Turbojet engine equipped with means for maintaining its operation in event of failure of its main fuel supply circuit

Abstract

The invention relates to a turbojet engine which comprises a combustion chamber and a spray pipe. A main circuit (11) comprising a main centrifugal pump (14) and a main positive displacement pump (16) supplying fuel to the injector (18) of the combustion chamber via a main regulator (17); an auxiliary circuit (13) including an auxiliary positive displacement pump (24) for supplying pressurized fuel to an actuator (25) of the injection pipe via an auxiliary regulator (26); an afterburner circuit (12) including an afterburner centrifugal pump (21), an afterburner regulator (22), and an afterburner injector (23) supplied by the afterburner pump (21) via the afterburner regulator (22); according to the invention, a backup system (27) connected to the auxiliary regulator (26) and to the injectors (18) is provided to supply fuel to these injectors (18) using the auxiliary pump (24) in order to restart the turbojet engine in the event of a failure of the main circuit (11).

Description

Technical Field

[0001] The invention relates to a fuel supply system equipped with a single-jet aircraft turbojet engine, arranged to supply fuel to the engine, including in the event of a failure of a main supply circuit of the supply system. Background Art

[0002] The present invention relates to the fueling of aircraft engines, such as single-engine military aircraft, in an attempt to maintain a fuel supply to the aircraft engine in the event of a failure of a primary fuel supply circuit equipped with the engine.

[0003] exist Figure 1 Such a turbojet engine 1 extending along an axis of rotation AX comprises, upstream AM thereof, an intake sleeve allowing the air to pass through a low-pressure compressor 2 before being divided into a central primary flow and a secondary flow surrounding the primary flow.

[0004] The primary flow is then compressed in the high pressure compressor 3 before reaching the combustion chamber 4, after which it is expanded through the high pressure turbine 6 and the low pressure turbine 7 before being discharged to the rear. The secondary flow is led directly to the rear.

[0005] The turbojet engine is equipped with an afterburner 9 downstream AV of the turbine 7 , in which the secondary flow merges with the primary flow and in which fuel is injected to produce additional combustion making it possible to increase the thrust.

[0006] Extending from the afterburner is a nozzle 10 operated by a cylinder not shown, making it possible to orient the flow leaving the engine in order to increase the maneuverability of the vehicle and / or to modify the section of the neck of the nozzle in order to adapt it to the operating conditions.

[0007] Such engines are equipped with a main fuel supply circuit comprising a pump and a regulator to feed the injectors in order to supply fuel to the combustion chambers, but a fault in this main circuit can lead to a stop of the engine.

[0008] In order to allow restarting the engine if such a fault occurs, one possibility consists in providing redundancy of the primary circuit. This entails an increase in the mass of the engine, since an additional pump and its mechanical drive system must then be provided via the rotating engine shaft.

[0009] Another possibility consists in providing redundancy of only some components of the main circuit, but this does not cover the case of a main circuit pump failure.

[0010] The object of the present invention is to provide a solution that allows restarting and restoring the operation of such an engine in the event of a failure of its main supply circuit, without significantly increasing the masses. Summary of the invention

[0011] To this end, the present invention relates to a turbojet engine comprising:

[0012] - Combustion chamber and nozzle;

[0013] - a main circuit comprising a main centrifugal pump and a main positive displacement pump which supplies fuel to the injectors of the combustion chambers via a main regulator;

[0014] an auxiliary circuit including an auxiliary positive displacement pump for supplying pressurized fuel to the nozzle cylinder via an auxiliary regulator;

[0015] It is characterized in that the turbojet engine comprises a backup system connected to the auxiliary regulator and the injectors in order to supply fuel to these injectors through an auxiliary pump, in order to restart the turbojet engine in the event of a failure of the primary circuit.

[0016] This configuration allows the engine to be operated in the event of a simple failure of the main power supply circuit which could cause the engine to shut down, without having to add a backup pump or a mechanical drive element for such a backup pump.

[0017] The invention also relates to a turbojet engine as defined herein, in which the backup system comprises a pressure limiter.

[0018] The invention also relates to a turbojet engine as defined thereby, wherein the backup system comprises a backup regulator and wherein the pressure limiter is interposed between the backup regulator and an auxiliary regulator to which the backup system is connected.

[0019] The invention also relates to a turbojet engine thus defined, in which the backup system comprises a control valve interposed between the auxiliary regulator and the pressure limiter in order to supply the pressure limiter when the valve is in the open state.

