Fuel circuit of an aircraft turbomachine comprising a thermal energy transfer system with an oil circuit and method of cooling said oil circuit.

Abstract

A fuel circuit (10) of an aircraft turbomachine comprising a thermal energy transfer system (1) with an oil circuit (20) comprising: - an upstream line (5) supplied with fuel (C) by a pump (12) and by the excess of a metering valve (15); - a downstream line (8) opening towards the metering valve (15), and - a fuel distributor (2) controllable between a first position (P1), in which the fuel (C) circulates via a low flow line (6) comprising a first oil-fuel heat exchanger (3), and a second position, in which the fuel (C) circulates via a high flow line (7), a second heat exchanger (4) generating lower pressure losses than the first heat exchanger (3) being mounted on one of the high flow line (7), the upstream line (5) and the downstream line (8). Abstract figure: Figure 1

Description

Title of the invention: Fuel circuit of an aircraft turbomachine comprising a thermal energy transfer system with an oil circuit and method for cooling said oil circuit. Technical field

[0001] The present invention relates to an aircraft turbomachine and more specifically aims at a fuel circuit comprising a thermal energy transfer system with an oil circuit and its method for cooling said oil circuit.

[0002] In a known manner, an aircraft comprises one or more turbomachines each equipped with a combustion chamber in which air and fuel react together, so as to release the energy necessary for the thrust of the aircraft. The air is taken from outside the turbomachine and guided towards the combustion chamber by an air stream. The fuel is conveyed from at least one tank via a fuel circuit.

[0003] In a known manner, the fuel circuit of an aircraft turbomachine comprises, from upstream to downstream, a low-pressure pump configured to take fuel from a tank of the aircraft, a filter, a high-pressure pump and a metering valve known to those skilled in the art by the abbreviation FMU (“Fuel Metering Unit”). The metering valve distributes the fuel into injectors which spray it in the form of droplets into the combustion chamber. The metering valve also guides the excess fuel into a recirculation line to be reinjected downstream or upstream of the low-pressure pump.

[0004] In a known manner, the fuel circuit also comprises an oil-fuel type heat exchanger mounted between the low-pressure pump and the metering valve. Such a heat exchanger makes it possible to transfer thermal energy between the fuel circuit and an oil circuit ensuring the lubrication and cooling of the equipment in the turbomachine. During the flight of the aircraft, the heat exchanger allows the oil circuit to transfer to the fuel circuit the heat accumulated in contact with the equipment. When starting the turbomachine, the heat exchanger also makes it possible to heat the fuel before it is injected into the combustion chamber.

[0005] In practice, for certain operating points of the turbomachine, in particular during an idling phase, the heat exchanger does not allow the oil circuit to be sufficiently cooled because the fuel flow rate is too low. This causes the oil circuit to heat up, which can reduce the lubrication and turbomachine cooling.

[0006] To overcome this drawback, it is known from application EP0721061A1 to add an air-oil type heat exchanger to the oil circuit. Valves make it possible to guide the oil into the air-oil exchanger and into the oil-fuel exchanger or to bypass them depending on the temperature of the oil. Such an air-oil exchanger requires providing an air intake in the air stream reducing the performance of the aircraft, or outside the turbomachine which affects the aerodynamics. In addition, the performance of such an air-oil exchanger depends on the temperature of the air taken which can vary greatly depending on climatic conditions, which can freeze the oil or heat it undesirably.

[0007] The invention thus aims to eliminate at least some of these drawbacks. PRESENTATION OF THE INVENTION

[0008] The invention relates to a fuel circuit of an aircraft turbomachine comprising: • a pump configured to draw fuel from a tank, • a metering valve configured to distribute the fuel among a plurality of injectors and to guide excess fuel into a recirculation line, • a thermal energy transfer system configured to cool an oil circuit of the aircraft turbomachine, the thermal energy transfer system comprising an upstream line, supplied with fuel by the pump and by the recirculation line, and a downstream line opening towards the metering valve, the thermal energy transfer system comprising a fuel distributor controllable between at least: • a first position, in which the fuel flows from the upstream line to the downstream line via a low flow line, on which at least one first oil-fuel type heat exchanger is mounted, and • a second position, in which the fuel circulates from the upstream line to the downstream line via a high flow line separate from the low flow line, at least one second oil-fuel type heat exchanger being mounted on one of the high flow line, the upstream line and the downstream line, the second heat exchanger being configured to generate pressure losses lower than those generated by the first heat exchanger, so as to regulate the heat exchanges with the oil circuit.

