Fuel-conditioning system for conditioning the fuel supplied to an aircraft turbine engine

Abstract

The present invention relates to a fuel conditioning system (SC) configured to supply an aircraft turbine engine (M) with fuel (Q) coming from a cryogenic tank (R), the conditioning system comprising: - a main fuel circuit (1) configured to be connected at its inlet to the cryogenic tank (R) and at its outlet to the turbine engine (M), a main fuel flow (Qp) circulating from upstream to downstream in the fuel circuit (1); - a pumping system (21) mounted on the fuel circuit (1); - a first heat exchanger (31) mounted downstream of the pumping system (21); - a secondary fuel circuit (2) connected at its inlet and at its outlet to the main fuel circuit (1), at the inlet via a directional-control valve (4) positioned between the pumping system (21) and the first heat exchanger (31) and at the outlet by a junction (6) positioned downstream of the first heat exchanger (31).

Description

[0001] DESCRIPTION

[0002] TITLE: Fuel conditioning system for powering an aircraft turbomachine

[0003] FIELD OF INVENTION

[0004] The invention relates to the field of aircraft comprising turbomachines powered by fuel stored in a cryogenic tank.

[0005] STATE OF THE ART

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

[0007] In order to be injected into the combustion chamber of a turbomachine, the fuel must be conditioned, that is, pressurized and heated, to allow for optimal combustion. Conditioning is necessary, for example, to reduce the risk of icing / solidification of the water vapor contained in the air circulating in the turbomachine, particularly at the turbomachine's fuel injectors.

[0008] With reference to Figure 1, a prior art SCAA conditioning system is shown, comprising a fuel circuit 100 connected at its inlet to a cryogenic tank R and at its outlet to the combustion chamber of a turbomachine M. As is known, the cryogenic tank R belongs to an aircraft frame of reference REF-A, while the turbomachine M belongs to a turbomachine frame of reference REF-M. A fuel flow Q circulating from upstream to downstream in the fuel circuit 100 passes successively through a pumping system 101 and a heating module 102.

[0009] The pumping system 101 is configured to circulate the fuel flow Q in the fuel circuit 100. The heating module 102 is configured to supply calories to the fuel flow Q in order to warm it so that it can be injected into the turbomachine M.

[0010] In practice, the fuel heating stage requires extracting heat from heat sources within the aircraft. For example, heat generated by the turbomachine can be used (heat from the lubricating oil, heat from the turbine outlet, heat from the nozzle, etc.). Heat from within the aircraft can also be used (air from the cabin, heat from electrical or electronic systems, etc.).

[0011] In this respect, we know for example from patent application FR2005628À1, an architecture, also represented in Figure 1, in which a heat transfer fluid F passes through a heat exchanger EX in which it extracts calories from the hot sources C available on board the aircraft and is then routed via a circulation loop BC to the heat module 102, to heat the fuel Q. This circulation loop BC of the heat transfer fluid F allows the thermal power supplied to the hydrogen to be regulated.

[0012] However, such an architecture requires the addition of a recirculation pump PR, which significantly increases the aircraft's mass. Furthermore, the architecture exhibits high thermal inertia, resulting in a lengthy fuel heating process. The temperature of the heat transfer fluid F in the circulation loop BC must also follow a predefined range. Specifically, the temperature T at the inlet of the turbomachinery reference frame REF-M must be above a predetermined minimum temperature Tmin to prevent any risk of the heat sources C freezing due to the heat transfer fluid F. Conversely, at the inlet of the aircraft reference frame REF-A, i.e., at the outlet of the turbomachinery reference frame REF-M, the temperature T must be below a predetermined maximum temperature Tmax to comply with the aircraft manufacturer's regulations and ensure the safe delivery of the heat transfer fluid F as close as possible to the tank R.Such a limitation of the temperature range leads to an increase in the flow rate of the heat transfer fluid in the circulation loop which leads to an increase in the circulation volume and therefore the use of bulkier and heavier piping, which is not desirable in an aeronautical context which aims to reduce the mass of aircraft.