[0020] The invention also relates to a turbojet engine as defined herein, in which the backup system comprises a solenoid valve connected to the controlled valve in order to open or close the controlled valve.

[0021] The invention also relates to a turbojet engine as defined herein, in which the main positive displacement pump is a gear pump.

[0022] The invention also relates to a turbojet engine thus defined, in which the backup system comprises a switch connected to the afterburner regulator and to the injector, in order to supply the injector from the auxiliary pump, through the afterburner regulator, in order to restart the engine in the event of a failure of the primary circuit.

[0023] The invention also relates to a turbojet engine thus defined, in which the switch is connected to the afterburner regulator by a duct equipped with a non-return valve in order to stop the supply of the afterburner regulator through the auxiliary circuit when the afterburner pump is activated.

[0024] The invention also relates to a turbojet engine as defined herein, in which the backup system comprises a pressure selector connected to the main regulator and to the pressure limiter, in order to activate the backup system when the pressure of the main regulator is lower than the pressure of the pressure limiter.

[0025] The invention also relates to a turbojet engine as defined thereby, in which the pressure selector comprises an output connected to a variable geometry component of the turbojet engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a longitudinal cross-sectional view of a known afterburner turbojet engine;

[0027] Figure 2 It is a schematic diagram of the fuel supply circuit of a military engine;

[0028] Figure 3 is a schematic diagram of a fuel supply circuit of a military engine according to the present invention;

[0029] Figure 4 is a schematic diagram of a regulator in the case where the auxiliary positive displacement pump is of the variable displacement type;

[0030] Figure 5 is a schematic diagram of a fuel supply circuit of a military engine according to a second embodiment of the present invention in a normal operating configuration;

[0031] Figure 6 is a schematic diagram of a fuel supply circuit of a military engine according to a second embodiment of the present invention in a restart configuration when a main circuit fails;

[0032] Figure 7 is a schematic diagram of a fuel supply circuit of a military engine according to a second embodiment of the present invention in an operating configuration after restarting following a main circuit failure. DETAILED DESCRIPTION

[0033] like Figure 2 As shown, the military engine includes a main fuel supply circuit 11 , an afterburner fuel supply circuit 12 and an auxiliary fuel supply circuit 13 .

[0034] The primary circuit 11 is used to supply fuel to the main combustion chambers of the engine and to supply the variable geometry components of the engine with the power required to operate them, such as fixed compressor blades with hydraulically operated variable pitch.

[0035] This primary circuit 11 comprises a main centrifugal pump 14 mounted in series with a main positive displacement pump 16 to supply a main hydromechanical regulator 17 which in turn supplies injectors 18 of the main combustion chambers of the engine.

[0036] The main pump 14 is a centrifugal pump, so that it delivers a fuel flow proportional to the square of its rotational speed. The pump 16 is here a gear pump, which consists of a positive displacement pump, so that it delivers a flow proportional to its rotational speed. Both pumps are driven by the rotating engine shaft via a gearbox usually called AGB (auxiliary gearbox).

[0037] The positive displacement pump 16 is dimensioned to supply sufficient fuel flow to allow the engine to be started, ie when its speed is low.

[0038] The flow delivered by the pumps 14 and 16 supplies a regulator 17 which is controlled to adjust the supply flow to the ejector 18 to a desired value, in particular depending on the control of the pilot, in order to obtain a desired thrust value.

[0039] This flow also supplies the variable geometry components 19 of the engine, such as fixed variable compressor pitch vanes, the pitch of which is hydraulically controlled by the circuit carrying the fuel.

[0040] The afterburner circuit 12 serves to supply fuel to the afterburner of the engine, which afterburner is intended to be activated from time to time during flight.

[0041] The afterburner circuit 12 comprises a centrifugal afterburner pump 21 located downstream of the main pump 14 and upstream of an afterburner regulator 22. It is also driven by the rotating engine shaft. The pump 21 supplies the afterburner injectors 23 via the afterburner regulator 22, which is also controlled to regulate the supply flow of the injectors 23.

[0042] The main circuit 11 and the afterburner circuit 12 are so-called low-pressure circuits. They deliver fuel to the injectors at a pressure in the range of 70 bar.

[0043] On the other hand, the auxiliary circuit 13 supplies the nozzle cylinder at the engine output to adjust the orientation of this nozzle in order to increase the maneuverability of the aircraft during its flight and / or to modify the section of the aircraft's neck in order to adapt it to the operating conditions.

