CRYOGENIC RECONDENSER FUEL SYSTEM

Abstract

The invention relates to a cryogenized fuel storage assembly (10) comprising - a tank (12) in which fuel is present in liquid form and in gaseous form, the gaseous form resulting from the evaporation of the fuel in liquid form, - a liquid fuel circuit (14) connecting the tank (12) to components intended to be supplied with fuel in liquid form, which comprises a pump (16) for pressurizing the liquid fuel - a gaseous fuel circuit (20) taking fuel in gaseous form from the tank (12), characterized in that it comprises a heat exchange member (24) supplied by the liquid fuel circuit (14) and by the gaseous fuel circuit (20), in which the fuel in liquid form and the fuel in gaseous form are capable of exchanging heat to cause at least partial condensation of the taken gaseous fuel. Figure for abstract: Figure 1

Description

Title of the invention: CRYOGENIC FUEL CIRCUIT WITH RECONDENSATION Technical field

[0001] The invention relates to a cryogenic fuel storage assembly comprising a fuel tank and means for managing the fuel in the gaseous phase in the tank, which results from the evaporation of the liquid fuel. STATE OF THE PRIOR ART

[0002] Certain aircraft use fuel brought to a very low temperature for their operation, in particular due to a reduced environmental impact compared to fuel at ambient temperature.

[0003] This cryogenized fuel is stored in a thermally insulated tank to maintain the lowest possible fuel temperature.

[0004] However, due to the temperature difference with the outside of the tank, heat penetrates the tank and then heats the fuel.

[0005] A portion of the fuel then evaporates, resulting in the fuel being present in the tank in both liquid and gaseous form.

[0006] As heat enters the tank, the fuel gradually evaporates, increasing the gaseous fuel pressure inside the tank.

[0007] A system for regulating the quantity of gaseous fuel is then provided, in order to limit the pressure in the tank.

[0008] Such regulation systems comprise, for example, a heat exchanger through which the gaseous fuel circulates to be cooled and thus condense.

[0009] The cold source of the heat exchanger is a source external to the device, which complicates the system and makes the device on which the system is intended to be mounted heavier.

[0010] The aim of the invention is to propose a storage assembly comprising means for regulating the quantity of gaseous fuel present inside the tank which does not include an external cold source. Statement of the invention

[0011] The invention provides a cryogenized fuel storage assembly for an aircraft turbomachine comprising - a tank in which fuel is present in liquid and gaseous form, the gaseous form resulting from the evaporation of the fuel in liquid form, - a liquid fuel circuit connecting the tank to components intended to be supplied with fuel in liquid form, the liquid fuel circuit comprising a liquid fuel pressurization pump, - a gaseous fuel circuit taking fuel in gaseous form from the tank, characterized in that it comprises a heat exchange member supplied by the liquid fuel circuit and by the gaseous fuel circuit, in which the fuel in liquid form coming from the liquid fuel circuit and the fuel in gaseous form coming from the gaseous fuel circuit are capable of exchanging heat to cause at least partial condensation of the gaseous fuel coming from the gaseous fuel circuit.

[0012] According to such an assembly, the gaseous fuel flow is cooled by the liquid fuel. The heat exchange takes place internally, which makes the assembly simpler to integrate into a structure such as that of an aircraft.

[0013] Preferably, the heat exchange member comprises a mixing chamber into which the gaseous fuel flow is injected into the liquid fuel flow.

[0014] Preferably, the gaseous fuel circuit comprises a compressor at the outlet of which the pressure of the gaseous fuel is equal to a predetermined pressure.

[0015] Preferably, the pressure of the gaseous fuel at the outlet of the compressor is equal to the pressure of the liquid fuel at the outlet of the liquid fuel pressurization pump.

[0016] Preferably, the heat exchange member further comprises a heat exchanger arranged upstream of the mixing chamber and in which the flow of liquid fuel takes heat from the gaseous fuel.

[0017] Preferably, the heat exchange member comprises a heat exchanger in which the liquid fuel flow takes heat from the gaseous fuel.

[0018] Preferably, the gaseous fuel circuit comprises a compressor at the outlet of which the pressure of the gaseous fuel is equal to a predetermined pressure greater than the pressure of the liquid fuel at the outlet of the pressurization pump.

[0019] Preferably, the gaseous fuel circuit comprises an expansion valve arranged downstream of the heat exchanger, at the outlet of which the gaseous fuel pressure is substantially equal to the gaseous fuel pressure in the tank.

