure 350a where, potentially, it becomes charged with dihydrogen, and the gases thus present in the first sub-enclosure 350a pass through the separation wall 351 through the air passage 352c to enter the second sub-enclosure 350b, from where they exit through the air outlet 352b towards the outside of the aircraft 100.

[0069] As previously, the gases which escape through the air outlet 352b are ejected directly towards the outside of the nacelle 149 via a dedicated pipe which opens outside by passing through a cover 147, or directly into the secondary flow 20.

[0070] As before, a pressure limiter 254 can be mounted on the second wall 251b of one and / or the other of the sub-enclosures 350a-b.

[0071] [Fig.4] shows a propulsion assembly 151 according to a third embodiment of the invention which is generally identical to the second embodiment of [Fig.3] but with a different ventilation system 452.

[0072] There we find the enclosure 350 made up of two sub-enclosures 350a-b and separated by the separation wall 351, where the injection zone 210 is arranged in the first sub-enclosure 350a and where the downstream pipe 170b passes through the second sub-enclosure 350b then the first sub-enclosure 350a to reach the injection zone 210 by passing through the separation wall 351.

[0073] In this embodiment, the second sub-enclosure 350b is entirely closed so as to prevent any hydrogen that may be present therein from escaping. According to a particular embodiment, the second sub-enclosure 350b is inerted with nitrogen for example, or it is evacuated.

[0074] In this embodiment, the passage of the downstream pipe 170b through the separation wall 351 is carried out in a sealed manner at the level of a crossing system 458. Such a crossing system 458 is known to those skilled in the art and is not described more precisely because it is not directly part of the invention.

[0075] In this particular embodiment, the ventilation system 452 takes the form of an air inlet 452a passing through the second wall 251b of the first sub-enclosure 350a and an air outlet 452b passing through the second wall 251b of the first sub-enclosure 350a. There is therefore no longer any passage of air through the separation wall 351.

[0076] Thus, an external air flow coming for example from the secondary flow 20 enters the first sub-enclosure 350a through the air inlet 452a. The air flow then passes through the first sub-enclosure 350a where, potentially, it is charged with dihydrogen, and the gases thus present in the first sub-enclosure 350a exit through the air outlet 452b towards the outside of the aircraft 100.

[0077] In this embodiment, the passage of the downstream pipe 170b through the separation wall 351 is preferably carried out in a sealed manner to avoid any passage of dihydrogen coming from a leak inside a sub-enclosure 350a-b towards the other sub-enclosure 350b-a.

[0078] As previously, the gases which escape through the air outlet 452b are ejected directly towards the outside of the nacelle 149 via a dedicated pipe which opens outside by passing through a cover 147, or directly into the secondary flow 20.

[0079] As previously, a pressure limiter 254 can be mounted on the second wall 251b of one and / or the other of the sub-enclosures 350a-b.

[0080] According to a particular embodiment of the invention, the treatment system 202 is a pump, in particular a high pressure pump, which is housed in the second sub- enclosure 350b and which propels the dihydrogen towards the combustion chamber 158. This installation where the pump is alone in a sub-enclosure 350b ensures thermal insulation around the pump.

[0081] The treatment systems 204 and 206 are here heat exchangers which ensure heat exchanges between the dihydrogen and heat transfer fluids circulating in exchange pipes 204a-b and 206a-b which are fluidically connected to a hot source.

[0082] In an alternative embodiment of each of the embodiments described, to detect the presence of dihydrogen in the enclosure 250 or the sub-enclosures 350a-b, said enclosure 250 and each sub-enclosure 350a-b are equipped with a monitoring system 264 adapted to detect a change in said enclosure 250 and said sub-enclosure 350a-b. The monitoring system 264 may be, for example, a pressure sensor, a dihydrogen detector, or others.

[0083] The propulsion assembly 151 comprises a shut-off valve 262 mounted on the downstream pipe 170b, upstream of the first treatment system 202, where the shut-off valve 262 can alternately take an open position in which the dihydrogen can pass or a closed position where the dihydrogen is prevented from passing. The shut-off valve 262 is preferably an electrically, pneumatically, or other controlled valve.