[0044] The auxiliary circuit 13 is a so-called high-pressure circuit, because it is dedicated to supplying the nozzle cylinder. It delivers supply at a pressure in the range of 200 bar, with a lower flow rate than the flow rate of the low-pressure circuit.

[0045] This auxiliary circuit 13 comprises an auxiliary positive displacement pump 24 , located downstream of the main pump 14 , similar to the afterburner pump 21 , and supplying the cylinders 25 of the nozzle via an auxiliary regulator 26 .

[0046] This pump 24 is a positive displacement pump, optionally of the variable displacement type, and it is also driven by the rotating engine shaft.

[0047] The auxiliary regulator 26 is controlled to deliver appropriate pressures and flows to the different cylinders of the nozzle in order to give the nozzle an orientation corresponding to the set point value and / or to modify the section of the neck of the nozzle.

[0048] According to the invention, a backup system 27 connected to the auxiliary regulator 26 and the injector 18 is provided to supply fuel to the injector 23 in case of a failure of the main circuit 11 , for example at the main pump 14 or the main regulator 17 .

[0049] like Figure 3 As shown, the backup system 27 includes a backup regulator 28 , a pressure limiter 29 , a control valve 31 , and a solenoid valve 32 .

[0050] The backup regulator 28 is connected to the auxiliary regulator 26 via a pressure limiter 29 and a controlled valve 31 which is controlled by a solenoid valve 32 so as to be closed in normal operation and to be opened in the event of a failure of the main circuit 11 .

[0051] The valve 31 comprises a body 33 in which a piston 34 slides, dividing the body 33 into a control chamber 36 which can be opened or closed and a flow chamber 37. A spring 38 housed in the control chamber tends to move the piston 34 continuously towards the flow chamber 37 to keep the piston 34 closed.

[0052] The flow chamber 37 is continuously connected to the high-pressure output of the regulator 26 and is also connected to the pressure limiter 29 when the valve 31 is in the open state.

[0053] The control chamber 36 is supplied via the high-pressure output of the regulator 26, which ends in the solenoid valve 32. In normal operation, the solenoid valve 32 remains closed, so that the pressures in the two chambers 36 and 37 of the valve 31 are substantially the same, and the two chambers 36 and 37 of the valve 31 are then kept closed by the action of the spring 38.

[0054] When a fault is detected at the main circuit 11, the solenoid valve 32 is commanded to open and the exhaust flow passes through it to the return circuit. This causes a drop in pressure in the control chamber 36, causing the piston 34 to move away from the chamber 37 so as to open it. This opening allows the fuel to flow from the regulator 26 through the valve 31 to the pressure limiter 29, which feeds the regulator 28 located downstream thereof, making it possible to feed the injector 18.

[0055] Thus, during operation, a failure of the primary circuit can cause the engine to stop, its injectors 18 no longer being supplied with fuel. In this case, the auxiliary positive displacement pump 24 is active, which continues to deliver a flow: opening the solenoid valve 32 then makes it possible to open the valve 31 to supply the restrictor 29 and the backup regulator 28, thereby supplying fuel from the pump 24 to the injectors 18. Under these conditions, including if the engine is running at low speed, the auxiliary pump 24 is of the positive displacement type, which generates sufficient flow to restart the engine.

[0056] In fact, before opening the solenoid valve 32, the various actuators and solenoid valves of the auxiliary regulator 26 are controlled to lock the nozzle cylinders in the reference position and no longer supply them. The cylinders will then be in the retracted position and cannot be actuated. Thus, when the solenoid valve 32 is open, the auxiliary pump 24 is completely dedicated to supplying fuel to the injectors 18 and the nozzle that cannot be manipulated occupies the reference configuration.

[0057] Once the engine has been restarted, the auxiliary pump supplies a minimum fuel flow, lower than that of the main pump 14, allowing the aircraft to return to its base. If necessary, the afterburner can be used, provided that the afterburner circuit 12 is provided, which is separate and independent from the circuits 11 and 13.

[0058] In this operation, the pressure limiter 29 compensates for the differential pressure between the auxiliary circuit 13 (high pressure) and the nominal supply pressure of the injector 18 (low pressure). The pressure limiter 29 receives high-pressure fuel at an input and delivers fuel at a low pressure corresponding to the pressure of the circuit 11 at an output.

[0059] When the auxiliary positive displacement pump 24 is a fixed displacement pump, the structure of the backup regulator 28 is the same as that of the main regulator 17 .

