DOUBLE-WALLED HEAT EXCHANGER FOR A FUEL CONDITIONING SYSTEM

Abstract

The present invention relates to a heat exchanger for a turbomachine fuel conditioning system, the heat exchanger comprising: - a circulation space for the fuel to be heated, delimited by a first wall; - a circulation space for a hot fluid, delimited by a second wall; and - a heat exchange space between the fuel circulation space and the hot fluid circulation space, the heat exchange space being adapted to contain an inert gas and is delimited by the first and second walls, the first and second walls being connected by arms such that, during operation, the hot fluid heats the fuel by heat conduction through the first wall, the arms, and the second wall. Figure for the abstract: Fig. 3

Description

Title of the invention: DOUBLE-WALLED HEAT EXCHANGER FOR A FUEL CONDITIONING SYSTEM technical field

[0001] This presentation relates to the field of aircraft comprising one or more turbomachines powered by fuel stored in a cryogenic tank. More specifically, this presentation relates to a fuel conditioning system for supplying fuel to an aircraft turbomachine. STATE OF THE ART

[0002] A fuel, in particular hydrogen, for powering an aircraft turbomachine can be stored in liquid form to limit the size and mass of the aircraft's tanks. For example, the fuel can be stored at a temperature of around 20 to 22 Kelvin (-253 to -251°C) in a cryogenic tank on the aircraft.

[0003] It is possible to implement a conditioning system comprising a fuel circuit connected, at the inlet, to the cryogenic tank and, at the outlet, to the combustion chamber of the turbomachine. In order to be injected into the combustion chamber of the turbomachine while ensuring optimal combustion, the fuel must be conditioned, that is to say, pressurized and heated.

[0004] In order to limit the energy consumption of the turbomachine, it is possible to use the heat from the hot gases produced by the turbomachine to heat the fuel circulating in the conditioning system.

[0005] However, it is necessary to avoid contamination between the fuel and an oxidizer (such as the air contained in the hot gases). Indeed, a mixture of fuel and air can easily ignite. The use of a conventional heat exchanger in which the oxidizer and the fuel to be heated are separated by a single wall does not eliminate this risk. In fact, a rupture in the wall would cause the contamination that must be avoided. GENERAL STATEMENT

[0006] One aim of the presentation is to propose a system reducing the risks of contamination of the fuel supplying a turbomachine during the heating of the fuel by a flow of hot air from the engine.

[0007] To this end, according to one aspect of this description, a heat exchanger for a fuel conditioning system of a turbomachine is proposed, the heat exchanger comprising: - a space for the circulation of a fuel to be heated, delimited by a first wall; - a space for the circulation of a hot fluid, delimited by a second wall; and

[0008] an exchange space between the circulation space of a fuel and the circulation space of a hot fluid, the exchange space being adapted to contain an inert gas and is delimited by the first wall and the second wall, the first wall and the second wall being connected by arms so that, in operation, the hot fluid heats the fuel by heat conduction through the first wall, the arms and the second wall.

[0009] This allows the fuel to be heated by reusing heat produced by the turbomachine while limiting the risk of fuel contamination by the hot fluid from the turbomachine. The presence of a double wall separating the fuel flow from the hot fluid prevents fuel contamination by the hot fluid in the event of a rupture of either the first or second wall.

[0010] Moreover, such an exchanger makes it possible to do without the use of an intermediate circuit comprising a circulation loop for a heat transfer fluid, such an intermediate circuit necessarily comprising a pump for the circulation of the heat transfer fluid in order to promote convection in the heat transfer fluid and two separate exchangers between the intermediate circuit and the fuel and the hot fluid.