[0013] The invention aims to eliminate at least some of these drawbacks by providing a fuel conditioning system that enables efficient and reliable fuel heating. In particular, the conditioning system aims to minimize the mass and size of the fluid circulation piping, while ensuring that the fuel remains within the narrow temperature range required for injection into the combustion chamber of a turbomachine.

[0014] DESCRIPTION OF THE INVENTION The invention has as its first object a fuel conditioning system configured to supply an aircraft turbomachine with fuel from a cryogenic tank, the conditioning system being defined in an aircraft frame of reference and a turbomachine frame of reference, the cryogenic tank extending in the aircraft frame of reference and the turbomachine extending in the turbomachine frame of reference, the conditioning system comprising: a main fuel circuit configured to be connected inlet to the cryogenic tank and outlet to the turbomachine, a main fuel flow circulating from upstream to downstream in the fuel circuit;

[0015] - a pumping system mounted on the fuel circuit, the pump being configured to raise the pressure of the main fuel flow in the fuel circuit to a first pressure, the main fluid then being at a first temperature; a first heat exchanger mounted downstream of the pumping system, the first heat exchanger being configured to heat the main fuel flow to a circulation temperature; and

[0016] - a secondary fuel circuit connected at the inlet and outlet to the main fuel circuit, at the inlet by a distribution valve positioned between the pumping system and the first heat exchanger and at the outlet by a junction positioned downstream of the first heat exchanger, a secondary fuel flow circulating from upstream to downstream in the secondary fuel circuit at a second temperature lower than the circulation temperature; in which, downstream of the junction, the main fuel flow is at a mixing temperature lower than or equal to the circulation temperature.

[0017] This conditioning system advantageously allows for the regulation of the primary fuel flow temperature using a portion of that same fuel flow. Specifically, the distribution valve allows a secondary portion of the primary fuel flow to circulate in the secondary circuit while a primary portion circulates in the primary circuit to be heated to the circulation temperature. The primary portion, heated by the first heat exchanger, is then mixed at the junction with the secondary portion, which has not been heated by the first heat exchanger and is therefore at a lower temperature. Depending on the proportion of secondary fuel flow relative to the primary fuel, it is possible to adjust the mixing temperature, ideally matching the injection temperature.It is therefore possible to regulate the mixing temperature with a simple conditioning system whose mass is limited and avoiding the bulk of fluid circulation pipes.

[0018] The conditioning system is defined in an aircraft datum (REF-A) and a turbomachine datum (REF-M). Preferably, the cryogenic tank extends in the aircraft datum (REF-A) and the turbomachine extends in the turbomachine datum (REF-M). Furthermore, the pumping system, the first heat exchanger, and the valve preferably extend in the aircraft datum (REF-A).

[0019] According to specific embodiments that can be used alone or in combination:

[0020] - the conditioning system further includes a control element for the distribution valve allowing the flow rate of secondary fuel in the secondary fuel circuit to be regulated by actuating the distribution valve;

[0021] - the conditioning system further includes a temperature sensor positioned downstream of the junction between the main fuel circuit and the secondary fuel circuit and allowing the mixing temperature (Tm) of the main fuel flow downstream of the junction to be measured, the control unit allowing the flow rate of secondary fuel in the secondary fuel circuit to be regulated according to the measured mixing temperature (Tm) by actuating the distribution valve;

[0022] - the control unit is configured to compare the mixture temperature (Tm) to a setpoint temperature (Te) and, if the mixture temperature is different from the setpoint temperature (Te), to regulate the flow of the secondary fuel so that the mixture temperature (Tm) is equal to the setpoint temperature (Te);

[0023] - the main fuel flow (Qp) circulating in the main circuit upstream of the distribution valve has a main flow rate (d), and in which the secondary fuel flow (Qs) circulating in the secondary circuit has a second flow rate (d2) between 0% and 100% of the main flow rate (d);

[0024] - the conditioning system further includes a preheating element positioned between the pumping system and the distribution valve, the preheating element allowing the main fuel flow (Qp) which is at a first temperature (T1) to be heated to an intermediate temperature (Ti);

[0025] - the conditioning system further includes a second heat exchanger mounted downstream of the first heat exchanger; and

[0026] - The second heat exchanger is mounted upstream of the junction. The invention also relates to an aircraft comprising a cryogenic tank, a turbomachine, and a conditioning system as previously described.