[0060] If the positive displacement pump 24 is a variable displacement pump, it can deliver a flow and pressure that depends not only on the engine speed. Figure 4 As shown, the regulator 28 then advantageously comprises means for delivering a predetermined output flow and pressure, ie independently of the volume set point of this pump 24 .

[0061] The regulator 28 then comprises a variable restriction 41 receiving fuel from the pressure limiter 29, the variable restriction 41 being controlled via the differential pressure of the metering valve 42 it supplies. Figure 4 As can be seen in FIG. 4 , the metering valve 42 is controlled by a servo valve 43 to deliver a higher or lower flow to the injector 18 via a sealing valve 44 .

[0062] The variable restriction 41 is then connected upstream and downstream of the metering valve 42 so as to adapt the restriction it introduces to the pressure difference between the inlet and the outlet of the metering valve 42 controlled by the servo valve 43 .

[0063] Under these conditions, when the servo valve 43 is commanded to increase the flow rate, the servo valve 43 moves the metering valve 42 to increase its output flow rate. Under these conditions, the pressure difference between the inlet and outlet of the metering valve 42 decreases, which controls the variable restriction 41 to reduce the restriction it causes in order to increase the pressure upstream of the metering valve 42, thereby restoring the appropriate pressure difference between upstream and downstream of the metering valve 42. In other words, the variable restriction 41 makes it possible to adapt the pressure at the end of the metering valve 42 to adjust the flow rate to be injected.

[0064] Valve 44 is fed by metering valve 42 and is connected to injector 18. In normal operation, pressure limiter 29 is closed by valve 31. Backup regulator 28 then returns to low pressure from centrifugal pump 14. When the pressure at injector 18 is higher than the low pressure, the spring-assisted sliding of valve 44 ensures tightness between the main circuit and the backup system.

[0065] In this first embodiment, any variable geometry components of the engine are returned to a fixed or default position in which they do not need to be controlled when a fault is detected at the primary circuit 11 .

[0066] According to the corresponding Figures 5 to 7 In a second embodiment, the standby regulator is arranged to restart the engine by first locking the cylinders 25 to actuate the auxiliary positive displacement pump 24, and then using the centrifugal afterburner pump 21 to make the cylinders 25 manipulable again to resume almost normal operation of the engine.

[0067] In this second embodiment, the main circuit 11, the afterburner circuit 12 and the auxiliary circuit 13 have the same Figure 2 In the embodiment of FIG. 1 , the circuits 11 and 12 are also low-pressure circuits, and the auxiliary circuit 13 is also a high-pressure circuit.

[0068] like Figure 5 As shown, a backup system, generally designated 46 , is connected to the auxiliary regulator 26 , the afterburner regulator 22 , the variable geometry component 19 , and the combustion injector 18 .

[0069] As in Figure 3 In the case of a pressure drop, the backup system 46 includes a valve 31 connected to the output of the auxiliary regulator 26, a solenoid valve 32 and a pressure limiter 29. Actuating the solenoid valve 32 makes it possible to open the valve 31 to supply the output of the auxiliary regulator 26 to the pressure limiter 29. The backup system 46 also includes a pressure selector 47 and a switch 48.

[0070] The pressure selector 47 has one of its inputs connected to the output of the pressure limiter 29 and the other of its inputs connected to the output of the main regulator 17 , and its output is directly connected to the variable geometry component 19 .

[0071] In normal operation, the solenoid valve 32 is closed so that the pressure limiter 29 is not pressurized: its output pressure is lower than the output pressure of the regulator 17. Under these conditions, the selector 47 selects the regulator 17 as the supply source to supply the variable geometry component 19, and the injectors 18 are also supplied by this regulator 17, since they are directly connected to the output of this regulator.

[0072] The switch 48 (here a slide valve) is continuously returned by a spring into its so-called normal position, in which this switch connects the output of the afterburner regulator 22 to the afterburner injectors 23 in order to supply them.

[0073] When a fault is detected on the main circuit 11, the solenoid valve 32 is controlled to open in order to pressurize the pressure limiter 29, so that this limiter 29 supplied by the auxiliary pump 24 then becomes the supply source for the variable geometry component 19. In addition, this limiter 29 is connected to the switch 48, so that its pressurization causes this switch 48 to switch from its normal state to its emergency state, which corresponds to Figure 6 The situation in .

