Fuel conditioning system for powering an aircraft turbomachine

Abstract

The present invention relates to a fuel conditioning system (SC) configured to supply an aircraft turbomachine (M) with fuel (Q) from a cryogenic tank (R), 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 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 inlet and outlet to the main fuel circuit (1), inlet by a distribution valve (4) positioned between the pumping system (21) and the first heat exchanger (31) and outlet by a junction (6) positioned downstream of the first heat exchanger (31).

Description

Title of the invention: Fuel conditioning system for powering an aircraft turbomachine. FIELD OF THE INVENTION

[0001] The invention relates to the field of aircraft comprising turbomachines powered by fuel stored in a cryogenic tank. STATE OF THE ART

[0002] It is known to store fuel, particularly hydrogen, in liquid form to limit the size and mass of aircraft tanks. For example, fuel is stored at a temperature of approximately -253 to -251°C (20 to 22 Kelvins) in a cryogenic tank on the aircraft.

[0003] In order to be injected into the combustion chamber of a turbomachine, the fuel must be conditioned, that is to say, 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, in particular, at the turbomachine's fuel injectors.

[0004] With reference to [Fig. 1], a prior art SC AA 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.

[0005] 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.

[0006] 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 the aircraft can also be used (air from the cabin, heat from electrical or electronic systems, etc.).

[0007] In this respect, we know, for example, from patent application FR2005628A1, of an architecture, also represented in [Fig.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 makes it possible to regulate the thermal power supplied to the hydrogen.

[0008] 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 hot sources C freezing due to the heat transfer fluid F. On the other hand, 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 in turn leads to an increase in the circulation volume and therefore the use of bulkier and heavier piping, which is undesirable in an aeronautical context that aims to reduce the mass of aircraft.

[0009] The invention thus aims to eliminate at least some of these drawbacks by providing a fuel conditioning system that allows for efficient and reliable fuel heating. The conditioning system is specifically designed to limit the mass and size of the fluid circulation piping, while ensuring that the fuel is within the narrow temperature range required for injection into the combustion chamber of a turbomachine. Description of the invention

[0010] The invention relates first to a fuel conditioning system configured to supply an aircraft turbomachine with fuel from a cryogenic tank, the conditioning system (CS) 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 configured to be connected inlet to the cryogenic tank and outlet to the turbomachine, with a main fuel flow circulating from upstream to downstream in the fuel circuit; - 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 - 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 (T2) lower than the circulation temperature (Te); in which, downstream of the junction, the main fuel flow is at a mixing temperature less than or equal to the circulation temperature.

[0011] This conditioning system advantageously allows the circulation temperature of the main fuel flow to be regulated using a portion of that same fuel flow. In particular, the distribution valve allows a secondary portion of the main fuel flow to circulate in the secondary circuit while a main portion circulates in the main circuit to be heated to the circulation temperature. The main portion, which has been 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 main fuel flow, it is possible to adjust the mixing temperature, which preferably corresponds to the injection temperature.

[0012] It is thus possible to regulate the mixing temperature with a simple conditioning system whose mass is limited and avoiding the congestion of fluid circulation pipes.

[0013] The conditioning system is defined in an aircraft reference frame (REF-A) and a turbomachine reference frame (REF-M). Preferably, the cryogenic tank extends in the aircraft reference frame (REF-A) and the turbomachine extends in the turbomachine reference frame (REF-M). Furthermore, the pumping system, the first heat exchanger, and the valve preferably extend in the aircraft reference frame (REF-A).

[0014] According to particular embodiments which may be taken alone or in combination: - 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; - 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; - 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 secondary fuel so that the mixture temperature (Tm) is equal to the setpoint temperature (Te); - 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); - 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 (Tl) to be heated to an intermediate temperature (Ti); - the conditioning system further includes a second heat exchanger mounted downstream of the first heat exchanger; and - the second heat exchanger is mounted upstream of the junction. The invention relates, as a second object, to an aircraft comprising a cryogenic tank, a turbomachine, and a conditioning system as previously described.

[0015] The invention relates, as a third object, to a method of 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: - a step El consisting of heating the main fuel stream (Qp) in the first heat exchanger 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; - 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 higher than the setpoint temperature, act on the distribution valve to increase the secondary fuel flow rate in the secondary circuit so that the mixture temperature is identical to the setpoint temperature.

[0016] This method allows for precise control of the mixture temperature, which is preferably the injection temperature of the primary fuel into the combustion chamber. In particular, it is possible to regulate the secondary fuel flow in the secondary circuit in real time and thus rapidly adapt the mixture temperature to the setpoint temperature, preferably corresponding to the desired injection temperature.

