Purge circuit for an aircraft fuel conditioning system, associated purging method

Abstract

A purge circuit (CP) for a fuel conditioning system supplying at least one aircraft turbomachine with fuel from a cryogenic tank, the purge circuit (CP) comprising an inlet connected to a purge point and an outlet connected to an external environment (EXT) of the aircraft, the purge circuit (CP) comprising at least one vaporization device (3) comprising an expansion tank (30) having a supply opening (30A) connected to the purge point by an upstream pipe (31) and an outlet opening (30B) connected to the external environment (EXT), the expansion tank (30) comprises a volume configured to allow expansion of the fuel flow (Q) in the liquid state (QL) so that it vaporizes in the gaseous state (QG). Abstract figure: Figure 4

Description

Title of the invention: Purge circuit for an aircraft fuel conditioning system, associated purge method Technical field

[0001] The present invention relates to the field of aircraft comprising turbo-machines powered by fuel stored in a cryogenic tank.

[0002] 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 and those in circulation requiring the implementation of technological solutions in order 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.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance 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 with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work covers 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, and, as essential complements to technological progress, aeronautical biofuels.

[0006] It is known to store fuel, in particular hydrogen, in liquid form to limit the size and mass of the aircraft tanks. For example, the fuel is stored at a temperature of the order of 20 to 22 Kelvins (-253 to -251°C) in a cryogenic tank of the aircraft.

[0007] In order to be able to be injected into the combustion chamber of a turbomachine, the fuel must be conditioned, i.e. pressurized and heated, in order to allow optimal combustion. Conditioning is for example necessary to reduce the risk of icing / solidification of the water vapor contained in the air circulating in the turbomachine, in particular, at the fuel injectors of the turbomachine. With reference to [Fig.l], there is shown an SCAA conditioning system according to the prior art comprising a fuel circuit CQ connected at the inlet to a cryogenic tank RC and at the outlet to the combustion chamber CC of a turbomachine T. A fuel flow Q circulating from upstream to downstream in the fuel circuit CQ successively passes through a mechanical pump 101 and a heating module 102. The heating module 102 is configured to provide calories to the fuel flow Q in order to heat it so that it can be injected into the turbomachine T.

[0008] In a known manner, in order to carry out maintenance operations or to respond to a malfunction, it is necessary to rapidly purge at least part of the fuel circuit known as the “portion to be purged PAP”. The portion to be purged PAP comprises a purge point PP to which a purge circuit CP is connected. Conventionally, the purge circuit CP connects the purge point PP to the external environment EXT so as to allow fuel Q to be expelled from the portion to be purged PAP rapidly.

[0009] The portion to be purged PAP must be purged under different conditions, for example, in the event of maintenance or malfunction. There are cut-off valves in the fuel circuit CQ which make it possible to create safety barriers to prevent leaks. In practice, in the event of an alarm, when the cut-off valves are closed, fuel continues to be pumped into the cryogenic tank RC due to inertia and it is necessary to divert the fuel flow Q to the external environment EXT. It is also necessary to divert the fuel flow Q to the external environment EXT when adjusting the pump (cold setting).

[0010] For safety reasons, it is desirable that the fuel flow Q be expelled in the gaseous state into the external environment EXT. This is problematic when the portion to be purged PAP of the fuel circuit CQ comprises a fuel flow in the liquid state.

[0011] An immediate solution to eliminate this drawback is to provide a heat exchanger in the purge circuit. To change from the liquid state to the gaseous state, it is necessary to provide a large amount of thermal or electrical energy, which is problematic. Furthermore, the purge circuit is generally far from the aircraft's heat sources, which requires the provision of complex hot flow circuits, which increases the cost and mass.

[0012] The invention thus aims to eliminate at least some of these drawbacks by proposing a new purge circuit for a cryogenic fuel conditioning system. PRESENTATION OF THE INVENTION

[0013] The invention relates to a purge circuit for a fuel conditioning system supplying at least one aircraft turbomachine with fuel from a cryogenic tank, the conditioning system comprising a fuel circuit connected at the inlet to the cryogenic tank and at the outlet to the turbomachine, a fuel flow circulating from upstream to downstream in the fuel circuit, the fuel circuit comprising at least one portion to be purged comprising a purge point, the purge circuit comprising: • an inlet connected to the purge point and an outlet connected to an environment outside the aircraft, • the purge circuit comprising at least one vaporization device comprising an expansion tank having a supply opening connected to the purge point by an upstream pipe and a discharge opening connected to the external environment, the expansion tank comprises a volume configured to allow expansion of the fuel flow in the liquid state so that it vaporizes in the gaseous state.

[0014] Preferably, the fuel flow vaporizes into the gaseous state without external energy input, which is advantageous and allows the purge circuit to be positioned with few constraints without increasing its cost. An expansion tank makes it possible to control the exothermic decompression of the fuel.