[0011] Advantageously, but optionally:

[0012] - the exchange space has an alveolar structure and comprises: cavities between the first wall and the second wall, the cavities being delimited by the arms and being configured to store the inert gas;

[0013] - the first wall includes initial fins to increase heat exchange thermal conduction between the inert gas and the fuel, the first fins extending perpendicularly in projection from the first wall into the fuel circulation space;

[0014] - the second wall includes second fins to increase the exchange thermal conduction between the hot fluid and the inert gas, the second fins extending perpendicularly from the second wall into the circulation space of a hot fluid;

[0015] - the first fins and / or the second fins are pins or plates straight, wavy or polyhedral;

[0016] - the first fins and / or the second fins respectively have several parallel alignments with each other and offset from each other;

[0017] - the first fins have several straight, curved or polyhedral, parallel to each other, to form labyrinthine circulation channels for the fuel along the first wall;

[0018] - the arms can be pawns, plates, polyhedral walls, plates crossed, forming lattice-like cavities, double cones or cylinders;

[0019] - the heat exchanger includes a control device configured to, in operation, control the pressure of the inert gas in the exchange space, the control device being further configured to detect a variation in the gas pressure in the exchange space relative to a determined threshold.

[0020] According to another aspect, a fuel conditioning system is proposed for supplying a turbomachine with fuel stored in a cryogenic tank, the system comprising: - an exchanger as previously described, the space for the circulation of a fuel comprising an inlet and an outlet; - a first fuel circuit comprising an inlet connected to the cryogenic tank and an outlet connected to the inlet of the fuel circulation space; and - a second fuel circuit comprising an inlet connected to the outlet of the fuel circulation space and an outlet connected to a turbomachine.

[0021] Advantageously but optionally:

[0022] - the conditioning system includes a heat circuit, the heat circuit connecting the circulation space of a hot fluid to a hot source;

[0023] - the inert gas contained in the exchange space is helium, neon, argon, krypton, xenon, or nitrogen.

[0024] According to another aspect, an assembly is proposed comprising a turbomachine and a conditioning system as previously described, the circulation space of a hot fluid being in fluidic communication with a hot part of the turbomachine and the circulation space of a fuel being in fluidic communication with a fuel supply of the turbomachine. DESCRIPTION OF THE FIGURES

[0025] Fig. 1 illustrates an aircraft schematically.

[0026] Fig. 2 illustrates a schematic cross-sectional view of an aircraft propulsion assembly;

[0027] Figure 3 schematically illustrates a fuel conditioning system;

[0028] Fig. 4a illustrates a cross-sectional view of a plate heat exchanger according to a first embodiment;

[0029] Fig. 4b illustrates a cross-sectional view of a tubular heat exchanger according to a second embodiment;

[0030] Fig. 5 schematically illustrates a cross-sectional view of a heat exchanger according to a third embodiment;

[0031] Fig. 6a, Fig. 6b, Fig. 6c and Fig. 6d illustrate a top view of different fins and fin arrangements on the first wall, according to different embodiments of the present description;

[0032] Fig. 7a, Fig. 7b and Fig. 7c illustrate a top view of different fins and fin arrangements on the second wall, according to different embodiments of the present description;

[0033] Fig. 8a, Fig. 8b and Fig. 8c illustrate a cross-sectional view of different arm arrangements in the exchange space, according to different embodiments of the present exposition.

[0034] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0035] The present description relates to a fuel conditioning system 3 for an aircraft engine 2 100, such as an aircraft as illustrated in [Fig. 1]. Such an aircraft 100 comprises a fuselage which, in the case of an aircraft, consists of a fuselage, a wing comprising two wings, tail assemblies, flight control surfaces and landing gear.

[0036] The engine 2 (or turbomachine) is configured to be fixed to the airframe of the aircraft 100, for example under its wings, in the case of an airplane, by means of a pylon (or mast). The propulsion unit 1 can also be mounted on the wing of the airplane or at the rear of its fuselage, or even be integrated into its fuselage.

[0037] The engine 2 may be a twin-body, twin-flow, direct-drive ducted turbojet, as described below, but may also have a different number of bodies and / or flows, and / or be another type of turbojet, such as a geared turbojet or a turboprop, with or without afterburner, ducted or unducted.

[0038] Unless otherwise specified, the terms "upstream" and "downstream" are used with reference to the overall direction of airflow through the propulsion assembly 1 in operation.