[0084] The propulsion assembly 151 comprises a control unit 260 which is connected to each monitoring system 264 and to the shut-off valve 262 and depending on the information delivered by each monitoring system 264, the control unit 260 controls the shut-off valve 262 to open when dihydrogen is not detected or to close when dihydrogen is detected.

[0085] To help better evacuate the dihydrogen in the event of a leak in the enclosure 250 and each sub-enclosure 350a-b fluidically connected to an air outlet 252b, 352b, 452b, a fan 266 controlled by the control unit 260 can be installed in the enclosure 250 and each sub-enclosure 350a-b.

[0086] Thus, when the presence of dihydrogen is detected in the enclosure 250 or a sub-enclosure 350a-b by the monitoring system 264 concerned, the control unit 260 commands the starting of the fan 266 concerned so as to accelerate the evacuation of the dihydrogen through the air outlet 252b, 352b, 452b concerned.

[0087] [Fig.5] shows a variant which is applied here to the processing system 202, but it can be applied to each processing system 204, 206.

[0088] In this variant, the treatment system 202 is divided into a treatment part 202a and a non-treatment part 202b which are sealed relative to each other.

[0089] The treatment part 202a is the part in which the dihydrogen is treated, such as for example the pipes of an exchanger in which the dihydrogen circulates, the part of a pump where dihydrogen circulates, etc.

[0090] The non-treatment part 202b is the part in which dihydrogen is absent, such as the pipes of an exchanger in which a heat transfer fluid circulates, the motor of a pump, etc.

[0091] The second wall 251b is crossed by an opening 502 which is communicating between the interior of the enclosure 250 or the corresponding sub-enclosure 350a-b and the exterior of the propulsion assembly 151 and here of the enclosure 250 or the corresponding sub-enclosure 350a-b.

[0092] The treatment system 202 is arranged through the opening 502 and is sealed to the second wall 251b such that the treatment portion 202a is disposed in the corresponding enclosure 250 or sub-enclosure 350a-b and the non-treatment portion 202b is disposed outside the corresponding enclosure 250 or sub-enclosure 350a-b.

[0093] According to one embodiment, the control unit 260 comprises, connected by a communication bus 600: a processor or CPU 601 (“Central Processing Unit” in English); a random access memory RAM 602 (“Random Access Memory” in English); a read only memory ROM 603 (“Read Only Memory” in English); a storage unit 604 such as a hard disk or a storage media reader, such as an SD card reader (“Secure Digital” in English); at least one communication interface 605, allowing for example the control unit to communicate with the monitoring systems, the shut-off valve, the fans, etc.

[0094] The processor is capable of executing instructions loaded into RAM from ROM, external memory (not shown), a storage medium (such as an SD card), or a communications network. When the equipment is powered on, the processor is capable of reading instructions from RAM and executing them. These instructions form a computer program causing the processor to implement all or part of the described algorithms and steps.

[0095] All or part of the algorithms and steps described below can be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP (“Digital Signal Processor”) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, for example an FPGA (“Field-Programmable Gate Array”) or an ASIC (“Application-Specific Integrated Circuit”).

Claims

Claims

1. Propulsion assembly (151) for an aircraft (100) comprising: - a nacelle (149), - a motorization system (150) housed in the nacelle (149) and comprising a core (152) which is enclosed in a casing (154) and which has a combustion chamber (158), - a supply pipe (170a-b) intended to convey di-hydrogen to the combustion chamber (158) by passing through the casing (154) at an injection zone (210), - at least one treatment system (202, 204, 206) arranged on the supply pipe (170a-b) and intended to treat said di-hydrogen passing through the supply pipe (170a-b), and - a closed enclosure (250, 350), delimited by a first wall (251a) and a second wall (251b) and containing a downstream pipe (170b) of the supply pipe (170a-b), at least one treatment system (202, 204, 206) and the injection zone (210),where the first wall (251a) consists of a part of the casing (154).,

2. Propulsion assembly (151) according to claim 1, characterized in that said enclosure (250, 350) comprises at least one ventilation system (252a-b, 254) intended to ensure the evacuation of the gases present in the enclosure (250, 350) towards the exterior of the aircraft (100).

