AIRCRAFT TURBOMACHINE COMPRISING A HEAT PUMP

Abstract

Aircraft turbomachine comprising: - a fuel supply system (12) for a combustion chamber of the turbomachine; - a heat pump (15) comprising a closed circuit (20) in which a heat transfer fluid circulates, the circuit (20) comprising an evaporator (21) configured to exchange heat with oil of the turbomachine, a first condenser (22) configured to exchange heat with the fuel of the supply system (12), a second condenser (23) which is mounted in parallel with the first condenser (22) and which is configured to exchange heat with a cold source (24) which is separate from the fuel, an expansion valve (25) configured to expand the heat transfer fluid before entering the evaporator (21), a compressor (26) configured to compress the heat transfer fluid before entering the condensers (22, 23), and a metering device (27) configured to adjust the flow rate of heat transfer fluid entering the first condenser (22).Figure for abstract: 2.

Description

Title of the invention: AIRCRAFT TURBOMACHINE COMPRISING A HEAT PUMP Technical field of the invention

[0001] The present invention relates to an aircraft turbomachine comprising a heat pump, as well as to a method for adjusting the temperature of the fuel in a supply system of a combustion chamber of such a turbomachine. Technical background

[0002] A dual-flow turbomachine conventionally comprises a fan driven by a power turbine, and a gas generator whose generated gases are used to drive the power turbine. The gas generator comprises at least one compressor, a combustion chamber and at least one turbine. The fan generates an air flow which is divided into a primary flow intended to supply the gas generator and a secondary flow which contributes predominantly to the thrust provided by the turbomachine.

[0003] The turbomachine also comprises different oil circuits which have the function, for example, of lubricating moving elements (bearings, toothed wheels, etc.) and / or cooling electrical machines of the turbomachine.

[0004] For the oil to fully perform its functions, it is essential to maintain its temperature within a given range, in particular using a cooling system.

[0005] Engine manufacturers today face a major challenge. Indeed, new turbomachine architectures integrate more oil circuits due in particular to the installation of a reducer (between the power turbine and the fan) and / or increased use of electric generators in order to reinforce the hybridization of the turbomachine.

[0006] These additional oil circuits inevitably imply an increase in the thermal power to be dissipated, and consequently an obligation to review the existing cooling system.

[0007] To meet this need, it is known from document FR2993610A1 in the name of the applicant to cool the oil with a heat pump.

[0008] Such a heat pump comprises a closed circuit in which a heat transfer fluid circulates, the circuit comprising in particular an evaporator, a condenser, a compressor and an expansion valve.

[0009] More precisely, the evaporator vaporizes the heat transfer fluid by taking heat from the oil (hot source). The condenser condenses the heat transfer fluid by Removing heat into an air stream (cold source). The compressor compresses the heat transfer fluid (gaseous state) to increase its pressure before it passes through the condenser. The expansion valve expands the heat transfer fluid (liquid state) to lower its pressure before it passes through the evaporator.

[0010] In the aforementioned document, the heat pump is only used to cool the oil.

[0011] However, engine manufacturers note that it might be advantageous to use the pump heat for other functions, including heating the fuel before it is injected into the combustion chamber.

[0012] Indeed, it has been found that the temperature of the injected fuel is an essential parameter, in particular for improving the efficiency of the combustion chamber and minimizing the specific consumption of the turbomachine. It thus turns out that the higher the temperature of the injected fuel, the better the efficiency and consumption.

[0013] However, it has also been found that the temperature of the injected fuel must not exceed a critical temperature (e.g. 150 degrees) above which the fuel is subject to coking.

[0014] Indeed, beyond the critical temperature, the fuel oxidizes and cokes. The coking of the fuel results in the appearance of a blackish deposit in the various equipment of the fuel system (and in particular the injectors), this deposit accumulating over time and causing progressive fouling. This fouling inevitably degrades the injection, and consequently the homogeneity of the carburetion, and more generally the performance of the combustion chamber and the turbomachine.

[0015] Conventionally, existing fuel systems do not include any device dedicated to heating the injected fuel, with engine manufacturers favoring other functions, and in particular fuel defrosting.

[0016] Engine manufacturers also note that the equipment (evaporator, condenser(s), etc.) of the heat pump is sized to cope with the worst case, namely a case in which the oil has a significant thermal power to dissipate (for example a high operating speed combined with a high outside temperature) and the air flow (cold source) has a high temperature. However, in practice, the equipment only operates occasionally at its maximum capacity. Thus, engine manufacturers point out that it could be advantageous to exploit the capacities of the equipment available for other occasions, and in particular the heating of the fuel before its injection into the combustion chamber.

