Fuel supply system for an aircraft engine

Abstract

The system comprises: - a fuel tank; - a suction duct connected to the tank and positioned higher than the tank; - an electric pump (36); - a supply pump configured to be mechanically driven by the accessory gear box and connected at the outlet to the fuel supply circuit of the engine; and - an air discharge (26). The electric pump (36) communicates with the suction duct independently of the supply pump and with the discharge. The supply pump communicates with the suction duct independently of the electric pump.

Description

Technical Field

[0001] This invention relates to fuel circuits for aircraft engines. In particular, it relates to fuel supply for helicopter turboshaft engines. Background Technology

[0002] In the fuel circuit of an aircraft gas turbine engine, the flow rate is typically supplied to a so-called "high-pressure" (HP) positive displacement pump, which is driven by the gas turbine engine rotor via an accessory gearbox—in other words, via a gear train driven by the gas turbine engine shaft. The rotor itself is configured to rotate through the combustion of fuel. A so-called "low-pressure" (BP) centrifugal pump can also be installed upstream of the positive displacement pump to ensure sufficient pressure at the pump inlet, thereby preventing cavitation.

[0003] On some aircraft (usually helicopters), the engine is mounted in the upper part of the aircraft, while the fuel tank is located in the lower part.

[0004] The proper functioning of the engine's fuel circuit is only guaranteed if liquid fuel is present at the inlet of the high-pressure pump. However, air or fuel vapor may be present in the circuit during startup or restart.

[0005] For example, after maintenance operations that result in the removal or installation of engine or fuel circuit equipment components, the presence of air may be noticed upon the first restart. Similarly, intake air may occur at dynamic or semi-dynamic seals or valves when the engine is stopped. Here again, the presence of air is noticed upon the first engine restart in the morning. Meanwhile, the presence of vapor may be a result of fuel evaporation when restarting a hot engine in the presence of volatile fuels. The presence of air or vapor in the fuel circuit can hinder, delay, or potentially interrupt fuel supply during startup, thus affecting the success of fuel delivery.

[0006] To address this problem, it is known to use one or more pumping components (typically electrically operated) located in the fuel tank, designed to facilitate fuel supply by compressing any air bubbles. Similarly, in the presence of such a pumping system on the tank side, an exhaust closure component in the engine connected to a return passage toward the tank is currently used to vent air before engine start-up.

[0007] However, even if there is an initial risk of evacuation of the fuel column extending from the tank to the engine, aircraft manufacturers may want to avoid installing pumping components at the tank. This application is specifically designed for small and medium-sized engines. In other words, the engine must be self-starting. Aircraft manufacturers may also want to eliminate the need for return piping towards the tank.

[0008] Therefore, the purpose of this invention is to eliminate the pumping components in the fuel storage tank, or also to eliminate the return pipe toward the storage tank. Summary of the Invention

[0009] Therefore, according to the present invention, a liquid fuel supply system for an aircraft engine is provided, the system comprising:

[0010] - Fuel storage tank

[0011] - A suction pipe that connects to the storage tank and is positioned above the tank.

[0012] - Electric pump,

[0013] - A fuel supply pump configured to be mechanically driven by an accessory gearbox and connected at its outlet to the engine's fuel supply circuit, and

[0014] -Air exhaust vent

[0015] The electric pump is connected to the suction pipeline independently of the supply pump and is also connected to the discharge port. The supply pump is connected to the suction pipeline independently of the electric pump.

[0016] Therefore, the electric pump is capable of purging any gas in the fuel circuit located upstream of the supply pump. This electric pump is driven by an electric motor, independent of the rotation of the gears in the accessory gearbox driven by the rotation of the high-pressure (HP) shaft of the gas turbine engine. Thus, the electric pump can be actuated specifically before the gas turbine engine is started, ensuring that the fuel pumped by the supply pump at startup is free of air bubbles. Under these conditions, it is no longer necessary to have a pump in the tank itself to purge gas before starting the gas turbine engine. It should be noted that once the air is purged, the device does not discharge any liquid to the outlet.