[0027] The invention has as its third object a method for supplying fuel to an aircraft turbomachine (M) from fuel (Q) from a cryogenic tank (R) by means of the conditioning system (SC) as previously described, a main fuel flow circulating from upstream to downstream in the main fuel circuit, the method comprising:

[0028] - a step E1 consisting of heating the main fuel stream (Qp) in the first heat exchanger to at least the circulation temperature (Te);

[0029] - a step E2 consisting of measuring the temperature of the main fuel flow (Qp) downstream of the junction;

[0030] - a step E3 consisting of comparing the temperature of the main fuel flow (Qp) to a setpoint temperature (Te); and if the measured temperature is equal to the setpoint temperature, keep the distribution valve closed, or if the measured temperature is greater than the setpoint temperature, act on the distribution valve so as to increase the flow rate of secondary fuel flow in the secondary circuit so that the mixture temperature is identical to the setpoint temperature.

[0031] This process allows for precise control of the mixture temperature, which is ideally the primary fuel injection temperature into the combustion chamber. In particular, it enables real-time regulation of the secondary fuel flow in the secondary circuit, thus rapidly adapting the mixture temperature to the setpoint, preferably corresponding to the desired injection temperature.

[0032] In particular, as is known, aircraft A is configured to operate through a plurality of flight phases, for example, a takeoff phase, a cruise phase, a landing phase, and a taxi phase. Depending on the flight phase in which aircraft A is operating, the primary heat exchanger may not supply the same amount of heat to the primary fuel stream, and the intermediate temperature may therefore vary depending on the operating phase. It is then possible to adjust the secondary fuel flow rate in the secondary circuit to accommodate these variations. Furthermore, depending on the phase in which the aircraft is operating, the primary fuel flow rate injected into the combustion chamber may be higher or lower. It may then be necessary to adjust the secondary fuel flow rate in the secondary circuit.

[0033] DESCRIPTION OF THE FIGURES

[0034] Other features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the accompanying drawings, in which:

[0035] - [Fig. 1] represents a schematic view of a fuel conditioning system according to the prior art;

[0036] - [Fig. 2] represents a schematic view of a fuel conditioning system according to a first embodiment of the invention;

[0037] - [Fig. 3] represents a schematic view of a fuel conditioning system according to a second embodiment of the invention; and

[0038] - [Fig. 4] represents a schematic view of a method for supplying fuel to a turbomachine according to an embodiment of the invention.

[0039] DETAILED DESCRIPTION OF THE INVENTION

[0040] For the sake of clarity, only the essential elements for understanding the invention have been represented schematically, and this without regard to scale.

[0041] With reference to Figure 2, a fuel conditioning system SC is shown configured to supply an aircraft turbomachine M with fuel Q from a cryogenic tank R. The turbomachine M is configured to provide propulsion for the aircraft, in particular by driving at least one propulsion unit (not shown in Figure 2). In this example, the fuel Q is liquid hydrogen, but the invention applies to other types of fuel, for example, liquid methane or liquefied natural gas.

[0042] In this example, the fuel Q in the cryogenic tank R is stored at a temperature of approximately -253 to -251 °C (20 to 22 Kelvins). At this temperature, the fuel Q flow is liquid.

[0043] The conditioning system SC is defined in an aircraft frame of reference REF-A and in a turbomachine frame of reference REF-M. The cryogenic tank R extends in the aircraft frame of reference REF-A, while the turbomachine M extends in the turbomachine frame of reference REF-M. With reference to Figure 2, the conditioning system SC according to the invention comprises a fuel circuit 1 connected at its inlet to the cryogenic tank R and at its outlet to the turbomachine M. A fuel flow Q circulates from upstream to downstream in the fuel circuit 1. Hereafter, the terms "upstream" and "downstream" are defined with respect to the direction of flow of the fuel flow Q from upstream to downstream.

[0044] According to the invention, the conditioning system SC comprises a first pumping system 21, preferably high pressure. The first pumping system 21 is preferably mounted in the aircraft reference frame REF-A, that is to say as close as possible to the cryogenic tank R.