[0020] The invention also proposes an aircraft comprising at least one turbomachine and a storage assembly according to the invention, supplying said at least one turbomachine with liquid fuel.

[0021] The invention also proposes a method for regulating the quantity of fuel in gaseous form present inside the tank of a storage assembly according to the invention, characterized in that it comprises: - a step of sampling fuel in gaseous form from the tank, for circulating it in a liquid fuel circuit, - a step of condensation of at least part of the fuel in gaseous form taken.

[0022] Preferably, the method comprises a step of compressing the gaseous fuel which is carried out before the condensation step.

[0023] Preferably, the condensation step consists of a step of mixing the gaseous fuel into the liquid fuel stream.

[0024] Preferably, the condensation step consists of a heat exchange step between the gaseous fuel and the liquid fuel.

[0025] Preferably, the method comprises a step of expanding the at least partially condensed fuel, which is carried out after the condensation step. Brief description of the drawings

[0026] [Fig-1] is a schematic representation of a fuel storage assembly cryogenized carrying out the regulation of the quantity of gaseous fuel according to the invention.

[0027] [Fig.2] is a schematic representation of a cryogenized fuel storage assembly regulating the quantity of gaseous fuel according to a second embodiment of the invention.

[0028] [Fig.3] is a schematic representation of an example of a mixing chamber implemented in the second embodiment of the invention.

[0029] [Fig.4] is a schematic representation of another example of a mixing chamber implemented in the second embodiment of the invention.

[0030] [Fig.5] is a schematic representation of a cryogenized fuel storage assembly regulating the quantity of gaseous fuel according to a variant of the embodiment of the invention shown in [Fig.2]. Description of the embodiments

[0031] [Fig.l] shows a storage unit 10 for cryogenized fuel, intended for example to supply the turbomachines of an aircraft.

[0032] In this storage assembly, the fuel is brought to a very low temperature, for example close to zero degrees Celsius or much lower in the case of liquid hydrogen, and it is stored in a thermally insulating tank 12 to maintain it at this low temperature.

[0033] Inside the tank 12, the fuel is present in liquid form and in gaseous form.

[0034] The liquid fuel supplies the turbomachine(s) of the aircraft via a liquid fuel circuit 14. The liquid fuel circuit 14 comprises a pump 16 for pressurizing the liquid fuel, itself being supplied by booster pumps 18 arranged inside the tank 12.

[0035] The heating of the fuel in the tank 12, caused by the difference between the temperature of the ambient air and the temperature of the fuel in the tank 12, results in evaporation of a portion of the fuel.

[0036] The pressure of gaseous fuel in the tank 12 is therefore caused to increase progressively.

[0037] The storage assembly 10 also comprises a gaseous fuel circuit 20 making it possible to regulate the quantity of fuel in gaseous form present inside the tank 12.

[0038] The gaseous fuel circuit 20 comprises a compressor 22 making it possible to increase the pressure and the temperature of the gaseous fuel in the gaseous fuel circuit 20 and a heat exchange member 24 making it possible to cool this gaseous fuel, to cause its condensation.

[0039] According to the invention, the heat exchange member 24 is designed so that the gaseous fuel compressed by the compressor 22 exchanges heat with the liquid fuel flowing in the liquid fuel circuit 14.

[0040] The liquid fuel then draws heat from the gaseous fuel, causing both condensation of the gaseous fuel and an increase in the heat of the liquid fuel before this liquid fuel powers the turbomachine(s).

[0041] According to a first embodiment shown in [Fig.l], the heat exchange member 24 consists of a separate flow heat exchanger.

[0042] The gaseous fuel flow circulates in the hot part 26 of the heat exchanger 50, the liquid fuel flow circulates in the cold part 28 of the heat exchanger 50, without mixing with each other.

[0043] At the outlet of the heat exchanger 50, the gaseous fuel having lost heat has been cooled and has condensed.

[0044] The compression of the liquid by the compressor 22 combined with the fact that the temperature of the gaseous fuel leaving the heat exchanger 50 is not perfectly equal to the temperature of the liquid fuel leaving the heat exchanger 50, means that the temperature of the gaseous fuel leaving the heat exchanger 50 may have a temperature higher than the temperature of the liquid fuel present in the tank.

[0045] By way of non-limiting example, the gaseous fuel, after having condensed, has a temperature approximately 5K (Kelvin) higher than the temperature of the liquid fuel present in the tank.