[0017] The objective of the present invention is therefore to optimize the heat pump for allow not only to cool the oil but also to heat the fuel before its injection into the combustion chamber. Summary of the invention

[0018] The invention thus proposes an aircraft turbomachine comprising: - a fuel supply system for a combustion chamber of the turbomachine; - a heat pump comprising a closed circuit in which a heat transfer fluid circulates, the circuit comprising an evaporator configured to exchange heat with oil from the turbomachine, a first condenser configured to exchange heat with the fuel of the power system, a second condenser which is mounted in parallel with the first condenser and which is configured to exchange heat with a cold source which is separate from the fuel, an expansion valve configured to expand the heat transfer fluid before entering the evaporator, a compressor configured to compress the heat transfer fluid before entering the condensers, and a metering device configured to adjust the flow rate of heat transfer fluid entering the first condenser.

[0019] The first condenser and the associated metering device make it possible to heat the fuel at the outlet of the first condenser, and in other words before its injection into the combustion chamber, so as to improve the efficiency of the combustion chamber and minimize the specific consumption of the turbomachine.

[0020] The metering device makes it possible to adjust (or regulate) the flow rate of heat transfer fluid entering the first condenser, and consequently to adjust (or regulate) the temperature of the fuel leaving the first condenser, in particular so that it reaches its optimum injection temperature, so as to optimize efficiency and consumption.

[0021] The possibility of regulating the fuel temperature for all flight phases (takeoff, cruise, landing) and for each of the turbomachine's operating regimes, offers significant gains in efficiency and consumption.

[0022] The turbomachine according to the invention may comprise one or more of the following characteristics and / or steps, taken in isolation from one another or in combination with one another: - the doser is electrically controlled by a control system; - the fuel system comprises a fuel temperature sensor, the temperature sensor being located downstream of the first condenser and being electrically connected to the control system; - the first condenser is part of a first branch of the circuit, the second condenser is part of a second branch of the circuit, the circuit comprising a common part comprising at least the evaporator, the inlets of the branches are each connected to an outlet channel of the doser and the outlet of the common part is connected to an inlet channel of the doser; - the first condenser and the metering unit are part of a first branch of the circuit, the second condenser is part of a second branch of the circuit, the circuit comprising a common part comprising at least the evaporator, the inlets of the branches being connected to the outlet of the common part via a branch; - the common part includes from upstream to downstream the expansion valve, the evaporator and the compressor; - the cold source is an air flow.

[0023] The present invention also relates to a method for adjusting the fuel temperature of a fuel supply system of a combustion chamber of a turbomachine as described above, the method comprising the step of: a) adjust the fuel temperature at the outlet of the first condenser by adjusting the flow rate of heat transfer fluid entering the first condenser via the metering valve.

[0024] The method according to the invention may comprise one or more of the following characteristics and / or steps, taken in isolation from one another or in combination with one another: - the doser is electrically controlled by a control system according to a setpoint; - the metering unit control setpoint is determined by the control system from the temperature of the fuel downstream of the first condenser and a critical temperature above which the fuel is subject to coking. Brief description of the figures

[0025] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0026] [Fig-1] [Fig.l] is a schematic view in axial half-section of a turbomachine comprising a heat pump according to the invention;

[0027] [Fig.2] [Fig.2] is a detailed view of the heat pump according to a first mode of realization;

[0028] [Fig.3] [Fig.3] is a detailed view of the heat pump according to a second mode of realization. Detailed description of the invention

[0029] In [Fig.l] a turbomachine 1 of an aircraft 2 is partially represented. Aircraft 2 is for example an airplane.

[0030] As illustrated in [Fig.l], the turbomachine 1 is here a double-flow turbojet which conventionally comprises a ducted fan 3, a gas generator 4 and a power turbine 5.

[0031] More precisely, the fan 3 is rotatable about an axis X relative to a fixed structure 6 of the turbomachine 1. The fan 3 is driven in rotation by the power turbine 5 via a speed reducer 7.

[0032] The reducer 7 is for example an epicyclic gear reducer which has the advantage of having a high reduction ratio while being compact. The reducer 7 is housed and lubricated with oil in an enclosure which is commonly called an “oil enclosure”. The oil is more particularly intended to lubricate the moving elements of the reducer 7, and in particular the bearings and the toothed wheels.