[0045] The first pumping system 21 is configured to raise the pressure of the fuel stream Q from the cryogenic tank R in the main fuel circuit 1 to a first pressure P1, thereby raising the temperature of the fuel stream Q to a first temperature T1. Preferably, since the fuel stream Q has a saturation temperature Ts at the first pressure P1, the first temperature T1 is lower than the saturation temperature Ts at the first pressure P1. In this example, where the fuel Q is liquid hydrogen, the saturation temperature Ts is between -253 °C (20 K) and -250 °C (23 K).

[0046] The first pumping system 21 thus heats the fuel flow Q, which, at the first pressure P1, ensures that the fuel flow Q is not in liquid saturation, as is the case at the outlet of the cryogenic tank R. For example, at the outlet of the first pumping system 21, the fuel flow Q is at a temperature of -251°C (22.6 K) at a pressure of 5 bar. At such a pressure, the saturation temperature Ts of hydrogen is -246°C (27 K). Thus, the first pumping system 21 ensures that the fuel Q is in a liquid state at the outlet of the first pumping system 21.

[0047] With further reference to Figure 2, the SC conditioning system includes a first heat exchanger 31, mounted in the main fuel circuit 1, configured to transfer calories to the fuel flow Q in order to warm it up to allow its optimal injection into the turbomachine M.

[0048] The first heat exchanger can, for example, utilize heat generated by the turbomachine, such as heat from the lubricating oil, turbine outlet heat, nozzle heat, or other sources. Heat from the aircraft itself can also be used, such as cabin air, heat from electrical or electronic systems, or other sources. The first heat exchanger can also be an electric heating system. Alternatively, the first heat exchanger can be a fuel / fuel or fuel / heat transfer fluid type exchanger if it is part of a loop circulating a flow of hot fuel or hot heat transfer fluid.

[0049] Preferably, the first heat exchanger 31 is mounted, in the fuel circuit 1, in the aircraft reference frame REF-A, i.e. close to the cryogenic tank R, downstream of the first pumping system 21. The first heat exchanger 31 includes a fuel inlet 31 E, shown in Figure 2.

[0050] The first heat exchanger 31 is configured to heat the fuel stream Q to a circulation temperature Te, which is higher than the initial temperature T1 and the vaporization temperature of the fuel Q. In this example, for hydrogen, the circulation temperature Te is above -208°C (65K), preferably between -173 and -123°C (100 and 150K). Thus, the fuel stream Q at the outlet (i.e., downstream).

[0051] The conditioning system further includes a secondary fuel circuit 2 which is connected at the inlet and outlet to the main fuel circuit 1. At the inlet, the secondary fuel circuit 2 is connected to the main fuel circuit by means of a distribution valve 4 positioned downstream of the pumping system 21. The distribution valve 4 is configured to split the main fuel circuit 1 to add the secondary fuel circuit 2. A secondary fuel flow Qs, which is a portion of the main fuel flow Qp, then circulates in the secondary fuel circuit 2.

[0052] At the outlet, the secondary fuel circuit 2 is connected to the main fuel circuit by a junction 6 positioned downstream of the first heat exchanger 31. At the junction 6, the secondary fuel flow thus joins the main fuel flow and mixes with the latter.

[0053] Preferably, the secondary fuel circuit 2 does not have a heat exchanger, and the secondary fuel flow Qs remains at the initial temperature T1. When the secondary fuel flow Qs mixes with the primary fuel flow Qp at junction 6, the secondary fuel flow Qs is therefore at temperature T1, and the primary fuel flow Qp is at temperature Te. The temperature of the primary fuel flow Qp downstream of junction 6 is thus a mixing temperature Tm that is greater than T1 and less than or equal to Te.

[0054] According to a possible embodiment not shown, the secondary fuel circuit 2 may include a secondary heat exchanger capable of heating the secondary fuel flow Qs. In this embodiment, the secondary flow Qs is heated to a temperature higher than the first temperature T1 but lower than the circulation temperature Te. Thus, during mixing between the secondary fuel flow Qs and the main fuel flow Qp at junction 6, the secondary fuel flow Qs cools the main fuel flow Qp in proportions that depend on the ratio of secondary fuel flow Qs to main fuel flow Qp.