[0009] The thermal energy transfer system according to the invention comprises advantageously ously several heat exchangers of different sizes and several possible paths for the fuel, which makes it possible to adjust the heat exchanges between the fuel circuit and the oil circuit of an aircraft turbomachine according to the fuel flow rate. The thermal energy transfer system is advantageously supplied by the fuel coming, on the one hand, from the tank, and on the other hand, from the recirculation line, for optimized heat exchanges. The cooling of the oil circuit is ensured efficiently and reliably at low flow rates, without reducing performance over the rest of the flight envelope.

[0010] According to one aspect of the invention, the fuel dispenser is of the passive control type depending on a parameter of the fuel or the oil. Such a fuel dispenser advantageously does not require any control by the operator or a control member. The system is advantageously simpler and less expensive.

[0011] According to one aspect of the invention, the fuel distributor is in the form of a pressure relief valve configured to move into the second position when the fuel pressure losses generated by the first heat exchanger exceed a first predetermined threshold. Such a passive distributor advantageously makes it possible to avoid an undesirable increase in fuel pressure.

[0012] According to one aspect of the invention, the fuel distributor is in the form of a thermostatic valve configured to move into the second position when the oil temperature is below a second predetermined threshold. Such a passive distributor advantageously allows simple and effective control of the temperature of the oil circuit.

[0013] According to another aspect of the invention, the fuel distributor is of the active control type, preferably electrical. Such an active distributor advantageously allows more flexible and more reliable control.

[0014] According to one aspect of the invention, the fuel circuit comprises an auxiliary fuel distributor mounted in bypass of the fuel distributor and controllable between the first position and the second position. This increases reliability and in particular makes it possible to avoid an undesirable increase in fuel pressure.

[0015] According to one aspect of the invention, the fuel distributor is also controllable in a third position, in which the fuel flows from the upstream line to the downstream line via a very low flow line, on which is mounted at least one third oil-fuel type heat exchanger configured to generate pressure losses greater than that generated by the first heat exchanger. A greater number of heat exchangers of different sizes and possible paths for the fuel allows more precise regulation of the heat exchanges between the oil circuit and the fuel circuit.

[0016] The invention also relates to a fuel circuit assembly as described previously and an oil circuit of an aircraft turbomachine, in which the first heat exchanger and the second heat exchanger are mounted in series on the oil circuit. This does not impact the size of the oil circuit.

[0017] According to one aspect of the invention, the oil circuit comprises at least one bypass line, mounted as a bypass of the first heat exchanger, and at least one controllable oil distributor between at least: • a main position, in which the oil circulates in the first heat exchanger and the second heat exchanger, and • a secondary position, in which the oil circulates in the bypass line and the second heat exchanger.

[0018] Such a bypass line advantageously allows the oil to pass through only one heat exchanger, for example when the oil flow rate is high or its temperature low.

[0019] The invention also relates to a method for cooling an oil circuit of an aircraft turbomachine by means of a fuel circuit as described previously, the control method comprising a step of controlling the first position or the second position of the fuel distributor of the fuel circuit. PRESENTATION OF THE FIGURES

[0020] 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.

[0021] [Fig.l] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of an aircraft turbomachine according to a first embodiment of the invention, in which the fuel distributor is of the active control type in the first position and the second heat exchanger is mounted on the high flow line.

[0022] [Fig.2] is a schematic representation of the thermal energy transfer system of [Fig.l], when the fuel dispenser is in the second position.

[0023] [Fig. 3] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of an aircraft turbomachine according to a second embodiment of the invention, in which the second heat exchanger is mounted on the downstream line.

[0024] [Fig.4] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of a turbomachine. aircraft according to a third embodiment of the invention, in which the second heat exchanger is mounted on the upstream line.

[0025] [Fig. 5] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of an aircraft turbomachine according to a fourth embodiment of the invention, in which the fuel distributor is a passive thermostatic valve.

[0026] [Fig. 6] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of an aircraft turbomachine according to a fifth embodiment of the invention, in which the fuel distributor is a passive pressure relief valve.

[0027] [Fig.7] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of an aircraft turbomachine according to a sixth embodiment of the invention, in which the oil circuit comprises a bypass line of the first heat exchanger.

[0028] [Fig. 8] is a schematic representation of a heat exchange transfer system between a fuel circuit and an oil circuit of an aircraft turbomachine according to a sixth embodiment of the invention, in which the oil circuit comprises a bypass line of the first heat exchanger.

