Method of heating fuel in a turbine fuel supply system

Abstract

A method of heating fuel of an automatic fuel supply system (19), a turbine comprising a heat pump (14) comprising a closed circuit (20) in which a heat transfer fluid circulates, the circuit (20) comprises an evaporator (21) configured to exchange heat with the oil of the turbine, a first condenser (22) configured to exchange heat with the fuel, an expansion valve (23) configured to expand the heat transfer fluid before the heat transfer fluid enters the evaporator (21), and a compressor (24) configured to compress the heat transfer fluid before the heat transfer fluid enters the first condenser (22), the method comprises the steps of c) heating the fuel by operating the heat pump (14) according to a combined cycle in which the compressor (24) is driven at a determined rotational speed in order to supply excess power to the heat transfer fluid to heat the fuel.

Description

Technical Field

[0001] The present invention relates to a method for heating fuel in a fuel supply system for supplying a turbine, and a turbine configured to implement the method. Background Technology

[0002] A dual-flow turbine typically includes a fan driven by a power turbine and a gas generator, the gas of which is used to drive the power turbine. The gas generator includes at least one compressor, a combustion chamber, and at least one turbine. The fan generates an airflow that is divided into a primary flow configured to supply the gas generator and a secondary flow that primarily contributes to the thrust provided by the turbine.

[0003] Turbines also include various oil circuits, the function of which is, for example, to lubricate the moving parts of the turbine (bearings, gears, etc.).

[0004] In order for oil to perform its function effectively, it is crucial to maintain its temperature within a given range, in particular, using a cooling system.

[0005] Engine manufacturers are currently facing a major challenge. In fact, the new turbine architecture incorporates more oil circuits, mainly due to the inclusion of a reduction gear (between the power turbine and the fan) and / or the increased use of a generator to enhance the hybrid nature of the turbine.

[0006] These additional oil circuits inevitably mean an increase in the heat power to be dissipated, thus necessitating an inspection of the existing cooling system.

[0007] To meet this need, the use of heat pump cooling oil is known from the applicant's document FR2993610A1.

[0008] This type of heat pump includes a closed loop through which a heat transfer fluid flows, specifically including an evaporator, a condenser, a compressor, and an expansion valve.

[0009] More specifically, the evaporator evaporates the heat transfer fluid by extracting heat from the oil (heat source). The condenser condenses the heat transfer fluid, releasing the heat into the air stream (cold source). The compressor compresses the heat transfer fluid (gaseous) to increase its pressure, and then it passes through the condenser. The expansion valve expands the heat transfer fluid (liquid) to decrease its pressure, and then it passes through the evaporator.

[0010] In the aforementioned literature, heat pumps are only used for cooling oil.

[0011] However, engine manufacturers have noted that using heat pumps for other functions, particularly fuel heating, could be advantageous.

[0012] Fuel heating is essential when the fuel temperature drops below a critical temperature, below which the fuel is prone to freezing. In particular, when the turbine has been stationary for an extended period and external conditions are cold, it may be necessary to heat the fuel to start the turbine.

[0013] Typically, to meet this requirement, turbines include a separate system dedicated to heating the fuel, which in particular includes a fuel / oil heat exchanger. More specifically, once the oil is heated, the oil's thermal power is used to heat the fuel via the heat exchanger.

[0014] Engine manufacturers also note that heat pump compressors are designed to handle worst-case scenarios, where the oil has a large amount of heat power to dissipate (e.g., high operating speeds combined with high external temperatures) and the airflow (cold source) is at a high temperature. However, in practice, compressors sometimes operate at only maximum capacity. Therefore, engine manufacturers point out that it may be advantageous to use the compressor's capacity for other purposes, particularly fuel heating.

[0015] Therefore, the object of this invention is to optimize the heat pump so that it can not only cool oil but also heat fuel. Summary of the Invention

[0016] Therefore, the present invention proposes a method for heating fuel in a fuel supply system for a turbine, the turbine including a heat pump, the heat pump including a closed loop in which a heat transfer fluid flows, the loop including an evaporator configured to exchange heat with the turbine's oil, a first condenser configured to exchange heat with the fuel, an expansion valve configured to expand the heat transfer fluid before it enters the evaporator, and a compressor configured to compress the heat transfer fluid before it enters the first condenser, the method comprising the following steps: c) The fuel is heated by operating a heat pump according to a combined cycle in which a compressor is driven at a defined rotational speed to supply excess power configured to heat the fuel to the heat transfer fluid.