[0033] The gas generator 4 here comprises a low-pressure compressor 8, a high-pressure compressor 9, a combustion chamber 10 and a high-pressure turbine 11 (or expansion turbine). The high-pressure compressor 9 is driven in rotation by the high-pressure turbine 11. The low-pressure compressor 8 is driven by the blower 3.

[0034] The combustion chamber 10 is supplied with fuel by a fuel supply system 12 (commonly called "fuel system" and hereinafter called fuel system) of the turbomachine 1.

[0035] As illustrated in [Fig.l], the air flow F generated by the fan 3 is divided, by the fixed structure 6 of the turbomachine 1, into a primary flow f1 which enters a primary vein 13 to supply the gas generator 4, and into a secondary flow f2 which flows in a secondary vein 14 around the gas generator 4, to provide the majority of the thrust.

[0036] The example illustrated in [Fig.l] is in no way limiting, the turbomachine 1 could for example be a differently configured turbojet, a turboprop, a turbo-engine or even a turbomachine comprising one or more unducted fans (for example of the UDF type for “Unducted Fan” in English or even of the USF type for “Unducted Single Fan” in English).

[0037] As illustrated in [Fig.l], the turbomachine 1 further comprises a heat pump 15. The heat pump 15 is here arranged in a compartment 16 defined between a casing 17 surrounding the fan 3 (commonly called “fan casing”) and fairings of a nacelle 18 of the turbomachine 1. As a variant, the heat pump 15 could for example be arranged in an inter-vein compartment.

[0038] The heat pump 15 has the main function of cooling the oil of an oil supply system 19 (commonly referred to as the “oil system” and hereinafter called oil system) of the turbomachine 1.

[0039] According to the invention, the heat pump 15 also has the auxiliary function of heating the fuel of the fuel system 12 before it enters the combustion chamber 10.

[0040] For this, the heat pump 15 comprises a closed circuit 20 in which a heat transfer fluid circulates. The circuit 20 comprises an evaporator 21 configured to exchange heat with oil from the oil system 19, a first condenser 22 configured to exchange heat with the fuel from the fuel system 12, a second condenser 23 which is connected in parallel with the first condenser 22 and which is configured to exchange heat with a cold source 24 which is distinct from the fuel, an expansion valve 25 configured to expand the heat transfer fluid before entering the evaporator 21, a compressor 26 configured to compress the heat transfer fluid before entering the condensers 22, 23, and a metering device 27 configured to adjust the flow rate of heat transfer fluid entering the first condenser 22.

[0041] The first condenser 22 and the associated metering device 27 make it possible to heat the fuel at the outlet of the first condenser 22, and in other words before its injection into the combustion chamber 10, so as to improve the efficiency of the combustion chamber 10 and minimize the specific consumption of the turbomachine 1.

[0042] The metering device 27 makes it possible to adjust (or regulate) the flow rate of heat transfer fluid entering the first condenser 22, and consequently to adjust (or regulate) the temperature of the fuel leaving the first condenser 22, in particular so that it reaches its optimum injection temperature, so as to optimize efficiency and consumption.

[0043] The possibility of regulating the fuel temperature for all flight phases (takeoff, cruise, landing) and for each of the operating regimes of the turbomachine 1, offers significant gains in efficiency and consumption.

[0044] By convention, in the present application, the terms “upstream” and “downstream” or even “inlet” and “outlet” are defined either in relation to the direction of circulation of the heat transfer fluid in the closed circuit 20 of the heat pump 15, or in relation to the direction of circulation of the fuel in the fuel system 12, depending on the context.

[0045] As indicated above, the oil cooled by the heat pump 15 comes from the oil system 19.

[0046] The oil system 19 may comprise one or more lubrication circuits in which oil circulates and which are intended to lubricate moving elements of the turbomachine 1.

[0047] The oil system 19 may comprise one or more cooling circuits in which oil circulates and which are each intended to cool one or more electrical machines of the turbomachine 1.

[0048] As illustrated in Figures 1 to 3, the oil system 19 comprises at least one lubrication circuit intended to lubricate the reducer 7, and more precisely the bearings and the toothed wheels of the reducer 7. The oil system 19 also comprises at least one cooling circuit intended to cool an electric generator 28 of the turbomachine 1 which is located in the compartment 16. The electric generator 28 can participate in particular in the hybridization of the turbomachine 1.

[0049] As indicated above, the fuel heated by the heat pump 15 comes from the fuel system 12.

[0050] Advantageously, the fuel system 12 comprises injectors 29 distributed around the axis X to inject fuel into the combustion chamber 10.

[0051] Advantageously, the fuel system 12 comprises a fuel circuit in heat exchange with the first condenser 22.