[0029] 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

[0030] With reference to [Fig.l], the invention relates to an aircraft turbomachine comprising a combustion chamber 17 in which air and fuel C react together, so as to release the energy necessary for the thrust of the aircraft. The aircraft turbomachine conventionally comprises: • an air stream (not shown) configured to take air from outside the turbomachine and guide it into the combustion chamber 17, • a fuel circuit 10 configured to convey the fuel into the combustion chamber 17, and • an oil circuit 20 providing lubrication and cooling of the aircraft turbomachine equipment.

[0031] With reference to [Fig.l], the fuel circuit 10 conventionally comprises from upstream to downstream a pump 12, called a “low pressure pump”, configured to take the fuel C from one or more tanks 11 on board the aircraft, a filter 13, a high pressure pump 14 configured to accelerate the fuel C and a metering valve 15 known to those skilled in the art by the abbreviation FMU (“Fuel Metering Unit »). The metering valve 15 is configured to distribute the fuel C into injectors 16 which spray it in the form of droplets into the combustion chamber 17. The metering valve 15 also guides the excess fuel C into a recirculation line 18 to be reinjected downstream of the low-pressure pump 12.

[0032] According to the invention and with reference to FIGS. 1 and 2, the fuel circuit 10 comprises a thermal energy transfer system 1 configured to cool the oil circuit 20. The thermal energy transfer system 1 according to the invention comprises: • an upstream line 5, supplied with fuel C by the low pressure pump 12 and by the recirculation line 18, • a downstream line 8 leading to the metering valve 15, • a fuel distributor 2 controllable between: • a first position PI illustrated in figure 1, in which the fuel C circulates from the upstream line 5 to the downstream line 8 via a low flow line 6, on which a first heat exchanger 3 of the oil-fuel type is mounted, and • a second position P2 illustrated in figure 2, in which the fuel C circulates from the upstream line 5 to the downstream line 8 via a high flow line 7 separate from the low flow line 6, on which is mounted a second heat exchanger 4 of the oil-fuel type configured to generate pressure losses lower than those generated by the first heat exchanger 3, so as to regulate the thermal exchanges with the oil circuit 20.

[0033] Still according to the invention, the second heat exchanger 4 is alternately mounted on the downstream line 8, as illustrated in [Fig.3], or on the upstream line 5, as illustrated in [Fig.4].

[0034] As illustrated in [Fig.l], the thermal energy transfer system 1 is supplied by the fuel C coming from both the tank 10 and the recirculation line 18, which makes it possible to maximize the thermal exchanges with the oil circuit 20.

[0035] Advantageously, as illustrated in [Fig. 2], in the presence of a high fuel flow rate C, for example during takeoff, the fuel distributor 2 guides the fuel C successively in the upstream line 5, the high flow rate line 7 and the downstream line 8, so as to pass through only the second heat exchanger 4. The second heat exchanger 4 is advantageously sized for high fuel flow rates C, that is to say that it generates low pressure losses when the fuel C passes through it, which is sufficient to effectively cool the oil circuit 20 without causing an undesirable increase in the pressure of the fuel C.

[0036] As illustrated in [Fig.l], in the presence of a low flow rate of fuel C, for example during an idling phase, the fuel distributor 2 guides the fuel C successively in the upstream line 5, the low flow rate line 6 and the downstream line 8, so as to pass through the first heat exchanger 3 and, in certain cases also the second heat exchanger 4. The first heat exchanger 3 is advantageously dimensioned for low flow rates of fuel C, that is to say that it generates greater pressure losses when it is crossed by the fuel C. For example, the second heat exchanger 4 has more changes of direction and / or more asperities and / or more variations in passage sections and / or a smaller passage section and / or a greater length than the first heat exchanger 3. This makes it possible, despite the low flow rate of fuel C, to effectively cool the oil circuit 20.

[0037] The thermal energy transfer system 1 thus makes it possible to adjust the thermal exchanges between the fuel circuit 10 and the oil circuit 20 of the aircraft turbomachine as a function of the fuel flow rate C. The cooling of the oil circuit 20 is ensured efficiently and reliably at low flow rate, without reducing the performance at high flow rate.

[0038] According to a first aspect of the invention illustrated in Figures 1 and 2, the first heat exchanger 3 and the second heat exchanger 4 are mounted according to a parallel architecture, one on the low flow line 6 and the other on the high flow line 7. The fuel C thus passes only through the first heat exchanger 3 when it is guided in the low flow line 6 and only through the second heat exchanger 4 when it is guided in the high flow line 7.