[0039] The engine 2, as illustrated in [Fig. 2], comprises, from upstream to downstream, a blower 20, a compressor section 22, comprising a low-pressure compressor 220 and a high-pressure compressor 222, a combustion chamber 24, and a turbine section 26, comprising a high-pressure turbine 262 and a low-pressure turbine 260. The blower 20, the rotor parts of the section The compressor 22 and the rotor parts of the turbine section 26 are capable of being driven in rotation about the longitudinal axis XX relative to the engine casing 23 and the fan casing 25. The upstream portion of the nacelle 3 further defines an air inlet 29 through which the fan 20 draws in the airflow circulating through the propulsion assembly 1. The combustion chamber 24 includes a fuel injection rail and a plurality of ignition injectors. The injection rail and / or the ignition injectors constitute fuel-consuming components of the engine 2.

[0040] During operation, the fan 20 draws in an airflow, a portion of which passes through the engine casing 23 from one side to the other and is successively compressed within the compressor section 22, ignited within the combustion chamber 24 by fuel combustion, and expanded within the turbine section 26 before being ejected from the engine 2. In this way, the propulsion unit 1 generates thrust. This thrust can, for example, be used to power the aircraft 100 on which the propulsion unit 1 is mounted and attached.

[0041] The fuel conditioning system 3 allows the combustion chamber 24 injection rail to be supplied with fuel during the operation of the engine 2 and thus allows the air to be ignited. Fuel conditioning system

[0042] The fuel conditioning system 3, as illustrated by [Fig.3], comprises a fuel circuit 31, a heat circuit 32 and a heat exchanger 4.

[0043] The fuel circuit 31 is configured to carry fuel from a tank 33 to the engine 2, that is, to the fuel rail. The fuel circuit 31 may include a first portion 34, referred to as the first circuit 34, to connect the tank 33 to the heat exchanger 4, and a second portion 35, referred to as the second circuit 35, to connect the heat exchanger 4 to the engine 2. Furthermore, the fuel circuit 31 may include at least one pump 36 to control the fuel flow in the fuel circuit 31.

[0044] The heat circuit 32, or hot fluid circulation duct, carries heat to the heat exchanger 4 to heat the fuel in the control circuit. The heat circuit 32 connects the heat exchanger 4 to a heat source. The heat source can be the hot air flow exiting the turbine section 26. This allows for improved energy efficiency by reusing heat produced by the operation of the engine 2 to heat the fuel supplying the engine 2. Heat exchanger

[0045] The heat exchanger 4 is configured to heat the fuel circulating in the fuel circuit 31 in order to condition it. Indeed, to improve the operation of the engine 2, the fuel must be delivered to the injection rail at a temperature between 150 K and 350 K (i.e., -123°C to 77°C) depending on the phase of flight. Since the fuel can be stored in the tank 33 at a cryogenic temperature between -240°C and -260°C, it must be heated before being injected into the injection rail. The heat exchanger 4 therefore comprises a hot source, the hot fluid, and a cold source, the fuel.

[0046] The hot fluid can be the gas circulating in the engine 2 and whose temperature at the outlet of the turbine section 26 can vary between 400°C and 600°C. The hot fluid includes, among other things, oxygen.

[0047] The fuel to be heated may be hydrogen or, for example, methane or any other type of fuel that can be used in an engine 2. The fuel must therefore not come into contact with the hot fluid in order to avoid any risk of ignition.

[0048] The heat exchanger 4, as illustrated by figures 4A and 4B, comprises a circulation space for a fuel 41 to be heated delimited by a first wall 44, a circulation space for a hot fluid 42 delimited by a second wall 45 and an exchange space 43 included between the circulation space for a fuel 41 and the circulation space for a hot fluid 42.

[0049] The circulation space for a fuel 41 to be heated may be a conduit, a pipe, or any other type of space configured to allow the fuel to circulate in the heat exchanger 4 in a sealed manner. For simplicity, this will be referred to as the fuel line. The fuel line 41 comprises an inlet connected to an outlet of the first fuel circuit 34, one inlet of which is connected to the cryogenic tank 33, and an outlet connected to an inlet of the second fuel circuit 35, one outlet of which is connected to the engine 2.