[0017] This invention enables mass savings in aircraft. It reduces the risks associated with erroneous startups or maintenance operations. While requiring hydraulic connections at two points in the fuel circuit, it does not create any stress on the fuel circuit, particularly the pump. This solution also eliminates design limitations typically imposed on low-pressure pumps (if present) and certain hydromechanical units (HMUs). The invention can be readily applied to existing engines. This venting device does not necessarily require electrical electronics. The vent remains dry. It can also be seen that, due to the arrangement of this invention, the electric pump is decoupled from the main fuel circuit, thus preventing damage to the main fuel circuit. This invention eliminates the need to vent the engine after maintenance operations to repair the fuel circuit.

[0018] It is known that, in the case of a helicopter, the supply circuit, relative to the fuel flow from upstream to downstream, includes a tank, a low-pressure pump, a filter, and a high-pressure pump, with the tank positioned above the filter. Thus, an electric pump can be placed adjacent to the main filter to form a single unit. Therefore, when the low-pressure pump is positioned upstream of the filter, it will preferably (or even necessarily) be a centrifugal pump: this pump must be liquid-permeable even when stopped, allowing the electric pump to draw fuel from the tank. Conversely, a stopped positive displacement pump (e.g., a geared positive displacement pump) is practically impermeable to liquids.

[0019] Furthermore, the present invention may have at least one of the following features:

[0020] - The suction pipe is connected to the storage tank by means of a pipe that extends continuously upward from the storage tank;

[0021] - The system includes an air / liquid separation chamber that is fluidly connected in series between the outlet and the discharge port of the electric pump;

[0022] - A valve with a hydraulic safety function is fluidly connected in series between the outlet and the discharge port of the air / liquid separation chamber, and the valve is configured to close when liquid fuel enters the valve;

[0023] - The valve is configured to close when the pressure difference between the upstream end of the valve and the downstream end of the valve relative to the direction of fuel flow through the system is greater than a given threshold.

[0024] - The system includes a closure member extending in a conduit that forms a bypass relative to the electric pump, the closure member being configured to achieve connection when the electric pump is subjected to a differential pressure exceeding a given threshold;

[0025] - The system includes a checking device configured such that when the electric pump stops, no gas or liquid can enter the electric pump from a pipe located downstream of the electric pump in the direction of the fuel flow through the system. This device may be separate from or integrated into a valve.

[0026] - The electric pump is located at the highest point of the section of the fuel circuit extending upstream of the supply pump, relative to the direction of fuel flow through the system; and

[0027] - The supply pump forms a first supply pump, and the system includes a second supply pump that extends upstream of the electric pump relative to the direction of the fuel flow through the system.

[0028] The invention also provides an aircraft comprising an engine, such as a gas turbine engine, configured to be fueled by a system according to the invention, the engine comprising a high-pressure shaft configured to be rotatably driven by combustion of fuel and to drive a supply pump.

[0029] The aircraft could be, for example, a rotorcraft.

[0030] Finally, according to the present invention, a method for supplying fuel to an aircraft engine is provided, in which:

[0031] - A fuel supply pump independent of the engine; the engine's electric pump pumps fuel from a tank located on the aircraft and exhausts the fuel through a vent.

[0032] - Independent of the electric pump, the supply pump pumps fuel from the storage tank and supplies it to the engine. Attached Figure Description

[0033] Embodiments of the invention will now be described by way of non-limiting example with reference to the accompanying drawings, in which:

[0034] - Figure 1 This is an axial cross-sectional view of an aircraft turbojet engine according to an embodiment of the present invention;

[0035] - Figure 2 yes Figure 1 A perspective view of the accessory gearbox of a turbojet engine;

[0036] - Figure 3 and Figure 4 It shows Figure 1 The engine's fuel circuit;

[0037] - Figure 5 This is a detailed view of a portion of the loop in the previous image; and

[0038] - Figure 6 Two views showing the operation of the valve in the circuit of the previous figure;