[0039] In this example, the fuel distributor 2 is of the active control type, in particular electrically controlled, for example by a solenoid valve. The fuel distributor 2 is for example in the form of a slide valve mounted on the upstream line 5 and configured, in the first position P1, to guide all of the fuel C into the low flow line 6, and in the second position P2, to guide all of the fuel C into the high flow line 7.

[0040] According to a preferred aspect illustrated in Figures 1 and 2, the oil circuit 20 passes successively through the first heat exchanger 3 and the second heat exchanger 4. In other words, the first heat exchanger 3 and the second heat exchanger 4 are mounted in series on the oil circuit 20.

[0041] The embodiment of [Fig. 3] differs from that of figures 1 and 2 in that the second heat exchanger 4 is mounted on the downstream line 8. When the fuel distributor 2 is in the first position P1, the fuel C passes through the first heat exchanger 3 and then the second heat exchanger 4 which are mounted in series. In the second position P2, the fuel C passes only through the second heat exchanger 4. Such a series connection helps to improve the thermal efficiency of the system but slightly increases the pressure losses. The choice of series or parallel connection depends on the engine configuration.

[0042] The embodiment of [Fig.4] differs from that of [Fig.3] in that the second heat exchanger 4 is mounted on the upstream line 5. Thus, in the first position PI, the second heat exchanger 4 is located upstream of the first heat exchanger 3 and is therefore crossed first by the fuel C.

[0043] In the examples of Figures 3 and 4, the fuel distributor 2 is mounted on the high-flow line 7 and is configured, in the first position P1, to close the high-flow line 7 ([Fig.3]), and in the second position P2, to open the high-flow line 7. The fuel distributor 2 is in this example in the form of a slide valve and is actively controlled, for example by a solenoid valve. The fuel distributor 2 of Figures 1 and 2 could alternatively be used.

[0044] The embodiments of Figures 5 and 6 differ from those of Figures 1 and 2 in that the fuel distributor 2', 2” is of the passive control type, requiring no intervention from the operator or a control member. In the example of [Fig.6], the fuel distributor 2” is in the form of a pressure relief valve configured to move into the first position P1, when the fuel pressure losses C generated by the first heat exchanger 3 are less than a first predetermined threshold, and into the second position P2, when they exceed the first predetermined threshold.

[0045] In the example of [Fig. 5], the fuel distributor 2' is in the form of a thermostatic valve 2' configured to move into the first position P1 when the temperature of the oil H is higher than a second predetermined threshold, and into the second position P2 when the temperature of the oil H is lower than the second predetermined threshold. In this example, an auxiliary fuel distributor 30, such as a pressure relief valve, is also mounted in bypass of the fuel distributor 2' and controllable between the first position P1 and the second position P2. This forces passage into the high flow line 7 when the fuel pressure drops C exceed a predetermined threshold, to avoid an undesirable increase in pressure in the fuel circuit 10.

[0046] According to one aspect of the invention illustrated in [Fig.7], the oil circuit 20 comprises a bypass line 21 mounted as a bypass of the first heat exchanger 3 and an oil distributor 22 controllable between: • a main position RI, in which the oil H circulates in the first heat exchanger 3 and the second heat exchanger 4, and • a secondary position R2, in which the oil H circulates in the bypass line 21 and the second heat exchanger 4.

[0047] In this example, the oil distributor 22 is in the form of a pressure relief valve configured to move into the secondary position R2 when the oil pressure losses H through the first heat exchanger 3 exceed a threshold. Alternatively, or in a complementary manner as in the example of [Fig.7], an oil distributor 23 in the form of a thermostatic valve is mounted in bypass of the first heat exchanger 3 and configured to move into the secondary position R2 when the oil temperature H is above a threshold.

[0048] According to one aspect of the invention illustrated in [Fig.8], the fuel distributor 2, 2', 2” is also controllable in a third position P3, in which the fuel C circulates from the upstream line 5 to the downstream line 8 via a very low flow line 9, on which is mounted a third heat exchanger 31 of the oil-fuel type configured to generate pressure losses greater than that generated by the first heat exchanger 3. The thermal energy transfer system 1 thus advantageously comprises three fuel lines 6, 7, 9 extending in parallel, making it possible to precisely adapt the heat transfers with the oil circuit 20 as a function of the flow rate of the fuel C.

[0049] As illustrated in [Fig.8], the oil circuit 20 preferably passes in series through the first, second and third heat exchangers 3, 4, 31. A bypass line 21 of one or more heat exchangers may be provided as in the embodiment of [Fig.7].