[0017] This method allows the use of heat pumps to heat fuel.

[0018] This cycle is called a "combined cycle" because it combines oil cooling and oil heating functions.

[0019] When a heat pump operates in a combined cycle, the compressor provides excess / additional power to the heat transfer fluid for heating the fuel. The heat power extracted from the oil is obviously added to the excess power provided by the compressor to heat the fuel.

[0020] In other words, when the heat pump is running according to the combined cycle, the compressor provides more power than is required to cool the oil in order to simultaneously meet the need to heat the fuel.

[0021] Using heat pumps to heat fuel enables the elimination or reduction of existing systems dedicated to this function, which is particularly beneficial for turbine weight, overall size, structural simplification, specific consumption, and efficiency.

[0022] Furthermore, using a heat pump to heat fuel is more efficient than existing systems specifically designed for this function, allowing for a reduction in the total turbine heating time. This is especially true when the compressor drive speed is close to its maximum drive speed.

[0023] As a reminder, the aircraft can only take off when the temperature of the oil and fuel in the turbine reaches a threshold that ensures there is no risk of the turbine freezing.

[0024] The method according to the invention may include one or more of the following features and / or steps, taken individually or in combination with each other: - The determined rotational speed is greater than 50% of the compressor's maximum drive speed, preferably greater than 60% of the compressor's maximum drive speed, and more preferably greater than 70% of the compressor's maximum drive speed; -The method includes the following steps prior to step c): a) Compare the temperature of the fuel to a first reference temperature, below which the fuel will freeze; If the comparison in step a) indicates that the fuel temperature is below the first reference temperature, then the fuel is heated in step c). -The method includes the following steps prior to step c): b) Compare the temperature of the oil with a second reference temperature, which corresponds to the temperature of the oil at the end of preheating; If the comparison in step b) indicates that the oil temperature is higher than the second reference temperature, then the fuel is heated in step c).

[0025] The present invention also relates to a turbine configured to implement the method described above, the turbine including a heat pump, the heat pump including a closed loop in which a heat transfer fluid flows, the loop including: an evaporator configured to exchange heat with oil in the turbine, a first condenser configured to exchange heat with fuel in a fuel supply system, an expansion valve configured to expand the heat transfer fluid before it enters the evaporator, and a compressor configured to compress the heat transfer fluid before it enters the first condenser.

[0026] The turbine according to the invention may include one or more of the following features and / or steps, taken independently or in combination with each other: - The compressor is driven by an electric motor, which is electrically controlled by a control device; - The circuit includes a second condenser installed in parallel with the first condenser, the second condenser being configured to exchange heat with a heat source different from the fuel; -When the heat pump is running according to the combined cycle, the heat transfer fluid flows only in the first condenser; -The heat source is airflow; - The first condenser forms part of the first branch of the circuit, and the second condenser forms part of the second branch of the circuit. The circuit includes a common section including at least an evaporator, and the inlet of the branch is connected to the outlet of the common section via a three-way valve. Attached Figure Description

[0027] The invention will be better understood from the following description by way of non-limiting examples and with reference to the accompanying drawings, and other details, features and advantages of the invention will become clearer, wherein: [ Figure 1 ] Figure 1 This is a schematic axial half-sectional view of a turbine including a heat pump according to the present invention; [ Figure 2 ] Figure 2 This is a detailed view of the heat pump in the first embodiment; [ Figure 3 ] Figure 3 This is a detailed view of the heat pump in the second embodiment; [ Figure 4 ] Figure 4 This is a schematic diagram of a method for heating fuel in a turbine according to the present invention. Detailed Implementation

[0028] Figure 1 The turbine 1 used for the aircraft 2 is partially shown. The aircraft 2 is, for example, an airplane.

[0029] like Figure 1 As shown, turbine 1 is a dual-flow turbojet engine, which typically includes a duct fan 3, a gas generator 4, and a power turbine 5.

[0030] More specifically, the fan 3 can rotate about axis X relative to the fixed structure 6 of the turbine 1. The fan 3 is driven to rotate by the power turbine 5 via a reduction gear 7.

[0031] The reducer 7 is, for example, a rotary reducer, which has the advantages of being compact and having a high reduction ratio. The reducer 7 is housed in a housing commonly referred to as an "oil seal housing" and is lubricated with oil. The oil is specifically configured to lubricate the moving parts of the reducer 7, particularly the bearings and gears.