[0074] Before actuating the solenoid valve 32 , the cylinder 25 is locked in the reference position and is no longer supplied by the regulator 26 , so that the regulator can supply the injector 18 in order to restart the engine.

[0075] When the switch 48 is in the standby position, on the one hand, it connects one of the outputs of the limiter 29 to the input of the afterburner regulator 22 and, on the other hand, it connects the output of this regulator 22 to the fuel injector 18 instead of connecting it to the fuel injector 18.

[0076] In the corresponding Figure 6 In this case, the injector 18 is supplied by the auxiliary pump 24, sequentially through the auxiliary regulator 26, the pressure limiter 29 and the afterburner regulator 22.

[0077] Once the engine has been restarted and it has reached sufficient speed, the afterburner pump 21 can then be actuated to ensure nominal supply of the injectors 18, while releasing the auxiliary circuit 13 which can be controlled again in order to supply the cylinders 25 of the nozzles and the cylinders of the variable geometry 19 in the event of a main circuit failure leading to a reduction in the output pressure of the main pump 16.

[0078] As can be seen in the figure, the pipe connecting the switch 48 to the regulator 22 is equipped with a non-return valve 49, here a ball valve, so as to stop the supply to the regulator 22 from the auxiliary circuit 13 as soon as the pressure in the regulator 22 becomes higher than the pressure in the circuit 13 when the afterburner pump 21 is activated.

[0079] exist Figure 7 In the situation shown in FIG. 1 , the engine is effectively supplied with fuel by the afterburner circuit 12 and, despite a failure of the main supply circuit 11 , the nozzle of the engine and its variable geometry component 19 are steerable thanks to the auxiliary circuit 13 .

[0080] In this configuration, the invention allows the use of the turbojet engine in all flight conditions, except when using the afterburner circuit.

Claims

1. Turbojet engine, include: - Combustion chamber and nozzle; - a main circuit (11) comprising a main centrifugal pump (14) and a main positive displacement pump (16) which supplies fuel to the injectors (18) of the combustion chambers via a main regulator (17); an auxiliary circuit (13), the auxiliary circuit comprising an auxiliary positive displacement pump (24), the auxiliary positive displacement pump supplying pressurized fuel to the nozzle cylinder (25) via an auxiliary regulator (26); An afterburner circuit (12) comprising a centrifugal afterburner pump (21), an afterburner regulator (22), and an afterburner injector (23) supplied by the afterburner pump (21) through the afterburner regulator (22); Characterized in that the turbojet engine comprises a backup system (27; 46) connected to the auxiliary regulator (26) and the injector (18) to supply fuel to the injector (18) through an auxiliary pump (24) in order to restart the turbojet engine in the event of a failure of the main circuit (11).

2. The turbojet engine according to claim 1, in, The backup system (27; 46) comprises a pressure limiter (29).

3. The turbojet engine according to claim 2, in, The backup system (27) comprises a backup regulator (28), and wherein a pressure limiter (29) is interposed between the backup regulator (28) and an auxiliary regulator (26), to which the backup system (27) is connected.

4. The turbojet engine according to claim 2, in, The backup system (27; 46) comprises a controlled valve (31) interposed between the auxiliary regulator (26) and the pressure limiter (29) to supply the pressure limiter (29) when the valve (31) is in an open state.

5. The turbojet engine according to claim 4, in, The backup system (27; 46) comprises a solenoid valve (32) connected to the controlled valve (31) to open or close the controlled valve.

6. The turbojet engine according to claim 1, in, The main positive displacement pump (16) is a gear pump.

7. The turbojet engine according to claim 2, in, The backup system (46) comprises a switch (48) connected to the afterburner regulator (22) and the injector (18) to supply the injector (18) from the auxiliary pump (24) through the afterburner regulator (22) in order to restart the turbojet engine in the event of a failure of the main circuit (11).

8. The turbojet engine according to claim 7, in, The switch (48) is connected to the afterburner regulator (22) through a pipe equipped with a non-return valve (49) to stop the supply of the afterburner regulator (22) through the auxiliary circuit (13) when the afterburner pump (21) is activated.

9. The turbojet engine according to claim 7, in, The backup system (46) includes a pressure selector (47) connected to the main regulator (17) and the pressure limiter (29) to activate the backup system when the pressure of the main regulator (17) is lower than the pressure of the pressure limiter (29).

10. The turbojet engine according to claim 9, in, The pressure selector (47) comprises an output connected to a variable geometry component (19) of the turbojet engine.

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