[0046] The flow of gaseous fuel which leaves the heat exchanger, which has been cooled and condensed, then circulates through an expansion valve 30 by which its pressure and temperature are lowered so that the pressure of the fuel at the outlet of the expansion valve 30 is equal to the pressure of the gaseous fuel in the tank 12. The expansion causes the evaporation of part of the liquid fuel which had condensed in the heat exchanger 50, but the temperature of the two-phase mixture is lowered.

[0047] The temperature and pressure of the fluid leaving the expansion valve 30 are substantially identical to the temperature and pressure of the liquid present in the reservoir. This fluid leaving the expansion valve 30 also contains a small proportion of gas, in particular less than 10%, whereas this fluid was 100% gaseous when it was extracted from the reservoir. This fluid is also potentially hotter than the temperature of the liquid present in the reservoir.

[0048] The pressures of gaseous fuel and liquid fuel circulating respectively in the gaseous fuel circuit flow 20 and in the liquid fuel circuit 14, are regulated to promote heat exchange, in particular to increase the subcooling of the liquid.

[0049] By way of non-limiting example, the liquid fuel pressure at the outlet of the pump 16 is at least equal to 10 bars and the gaseous fuel pressure at the outlet of the compressor 22 is between 4 and 8 bars.

[0050] [Fig. 2] shows another embodiment of the invention according to which the heat exchange member 24 consists of a mixing chamber 52.

[0051] The gaseous fuel introduced into the mixing chamber 52 is at a temperature higher than the temperature of the liquid fuel introduced into the mixing chamber 52.

[0052] By mixing with the liquid fuel in the mixing chamber 52, the gaseous fuel exchanges heat directly with the liquid fuel with which it is mixed.

[0053] The pump 16 and the compressor 22 are configured so that the flow rates and pressures of the gaseous fuel and the liquid fuel allow the condensation of all of the injected gaseous fuel, while avoiding the vaporization of the liquid fuel.

[0054] In addition, the pressure of the gaseous fuel injected into the mixing chamber 52 is preferably identical to the pressure of the liquid fuel.

[0055] According to a preferred, but non-limiting, embodiment, the pressure of the gaseous fuel and the pressure of the liquid fuel injected into the mixing chamber 52 are approximately 10 bars.

[0056] This pressure value, in the case of hydrogen as fuel, makes it possible to incorporate a quantity of gaseous fuel close to 20% of the liquid fuel flow rate.

[0057] Here again, by passing through the compressor 22 to reach the predefined pressure, the temperature of the gaseous fuel increases and becomes higher than the temperature of the liquid fuel at the outlet of the pump 16. By mixing with the liquid fuel, the gaseous fuel is then cooled and condenses.

[0058] Thus, at the outlet of the mixing chamber 52, all of the fuel is in liquid form, its temperature being higher than the temperature of the liquid fuel at the outlet of the pump 16 and lower than the temperature of the gaseous fuel at the outlet of the compressor 22.

[0059] Figures 3 and 4 show two non-limiting examples of embodiments of the mixing chamber 52.

[0060] According to the embodiment shown in [Fig. 3], the mixing chamber 52 comprises a tubular conduit 34 through which the liquid fuel circulates and a gas inlet tube 36 which extends partly into the tubular conduit 34.

[0061] The end 38 of the gas inlet tube 36 which extends into the tubular conduit 34 is open and comprises a plurality of orifices 40 which make it possible to mix the gaseous fuel as efficiently as possible with the liquid fuel in the form of fine bubbles 42, thus promoting heat transfer.

[0062] Such a mixing chamber 52 is known as a "gas sparger".

[0063] According to the embodiment shown in [Fig.4], the mixing chamber 52 comprises two coaxial inlets 44, 46, each associated with the liquid fuel or the gaseous fuel. A section reduction 48 is located downstream of the inlets 44, 46, to cause acceleration of the liquid fuel and promote the suction of gaseous fuel.

[0064] Such a mixing chamber 52 is known as a "jet ejector".

[0065] Whatever the embodiment of the heat exchange member 24, the compressor 22 is designed so as to maintain the pressure of gaseous fuel in the tank at a predefined pressure called the setpoint.

[0066] Therefore, it continuously draws gaseous fuel from the tank.

[0067] [Fig. 5] shows an alternative embodiment of the heat exchange member 24 comprising a mixing chamber 52 combined with a heat exchanger 50.

[0068] According to this variant, the gaseous fuel and the liquid fuel are first brought to the same pressure by means of the compressor 22 and the pump 16, they are then brought to a heat exchanger 50 to be brought to the same temperature.