[0055] The SC conditioning system according to this embodiment of the invention thus makes it possible to regulate the circulating temperature of the main fuel flow Qp using a portion of that same fuel flow. In particular, the distribution valve 4 allows a secondary portion of the main fuel flow Qp to circulate in the secondary circuit 2, while a main portion circulates in the main circuit 1 to be heated to the circulation temperature. The main portion, which has been heated by the first heat exchanger 31, is then mixed at junction 6 with the secondary portion, which has not been heated by the first heat exchanger 31 and is therefore at a lower temperature. Depending on the proportion of secondary fuel flow Qs relative to the main fuel Qp, it is possible to adjust the mixing temperature, which preferably corresponds to the injection temperature Ti in the combustion chamber.

[0056] It is therefore possible to regulate the mixing temperature with a simple conditioning system whose mass is limited and avoiding the bulk of fluid circulation pipes.

[0057] In this embodiment, the conditioning system SC further includes a control element 41 for the distribution valve 4, which regulates the flow rate of the secondary fuel Qs in the secondary fuel circuit 2 by actuating the distribution valve 4. The control element 41 can thus keep the valve closed or open it more or less to cool the main fuel flow Qp to the desired degree. Preferably, the conditioning system SC includes a temperature sensor 8 positioned downstream of the junction 6 between the main fuel circuit 1 and the secondary fuel circuit 2, which measures the mixture temperature (Tm) of the main fuel flow Qp downstream of the junction 6.The control unit 41 then allows the secondary fuel flow rate Qs in the secondary fuel circuit 2 to be regulated according to the measured mixture temperature (Tm) by actuating the distribution valve 4.

[0058] In particular, the control unit 41 is configured to compare the mixture temperature Tm to a setpoint temperature Tv, the setpoint temperature Tv preferably being the injection temperature Ti in the combustion chamber. If the mixture temperature Tm differs from the setpoint temperature Tv, the control unit 41 regulates the flow rate of the secondary fuel flow Qs circulating in the secondary fuel circuit 2 so that the mixture temperature Tm equals the setpoint temperature Tv. Specifically, the higher the mixture temperature Tm is relative to the setpoint temperature Tv, the more the control unit 4 opens the distribution valve 4 in order to increase the proportion of secondary flow Qs and lower the mixture temperature Tm.Conversely, if the mixing temperature is close to or the same as the setpoint temperature Tv, the control unit 41 can reduce the opening of the distribution valve 4 or even close it.

[0059] The control unit 41 thus allows the secondary fuel flow Qs circulating in the secondary fuel circuit 2 to be regulated in real time and according to the operating phase of the turbomachine, by controlling the opening of the distribution valve 4, and therefore the proportion of secondary fuel flow Qs relative to the main fuel flow Qp.

[0060] In particular, the main fuel flow Qp circulating in the main circuit 1 between the distribution valve 4 and the junction 6 has a first flow rate d1, and the secondary fuel flow Qs circulating in the secondary circuit 2 has a second flow rate d2. The second flow rate (d2) can be between 0% and 100% of the main flow rate (d) which corresponds to the flow rate of the fuel circulating upstream of the distribution valve 4. Notably, a secondary portion p2 of the main flow Qp, which represents 0% to 100% of the main fuel flow Qp upstream of the distribution valve 4, circulates in the secondary fuel circuit 2 and a main portion p1 of the main flow Qp, which therefore represents 100% to 0% of the main fuel flow Qp upstream of the distribution valve 4, circulates in the main circuit between the distribution valve 4 and the junction 6.Downstream of junction 6, the secondary portion p2 at the first temperature T1 and the main portion p1 at the circulation temperature Te were joined to reform the main flow Qp at the mixing temperature Tm.

[0061] The control unit 41 thus allows the mixing temperature Tm to be adjusted relative to the setpoint temperature Tv by regulating the opening of the distribution valve and therefore the proportion of the secondary portion p2 relative to the main portion p1.