3. Propulsion assembly (151) according to claim 2, characterized in that at least one ventilation system (252a-b) takes the form of an air inlet (252a) passing through the second wall (251b) and through which air outside the aircraft (100) enters the enclosure (250, 350) and an air outlet (252b) passing through the second wall (251b) and through which the gases present in the enclosure (250, 350) escape to the outside of the aircraft (100).

4. Propulsion assembly (151) according to one of claims 2 or 3, characterized in that at least one ventilation system (254) takes the form of a pressure limiter (254) mounted on the second wall (251b) and through which the gases present in the enclosure (250, 350) escape to the outside of the aircraft (100).

5. Propulsion assembly (151) according to claim 1, characterized in that said enclosure (350) consists of a first sub-enclosure (350a) in which the injection zone (210) is arranged and a second sub-enclosure (350b) separated from the first sub-enclosure (350a) by a separation wall (351), where the downstream pipe (170b) passes through the second sub-enclosure (350b) then the first sub-enclosure (350a) to reach the injection zone (210) by passing through the separation wall (351), where each sub-enclosure (350a-b) is closed and delimited by a first wall (251a), a second wall (251b) and the separation wall (351) where the first wall (251a) delimiting each sub-enclosure (350a-b) is made up of a part of the casing (154).

6. Propulsion assembly (151) according to claim 5, characterized in that it comprises a ventilation system (352) taking the form of an air inlet (352a) passing through the second wall (251b) of the first sub-enclosure (350a) and through which air outside the aircraft (100) enters the first sub-enclosure (350a), an air outlet (352b) passing through the second wall (251b) of the second sub-enclosure (350b) and through which the gases present in the second sub-enclosure (350b) escape to the outside of the aircraft (100) and an air passage (352c) passing through the separation wall (351) and opening on one side into the first sub-enclosure (350a) and on the other side into the second sub-enclosure (350b).

7. Propulsion assembly (151) according to claim 5, characterized in that it comprises a ventilation system (452) taking the form of an air inlet (452a) passing through the second wall (251b) of the first sub-enclosure (350a) and through which air outside the aircraft (100) enters the first sub-enclosure (350a), an air outlet (452b) passing through the second wall (251b) of the first sub-enclosure (350a) and through which the gases present in the first sub-enclosure (350a) escape to the outside of the aircraft (100).

8. Propulsion assembly (151) according to claim 7, characterized in that the passage of the downstream pipe (170b) through the separation wall (351) is carried out in a sealed manner.

9. Propulsion assembly (151) according to one of claims 5 to 8, characterized in that at least one sub-enclosure (350a-b) has a ventilation system (254) taking the form of a pressure limiter (254) mounted on the second wall (251b) of said sub-enclosure (350a-b) and through which the gases present in said sub-enclosure (305a-b) escape to the outside of the aircraft (100).

10. Propulsion assembly (151) according to one of claims 1 to 9, characterized in that at least one treatment system (202) comprises a treatment part (202a) in which the dihydrogen is treated and a non-treatment portion (202b) in which dihydrogen is absent, in that the treatment portion (202a) and the non-treatment portion (202b) are sealed relative to each other, in that the treatment system (202) is arranged through an opening (502) of the second wall (251b) and sealed to said second wall (251b) and in that the treatment portion (202a) is arranged in the corresponding enclosure (250) or sub-enclosure (350a-b) and the non-treatment portion (202b) is arranged outside the corresponding enclosure (250) or sub-enclosure (350a-b).

11. Aircraft (100) comprising a dihydrogen tank (172) and at least one propulsion unit (151) according to one of the preceding claims where the supply pipe (170a-b) is fluidically connected to the dihydrogen tank (172).

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