[0039] - Figures 7A to 7C The following three steps of valve operation are shown in another embodiment; and

[0040] - Figure 8 This is an axial cross-sectional view of a detailed exemplary embodiment of this valve. Detailed Implementation

[0041] Figure 1 An aircraft turbojet engine 2 according to an embodiment of the present invention is shown, which is a twin-shaft aircraft turbojet engine. The aircraft turbojet engine extends about a main longitudinal axis XX. The aircraft turbojet engine includes a high-pressure shaft 4 and a low-pressure shaft 6. The aircraft turbojet engine includes, from left to right (i.e., from upstream to downstream, relative to the airflow flowing through the main flow path operating in the gas turbine engine): a fan 8, a high-pressure compressor 10, a combustion chamber 12, a high-pressure turbine 14, and a low-pressure turbine 16.

[0042] The high-pressure shaft 4 is configured to be driven by the combustion of fuel.

[0043] The turbojet engine includes a radial shaft 20 that engages with a high-pressure shaft 4 in a manner known per se to be rotatably driven by the high-pressure shaft.

[0044] The turbojet engine also includes Figure 2 The accessory gearbox 18 shown houses certain equipment components. The gearbox includes a transmission shaft 22, which is parallel to, away from, the main axis XX and rotatably driven by a radial shaft 20. From the power connector in the engine core, via the radial shaft 20 and the transmission shaft 22, the accessory gearbox 18 drives and supports equipment components such as fuel pumps, generators, lubrication units, starters, degreasers, and other components in a manner known per se. These components collectively form all the auxiliary equipment for the engine and for generating electricity for the aircraft.

[0045] The following is a description of the fuel supply circuit of the turbojet engine, and in particular the components of the circuit (some of which are carried by the accessory gearbox 18).

[0046] The circuit includes suction pipe 24 ( Figure 4 ), emission outlet 26 ( Figure 5 ) and formed exports 28 ( Figure 4 The downstream supply pipes, suction pipes, discharge outlets, and each of the downstream supply pipes lead to the outside of the box.

[0047] In this configuration, the circuit also includes a low-pressure supply pump 30 and a high-pressure supply pump 32. These two pumps are driven by an axial secondary rotor 22 rotating in a manner known per se, which will not be described further.

[0048] The circuit also includes a starting device 34, and in particular an electric pump 36 for starting fuel pumping.

[0049] The aircraft is also equipped with at least one fuel tank 40 located outside the gas turbine engine, such as Figure 4 As shown.

[0050] Figure 3 and Figure 4 The main arrangement of the fuel circuit is shown. The low-pressure pump 30 is connected to the storage tank 40 via pipe 24 and pipe 42. Pipe 42 extends continuously upward from the storage tank.

[0051] Therefore, the low-pressure pump ensures the initial pressure rise of the fuel in the circuit. This low-pressure pump delivers fuel to the reheater 44 (where the fuel is heated by oil), then to the filter 46, and finally to the high-pressure pump 32. The high-pressure pump 32 delivers fuel to the regulator 48, which forms the fuel metering unit, then through the flow distribution member 50 for the injectors, and finally to the turbojet engine injector 52. Thus, the following components are arranged in series in the circuit from upstream to downstream, relative to the flow direction of the fuel through the circuit: low-pressure pump 30, reheater 44, filter 46, high-pressure pump 32, regulator 48, distribution member 50, and injector 52. The regulator 48 is also connected to the fuel circuit upstream of the reheater 44 via a return pipe to return excess pumped fuel back into the circuit. In a variant, the return can also be achieved downstream of the reheater.

[0052] The starting device 34 is connected to the reheater 44 downstream of the reheater 44 via a bypass pipe 54, thus branching the pipe from the reheater 44 to the filter 46. The first case involves connecting the starting device 34 to a high point upstream of the high-pressure pump 32; in... Figure 5 In this case, the device is connected to the high point in the filter block upstream of the filter media.

[0053] Therefore, the starting device 34 is located downstream of the reheater 44. The same applies to the filter 46. However, the device and the filter are not located downstream of each other.