[0032] The gas generator 4 includes a low-pressure compressor 8, a high-pressure compressor 9, a combustion chamber 10, and a high-pressure turbine 11 (or an expansion turbine). The high-pressure compressor 9 is driven to rotate by the high-pressure turbine 11. The low-pressure compressor 8 is driven by a fan 3.

[0033] like Figure 1 As shown, the airflow F generated by the fan 3 is divided into a primary flow f1 and a secondary flow f2 by the fixed structure 6 of the turbine 1. The primary flow f1 enters the primary pipe 12 to supply the gas generator 4, and the secondary flow f2 flows in the secondary pipe 13 surrounding the gas generator 4 to provide most of the thrust.

[0034] Figure 1 The examples shown are by no means limiting; turbine 1 may be, for example, a turbojet engine, a turboprop engine, a turboshaft engine, or even a turbine including one or more ductless fans (e.g., UDF (ductless fan) type or USF (ductless single fan) type).

[0035] like Figure 1 As shown, turbine 1 also includes heat pump 14. Heat pump 14 is located in a compartment 15 defined between the casing 16 (generally referred to as the "fan casing") surrounding fan 3 and the cowling of nacelle 17 of turbine 1. Alternatively, heat pump 14 may be located, for example, in a duct compartment.

[0036] The heat pump 14 is configured to cool the oil in the oil supply system 18 (generally referred to as the "oil system" and hereinafter referred to as the "oil system") of the turbine 1 when the turbine 1 is running in a "normal" cycle.

[0037] According to the invention, the heat pump 14 is also configured to heat the fuel in the fuel supply system 19 (generally referred to as the "fuel system" and hereinafter referred to as the "fuel system") of the turbine 1 when operating in a "combined" cycle, while cooling the oil in the oil system 18.

[0038] To achieve this, the heat pump 14 includes a closed loop 20 in which a heat transfer fluid flows. The loop 20 includes an evaporator 21 configured to exchange heat with oil from the oil system 18, a first condenser 22 configured to exchange heat with fuel from the fuel system 19, an expansion valve 23 configured to expand the heat transfer fluid before it enters the evaporator 21, and a compressor 24 configured to compress the heat transfer fluid before it enters the first condenser 22.

[0039] As is customary, in this application, the terms “upstream” and “downstream” or “inlet” and “outlet” are defined relative to the flow direction of the heat transfer fluid in the closed loop 20 of the heat pump 14.

[0040] As described above, the oil cooled by the heat pump 14 comes from the oil system 18.

[0041] The oil system 18 may include one or more lubrication circuits through which oil flows and which one or more lubrication circuits are configured to lubricate movable elements of the turbine 1.

[0042] The oil system 18 may include one or more cooling circuits through which oil flows and which one or more cooling circuits are configured to cool the motor of the turbine 1.

[0043] like Figures 1 to 3 As shown, the oil system 18 includes at least one lubrication circuit configured to lubricate the reducer 7, and more specifically, the bearings and gears of the reducer 7. The oil system 18 also includes at least one cooling circuit configured to cool the generator 25 of the turbine 1. The generator 25 can be specifically used to enable hybrid operation of the turbine 1.

[0044] As described above, the fuel heated by the heat pump 14 comes from the fuel system 19.

[0045] The fuel system 19 may include one or more loops through which fuel flows and the one or more loops are configured to supply variable geometries (e.g., variable pitch guide vanes or blades) to actuate them.

[0046] The fuel system 19 may include one or more loops through which fuel flows and which loops are configured to supply the combustion chamber 10 of the gas generator 4.

[0047] like Figures 1 to 3 As shown, the fuel system 19 includes at least one circuit configured to supply a variable geometry and at least one circuit configured to supply the combustion chamber 10.

[0048] Advantageously, the compressor 24 is driven by an electric motor 26, which is electrically controlled by a control device 27.

[0049] The circuit 20 of the heat pump 14 may include a second condenser 28 installed in parallel with the first condenser 22. The second condenser 28 is configured to exchange heat with a heat source 29 that is different from the fuel.

[0050] Advantageously, the heat source 29 is an airflow. The airflow can be drawn from one of the ducts 12 and 13 of the turbine 1 or from the outside of the turbine 1.

