Fuel conditioning system for powering an aircraft turbine engine and associated method

Abstract

A fuel conditioning system configured to supply an aircraft turbine engine positioned in an engine reference frame with fuel from a cryogenic tank positioned in an aircraft reference frame, the conditioning system comprising a fuel circuit in which a fuel flow circulates, the fuel circuit comprising at least a first heat exchanger in the aircraft reference frame, at least a second heat exchanger in the engine reference frame, the first heat exchanger being connected to the second heat exchanger by a connecting pipe connecting the aircraft reference frame to the engine reference frame, the system comprising at least one heating coil wound around the connecting pipe so as to define a plurality of turns, the heating coil being configured to circulate a heating fluid so as to heat the connecting pipe. Abstract figure: Figure 3

Description

Title of the invention: Fuel conditioning system for supplying an aircraft turbine engine and associated method Technical field

[0001] The present invention relates to the field of aircraft comprising one or more turbomachines powered by fuel stored in a cryogenic tank.

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various States. In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

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

[0005] This sustained research and development work covers new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0006] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, the invention relates to the field of aircraft comprising one or more turbomachines powered by fuel stored in a cryogenic tank.

[0007] It is known to store fuel, in particular hydrogen, in liquid form to limit the size and mass of the aircraft tanks. For example, the fuel is stored at a temperature of the order of 20 to 22 Kelvins (-253 to -251°C) in a cryogenic tank of the aircraft.

[0008] In order to be injected into the combustion chamber of a turbomachine, the fuel must be conditioned, i.e. pressurized and heated, in order to allow optimal combustion. Conditioning is for example necessary to reduce the risk of icing, i.e. solidification of the water vapor contained in the air circulating in the turbomachine, in particular, at the fuel injectors of the turbomachine. With reference to [Fig.l], there is shown an SCAA conditioning system according to the prior art comprising a fuel circuit 101 connected at the inlet to a cryogenic tank R and at the outlet to the combustion chamber CC of a turbomachine M. A fuel flow Q circulating from upstream to downstream in the fuel circuit 101 successively passes through a mechanical pump 102 and a heating module 103. The pump 102 makes it possible to circulate the fuel flow from upstream to downstream.

[0009] In a known manner, a heating module 103 allows the circulation of one or more hot fluids to provide calories to the fuel flow Q. Each hot fluid can be either a heat transfer fluid or a fluid originating from a hot source available on board the aircraft (such as, for example, hot air, hot gases leaving the turbomachine, hot engine oil, etc.). Due to the very low temperature of the fuel flow Q leaving the cryogenic tank R, there is a risk that the hot fluid, circulating in the heating module 103, will freeze in the heating module 103, which may damage the heating module 103 or affect its efficiency.

[0010] With reference to [Fig. 2], a fuel conditioning system SCAA2 is known comprising two separate heat exchangers 131, 132 mounted successively in the fuel circuit 101. The first heat exchanger 131, in which a hot fluid circulates, makes it possible to heat the fuel flow Q to a primary temperature T1, higher than the solidification temperature of the hot fluid, so that the fuel is in the gaseous state in a connecting pipe Z1 connecting the first heat exchanger 131 to the second heat exchanger 132. The second heat exchanger 132, in which a hot fluid circulates, makes it possible to heat the fuel flow to a secondary temperature T2, higher than the primary temperature TL. The fuel flow Q, having reached a sufficiently high temperature at the outlet of the second exchanger 132, can then be introduced into the turbomachine M.The fuel flow Q thus circulates from an aircraft reference frame RA, comprising the cryogenic tank R and the first heat exchanger 131, to a . RM engine reference, including the second heat exchanger 132 and the M engine.

[0011] The connecting pipe ZI makes it possible to connect the aircraft reference frame RA to the engine reference frame RM along a complex connecting path with a small footprint. The connecting pipe ZI is in contact with the ambient air which is likely to generate icing given that the fuel has a low temperature in the connecting pipe ZI.

[0012] In order to ensure the proper functioning of the fuel circuit 101, it is necessary to ensure the thermal insulation of the connecting pipe ZI.

[0013] It is known to use a connecting pipe comprising an internal pipe in which the fuel circulates and an external pipe placed under vacuum so as to form thermal insulation and reduce the risk of icing with the ambient air likely to damage the connecting pipe. This has the disadvantage of increasing the weight of the connecting pipe and thus increasing the fuel consumption of the aircraft. This also has the disadvantage of requiring so-called "bayonet" connections, known to those skilled in the art, in order to guarantee the vacuum between the pipes of the connecting pipes connected together. These bayonet connections are complex to produce and install, and make the handling and maintenance operations of the connecting pipe more restrictive.