[0017] 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 first heat exchanger may not supply the same amount of heat to the main fuel flow, and the intermediate temperature may therefore vary depending on the operating phase of the aircraft. It is then possible to adjust the secondary fuel flow rate circulating in the secondary circuit to adapt to these variations. Furthermore, depending on the phase in which the aircraft is operating, the main fuel flow rate to be injected into the combustion chamber may be higher or lower. It may then be necessary to adjust the secondary fuel flow rate circulating in the secondary circuit. DESCRIPTION OF THE FIGURES

[0018] 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: - [Fig.l] represents a schematic view of a fuel conditioning system according to the prior art; - [Fig. 2] represents a schematic view of a fuel conditioning system according to a first embodiment of the invention; - [Fig. 3] represents a schematic view of a fuel conditioning system according to a second embodiment of the invention; and - [Fig.4] represents a schematic view of a method for supplying fuel to a turbomachine according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] For reasons of clarity, only the essential elements for understanding the invention have been represented schematically, and this without regard to scale.

[0020] With reference to [Fig. 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 [Fig. 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.

[0021] 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.

[0022] The SC conditioning system is defined in an aircraft reference frame REF-A and in a turbomachine reference frame REF-M. The cryogenic tank R extends in the aircraft reference frame REF-A while the turbomachine M extends in the turbomachine reference frame REF-M.

[0023] With reference to [Fig.2], the conditioning system SC according to the invention comprises a fuel circuit 1 connected at the inlet to the cryogenic tank R and at the 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.

[0024] 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.

[0025] The first pumping system 21 is configured to raise the pressure of the fuel flow Q from the cryogenic tank R in the main fuel circuit 1 to a first pressure PI allowing a temperature rise of the fuel flow Q to a first temperature TL. Preferably, the fuel flow Q having a saturation temperature Ts at the first pressure PI, the first temperature Tl is lower than the saturation temperature Ts at the first pressure PL. In this example where the fuel Q is liquid hydrogen, the saturation temperature Ts is between -253°C (20K) and -250°C (23K).

[0026] The first pumping system 21 thus allows the fuel flow Q to be heated, which ensures, at the first pressure PI, 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.

[0027] Still with reference to [Fig.2], the conditioning system SC 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.

[0028] The first heat exchanger can, for example, use heat generated by the turbomachine, such as heat from the lubricating oil, heat from the turbine outlet, heat from the nozzle, 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. The first heat exchanger can also 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.

[0029] 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 31E, shown in [Fig.2].

[0030] The first heat exchanger 31 is configured to heat the fuel flow Q to a circulation temperature Te, which is higher than the first temperature Tl and the vaporization temperature of the fuel Q. In this example, for hydrogen, the circulation temperature Te is higher than -208°C (65K), preferably between -173 and -123°C (100 and 150K). Thus, the fuel flow Q at the outlet (i.e., downstream).

[0031] 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.

[0032] 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.

[0033] Preferably, the secondary fuel circuit 2 does not include a heat exchanger, and the secondary fuel flow Qs remains at the initial temperature Tl. 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 Tl, 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 Tl and less than or equal to Te.

[0034] 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 Tl 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.

[0035] 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 from 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 the 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 primary fuel Qp, it is possible to adjust the mixture temperature which preferably corresponds to the injection temperature Ti in the combustion chamber.

[0036] It is thus possible to regulate the mixing temperature with a simple conditioning system whose mass is limited and avoiding the congestion of fluid circulation pipes.

[0037] In this embodiment, the conditioning system SC further includes a control element 41 of the distribution valve 4 allowing the secondary fuel flow rate Qs to be regulated in the secondary fuel circuit 2 by actuating the distribution valve 4. The control element 41 can thus leave the valve closed or open it more or less so as to cool the main fuel flow Qp in the desired proportions.

[0038] 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 and allowing the mixing temperature (Tm) of the main fuel flow Qp downstream of the junction 6 to be measured. The control element 41 then allows the secondary fuel flow rate Qs to be regulated in the secondary fuel circuit 2 according to the measured mixing temperature (Tm) by actuating the distribution valve 4.

[0039] In particular, the control element 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 element 41 regulates the flow rate of the secondary fuel flow Qs circulating in the secondary fuel circuit 2 so that the mixture temperature Tm is equal to the setpoint temperature Tv. Specifically, the higher the mixture temperature Tm is relative to the setpoint temperature Tv, the more the control element 41 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.

[0040] The control unit 41 thus makes it possible to regulate the secondary fuel flow Qs circulating in the secondary fuel circuit 2 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.