[0052] As illustrated in Figures 1 to 3, the fuel system 12 comprises an annular row of injectors 29 which are distributed around the axis X, the injectors 29 being secured to a bottom of the combustion chamber 10. The fuel system 12 also comprises a fuel circuit in heat exchange with the first condenser 22.

[0053] Advantageously, the doser 27 is electrically controlled by a control system 30.

[0054] Advantageously, the fuel system 12 comprises a fuel temperature sensor 31, the temperature sensor 31 being located downstream of the first condenser 22 in the fuel circuit. The temperature sensor 31 may be electrically connected to the control system 30.

[0055] The control system 30 can be the control computer of the turbomachine 1 which is conventionally of the FADEC type for “Full Authority Digital Engine Control” in English, or even a separate computer.

[0056] The circuit 20 of the heat pump 15 may have a first architecture, namely: - the first condenser 22 is part of a first branch 32 of the circuit 20; - the second condenser 23 is part of a second branch 33 of the circuit 20; - the circuit 20 comprises a common part 34 comprising at least the evaporator 21; - the inputs of branches 32, 33 are each connected to an output channel of the metering device 27 and the output of the common part 34 is connected to an input channel of the metering device 27.

[0057] The metering device 27 of the first architecture is thus a three-way metering device 27. The metering device 27 can also be configured to adjust the flow rate of heat transfer fluid entering the second condenser 23.

[0058] The circuit 20 of the heat pump 15 may also have a second ar- architecture, namely: - the first condenser 22 and the metering device 27 are part of a first branch 32 of the circuit 20; - the second condenser 23 is part of a second branch 33 of the circuit 20; - the circuit 20 comprises a common part 34 comprising at least the evaporator 21; - the inputs of branches 32, 33 are connected to the output of the common part 34 via a branch 35.

[0059] The metering device 27 of the second architecture is thus a two-way metering device 27.

[0060] Advantageously and whatever the architecture of the circuit 20 of the heat pump 15, the common part 34 of the circuit 20 comprises from upstream to downstream the expansion valve 25, the evaporator 21 and the compressor 26.

[0061] Advantageously, the cold source 24 is an air flow. The air flow can be taken from one of the veins 13, 14 of the turbomachine 1, or else from outside the turbomachine 1.

[0062] According to the first embodiment illustrated in [Fig.2], the circuit 20 of the heat pump 15 comprises: - a common part 34 comprising from upstream to downstream the expansion valve 25, the evaporator 21 and the compressor 26; - a first branch 32 comprising the first condenser 22; - a second branch 33 comprising the second condenser 23; - a metering device 27 comprising an input channel and two output channels, the input channel being connected to the output of the common part 34, and each output channel is connected to the input of one of the branches 32, 33.

[0063] The compressor 26 is driven by an electric motor 36.

[0064] The metering device 27 and the electric motor 36 are here electrically controlled by a control system 30 which is the control computer of the turbomachine 1.

[0065] The control system 30 here controls the flow rates of heat transfer fluid entering the condensers 22, 23, via the metering device 27.

[0066] The fuel system 12 here comprises a fuel temperature sensor 31 which is located downstream of the first condenser 22 in the fuel circuit. The temperature sensor 31 is electrically connected to the control system 30, so as to provide it in real time with the temperature of the fuel located downstream of the first condenser 22.

[0067] The cold source 24 of the second condenser 23 is here a flow of air coming from the secondary vein 14.

[0068] According to the second embodiment illustrated in [Fig.3], the circuit 20 of the heat pump 15 comprises: - a common part 34 comprising from upstream to downstream the expansion valve 25, the evaporator 21 and the compressor 26; - a first branch 32 comprising from upstream to downstream the metering unit 27 and the first condenser 22; - a second branch 33 comprising the second condenser 23; - a branch 35 to connect the inputs of branches 32, 33 to the output of the common part 34.

[0069] Unlike the embodiment of [Fig.2], the metering device 27 here has two channels, namely an inlet channel and an outlet channel.

[0070] The compressor 26 is driven by an electric motor 36.

[0071] The metering device 27 and the electric motor 36 are here electrically controlled by a control system 30 which is the control computer of the turbomachine 1.

[0072] The control system 30 here controls the flow rate of heat transfer fluid entering the first condenser 22, via the metering device 27.

[0073] The fuel system 12 here comprises a fuel temperature sensor 31 which is located downstream of the first condenser 22 in the fuel circuit. The temperature sensor 31 is electrically connected to the control system 30, so as to provide it in real time with the temperature of the fuel located downstream of the first condenser 22.