[0014] In order to eliminate these drawbacks, it is known to use a connecting pipe having a single conduit and to insulate it by surrounding it with a layer of insulating material. These materials are however very sensitive to surface defects, and a crack in the material exposes the external wall of the pipe to the ambient air. The water present in the ambient air is then likely to freeze on contact with the pipe in which the fuel flow circulates.

[0015] The invention thus aims to eliminate at least some of these drawbacks, by proposing a simple temperature conditioning system that is not very sensitive to exposure to ambient air. PRESENTATION OF THE INVENTION

[0016] The invention relates to a fuel conditioning system configured to supply an aircraft turbine engine positioned in an engine reference frame using fuel from a cryogenic tank positioned in an aircraft reference frame, the conditioning system comprising a fuel circuit connected at the inlet to the cryogenic tank and at the outlet to the turbine engine, a fuel flow circulating from upstream to downstream in the fuel circuit, the fuel circuit comprising: • at least one first heat exchanger in the aircraft reference frame configured to heat the fuel stream, • at least one second heat exchanger in the engine reference configured to heat the fuel flow before supplying the aircraft turbine engine, • the first heat exchanger being connected to the second heat exchanger by at least one connecting pipe connecting the aircraft reference frame to the engine reference frame.

[0017] The fuel conditioning system is notable in that it comprises at least one heating coil wound around the connecting pipe so as to define a plurality of turns, the heating coil being configured to circulate a heating fluid so as to heat the connecting pipe.

[0018] The fuel conditioning system advantageously makes it possible to maintain the outer wall of the connecting pipe at a temperature above 0°C despite the temperature difference between the ambient air and the fuel flow circulating in said connecting pipe. The fuel conditioning system thus makes it possible to eliminate the appearance of frost on the outer wall of the connecting pipe, and thus guarantees its thermal insulation. The fuel conditioning system advantageously allows the use of a cheap, compact, and easy-to-maintain single-wall pipe. In addition, the installation of the heating coil is simple, practical and quick. The fuel conditioning system is ideal for connecting different reference points that are far apart with complex connecting paths.The heating coil can be rolled around different types of connecting pipes and adapted to their geometry and route. Using a heating coil eliminates the need for protection covering the entire connecting pipe, which reduces the cost and weight of thermal insulation.

[0019] According to one aspect, the heating coil extends over the entire length of the connecting pipe. As a result, the entire connecting pipe is protected from the occurrence of frost.

[0020] According to one aspect, the connecting pipe extending along a pipe axis, the turns of the heating coil are spaced apart along the pipe axis by a spacing pitch of between 5 mm and 100 mm. This makes it possible to reduce the mass of the heating coil while making it possible to protect the exposed portions of the outer wall of the connecting pipe from freezing. The spacing pitch takes advantage of thermal conduction through the outer wall of the connecting pipe to heat the exposed portions.

[0021] According to one aspect, the fuel stream is hydrogen.

[0022] According to one aspect, the heating fluid has a temperature of between 300 and 500 Kelvin. This optimizes the heating of the outer wall of the connecting pipe, keeping its temperature above 0°C. In addition, this allows the outer wall of the connecting pipe to be heated without overheating the fuel flow, allowing it to be transported under ideal conditions.

[0023] According to one aspect, the heating fluid is fuel previously heated in the engine reference frame. This advantageously makes it possible to reduce the weight of the aircraft because it makes it possible to do away with a tank for the heating fluid. In addition, this makes it possible to do away with the presence of a heat exchanger dedicated to the heating fluid. The risk of heating fluid icing in the heating coil is thus zero.

[0024] According to one aspect, the heating fluid is reinjected into the fuel circuit at the connecting pipe. This makes it possible to limit the length of the heating coil for the circulation of the heating fluid by avoiding the need to provide a pipe for the return. This makes it possible to require fewer calories during its passage through the second heat exchanger, and thus makes it possible to reduce the energy consumption of the aircraft. The heating circuit advantageously has a simpler structure and a reduced length.

[0025] The invention also relates to an aircraft comprising a fuel conditioning system as described above.

[0026] The invention also relates to a method for conditioning fuel for an aircraft turbine engine using fuel from a cryogenic tank using a conditioning system as described above, the method comprising steps consisting of: • Circulate a flow of fuel through the connecting pipe, and • Circulate a heating fluid through the heating coil of way to heat the connecting pipe. PRESENTATION OF FIGURES

[0027] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0028] [Fig.l] is a schematic representation of a fuel conditioning system according to a first prior art.