[0051] Advantageously, when the circuit 20 includes a first condenser 22 and a second condenser 28, the heat transfer fluid flows only in the first condenser 22 when the heat pump 14 is operating according to the combined cycle. This arrangement minimizes the time spent heating the fuel and thus minimizes the total heating time of the turbine 1.

[0052] The circuit 20 of the heat pump 14 may include a separate compressor to compress the heat transfer fluid entering the second condenser 28.

[0053] In the case where loop 20 includes a first condenser 22 and a second condenser 28, the first condenser 22 may form part of a first branch 30 of loop 20, the second condenser 28 may form part of a second branch 31 of loop 20, and loop 20 may include a common portion 32 including at least an evaporator 21. In this case, the inlets of branches 30 and 31 may be connected to the outlet of the common portion 32 via a three-way valve 33.

[0054] The three-way valve 33 can be in a predetermined position (TOR three-way valve, TOR is an abbreviation for Tout ou Rien, meaning "open or closed") or can be controlled within a predetermined adjustment range, for example, to precisely regulate the flow rate of the heat transfer fluid entering each of the branches 30, 31.

[0055] Advantageously, the three-way valve 33 is controlled by the control device 27 based on the temperature of the oil to be cooled and the temperature of the fuel to be heated. Of course, the control device 27 can also consider other parameters to control the three-way valve 33.

[0056] according to Figure 2 In the embodiment shown, the circuit 20 of the heat pump 14 includes only the first condenser 22, which exchanges heat with the fuel in the fuel system 19.

[0057] The compressor 24 is driven by an electric motor 26, which is electrically controlled by a control device 27. The control device 27 is a calculator, which can be a Full Authority Digital Engine Control (FADEC) type calculator or a standalone calculator.

[0058] according to Figure 3 In the embodiment shown, the circuit 20 of the heat pump 14 includes a first condenser 22 that exchanges heat with fuel in the fuel system 19 and a second condenser 28 that exchanges heat with a heat source 29, in which case the heat source 29 is an airflow from the secondary duct 13.

[0059] More specifically, loop 20 includes: - Common part 32, which includes expansion valve 23, evaporator 21 and compressor 24 from upstream to downstream; - A first branch 30 and a second branch 31 are installed in parallel with each other. The first branch 30 includes a first condenser 22, and the second branch 31 includes a second condenser 28.

[0060] The inlets of branches 30 and 31 are connected to the outlet of common section 32 via three-way valve 33.

[0061] The compressor 24 is driven by an electric motor 26.

[0062] The electric motor 26 and the three-way valve 33 are electrically controlled by the control device 27. The control device 27 is a calculator, which can be a Full Authority Digital Engine Control (FADEC) type calculator or a standalone calculator.

[0063] According to the present invention, the turbine 1 described above is configured to implement a fuel heating method, the method comprising the following steps: c) The fuel is heated by operating the heat pump 14 according to a combined cycle in which the compressor 24 is driven at a defined rotational speed to supply excess power configured to heat the fuel to the heat transfer fluid.

[0064] This method allows the use of the aforementioned heat pump 14 to heat fuel.

[0065] This cycle is called a "combined cycle" because it combines oil cooling and fuel heating functions.

[0066] When heat pump 14 operates in a combined cycle, compressor 24 provides excess / additional power to the heat transfer fluid specifically for heating the fuel. Clearly, the heat power extracted from the oil is added to the excess power supplied by compressor 24 to heat the fuel.

[0067] In other words, when the heat pump 14 is running according to the combined cycle, the power supplied by the compressor 24 is greater than the power required for cooling the oil, thus also meeting the need for heating the fuel.

[0068] Using a heat pump 14 to heat the fuel can eliminate or reduce the systems existing in the prior art that are dedicated to this function, and is particularly beneficial to the mass, overall size, structural simplification, specific consumption and efficiency of the turbine 1.

[0069] Furthermore, using heat pump 14 to heat fuel is more efficient than existing systems dedicated to this function, which allows for a reduction in the total heating time of turbine 1. This is especially true when the compressor 24 is driven near its maximum drive speed.

[0070] Such a heating method can be carried out, for example, during the cold start of turbine 1 in a cold external environment.

[0071] The specific rotational speed at which the compressor is driven during the combined cycle depends in particular on the temperature of the fuel.