[0050] The circulation space for a hot fluid 42 may be a conduit, a pipe, or any other type of space configured to allow the hot fluid to circulate in the heat exchanger 4 in a sealed manner. For simplicity, it will be referred to hereafter as a heat pipe. The heat pipe 42 includes an inlet connected to the heat circuit 32, one of whose inlets is connected to a hot source of the engine 2, such as, for example, the air at the compressor outlet, the engine oil 2, the air at the turbine section 26 outlet, etc.

[0051] The fuel line 41 defines a flow direction for fuel A and the heat line 42 defines a flow direction for hot fluid B. The flow direction of fuel A may be in the same direction as the flow direction of hot fluid B, in which case it is called a co-current heat exchanger, or it may be opposite to the direction of flow of the hot fluid B, we then speak of a counter-current exchanger, or orthogonal to the direction of flow of the hot fluid B, we then speak of a cross-flow exchanger.

[0052] The heat exchange space 43 is delimited by the first wall 44 and the second wall 45 and is adapted to contain an inert gas. The inert gas in the heat exchange space 43 prevents any ignition in the event of contact with the fuel A or the hot fluid B. The inert gas is helium, neon, argon, krypton, xenon, or nitrogen.

[0053] Thus, the heat exchange space 43 acts as a barrier between the fuel line 41 and the heat line 42, preventing any risk of contamination between the hot fluid and the fuel. In other words, the fuel is separated from the hot fluid in the heat exchanger 4 by two walls. In the event of a leak through the first wall 44 or the second wall 45, the fuel will not mix with the hot fluid, thus preventing the formation of an oxidizer. The presence of the heat exchange space 43 prevents the fuel from igniting in the event of a leak through the first wall 44 or the second wall 45.

[0054] The first wall 44 and the second wall 45 can be cylindrical and coaxial or planar and parallel. In this way, the heat exchanger 4 can be a plate heat exchanger or a shell and tube heat exchanger, etc. In the case of a plate heat exchanger, the fuel line 41 can be delimited by two first walls 44, each delimiting, together with a separate second wall 45, a heat exchange space 43, as illustrated by [Fig. 4a] (in this case, the fuel line 41 is symmetrically contained between two heat exchange spaces 43 and two heat lines 42). In any case, the heat exchange space 43 is delimited by the first wall 44 and the second wall 45 and thus contained between the fuel line 41 and the heat line 42 so as to improve heat exchange.

[0055] Thus, the heat exchanger 4 is a simple and compact double-walled exchanger. It allows efficient heat transfer between the hot fluid and the fuel, through the exchange space 43, in order to heat the fuel while limiting the risk of fuel contamination. The heat exchange between the hot fluid and the fuel occurs by conduction from the first wall 44 to the second wall 45 via the inert gas; in other words, the heat transfer in the exchange space 43 occurs by thermal conduction.

[0056] Furthermore, the first wall 44 may include fins 46 to increase heat exchange by conduction between the first wall 44 and the fuel A, as illustrated in [Fig. 5]. The fins 46 of the first wall 44 project from the first wall 44 into the fuel line 41. The fins 46 may be straight plates or pins of various shapes. The fins 46 may also be corrugated or polyhedral, that is, formed by non-corrugated plates parallel to each other and joined end to end on the first wall 44, as illustrated by figures 6a, 6b and 6c.

[0057] The fins 46 can extend parallel to each other and in a plane parallel to the direction of fuel flow A in the fuel line 41. The fins 46 can further have one or more straight, curved, or polyhedral alignments, parallel to each other, so as to channel the fuel flow A along the first wall 44 and thus improve heat exchange. The fins 46 can thus form a labyrinth on the first wall 44.