[0062] According to an alternative embodiment shown in Figure 3, the conditioning system further comprises a preheating element 51 positioned between the pumping system 21 and the distribution valve 4. This preheating element heats the main fuel flow Qp, which is at a first temperature T1, to an intermediate temperature Ti. This preheating element thus increases the temperature of the main fuel flow Qp before it enters the first heat exchanger 31, thereby preventing any risk of icing in the first exchanger.

[0063] The preheating element 51, which extends within the engine reference frame REF-M, can, for example, utilize heat generated by the turbomachine, such as heat from the lubricating oil, turbine outlet heat, nozzle heat, or other sources. Heat from the aircraft can also be used, such as cabin air, heat from electrical or electronic systems, or other sources. The first heat exchanger can also be an electric heating system. Alternatively, the first heat exchanger can be a fuel / fuel or fuel / heat transfer fluid type exchanger if it is part of a loop circulating a flow of hot fuel or hot heat transfer fluid.

[0064] According to the embodiment shown in Figure 3, the SC conditioning system according to the invention also includes a second heat exchanger 32, mounted downstream of the first heat exchanger 31, in the engine reference frame REF-M. This second heat exchanger 32 makes it possible to increase the temperature of the main fuel flow Qp, which is at a circulation temperature Tel after passing through the first heat exchanger 31, to a temperature Tc2.

[0065] Preferably, the second heat exchanger 32 is mounted upstream of junction 6. This prevents it from increasing the temperature of the main fuel stream after it has been mixed with the secondary fuel stream Qs. According to this embodiment, one of the first and second heat exchangers 31 or 32 can utilize heat generated by the turbomachine, such as heat from the lubricating oil, turbine outlet heat, nozzle heat, or other sources, or heat from the aircraft, such as cabin air, heat from electrical or electronic systems, or other sources. In this case, the other of the first and second heat exchangers 31 or 32 can be an electric heating system, a thermal storage system, a fuel cell, a gas turbine, or a burner.Thus, if one of the first and second heat exchangers 31 or 32 is insufficient to reach the desired circulation temperature Te, for example because of the flight phase not allowing heat to be generated by the turbomachine or the aircraft, the other of the first and second heat exchangers 31 or 32 can replace or supplement it with a heating mode independent of the operation of the aircraft.

[0066] In this embodiment shown in Figure 3, the conditioning system differs from the embodiment of Figure 2 in that it includes a preheating element 51 and a second heat exchanger 32. However, according to other possible embodiments, the conditioning system may include only one or the other of the preheating element 51 and the second heat exchanger 32.

[0067] Furthermore, the fuel circuit 1 may include interface conduits not shown allowing passage from one reference frame to another.

[0068] A method for supplying fuel to a turbomachine M will now be presented according to an embodiment of the invention, with reference to Figure 2 and Figure 4. In this example, the method comprises the following steps: a step E1 consisting of heating the main fuel flow Qp in the first heat exchanger 31 to at least the circulation temperature Te;

[0069] - a step E2 consisting of measuring the temperature of the main fuel flow Qp downstream of the junction, which corresponds to the mixture temperature Tm;

[0070] - a step E3 consisting of comparing the temperature of the main fuel flow Qp to a setpoint temperature Tv; and

[0071] - a step E4 according to which if the measured temperature is equal to the setpoint temperature Tv, keep the distribution valve 4 closed, or if the measured temperature is greater than the setpoint temperature Tv, act on the distribution valve 4 so as to increase the secondary fuel flow rate Qs in the secondary circuit 2 so that the mixture temperature Tm is identical to the setpoint temperature Tv.

[0072] According to a first embodiment, this process can be implemented while the distribution valve 4 is closed. The temperature of the main fuel flow Qp then corresponds to the circulation temperature Te. At step E4, the control device 41 decides whether to open the distribution valve 4 or leave it closed.

[0073] According to a second embodiment, this process can be implemented while the distribution valve 4 is open, allowing a portion of secondary flow p2, between 1% and 30% inclusive of the main fuel flow Qp, to pass into the secondary fuel circuit 2. The temperature of the main fuel flow Qp then corresponds to the mixture temperature Tm. At step E4, the control device 41 decides whether to increase the opening of the distribution valve 4, decrease the opening of the distribution valve 4, or close the distribution valve 4.