[0015] In one aspect, the fuel is exothermic decompression, preferably hydrogen.

[0016] According to one aspect, the upstream pipe of the vaporization device comprises a heating portion in contact with the expansion tank so as to allow heating of the fuel flow in the liquid state by thermal conduction. Preliminary heating makes it possible to provide energy to the fuel flow resulting directly from the exothermic decompression. This makes it possible to reduce the volume of the expansion tank while ensuring the change of state of the fuel flow.

[0017] According to one aspect, the expansion tank comprising a downstream portion configured to receive the flow of fuel in the gaseous state, the heating portion of the vaporization device is in contact at least with the downstream portion of the expansion tank. The downstream portion of the expansion tank is the hottest and provides more calories to the heating portion.

[0018] According to one aspect, the expansion tank comprising an upstream portion configured to receive the flow of fuel in the liquid state, the heating portion of the device vaporization is in contact with at least the upstream portion of the expansion tank.

[0019] According to one aspect, the heating portion is wrapped around the expansion tank. This allows for increased thermal conduction while limiting bulk.

[0020] According to one aspect, the heating portion is wrapped around the expansion tank from the downstream portion to the upstream portion. This allows for countercurrent circulation, which improves heat transfer. According to one aspect, the heating portion is in the form of a coil.

[0021] Also presented is a fuel conditioning system supplying at least one aircraft turbomachine with fuel from a cryogenic tank, the conditioning system comprising: • a fuel circuit connected at the inlet to the cryogenic tank and at the outlet to the turbomachine, a fuel flow circulating from upstream to downstream in the fuel circuit and at least one heat exchanger, mounted in the fuel circuit, configured to transmit calories to the fuel flow, the fuel circuit comprising at least one portion to be purged comprising a purge point, and • a purge circuit, as presented previously, connected to the purge point.

[0022] Also presented is an aircraft comprising a turbomachine and a fuel conditioning system as presented previously for supplying the turbomachine with fuel from a cryogenic tank.

[0023] Also presented is a method of purging a portion to be purged of a fuel circuit of a fuel conditioning system as presented previously, the method comprising steps consisting of: • Open the purge circuit so as to purge the portion of the fuel circuit to be purged and • Circulate a flow of fuel in the liquid state into the expansion tank of the vaporization device so that it vaporizes into the gaseous state.

[0024] The method comprises a step of circulating the flow of fuel in the liquid state in a heating part of the upstream pipe in order to increase the temperature. PRESENTATION OF FIGURES

[0025] The invention will be better understood on reading the description which follows, 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.

[0026] [Fig.l] is a schematic representation of a conditioning system of fuel according to the prior art.

[0027] [Fig. 2] is a schematic representation of a fuel conditioning system according to one embodiment of the invention with a purge circuit comprising a vaporization device.

[0028] [Fig.3] is a schematic representation of a first variant of the vaporization device with an expansion tank.

[0029] [Fig.4] is a schematic representation of a second variant of the vaporization device with an expansion chamber and a heating part wrapped around the expansion tank.

[0030] 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

[0031] With reference to [Fig. 2], there is shown a fuel conditioning system SC configured to supply an aircraft turbomachine T with fuel Q from a cryogenic tank RC. The turbomachine T is configured to provide propulsion for the aircraft, in particular, by driving at least one propulsion member (not shown in [Fig. 2]). In this example, the fuel is hydrogen but the invention applies to other types of fuel with exothermic decompression Q. The invention is particularly advantageous with liquid hydrogen. The invention also applies to liquid methane or liquefied natural gas.

[0032] With reference to [Fig. 2], the conditioning system SC comprises a fuel circuit CQ connected at the inlet to the cryogenic tank RC and at the outlet to the combustion chamber CC of the turbomachine T. The conditioning system SC also comprises a pump 1, preferably high pressure, configured to circulate a flow of fuel Q from upstream to downstream in the fuel circuit CQ.

[0033] With reference to [Fig. 2], the conditioning system SC comprises a heat exchanger 2 mounted in the fuel circuit CQ to transmit calories to the fuel flow Q in order to heat it to allow its optimal injection into the turbomachine T. It goes without saying that the conditioning system SC could comprise a plurality of heat exchangers supplied with heat sources of identical or different natures.

[0034] The fuel circuit CQ comprises a purge portion PAP which is configured to be purged independently. In this example, the purge portion PAP comprises fuel Q in the liquid state QL and is thermally insulated. The purge portion PAP comprises a purge volume.