[0041] 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. In particular, 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 pl 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 the junction 6, the secondary portion p2 at the first temperature Tl and the main portion pl at the circulation temperature Te have been joined to reform the main flow Qp at the mixing temperature Tm.

[0042] 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 pl.

[0043] According to an alternative embodiment shown in [Fig. 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.

[0044] The preheating element 51, which extends in the aircraft reference frame REF-A, can, for example, utilize heat generated by the turbomachine, such as heat from the lubricating oil, heat from the turbine outlet, heat from the nozzle, 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. The first heat exchanger can also be a fuel / fuel or fuel / heat transfer fluid type exchanger if the first exchanger is part of a loop circulating a flow of hot fuel or hot heat transfer fluid.

[0045] According to the embodiment shown in [Fig. 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 aircraft frame of reference 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.

[0046] Preferably, the second heat exchanger 32 is mounted upstream of the junction 6. Thus, it does not serve to increase the temperature of the main fuel stream once it has been mixed with the secondary fuel stream Qs.

[0047] 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, heat from the turbine outlet, heat from the nozzle, 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 the flight phase does not allow 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 aircraft operation.

[0048] In this embodiment shown in [Fig.3], the conditioning system differs from the embodiment of [Fig.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.

[0049] Furthermore, the fuel circuit 1 may include interface conduits not shown allowing passage from one reference frame to another.

[0050] A method for supplying fuel to a turbomachine M according to an embodiment of the invention will now be presented, with reference to [Fig.2] and [Fig.4]. In this example, the method comprises the following steps - a step El consisting of heating the main fuel flow 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, which corresponds to the mixture temperature Tm; - 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 Tv, keep the distribution valve 4 closed, or If the measured temperature is higher than the setpoint temperature Tv, adjust distribution valve 4 to increase the secondary fuel flow rate Qs in the secondary circuit 2 so that the mixing temperature Tm is identical to the setpoint temperature Tv.

[0051] 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 element 41 decides whether to open the distribution valve 4 or leave it closed.

[0052] 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.

[0053] This process thus allows a 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.

[0054] According to this method, the first pumping system 21 allows the fuel flow Q to be entirely in a liquid state. In this embodiment, the fuel Q is dihydrogen and is stored in a liquid state 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).

[0055] During step El, 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.

[0056] 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).

[0057] According to the first embodiment, this method can be implemented while the distribution valve 4 is closed. In the case where the circulation temperature Te of the main fuel flow Qp is between -23°C (250K) and 27°C (300K), the The distribution valve is kept closed. On the other hand, in the case where the circulation temperature Te of the main fuel flow Qp is greater than 27 °C (300K), the distribution valve 4 is opened so that the portion of secondary flow Qs circulating in the secondary fuel circuit 2 allows the mixture temperature Tm to be between -23°C (250K) and 27°C (300K).

[0058] According to the second embodiment, this method 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 a first case where the mixing temperature Tm of the main fuel flow Qp is between -23°C (250K) and 27°C (300K), the distribution valve is maintained in the same open state. In a second case where the mixing temperature Tm of the main fuel flow Qp is greater than 27°C (300K), 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 (250K) and 27°C (300K).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).

[0059] 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 (PI), the main fluid then being at a first temperature (Tl); - 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); in which, downstream of the junction, the main fuel flow (Qp) is at a mixing temperature (Tm) lower than or equal to the circulation temperature (Te).;

2. Conditioning system (CS) according to claim 1, further comprising a control element (41) for the distribution valve (4) for regulating the fuel flow rate secondary in the secondary fuel circuit (2) by operating the distribution valve (4).

3. Conditioning system (CS) according to claim 1 or 2, 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 enabling the measurement of the mixture temperature (Tm) of the main fuel flow downstream of the junction, the control member (41) enabling the regulation of the secondary fuel flow rate in the secondary fuel circuit (2) as a function of the measured mixture temperature (Tm) by actuating the distribution valve (4).

4. Conditioning system (CS) according to claim 3, wherein the control member (41) is configured to compare the mixing temperature (Tm) to a setpoint temperature (Tv) and to, if the mixing temperature is different from the setpoint temperature (Tv), regulate the flow of secondary fuel so that the mixing temperature (Tm) is equal to the setpoint temperature (Tv).

5. Conditioning system (CS) according to any one of the preceding claims, 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%.

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

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

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

9. Conditioning system (SC) according to any one of the preceding claims, 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 of heating the main fuel flow (Qp) in the first heat exchanger (31) to at least the circulation temperature (Te); - a step E2 of measuring the temperature of the main fuel flow (Qp) downstream of the junction (6); - a step E3 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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