[0054] It can also be seen that the low-pressure pump 30 is located upstream of the electric pump 36. This low-pressure pump is connected to pipe 24 independently of the electric pump 36. The same applies to the high-pressure pump 32. The low-pressure pump and the high-pressure pump are configured to be rotatably driven by the accessory gearbox 18.

[0055] The following is a reference Figure 5 Detailed description of the starting device 34.

[0056] The starting device 34 is connected to the inlet upstream of the filter 46.

[0057] The electric pump 36 is a small-volume pump, also known as a micro pump. The electric pump is located at the highest point of a portion of the fuel circuit that extends upstream of the high-pressure pump 32.

[0058] The device includes an air / fuel separation chamber 56 located downstream of the electric pump 36. This air / fuel separation chamber may be a chamber that operates by gravity and / or cyclone effects.

[0059] Therefore, it can be seen that the electric pump 36 is connected to the pipe 24 and the discharge port 26, and operates independently of the low-pressure pump and the high-pressure pump each time. Pump 36 is preferably located at a local low point so that it remains "wet" even when air enters, regardless of the source of that air. Specifically, wet pumps generally have better performance in the presence of air compared to dry pumps.

[0060] Air / fuel separation chamber 56 has the function of separating air and fuel in the following manner:

[0061] -Preferably, air is discharged in the emission direction, and

[0062] -Prioritizes delivering fuel to the pumping components. If the pump dries out by discharging fuel downstream during the air pumping stage, the air / fuel separation chamber allows the liquid to be brought back to the pump under gravity.

[0063] Therefore, the separation chamber can meet some of the following recommendations:

[0064] - Enter the pumping component at the lowest point;

[0065] - Depart from the outlet at a high point on an axis different from the inlet;

[0066] - Achieve low average speeds for air / fuel separation, such as less than 1 m / s.

[0067] The total volume of the downstream passage and separation chamber 56 of pump 36 must be greater than or equal to the volume required to submerge the pumping components.

[0068] The starting device 34 includes a valve 58 with a hydraulic safety function, which is fluidly connected in series between the outlet and the discharge port 26 of the air / fuel separator 56. The valve is configured to close when the pressure difference between the upstream and downstream ends of the valve exceeds a predetermined threshold.

[0069] This type of valve is known in itself and can be arranged in different ways. For example, refer to... Figure 6 The structure is described below to illustrate the working principle of the valve. The valve includes a body 60 and an annular member 62, which is slidably mounted in the body and includes a central passage for fluid. Thus, the passage 62 forms a movable orifice at the first opening of the valve. The valve also includes a finger 64, the rear end of which is rigidly attached to one end of the body, and the free end of which is oriented along the direction of member 62. A spring 66 is supported on the rear end of the finger and on the sliding member 62 to allow the sliding member to move away from the finger. The valve includes a lateral opening 67 extending opposite the spring and the finger. This opening communicates downstream with a discharge port 26.

[0070] Consider the difference between the upstream external pressure applied to the sliding member 62 and the downstream external pressure applied to the lateral opening 67.

[0071] Figure 6 The first view shows the valve in its pass configuration. The sliding member 62 is held away from the end of the finger 64 by a spring 66, allowing fluid to enter the valve through the sliding member and exit through the valve via a lateral opening 67. Thus, fluid flows through the valve from upstream to downstream. When the passing fluid is a gas (e.g., a mixture of air and fuel vapor flushed by the electric pump 36), the gas passing through the sliding member 62 causes almost no load loss between the upstream and downstream sides of the sliding member 62, allowing the valve to remain in its pass configuration.

[0072] When a large quantity of essentially liquid fuel reaches valve 58, it means that the liquid fuel is flushed through the valve by air and carried from the storage tank to the outlet of electric pump 36. The load loss generated by the liquid passing between the upstream and downstream of the valve causes a force to be generated on the sliding member 62. This force tends to displace the sliding member 62 against the action of spring 66 until the sliding member abuts against the finger 64. Then, the end of the finger blocks the orifice of the central channel of member 62, thereby blocking the flow of liquid. The valve is then in a non-pass configuration, such as... Figure 6 The second view is shown.