[0029] [Fig.2] is a schematic representation of a fuel conditioning system according to a second prior art.

[0030] [Fig. 3] is a schematic representation of a fuel conditioning system according to a first embodiment.

[0031] [Fig.4] is a schematic representation of a fuel conditioning system according to a second embodiment.

[0032] [Fig.5] is a schematic side view of a heating coil wrapped around a connecting pipe.

[0033] [Fig.6] is a schematic front sectional representation of a heating coil wound around a connecting pipe.

[0034] [Fig.7] is a schematic cross-sectional side view of a portion of a heating coil wrapped around a connecting pipe.

[0035] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0036] With reference to [Fig. 3], the invention relates to a fuel conditioning system SC configured to supply an aircraft turbine engine T positioned in an engine reference frame RM from fuel Fl coming from a cryogenic tank RI positioned in an aircraft reference frame RA. The fuel flow Fl is stored at a temperature of the order of 20 to 22 Kelvins (-253 to -251°C) in the cryogenic tank RL.

[0037] The engine reference system RM comprises elements integrated by an engine manufacturer, while the aircraft reference system RA comprises elements integrated by an aircraft manufacturer. The elements of two reference systems RM, RA are subject to different constraints, in particular pressure and temperature. Thus the fuel Fl must be conditioned and maintained at a predetermined temperature and pressure to be used in the turbine engine T without being altered by environmental constraints during its passage from the aircraft reference system RA to the engine reference system RM.

[0038] For this purpose, the conditioning system SC comprises a fuel circuit CF connected at the inlet to the cryogenic tank RI and at the outlet to the turbine engine T. A fuel flow Fl circulates from upstream to downstream in the fuel circuit CF.

[0039] In this example, the fuel circuit CF is a cryogenic fuel circuit for a turbomachine of an aircraft, in particular in which the fuel Fl is hydrogen.

[0040] With reference to [Fig.3], the fuel circuit CF transports the fuel Fl from the aircraft reference system RA to the engine reference system RM.

[0041] The CF fuel circuit comprises from upstream to downstream: • a first heat exchanger 31 in the aircraft reference frame RA configured to heat the fuel flow Fl, and • a second heat exchanger 32 in the RM engine reference configured to heat the fuel flow Fl before feeding the aircraft turbo-engine T, • a connecting pipe 1 connecting the first heat exchanger 31 to the second heat exchanger 32.

[0042] In this example, the fuel circuit CF comprises a pump 4 which takes a flow of fuel F1 from the cryogenic tank RI to circulate it in the fuel circuit CF.

[0043] The aircraft reference system RA comprises the cryogenic tank RI and the first heat exchanger 31 so as to heat the fuel to a sufficient temperature to allow the fuel flow F1 to be conveyed between the two reference systems RA, RM via the connecting pipe 1.

[0044] The engine reference RM comprises the second heat exchanger 32 and the turbo-engine T. The second heat exchanger 32 is configured to heat the fuel to an optimal temperature for its combustion in the turbo-engine T, for example, between 200K and 500K.

[0045] In this example, only two heat exchangers 31, 32 are present but their number could be different. In this example, the first heat exchanger 31 raises the fuel F1 to a transport temperature of between 80 and 200 Kelvin. The second heat exchanger 32 then raises its temperature to a usage temperature of between 200 and 500 Kelvin so as to supply the turbine engine T.

[0046] The connecting pipe 1 thus makes it possible to connect the aircraft reference system RA to the engine reference system RM and can extend along circulation paths of complex shape, the insulation and maintenance of which are complex as previously presented in the preamble.

[0047] In this example, with reference to [Fig.5] and [Fig.6], the connecting pipe 1 has an outer wall PI which extends along a pipe axis Xc from upstream to downstream, and in which the fuel FL circulates. In this example, the connecting pipe 1 is rigid, but it could also be flexible in order to adapt to the space constraints.

[0048] With reference to [Fig. 4], the fuel conditioning system SC comprises a heating coil 2 wound around the connecting pipe 1 so as to define a plurality of turns 21. The heating coil 2 is mounted on the connecting pipe 1 so as to heat its outer wall PI in order to prevent it from icing up in contact with the ambient air. Advantageously, the heating coil 2 also makes it possible to supply calories to the fuel F1 in the connecting pipe 1.

[0049] The heating coil 2 is configured to circulate a heating fluid F2 so as to heat the connecting pipe 1. For this purpose, it comprises a inlet 22 connected to a heating source and an outlet 23, as will be described in more detail later.