[0074] The cold source 24 of the second condenser 23 is here a flow of air coming from the secondary vein 14.

[0075] According to the invention, the turbomachines 1 described above allow the implementation of a method for adjusting the temperature of the fuel of the fuel system 12, the method comprising the step of: a) adjusting the temperature of the fuel at the outlet of the first condenser 22 by adjusting the flow rate of heat transfer fluid entering the first condenser 22 via the metering valve 27.

[0076] Such a method aims in particular to heat the fuel so that it reaches or approaches its optimal injection temperature, so as to improve the efficiency of the combustion chamber 10 and minimize the specific consumption of the turbomachine 1.

[0077] The optimum injection temperature generally corresponds to the critical temperature (e.g. 150 degrees) above which the fuel is subject to coking.

[0078] Such a method is for example implemented when the turbomachine 1 is in operation (heating time finished) and the external conditions are cold.

[0079] Such a method can obviously only be implemented if the heat pump 15 has the capacity available to heat the fuel without, however, degrading the re- oil cooling (main function).

[0080] Advantageously, the dosing device 27 is electrically controlled by the control system 30 according to a setpoint.

[0081] The setpoint is determined by the control system 30 from the temperature of the fuel located downstream of the first condenser 22 (provided by the temperature sensor 31) and the critical temperature above which the fuel is subject to coking. Other parameters can of course be taken into account by the control system 30 to determine the setpoint.

Claims

Claims

1. Turbomachine (1) of aircraft (2) comprising: - a fuel supply system (12) of a combustion chamber (10) of the turbomachine (1);- a heat pump (15) comprising a closed circuit (20) in which a heat transfer fluid circulates, the circuit (20) comprising an evaporator (21) configured to exchange heat with oil of the turbomachine (1), a first condenser (22) configured to exchange heat with the fuel of the supply system (12), a second condenser (23) which is mounted in parallel with the first condenser (22) and which is configured to exchange heat with a cold source (24) which is separate from the fuel, an expander (25) configured to expand the heat transfer fluid before entering the evaporator (21), a compressor (26) configured to compress the heat transfer fluid before entering the condensers (22, 23), and a metering device (27) configured to adjust the flow rate of heat transfer fluid entering the first condenser (22).;

2. Turbomachine (1) according to the preceding claim, characterized in that the metering device (27) is electrically controlled by a control system (30).

3. Turbomachine (1) according to the preceding claim, characterized in that the supply system (12) comprises a fuel circuit in heat exchange with the first condenser (22), and a fuel temperature sensor (31) located downstream of the first condenser (22) in the fuel circuit and electrically connected to the control system (30).

4. Turbomachine (1) according to one of the preceding claims, characterized in that the first condenser (22) is part of a first branch (32) of the circuit (20), the second condenser (23) is part of a second branch (33) of the circuit (20), the circuit (20) comprising a common part (34) comprising at least the evaporator (21), the inlets of the branches (32, 33) are each connected to an outlet channel of the metering device (27) and the outlet of the common part (34) is connected to an inlet channel of the metering device (27).

5. Turbomachine (1) according to one of claims 1 to 3, characterized in that the first condenser (22) and the metering device (27) are part of a first branch (32) of the circuit (20), the second condenser (23) is part of a second branch (33) of the circuit (20), the circuit (20) comprising a common part (34) comprising at least the evaporator (21), the inputs of the branches (32, 33) being connected to the output of the common part (34) via a branch (35).

6. Turbomachine (1) according to claim 4 or 5, characterized in that the common part (34) comprises from upstream to downstream the expander (25), the evaporator (21) and the compressor (26).

7. Turbomachine (1) according to one of the preceding claims, characterized in that the cold source (24) is an air flow.

8. Method for adjusting the temperature of the fuel of a supply system (12) of a combustion chamber (10) of a turbomachine (1) according to one of the preceding claims, the method comprising the step of: a) adjusting the temperature of the fuel at the outlet of the first condenser (22) by adjusting the flow rate of heat transfer fluid entering the first condenser (22) via the metering device (27).

9. Method according to the preceding claim, characterized in that the dosing device (27) is electrically controlled by a control system (30) according to a setpoint.

10. Method according to the preceding claim, characterized in that the control setpoint of the metering device (27) is determined by the control system (30), from the temperature of the fuel located downstream of the first condenser (22) in a fuel circuit in heat exchange with the first condenser (22) and from a critical temperature above which the fuel is subject to coking.

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