[0074] This process allows for simple and instantaneous regulation of the temperature of the fuel flow circulating in the main circuit 1 and therefore a fine and precise adjustment of the temperature at which the main fuel Qp is injected into the combustion chamber of the turbomachine.

[0075] According to this process, the first pumping system 21 allows the fuel flow Q to be entirely in a liquid state. In this implementation example, the fuel Q is dihydrogen and is stored in liquid form in the cryogenic tank R. The fuel Q is initially at a temperature between -248 and -243 °C (between 25 K and 30 K), preferably -248 °C (25 K).

[0076] During step E1, the first heat exchanger 31 increases the temperature of the main fuel stream Qp to at least the circulation temperature Te, which in this example is between -23°C (250 K) and 40°C (313 K), preferably between 2°C (275 K) and 40°C (313 K). Such heating can be carried out in the aircraft frame of reference REF-A, as close as possible to the cryogenic tank R, or in the engine frame of reference REF-M when the nozzle air is used for heating the fuel stream.

[0077] During steps E2 and E3, the temperature Te, or Tm if the distribution valve is open, is measured and compared to the setpoint temperature Tv. The setpoint temperature Tv is preferably the injection temperature and should, for example, be between -23°C (250K) and 27°C (300K), preferably between 2°C (275K) and 40°C (313K).

[0078] According to the first embodiment, this process can be implemented while the distribution valve 4 is closed. If the circulation temperature Te of the main fuel flow Qp is between -23 °C (250 K) and 27 °C (300 K), the distribution valve remains closed. Conversely, if the circulation temperature Te of the main fuel flow Qp is above 27 °C (300 K), the distribution valve 4 is opened so that the portion of the secondary flow Qs circulating in the secondary fuel circuit 2 allows the mixture temperature Tm to be between -23 °C (250 K) and 27 °C (300 K).

[0079] According to the second embodiment, this process can be implemented while the distribution valve 4 is open, allowing a portion of secondary flow p2 between 1% and 30% inclusive of the main fuel flow Qp to pass into the secondary fuel circuit 2. The temperature of the main fuel flow Qp then corresponds to the mixing temperature Tm. In the first case, where the mixing temperature Tm of the main fuel flow Qp is between -23 °C (250 K) and 27 °C (300 K), the distribution valve remains open. In the second case, where the mixing temperature Tm of the main fuel flow Qp is greater than 27 °C (300 K), the opening of the distribution valve 4 is increased so that the portion of secondary flow Qs circulating in the secondary fuel circuit 2 allows the mixing temperature Tm to be between -23 °C (250 K) and 27 °C (300 K).In a third case where the mixing temperature Tm of the main fuel flow Qp is less than -23°C (250K), the opening of the distribution valve 4 is reduced, or even closed, so that the portion of secondary flow Qs circulating in the secondary fuel circuit 2 allows the mixing temperature Tm to be between -23°C (250K) and 27°C (300K).

[0080] The feeding process thus makes it possible to cool, if necessary, the main fuel flow by means of a portion of the main fuel flow introduced into the secondary circuit 2 before the main flow has been heated by the first heat exchanger.