[0050] With reference to [Fig.5] and [Fig.6], the heating coil 2 is wound around the connecting pipe 1 so as to be in contact with the connecting pipe 1. This makes it possible to transmit heat from the heating coil 2 to the outer wall PI of the connecting pipe 1 more efficiently by thermal conduction.

[0051] Preferably, the heating coil 2 is made of a metallic material, for example, aluminum or stainless steel, and the outer wall PI of the connecting pipe 1 is also made of a metallic material, for example, aluminum or stainless steel, to allow better thermal conduction.

[0052] Preferably, the heating coil 2 extends over the entire length of the connecting pipe 1 so as to avoid any risk of icing.

[0053] With reference to [Fig.5], the turns 21 are spaced apart by a spacing pitch L21 along the pipe axis Xc so as to be disjointed. Preferably, the spacing pitch L21 is between 5mm and 100mm. Such a spacing pitch L21 makes it possible to optimize the mass of the heating coil 2 while allowing satisfactory heating of the connecting pipe 1, avoiding icing between the turns 21.

[0054] Indeed, as illustrated in [Fig.7], the turns 21 directly heat by thermal conduction certain covered portions P11 of the outer wall P11. The uncovered portions P12 of the outer wall P11, which are not in contact with the turns 21 due to the presence of the spacing pitch L21, are heated by thermal conduction through the outer wall P11 thanks to the covered portions P11. Thus, the uncovered portions P12 of the outer wall P11 which are in contact with the ambient air are heated and do not frost.

[0055] It goes without saying that the turns 21 could also be joined.

[0056] In this example, with reference to [Fig. 5], the turns 21 are wound in a circular manner so as to match the shape of the connecting pipe 1. It goes without saying that the shape of the turns 21, and therefore of the heating pipe 2, could be different depending on the shape of the connecting pipe 1.

[0057] In this example, with reference to [Fig. 5], all the turns 21 of the heating coil 2 have a circular section. This makes it easier to manufacture the heating coil 2. According to another aspect, the section of each turn 21 could be different depending on the area of ​​the connecting pipe 1 with which it is in contact, so as to better match its shape and optimize thermal conduction.

[0058] Preferably, with reference to Figures 3 and 4, the packaging system SC includes a heating circuit CC in which the heating fluid F2 circulates. Heating coil 2 belongs to the heating circuit CC.

[0059] According to a first embodiment, with reference to [Fig. 3], the heating fluid F2 is a heat transfer fluid circulating in a closed loop in the heating circuit CC. In this embodiment, the heating fluid F2 is heated by a heat source 33, in particular, a heat exchanger taking calories from the engine reference frame RM, preferably from the turbine engine T. The heating fluid F2 may be in the form of an inert gas, such as nitrogen or helium, or a liquid, such as oil.

[0060] According to a second embodiment, with reference to [Fig. 4], the heating circuit CC is fluidically connected to the fuel circuit CF. In this embodiment, the heating fluid F2 is fuel taken from the outlet of the second heat exchanger 32 in the engine reference frame RM. The inlet 22 of the heating coil 2 is connected to the fuel circuit CF downstream of the second heat exchanger 32. The outlet 23 of the heating coil 2 is connected to the fuel circuit CF downstream of the first heat exchanger 31, in particular to the connecting pipe 1. This makes it possible to limit the length of the heating coil 2 for the circulation of the heating fluid by avoiding the need to provide a pipe for the return. This makes it possible not to disturb the thermodynamic equilibrium of the fuel F1 before it passes through the first heat exchanger 31.The fuel Fl is thus heated and requires fewer calories from the second heat exchanger 32, thus reducing energy expenditure.

[0061] Preferably, the heating circuit CC comprises a member for driving the heating fluid F2, for example a pump, a compressor or a circulator to ensure flow in the heating coil 2.

[0062] A jet pump may be used to provide a vacuum to drive the fluid into the DC heating circuit.

[0063] Preferably, the heating fluid F2 has a heating temperature T2 of between 300 and 500 Kelvin. The heating fluid F2 thus transmits its heat through the wall of the heating coil 2 to the outer wall PI of the connecting pipe 1 so as to avoid any icing of the outer wall PL. The outer wall PI of the connecting pipe 1 is advantageously maintained at a temperature above 275 Kelvin, even if the entire surface of the outer wall PI is not covered by turns 21.

[0064] Preferably, the heating fluid F2 circulates counter-current to the fuel F1 circulating in the connecting pipe 1. This makes it possible in particular to improve the heat exchanges.