[0072] Advantageously, the determined rotational speed is greater than 50% of the maximum drive speed of the compressor 24, and preferably greater than 60% of the maximum drive speed of the compressor 24, and more preferably greater than 70% of the maximum drive speed of the compressor 24.

[0073] Prior to step c), the fuel heating method may include the following steps: a) Compare the temperature of the fuel to a first reference temperature, below which the fuel will freeze; If the comparison in step a) indicates that the fuel temperature is below the first reference temperature, then the fuel is heated in step c).

[0074] Step a) is used to check whether the fuel needs to be heated. Of course, a margin can be applied to the first reference temperature.

[0075] Prior to step c), the fuel heating method may include the following steps: b) Compare the temperature of the oil with a second reference temperature, which corresponds to the temperature of the oil at the end of its preheating; If the comparison performed in step b) indicates that the oil temperature is higher than the second reference temperature, then the fuel is heated in step c).

[0076] Step b) Ensure the oil is preheated before heating the fuel. Of course, a margin can be applied to a second reference temperature.

[0077] As described above, the heat pump 14 can also be operated according to one or more conventional cycles (depending on the structure of the heat pump 14) simply for cooling the oil.

[0078] according to Figure 4 The example shown includes steps a), b), and c) in chronological order of occurrence.

Claims

1. A method for heating fuel for supplying fuel to a fuel supply system (19) of a turbine (1), the turbine (1) including a heat pump (14), the heat pump including a closed loop (20) in which a heat transfer fluid flows, the loop (20) including: The method comprises the following steps: an evaporator (21) configured to exchange heat with the oil of the turbine (1), a first condenser (22) configured to exchange heat with the fuel, an expansion valve (23) configured to expand the heat transfer fluid before it enters the evaporator (21), and a compressor (24) configured to compress the heat transfer fluid before it enters the first condenser (22). c) The fuel is heated by operating the heat pump (14) according to a combined cycle in which the compressor (24) is driven at a defined rotational speed to supply the heat transfer fluid with excess power configured to heat the fuel.

2. The method according to claim 1, characterized in that, The determined rotational speed is greater than 50% of the maximum drive speed of the compressor (24), preferably greater than 60% of the maximum drive speed of the compressor (24), and more preferably greater than 70% of the maximum drive speed of the compressor (24).

3. The method according to any one of the preceding claims, characterized in that, The method includes the following steps prior to step c): a) Compare the temperature of the fuel to a first reference temperature, below which the fuel will freeze; If the comparison in step a) indicates that the fuel temperature is below the first reference temperature, then the fuel is heated in step c).

4. The method according to any one of the preceding claims, characterized in that, The method includes the following steps prior to step c): b) Compare the temperature of the oil with a second reference temperature, the second reference temperature corresponding to the temperature of the oil at the end of preheating; If the comparison in step b) indicates that the oil temperature is higher than the second reference temperature, then the fuel is heated in step c).

5. A turbine (1) configured to perform the method according to any one of the preceding claims, the turbine (1) comprising a heat pump (14) including a closed loop (20) in which a heat transfer fluid flows, the loop (20) comprising: An evaporator (21) configured to exchange heat with the oil of the turbine (1), a first condenser (22) configured to exchange heat with the fuel of the fuel supply system (19), an expansion valve (23) configured to expand the heat transfer fluid before it enters the evaporator (21), and a compressor (24) configured to compress the heat transfer fluid before it enters the first condenser (22).

6. The turbine (1) according to the preceding claim, characterized in that, The compressor (24) is driven by an electric motor (26), which is electrically controlled by a control device (27).

7. The turbine (1) according to claim 5 or 6, characterized in that, The circuit (20) includes a second condenser (28) installed in parallel with the first condenser (22), the second condenser (28) being configured to exchange heat with a heat source (29) different from the fuel.

8. The turbine (1) according to the preceding claim, characterized in that, When the heat pump (14) is running according to the combined cycle, the heat transfer fluid flows only in the first condenser (22).

9. The turbine (1) according to claim 7 or 8, characterized in that, The heat source (29) is an airflow.

10. The turbine (1) according to any one of claims 7 to 9, characterized in that, The first condenser (22) forms part of a first branch (30) of the circuit (20), and the second condenser (28) forms part of a second branch (31) of the circuit (20). The circuit (20) includes a common section (32), which includes at least the evaporator (21). The inlet of the branch (30, 31) is connected to the outlet of the common section (32) via a three-way valve (33).

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