[0073] Therefore, the valve functions as a hydraulic safety device that reacts to the passage of liquid. When a large amount of liquid fuel enters the valve, it closes. Specifically, the valve threshold, determined by the diameter of the orifice in the central channel of component 62 and the setpoint of spring 66, is selected such that the electric pump 36 can flush air through the check valve (see below) without locking the valve. When fuel enters the electric pump, the same volumetric flow rate generated by the electric pump due to the density difference between air and fuel locks the valve. Therefore, the valve distinguishes between air and fuel. This valve prevents liquid fuel from being discharged into the outlet after air has been expelled, without requiring a detection component.

[0074] The starting device 34 also includes a closing member 57, such as a ball and spring type closing member, to provide a check function. Therefore, this closing member is configured such that when the electric pump 36 stops, no gas or liquid can enter the electric pump 36 from the pipe located downstream of the electric pump. The valve 58 and the closing member 57 form a distribution member. Depending on the configuration selected for the valve, the closing member can be incorporated into the valve.

[0075] The closing member is particularly useful because the fuel in pipe 42 can cause depressurization along the entire starting device 34. In any case, on a helicopter, device 34 must be specifically sealed below the set value of spring 66. When the engine stops, the pressure at the inlet of the closing member is typically less than P0, where P0 is the pressure elevation relative to the height difference of the tank relative to the helicopter.

[0076] The device 34 may also include an overpressure closure member 69 extending in a conduit 70 that forms a bypass relative to the electric pump 36. Thus, the bypass conduit extends from the separation chamber 56 to the upstream inlet of the filter 46 in a manner parallel to the fluid flow of the conduit including the electric pump 36. The closure member 69 is configured to establish connection when the electric pump 36 experiences a differential pressure exceeding a predetermined threshold. Therefore, if necessary, the closure member can limit pressure once the valve is locked. This closure member is optional.

[0077] For example, the method of the present invention can be implemented as follows.

[0078] Assume the turbojet engine has stopped and has not yet started.

[0079] Start the electric pump 36. This does not require starting the turbojet engine.

[0080] The electric pump 36 first pumps the gas located in the pipe 42 that connects the electric pump to the storage tank, because if gas is found there, it is at least located at the top of pipe 42 all the way to the connection between the pipe and the suction pipe 24. The gas thus pumped passes through the low-pressure pump 30, the reheater 44, then through the electric pump 36, the separation chamber 56, and finally through the valve 58 and the closing member 57, and is discharged from the discharge port 26.

[0081] Gas is pumped first. When no gas is present, liquid fuel is pumped until it enters valve 58. At valve 58, the liquid fuel creates a pressure increase at the valve inlet, causing the valve to close.

[0082] Then the electric pump 36 is stopped because the fuel supply circuit is activated due to being almost continuously filled to the filter 46. Thus, it can be seen that the electric pump pumps fuel from the storage tank independently of the low-pressure and high-pressure pumps.

[0083] Then the turbojet engine (or turboshaft engine) is started to rotate the high-pressure shaft 4. Independent of the electric pump, low-pressure pumps and high-pressure pumps pump fuel from the storage tank to supply the gas turbine engine's injectors.

[0084] Therefore, one involves an electric pump used to start the fuel circuit, which expels air but not fuel. The vent remains dry due to valve 58.

[0085] Figures 7A to 7C and Figure 8 Another embodiment of valve 58' is shown. For example, this valve 58' is available when the aircraft is a helicopter. In this case, a check function is incorporated into the valve.

[0086] Valve 58' includes a cylinder 80 having a front opening 82 and a rear opening 84. A fuel supply line 86 connected to the separation chamber 56 includes branches such that the fuel supply line communicates with the front opening 82 on one side and the rear opening 84 on the other. A restraint 88 or nozzle is inserted between the branch and the front opening 82.