[0065] An example of implementation of a method for conditioning a fuel aircraft turboshaft engine T from fuel Fl from a cryogenic tank RI by means of the conditioning system SC will be presented.

[0066] The method comprises a step consisting of circulating fuel F1 in the connecting pipe 1. For this purpose, the fuel is taken from the tank R1 and then heated by the first heat exchanger 31 so that the fuel temperature is between 80 and 200K in the connecting pipe 1. Such a temperature is advantageous because it ensures the passage of vapor (or supercritical vapor) of the cryogenic fuel, thus guaranteeing stability of its density with regard to its temperature changes. This ensures better stability of the circuit as a whole despite the thermal inputs on the uncovered sections and the sections covered and heated by the heating coil 2.

[0067] The method comprises a step of circulating the heating fluid F2 in the heating coil 2 so as to heat the connecting pipe 1 so as to prevent it from icing. For this purpose, as illustrated in [Fig. 4], hot fuel F1 is taken downstream of the second heat exchanger 32, then injected into the heating coil 2. The fuel F1 circulating in the heating coil 2 is then reinjected into the connecting pipe 1.

[0068] At the outlet of the connecting pipe, the fuel Fl has slightly heated up and must be heated by the second heat exchanger 32 so that the fuel Fl can be consumed.

[0069] Thanks to the invention, the connecting pipe 1 can conveniently connect the two reference systems RA, RM by following complex paths given that it has a small footprint and is optimally protected against icing. The use of a heating coil 2 makes it possible to dispense with protection covering the entire connecting pipe 1, which reduces the cost and weight.

[0070] It goes without saying that the heating coil 2 could also be used to heat other components of the CF fuel circuit, for example, a valve, a compressor, a pump, or even a pipe connection.

[0071] It goes without saying that the heating coil 2 could also be used to heat an oil circuit.

Claims

Claims

1. Fuel conditioning system (SC) configured to supply an aircraft turbine engine (T) positioned in an engine reference frame (RM) from fuel (Fl) from a cryogenic tank (RI) positioned in an aircraft reference frame (RA), the conditioning system (SC) comprising a fuel circuit (CF) connected at the inlet to the cryogenic tank (RI) and at the outlet to the turbine engine (T), a fuel flow (Fl) circulating from upstream to downstream in the fuel circuit (CF), the fuel circuit (CF) comprising: • at least one first heat exchanger (31) in the aircraft reference frame (RA) configured to heat the fuel (Fl), • at least one second heat exchanger (32) in the engine reference frame (RM) configured to heat the fuel flow (Fl) before supplying the aircraft turbine engine (T),• the first heat exchanger (31) being connected to the second heat exchanger (32) by at least one connecting pipe (1) connecting the aircraft reference frame (RA) to the engine reference frame (RM), system characterized by the fact that it comprises at least one heating coil (2) wound around the connecting pipe (1) so as to define a plurality of turns (21), the heating coil (2) being configured to circulate a heating fluid (F2) so as to heat the connecting pipe (1).,

2. A fuel conditioning system (SC) according to claim 1, wherein the heating coil (2) extends along the entire length of the connecting pipe (1).

3. Fuel conditioning system (SC) according to one of claims 1 to 2, in which, the connecting pipe (1) extending along a pipe axis (Xc), the turns (21) of the heating coil (2) are spaced apart along the pipe axis (Xc) by a spacing pitch (L21) of between 5mm and 100mm.

4. Fuel conditioning system (SC) according to one of claims 1 to 3, wherein the fuel stream (Fl) is hydrogen.

5. A fuel conditioning system (FC) according to one of the claims-

6.

7.

8.

9. indications 1 to 4, in which the heating fluid (F2) has a temperature between 300 and 500 Kelvin. Fuel conditioning system (SC) according to one of claims 1 to 5, in which the heating fluid (F2) is fuel (Fl) previously heated in the engine reference (RM). Fuel conditioning system (SC) according to claim 6, wherein the heating fluid (F2) is reinjected into the fuel circuit (CF) at the connecting pipe (1). Aircraft comprising a fuel conditioning system (SC) according to one of claims 1 to 7. Method for conditioning fuel for an aircraft turbine engine (T) using fuel (Fl) from a cryogenic tank (RI) using a conditioning system (SC) according to one of claims 1 to 7, the method comprising steps consisting of: Circulate a flow of fuel (Fl) in the connecting pipe (1), and Circulate a heating fluid (F2) in the heating coil (2) so as to heat the connecting pipe (1).

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