[0069] The two fuel streams exiting the heat exchanger are then mixed in the mixing chamber 52.

[0070] By circulating in the heat exchanger 50, the gaseous fuel is cooled, it then condenses. At the outlet of the heat exchanger 50, the two fuel flows are in liquid form and at close temperatures.

[0071] The mixing of the two liquid fuel streams is then simplified compared to a mixing a gaseous fuel stream with a liquid fuel stream.

[0072] The regulation of the quantity of fuel in gaseous form present inside the tank 12 is thus carried out according to a method comprising: - a step of taking fuel in gaseous form from the tank 12, to circulate it in the gaseous fuel circuit 20 and - a step of condensation of at least part of the fuel in gaseous form taken.

[0073] This method notably comprises a step of compression of the gaseous fuel which is implemented before the condensation step.

[0074] As shown previously, according to the embodiments represented in figures 2 and following, the condensation step consists of a step of mixing the gaseous fuel in the flow of liquid fuel, via the mixing chamber 52.

[0075] More generally, the condensation step consists of a heat exchange step between the gaseous fuel and the liquid fuel.

[0076] The method also comprises a step of expanding the at least partially condensed fuel, which is implemented after the condensation step, at the outlet of the heat exchanger 50, via the expansion valve 30.

Claims

Claims

1. Storage assembly (10) for cryogenized fuel for an aircraft turbomachine comprising - a tank (12) in which fuel is present in liquid form and in gaseous form, the gaseous form resulting from the evaporation of the fuel in liquid form, - a liquid fuel circuit (14) connecting the tank (12) to components intended to be supplied with fuel in liquid form, the liquid fuel circuit (14) comprising a pump (16) for pressurizing the liquid fuel, - a gaseous fuel circuit (20) taking fuel in gaseous form from the tank (12), the storage assembly (10) comprising a heat exchange member (24) supplied by the liquid fuel circuit (14) and by the gaseous fuel circuit (20),wherein the fuel in liquid form from the liquid fuel circuit (14) and the fuel in gaseous form from the gaseous fuel circuit (20) are capable of exchanging heat to cause at least partial condensation of the gaseous fuel from the gaseous fuel circuit (20), wherein the gaseous fuel circuit (20) opens into the tank (12) and comprises a compressor (22) at the outlet of which the pressure of the gaseous fuel is equal to a predetermined pressure greater than the pressure of the liquid fuel at the outlet of the pressurization pump (16) and comprises an expansion valve (30) arranged downstream of the heat exchanger (50), at the outlet of which the pressure of the gaseous fuel is substantially equal to the pressure of the gaseous fuel in the tank (12).,

2. Storage assembly (10) according to claim 1, characterized in that the heat exchange member (24) comprises a mixing chamber (52) in which the flow of gaseous fuel is injected into the flow of liquid fuel.

3. Storage assembly (10) according to claim 1 or 2, characterized in that the gaseous fuel circuit (20) comprises a compressor (22) at the outlet of which the pressure of the gaseous fuel is equal to a predetermined pressure.

4. Storage assembly (10) according to claim 3, characterized in that that the pressure of the gaseous fuel at the outlet of the compressor (22) is equal to the pressure of the liquid fuel at the outlet of the liquid fuel pressurization pump (16).

5. Storage assembly (10) according to claim 2, characterized in that the heat exchange member (24) further comprises a heat exchanger (50) arranged upstream of the mixing chamber (52) and in which the flow of liquid fuel takes heat from the gaseous fuel.

6. Storage assembly (10) according to claim 1, characterized in that the heat exchange member (24) comprises a heat exchanger (50) in which the flow of liquid fuel takes heat from the gaseous fuel.

7. Aircraft comprising at least one turbomachine and a storage assembly (10) according to any one of the preceding claims, supplying said at least one turbomachine with liquid fuel.

8. Method for regulating the quantity of fuel in gaseous form present inside the tank (12) of a storage assembly (10) according to any one of the preceding claims, characterized in that it comprises: - a step of withdrawing fuel in gaseous form from the tank (12), to circulate it in a liquid fuel circuit (14), - a step of condensing at least a portion of the fuel in gaseous form withdrawn - a step of compressing the gaseous fuel which is implemented before the condensation step, in which the condensation step consists of a step of exchanging heat between the gaseous fuel and the liquid fuel, characterized in that it comprises a step of expanding the at least partially condensed fuel, which is implemented after the condensation step.

9. A method according to claim 8 in that the condensation step consists of a step of mixing the gaseous fuel into the liquid fuel stream.

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