[0087] The piston 90 is movably mounted by sliding within the cylinder 80, defining a front chamber 92 and a rear chamber 94 within the cylinder 80. The front chamber 92 communicates with the front opening 82 when the valve 98 is open, and the rear chamber 94 communicates with the rear opening 84. The discharge port 26 also opens laterally to the front chamber 92.

[0088] The piston 90 is retracted toward the rear opening 84 by a spring 96 with a high setpoint. The spring supports both the front end of the cylinder 80 and the shoulder of the piston. The spring 96 is, for example, selected so that the piston 90 travels toward the front of the cylinder when subjected to a pressure differential of at least 100 kPa. It is the placement of the valve 98 on the abutment portion that prevents the assembly from moving forward.

[0089] The valve is arranged such that the rear opening 84 never closes: this is because the surface S on which the fluid pressure of the piston 90 is applied in the rear chamber 94 must remain constant, such that the force F = P × S depends only on the pressure P. Therefore, a minimum distance will be maintained between the bottom of the rear chamber 94 and the piston 90, which is achieved here by a stop 77 formed by the piston's support abutting against the front annular shoulder of the cylinder 80. Figure 8 As shown.

[0090] A valve 98 is supported at the front end of piston 90. Valve 98 is movably mounted by sliding within the piston and is restored along the front end of the cylinder by a spring 100 with a low setpoint. The setpoint of the first spring 96 is higher than that of the second spring. The spring 100 with the low setpoint is selected such that valve 98 opens when subjected to a pressure differential of at least 15 kPa.

[0091] Figure 7AThe first position is shown, corresponding to the stop condition where the starting micropump 36 is not activated. Therefore, the fluid pressure at the micropump inlet is essentially equal to the (atmospheric) pressure in the discharge port 26, and the pressure differential applied to valve 58' is practically zero. Thus, the valve remains closed. Piston 90 rests on the shoulder of the cylinder without closing the rear opening 84. Simultaneously, valve 98 rests against the front end of the cylinder, closing the front opening 82, and thus disconnecting discharge port 26 from the conduit 86. The engine stops, and the pressure at the valve inlet is typically less than P0 (i.e., the pressure measurement altitude related to the altitude difference relative to the helicopter's tank).

[0092] exist Figure 7B In the second position, the micropump 36 is activated and the fluid at the inlet is essentially gaseous. Despite the presence of the restraint 88, the pressure of the gas discharged by the pump is sufficient to open the front opening 82 of the valve: the valve 98 moves to the right against the action of its spring 100. Simultaneously, the gas pressure is insufficient to push the piston 90 to the left by the gas in the right chamber 94, and the force of the piston's spring 96 prevails. Therefore, the front opening 82 of the valve remains open, and gas can be discharged into the outlet 26.

[0093] Finally, Figure 7C In the third position, the micropump 36 is activated and the fluid at the inlet is essentially liquid. Due to the presence of the restraint 88, the fluid pressure in the front chamber 92 is lower than the fluid pressure in the rear chamber 94. Because the spring 96 is configured such that the pressure differential applied to the piston 90 is dominant relative to the force of the spring, the piston 90 is pushed back to the left, thereby actuating the valve 98 until the valve 98 is supported against its seat while compressing the spring 100, thus closing the front opening 82 of the valve. Therefore, the discharge port 26 is no longer connected to the inlet pipe 86.

[0094] Therefore, the valve 58' is automatically locked by fuel and automatically unlocked by air.

[0095] Figure 8 A detailed exemplary embodiment of the valve is shown. Thus, in the closed position, the valve 98 is supported to the left against the O-ring 102. When the valve is open, air flows through the external longitudinal groove 104 formed on the cylindrical body of the valve to the discharge port. The cylinder 80 is here formed into two parts 81 and 83, that is, in Figure 8 The portion 81 on the right side surrounding the piston 90 and the portion 83 on the left side surrounding the front of the valve 98.

[0096] Applying this invention to rotorcraft such as helicopters is advantageous. In this case, it is advantageous to place the electric pump 36 at the highest point of the aircraft's fuel circuit, such as... Figure 4 As shown.