[0035] The portion to be purged PAP must be purged under different conditions, for example, in the event of maintenance or malfunction. There are cut-off valves in the fuel circuit CQ which make it possible to create safety barriers to prevent leaks. In practice, in the event of an alarm, when the cut-off valves are closed, fuel continues to be pumped into the cryogenic tank RC due to inertia and it is necessary to divert the fuel flow Q to the external environment EXT. It is also necessary to divert the fuel flow Q to the external environment EXT when adjusting the pump (cold setting).

[0036] With reference to [Fig.2], the conditioning system SC comprises a purge circuit CP comprising an inlet connected to a purge point PP of the fuel circuit CQ. The purge point PP belongs to the portion to be purged PAP as illustrated in [Fig.2],

[0037] The purge circuit CP comprises an external outlet connected to an external environment EXT of the aircraft. The fuel flow Q moves from upstream to downstream between the inlet and the outlet. This makes it possible to discharge any fuel flow Q in the event of a risk to operational safety. For this purpose, the purge circuit CP comprises a purge valve 4 moving at least between an open position allowing purging and a closed position prohibiting purging.

[0038] In this example, the purge circuit CP comprises a discharge valve 5 which is preferably controlled to control the discharge to the external environment EXT.

[0039] With reference to [Fig.2], the purge circuit CP comprises a vaporization device 3 to allow an expansion of the fuel flow Q in the liquid state QL so that it vaporizes in the gaseous state QG.

[0040] In this example, a single vaporization device 3 is shown, but it goes without saying that the purge circuit CP could comprise several.

[0041] According to a first embodiment, with reference to [Fig. 3], the vaporization device 3 comprises an expansion tank 30 having a supply opening 30A connected to the purge point PP by an upstream pipe 31 and an evacuation opening 30B connected to the external environment EXT, in particular, for a downstream pipe 32.

[0042] Preferably, the expansion tank 30 comprises a single supply opening 30A and a single discharge opening 30B, but it goes without saying that this could be different.

[0043] Advantageously, the expansion tank 30 is not thermally insulated.

[0044] As illustrated in [Fig. 3], the expansion tank 30 comprises an upstream portion 30L configured to receive the fuel flow Q in the liquid state QL and a downstream portion 30G configured to receive the fuel flow Q in the gaseous state QG.

[0045] In this example, the expansion tank 30 comprises a volume V30 configured to allow an expansion of the fuel flow Q in the liquid state QL so that it vaporizes in the gaseous state QG. For example, a volume V30 between 100L and 250L is suitable.

[0046] Advantageously, the vaporization device 3 makes it possible to carry out a decompression of the fuel flow Q which passes from the liquid state QL to the gaseous state QG. This controlled decompression makes it possible to expand the fuel flow which heats up. The presence of a controllable discharge valve 5 makes it possible to carry out a controlled decompression.

[0047] Preferably, the supply opening 30A and the discharge opening 30B are respectively positioned at the lower end and at the upper end of the expansion tank 30. This allows easy access to the liquid phase and the gaseous phase.

[0048] According to a second embodiment, with reference to [Fig. 4], the upstream pipe 31 of the vaporization device 3 comprises a heating portion 310 in contact with the expansion tank 30 so as to allow heating of the fuel flow Q in the liquid state QL by thermal conduction. Such a characteristic advantageously makes it possible to heat the fuel Q in the liquid state QL in a manner prior to its reheating by expansion. This makes it possible to increase the compactness and reduce the volume V30 of the expansion tank 30.

[0049] Preferably, the heating part 310 of the vaporization device 3 is in contact with the downstream part 30G of the expansion tank 30, this makes it possible to capture the calories of the fuel Q in the gaseous state QG.

[0050] Preferably, the heating part 310 of the vaporization device 3 is in contact with the upstream part 30L of the expansion tank 30, this makes it possible to capture the calories of the fuel Q in the liquid state QL.

[0051] In this embodiment, the heating part 310 is in contact with the downstream part 30G and the upstream part 30L of the expansion tank 30 in order to maximize the heat exchanges. Preferably, to optimize the heating, the vaporization device 3 allows a countercurrent exchange of calories, the heating part 310 extends over the expansion tank 30 from the downstream part 30G to the upstream part 30L.

[0052] In this example, with reference to [Fig.4], to optimize compactness, the heating portion 310 is wound around the expansion tank 30, in particular, from the downstream portion 30G to the upstream portion 30L. The heating portion 310 is preferably in the form of a coil.

[0053] An example of implementation of a method for purging the portion to be purged PAP of a fuel circuit CQ will now be presented with reference to the conditioning system SC of [Fig.2] with a vaporization device 3 according to [Fig.4]. The fuel Q in the portion to be purged PAP is in the liquid state QL.

[0054] The purging method comprises a step consisting of opening the purge valve 4 so as to circulate the purge volume of the portion to be purged PAP in the purge circuit CP.