[0050] It goes without saying that the number of fuel lines could be greater than three but this would increase the space requirement. Similarly, it goes without saying that other additional heat exchangers could be mounted in series with the first and / or the second and / or the third heat exchangers 3, 4, 31, but this would also increase the space requirement.

[0051] The invention also relates to a method for cooling the oil circuit 20 by means of the fuel circuit 10 consisting of controlling the movement of the fuel distributor 2, 2', 2” into one of the first, second and third positions P1, P2, P3. According to one aspect illustrated in Figures 1 to 4, the movement of the fuel distributor 2 is controlled actively, in particular by the operator or by a control member, for example during an idling phase of the aircraft turbomachine. According to another aspect illustrated in Figures 5 and 6, the movement of the fuel distributor 2', 2” is implemented passively when a parameter of the oil H or the fuel C, preferably acquired by measurement, exceeds a predetermined threshold.

Claims

Claims

1. Fuel circuit (10) of an aircraft turbomachine comprising: • a pump (12) configured to take the fuel (C) from a tank (11), • a metering valve (15) configured to distribute the fuel (C) between a plurality of injectors (16) and to guide the excess fuel (C) into a recirculation line (18), • a thermal energy transfer system (1) configured to cool an oil circuit (20) of the aircraft turbomachine, the thermal energy transfer system (1) comprising an upstream line (5), supplied with fuel (C) by the pump (12) and by the recirculation line (18), and a downstream line (8) opening towards the metering valve (15), the thermal energy transfer system (1) comprising at least one fuel distributor (2, 2', 2”) controllable between at least: • a first position (PI),in which the fuel (C) flows from the upstream line (5) to the downstream line (8) via a low flow line (6), on which is mounted at least one first heat exchanger (3) of the oil-fuel type, and • a second position (P2), in which the fuel (C) flows from the upstream line (5) to the downstream line (8) via a high flow line (7) separate from the low flow line (6), at least one second heat exchanger (4) of the oil-fuel type being mounted on one of the high flow line (7), the upstream line (5) and the downstream line (8), the second heat exchanger (4) being configured to generate pressure losses lower than those generated by the first heat exchanger (3), so as to regulate the heat exchanges with the oil circuit (20).,

2. Fuel circuit (10) according to claim 1, wherein the fuel distributor (2', 2”) is of the passive control type in function of a fuel (C) or oil (H) parameter.

3. Fuel circuit (10) according to claim 2, wherein the fuel distributor (2”) is in the form of a pressure relief valve configured to move into the second position (P2) when the fuel pressure losses (C) generated by the first heat exchanger (3) exceed a first predetermined threshold.

4. Fuel circuit (10) according to claim 2, wherein the fuel distributor (2') is in the form of a thermostatic valve configured to move into the second position (P2) when the temperature of the oil (H) is lower than a second predetermined threshold.

5. Fuel circuit (10) according to claim 1, wherein the fuel distributor (2) is of the active control type, preferably electrical.

6. Fuel circuit (10) according to one of claims 1 to 5, comprising an auxiliary fuel distributor (30) mounted in bypass of the fuel distributor (2, 2', 2”) and controllable between the first position (PI) and the second position (P2).

7. Fuel circuit (10) according to one of claims 1 to 6, in which the fuel distributor (2, 2', 2”) is also controllable in a third position (P3), in which the fuel (C) circulates from the upstream line (5) to the downstream line (8) via a very low flow line (9), on which is mounted at least one third heat exchanger (31) of the oil-fuel type configured to generate pressure losses greater than that generated by the first heat exchanger (3).

8. Assembly of a fuel circuit (10) according to one of claims 1 to 7 and of an oil circuit (20) of an aircraft turbomachine, in which the first heat exchanger (3) and the second heat exchanger (4) are mounted in series on the oil circuit (20).

9. Assembly according to claim 8, in which the oil circuit (20) comprises at least one bypass line (21), mounted as a bypass of the first heat exchanger (3), and at least one oil distributor (22) controllable between at least: • a main position (RI), in which the oil (H) circulates in the first heat exchanger (3) and the second heat exchanger (4), and • a secondary position (R2), in which the oil (H) circulates in the bypass line (21) and the second heat exchanger (4).

10. Method for cooling an oil circuit (20) of an aircraft turbomachine by means of a fuel circuit (10) according to one of claims 1 to 7, the control method comprising a step of controlling the first position (PI) or the second position (P2) of the fuel distributor (2, 2', 2”) of the fuel circuit (10).

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