[0058] For example, the fins 46 may have several alignments perpendicular to the direction of fuel flow A, in which the fins 46 are uniformly spaced. The respective fins 46 of two adjacent alignments may be offset in a direction perpendicular to the direction of fuel flow A. This further improves heat exchange between the fuel flow A and the first wall 44.

[0059] As illustrated in [Fig. 6d], the fins 46 may further have one or more continuous alignments to form circulation channels, for example in a labyrinth, for the fuel flow A along the first wall 44. As illustrated in Figures 7a, 7b, and 7c, the second wall 45 may also include fins 47 to increase heat exchange by conduction between the hot fluid and the second wall 45. The fins 47 of the second wall 45 project from the second wall 45 into the heat conduit 42. The fins 47 may be straight plates or pins of various shapes. The fins 47 may also be corrugated or polyhedral, that is, formed by plates that are not parallel to each other and are joined end to end on the second wall 45.

[0060] The fins 47 can extend parallel to each other and in a plane parallel to the direction of flow of the hot fluid B in the heat conduit 42. The fins 47 can further have one or more alignments so as to channel the fuel flow A along the first wall 44 and thus improve the heat exchange.

[0061] For example, the fins 47 may have several alignments perpendicular to the flow direction of the hot fluid B and in which the fins 47 are uniformly spaced. The respective fins 47 of two neighboring alignments may have an offset in a direction perpendicular to the flow direction of the hot fluid B.

[0062] The exchange space 43 is alveolar and comprises: cavities 48 between the first wall 44 and the second wall 45 and arms 49 connecting the first wall 44 to the second wall 45. The cavities 48 are configured to store the inert gas.

[0063] As illustrated in Figures 8a, 8b, and 8c, the arms 49 can have various shapes to improve thermal conduction and the resistance of the heat exchange space 43 in order to prevent leakage. The arms 49 can be shaped like a pin, a plate, a polyhedral wall (as illustrated particularly in [Fig. 8b]), crossed plates forming lattice cavities 48, a double cone, a cylinder, etc. Thus, heat exchange by conduction between the hot fluid and the fuel through the heat exchange space 43 is improved. Indeed, the heat transfer between the hot fluid and the fuel is a thermal conduction transfer through the first wall 44, the arms 49, and the second wall 45. The heat exchanger 4 therefore does not require a pump for the inert gas, which conducts heat by conduction and not by convection.The heat exchanger 4 is thus simpler and more compact than a system comprising an intermediate inert gas circuit including a heat exchanger with the hot fluid and a heat exchanger with the fuel, as well as a pump to allow convection in the gas circuit between the two heat exchangers.

[0064] The inert gas in the heat exchange space 43 can be at a pressure higher than the pressure of the hot fluid in the heat line 42 and the pressure of the fuel in the fuel line 41. The pressure of the hot fluid in the heat line 42 can be between 0.15 bar and 1.5 bar, the pressure of the fuel in the fuel line 41 can be between 2 bar and 60 bar, and the pressure of the inert gas in the heat exchange space 43 can be between 65 bar and 120 bar (assuming no leaks). The inert gas is under supercritical conditions. For example, the pressure and temperature of the inert gas are respectively higher than the critical pressure and critical temperature of the type of inert gas considered. This prevents condensation of the inert gas, which would cause a local pressure drop.Thus, in the event of a leak through the first wall 44 or the second wall 45, the inert gas under pressure escapes through the leak and thus prevents the fuel and the hot fluid from coming into contact.

[0065] Compared to a double-walled exchanger comprising, for example, a foam or a solid material in the exchange space 43, the presence of an inert gas in the exchange space 43 makes it possible to detect a leak by measuring the pressure of the gas in the exchange space 43.

[0066] The heat exchanger 4 may include a control device 50 for the pressure of the inert gas in the exchange space 43.

[0067] The control device 50 can control the pressure of the inert gas. The inert gas can have a constant volume in the exchange space 43 and a variable pressure depending on the operating conditions. The control device 50 is then configured to detect an abnormal pressure variation. Or, the inert gas can The system maintains a constant pressure and variable volume thanks to an expansion vessel 51. Depending on the thermal gradients, the volume of the inert gas varies in the exchange space 43, but at constant pressure (in the absence of leaks). The control device 50 is then configured to detect any pressure variation.