[0055] The flow of fuel in the liquid state QL first circulates in the heating part 310 in order to increase the temperature. Advantageously, the risk of icing is zero since the heat exchanges are carried out between two fuel flows. The flow of fuel Q advantageously circulates countercurrently while being in contact with the downstream part 30G then the upstream part 30L of the expansion tank 3. This preliminary heating ensures optimal passage to the gaseous state.

[0056] Then, the fuel flow in the liquid state QL circulates in the expansion tank 30 of the vaporization device 3 so that it vaporizes in the gaseous state QG. The fuel flow Q expands to an intermediate pressure and is discharged in a controlled manner to the external environment EXT by the discharge valve 5 or passively. The intermediate pressure is preferably higher than the saturated vapor pressure of the dihydrogen and lower than the external pressure.

[0057] The decompression of the fuel flow Q is exothermic, which makes it possible to heat the expansion tank 30, which contributes to the heating of the fuel flow Q in the heating part 310. Thus, it is the expansion which allows the change of state in the expansion tank 30.

[0058] Advantageously, it is not necessary to provide external energy or to use a heat source to enable the vaporization of the fuel flow Q in the purge circuit CP. The purge circuit CP can thus maintain a simple structure.

Claims

Claims

1. Purge circuit (CP) for a fuel conditioning system (SC) supplying at least one aircraft turbomachine (T) with fuel (Q) from a cryogenic tank (RC), the conditioning system (SC) comprising a fuel circuit (CQ) connected at the inlet to the cryogenic tank (RC) and at the outlet to the turbomachine (T), a fuel flow (Q) circulating from upstream to downstream in the fuel circuit (CQ), the fuel circuit (CQ) comprising at least one portion to be purged (PAP) comprising a purge point (PP), the purge circuit (CP) comprising: • an inlet connected to the purge point (PP) and an outlet connected to an external environment (EXT) of the aircraft,• the purge circuit (CP) comprising at least one vaporization device (3) comprising an expansion tank (30) having a supply opening (30A) connected to the purge point (PP) by an upstream pipe (31) and an evacuation opening (30B) connected to the external environment (EXT), the expansion tank (30) comprises a volume (V30) configured to allow an expansion of the fuel flow (Q) in the liquid state (QL) so that it vaporizes in the gaseous state (QG).,

2. Purge circuit (CP) according to claim 1 in which the upstream pipe (31) of the vaporization device (3) comprises a heating part (310) in contact with the expansion tank (30) so as to allow heating of the fuel flow (Q) in the liquid state (QL) by thermal conduction.

3. Purge circuit (CP) according to one of claims 2 wherein, the expansion tank (30) comprising a downstream part (30G) configured to receive the fuel flow (Q) in the gaseous state (QG), the heating part (310) of the vaporization device (3) is in contact at least with the downstream part (30G) of the expansion tank (30).

4. Purge circuit (CP) according to one of claims 2 to 3 in which, the expansion tank (30) comprising an upstream part (30L) configured to receive the fuel flow (Q) in the liquid state (QL), the heating part (310) of the vaporization device (3) is in contact at least with the upstream part (30L) of the expansion tank (30).

5. Purge circuit (CP) according to claims 3 and 4 wherein the heating part is wound around the expansion tank (30) from the downstream part (30G) to the upstream part (30L).

6. Purge circuit (CP) according to one of claims 1 to 5 wherein the heating part (310) is wound around the expansion tank (30).

7. Purge circuit (CP) according to claim 6 in which the heating part (310) is in the form of a coil.

8. Fuel conditioning system (SC) supplying at least one aircraft turbomachine (T) with fuel (Q) from a cryogenic tank (RC), the conditioning system (SC) comprising: • a fuel circuit (CQ) connected at the inlet to the cryogenic tank (RC) and at the outlet to the turbomachine (T), a fuel flow (Q) circulating from upstream to downstream in the fuel circuit (CQ) and at least one heat exchanger (2), mounted in the fuel circuit (CQ), configured to transmit calories to the fuel flow (Q), the fuel circuit (CQ) comprising at least one portion to be purged (PAP) comprising a purge point (PP), and • a purge circuit (CP) according to one of claims 1 to 7 connected to the purge point (PP).

9. Aircraft comprising a turbomachine (T) and a fuel conditioning system (SC) according to claim 8 for supplying the turbomachine (T) with fuel (Q) from a cryogenic tank (RC).

10. Method for purging a portion to be purged (PAP) of a fuel circuit (CQ) of a fuel conditioning system (SC) according to claim 8, the method comprising steps consisting of: • Opening the purge circuit (CP) so as to purge the portion to be purged (PAP) of the fuel circuit (CQ) and • Circulating a flow of fuel in the liquid state (QL) in the expansion tank (30) of the vaporization device (3) so that it vaporizes in the gaseous state (QG).

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