[0097] Of course, many modifications can be made to this invention without departing from its scope.

[0098] This invention is also applicable to other types of aircraft engines, such as hot piston engines for small helicopters.

[0099] The low-pressure pump 30 and the reheater 44 are not essential. Either or both of the low-pressure pump and the reheater can be omitted. If both are omitted, the supply system piping 24 is located just upstream of the connection between the main filter and the starting device 34.

Claims

1. A liquid fuel supply system for an aircraft engine (2), the liquid fuel supply system comprising: - Fuel storage tank (40) - Suction pipe (24), which is connected to the fuel tank (40) and positioned above the fuel tank (40). - Electric pump (36). - A fuel supply pump (32), which is configured to be mechanically driven by an accessory gearbox (18) and connected at its outlet to the fuel supply circuit of the engine (2), and - Air vent (26). The electric pump (36) is connected to the suction pipe independently of the fuel supply pump and to the air vent, while the fuel supply pump (32) is connected to the suction pipe independently of the electric pump. The liquid fuel supply system is configured to pump fuel using the electric pump when the aircraft engine and the fuel supply pump stop.

2. The liquid fuel supply system according to claim 1, wherein, The suction pipe (24) is connected to the fuel storage tank (40) by means of a first pipe (42) that extends continuously upward from the fuel storage tank.

3. The liquid fuel supply system according to claim 1, wherein, The liquid fuel supply system includes an air / liquid separation chamber (56) which is fluidly connected in series between the outlet of the electric pump (36) and the air outlet (26).

4. The liquid fuel supply system according to claim 3, wherein, A valve (58; 58') with a hydraulic safety function is fluidly connected in series between the outlet of the air / liquid separation chamber (56) and the air outlet (26), and the valve is configured to close when liquid fuel enters the valve.

5. The liquid fuel supply system according to claim 4, wherein, The valve (58) is configured to close when the pressure difference between the upstream end of the valve and the downstream end of the valve relative to the direction of fuel flow through the liquid fuel supply system is greater than a given threshold.

6. The liquid fuel supply system according to claim 1, wherein, The liquid fuel supply system includes a closure member (69) extending in a second conduit (70) that forms a bypass relative to the electric pump (36), the closure member being configured to achieve connection when the electric pump is subjected to a pressure differential exceeding a given threshold.

7. The liquid fuel supply system according to claim 4, wherein, The liquid fuel supply system includes a check device (57; 90, 98) such that when the electric pump stops, no gas or liquid can enter the electric pump (36) from a pipe located downstream of the electric pump relative to the direction of fuel flow through the liquid fuel supply system. The check device is separate from or integrated into the valve (58).

8. The liquid fuel supply system according to claim 1, wherein, The electric pump (36) is located at the highest point of a portion of the upstream extension of the fuel supply circuit relative to the direction of the fuel flow through the liquid fuel supply system from the fuel supply pump (32).

9. The liquid fuel supply system according to claim 1, wherein, The fuel supply pump (32) forms a first supply pump, and the liquid fuel supply system includes a second supply pump (30) which extends upstream of the electric pump (36) relative to the direction of the fuel flow through the liquid fuel supply system.

10. An aircraft comprising an engine (2) and a liquid fuel supply system according to claim 1, the engine being configured to be supplied with fuel by the liquid fuel supply system according to claim 1, the engine (2) comprising a high-pressure shaft (4) configured to rotatably drive and drive the fuel supply pump (32) by combustion of fuel.

11. The aircraft according to claim 10, wherein, The engine is a gas turbine engine.

12. A method for supplying fuel to an aircraft engine (2), the method comprising: - A fuel supply pump (32) independent of the engine, wherein the fuel supply pump and the engine are stopped, and the engine's electric pump (36) pumps fuel from a fuel tank (40) located on the aircraft and exhausts gas through an air vent (26), and - Independent of the electric pump, the fuel supply pump (32) pumps fuel from the fuel tank and supplies it to the engine.

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