[0068] Thus, a leak in the exchange space 43 can be easily detected and addressed. Detecting a leak can trigger the fuel supply shutdown.

Claims

Demands

1. Heat exchanger (4) for a fuel conditioning system (3) of a turbomachine (2), the heat exchanger (4) comprising: - a circulation space for a fuel (41) to be heated delimited by a first wall (44); - a circulation space for a hot fluid (42) delimited by a second wall (45); and - an exchange space (43) between the circulation space for a fuel (41) and the circulation space for a hot fluid (42), the exchange space (43) being adapted to contain an inert gas and is delimited by the first wall (44) and the second wall (45), the first wall (44) and the second wall (45) being connected by arms (49); the exchange space (43) being configured so that in operation, the hot fluid heats the fuel by heat conduction.

2. Exchanger (4) according to claim 1, wherein the exchange space (43) has a honeycomb structure and comprises: cavities (48) between the first wall (44) and the second wall (45), the cavities being delimited by the arms (49) and being configured to store the inert gas.

3. Heat exchanger (4) according to any one of claims 1 and 2, wherein the first wall (44) comprises first fins (46) to increase heat exchange by conduction between the inert gas and the fuel, the first fins (46) extending perpendicularly in projection from the first wall (44) into the circulation space of a fuel (41).

4. Exchanger (4) according to any one of claims 1 to 3, wherein the second wall (45) comprises second fins (47) to increase heat exchange by conduction between the hot fluid and the inert gas, the second fins (47) extending perpendicularly outward from the second wall (45) into the circulation space of a hot fluid (42).

5. Exchanger (4) according to any one of claims 3 to 4, wherein the first fins (46) according to claim 3 and / or the second fins (47) according to claim 4, are pins or straight, corrugated or polyhedral plates.

6. Exchanger (4) according to any one of claims 3 to 5, wherein the first fins (46) according to claim 3 and / or the second fins (47) according to claim 4, respectively have several parallel alignments with each other and offset from each other to improve heat exchange.

7. Heat exchanger (4) according to any one of claims 1 to 3, 5 and 6, wherein the first fins (46) have several straight, curved or polyhedral alignments, parallel to each other, to form labyrinthine fuel circulation channels along the first wall (44).

8. Exchanger (4) according to any one of claims 1 to 7, wherein the arms (49) may be pins, plates, polyhedral walls, crossed plates forming lattice cavities (48), double cones or cylinders.

9. Exchanger (4) according to any one of claims 1 to 8, comprising a control device (50) configured to, in operation, control a pressure of the inert gas in the exchange space (43), the control device (50) further being configured to detect a variation of the gas pressure in the exchange space (43) relative to a determined threshold.

10. Fuel conditioning system (3) for supplying a turbomachine (2) with fuel stored in a cryogenic tank (33), the system (3) comprising: - a heat exchanger (4) according to any one of claims 1 to 9, the fuel circulation space (41) comprising an inlet and an outlet; - a first fuel circuit (34) comprising an inlet connected to the cryogenic tank (33) and an outlet connected to the inlet of the fuel circulation space (41); and - a second fuel circuit (35) comprising an inlet connected to the outlet of the fuel circulation space (41) and an outlet connected to a turbomachine (2).

11. Conditioning system (3) according to claim 10, comprising a heat circuit (32), the heat circuit (32) connecting the circulation space of a hot fluid (42) to a hot source.

12. Conditioning system (3) according to any one of claims 10 and 11, wherein the inert gas contained in the exchange space (43) is helium, neon, argon, krypton, xenon or nitrogen.

13. Assembly comprising a turbomachine (2) and a conditioning system (3) according to any one of claims 10 to 12, the circulation space of a hot fluid (42) being in fluidic communication with a hot part of the turbomachine (2) and the circulation space of a fuel (41) being in fluidic communication with a fuel supply of the turbomachine (2).

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