Claims

DEMANDS 1. Fuel conditioning system (SC) configured to supply an aircraft turbomachine (M) with fuel (Q) from a cryogenic tank (R), the conditioning system (SC) being defined in an aircraft frame of reference (REF-A) and a turbomachine frame of reference (REF-M), the cryogenic tank (R) extending in the aircraft frame of reference (REF-A) and the turbomachine (M) extending in the turbomachine frame of reference (REF-M), the conditioning system comprising: a main fuel circuit (1) configured to be connected inlet to the cryogenic tank (R) and outlet to the turbomachine (M), a main fuel flow (Qp) circulating upstream to downstream in the fuel circuit (1); - a pumping system (21) mounted on the fuel circuit (1), the pump (21) being configured to raise the pressure of the main fuel flow (Qp) in the fuel circuit (1) to a first pressure (P1), the main fluid then being at a first temperature (T1); - a first heat exchanger (31) mounted downstream of the pumping system (21), the first heat exchanger (31) being configured to heat the main fuel flow (Qp) to a circulation temperature (Te); - a secondary fuel circuit (2) connected at the inlet and outlet to the main fuel circuit (1), at the inlet by a distribution valve (4) positioned between the pumping system (21) and the first heat exchanger (31) and at the outlet by a junction (6) positioned downstream of the first heat exchanger (31), a secondary fuel flow (Qs) circulating from upstream to downstream in the secondary fuel circuit (2) at a second temperature (T2) lower than the circulation temperature (Te); and - a control element (41) of the distribution valve (4) allowing the secondary fuel flow rate in the secondary fuel circuit (2) to be regulated by actuating the distribution valve (4); in which, downstream of the junction, the main fuel flow (Qp) is at a mixture temperature (Tm) less than or equal to the circulation temperature (Te), the conditioning system further comprising a temperature sensor (8) positioned downstream of the junction (6) between the main fuel circuit (1) and the secondary fuel circuit (2) and allowing the mixture temperature (Tm) of the main fuel flow downstream of the junction to be measured, the control element (41) allowing the secondary fuel flow rate in the secondary fuel circuit (2) to be regulated according to the measured mixture temperature (Tm) by actuating the distribution valve (4).

2. Conditioning system (SC) in which the secondary fuel circuit (2) is devoid of a heat exchanger so that the second temperature of the secondary fuel flow (Qs) is equal to the first temperature (T1).

3. Conditioning system (SC) according to any one of claims 1 and 2, wherein the control element (41) is configured to compare the mixing temperature (Tm) to a setpoint temperature (Tv) and, if the mixing temperature is different from the setpoint temperature (Tv), to regulate the flow of secondary fuel so that the mixing temperature (Tm) is equal to the setpoint temperature (Tv).

4. Conditioning system (CS) according to any one of claims 1 to 3, wherein the main fuel flow in the main circuit (1) upstream of the distribution valve has a main flow rate (d), and wherein the secondary fuel flow (Qs) in the secondary circuit (2) has a second flow rate (d2) between 0% and 100% of the main flow rate (d), preferably between 10% and 50%.

5. Conditioning system (SC) according to any one of claims 1 to 4, further comprising a preheating element (51) positioned between the pumping system (21) and the distribution valve (4), the preheating element (51) allowing the main fuel flow (Qp) which is at a first temperature (T1) to be heated to an intermediate temperature (Ti).

6. Conditioning system (CS) according to any one of claims 1 to 5, further comprising a second heat exchanger (32) mounted downstream of the first heat exchanger (31).

7. Conditioning system (CS) according to claim 6, wherein the second heat exchanger (32) is mounted upstream of the junction (6).

8. Conditioning system (CS) according to claim 7, wherein one of the first and second heat exchangers (31, 32) is in fluidic communication with the turbomachine or aircraft, the other of the first and second heat exchangers (31, 32) comprising an electric heating system, a thermal storage system, a fuel cell, a gas turbine or a burner.

9. Conditioning system (SC) according to any one of claims 1 to 8, further comprising a secondary heat exchanger mounted on the secondary circuit (2) and configured to heat the secondary fuel flow (Qs).

10. Aircraft comprising a cryogenic tank, a turbomachine and a conditioning system according to any one of claims 1 to 9.

11. A method for supplying fuel to an aircraft turbomachine (M) from fuel (Q) from a cryogenic tank (R) by means of a conditioning system (SC) according to any one of claims 1 to 9, a main fuel flow circulating from upstream to downstream in the main fuel circuit, the method comprising: - a step E1 consisting of heating the main fuel stream (Qp) in the first heat exchanger (31) to at least the circulation temperature (Te); - a step E2 consisting of measuring the temperature of the main fuel flow (Qp) downstream of the junction (6); - a step E3 consisting of comparing the temperature of the main fuel flow (Qp) to a setpoint temperature (Tv); and - a step E4 according to which if the measured temperature is equal to the setpoint temperature, keep the distribution valve closed, or if the measured temperature is greater than the setpoint temperature, act on the distribution valve so as to increase the flow rate of secondary fuel in the secondary circuit so that the mixture temperature is identical to the setpoint temperature.

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