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

Abstract

The invention relates to a turbojet engine comprising: a combustion chamber and a jet pipe; a main circuit (11) including a main centrifugal pump (14) and a main positive displacement pump (16) supplying fuel to the injectors (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 the actuators (25) of the jet pipe via an auxiliary regulator (26); a post-combustion circuit (12) including a post-combustion centrifugal pump (21), a post-combustion regulator (22) and post-combustion injectors (23) supplied by the post-combustion pump (21) via the post-combustion regulator (22); according to the invention, a backup system (27) connected to the auxiliary regulator (26) and to the injectors (18) is provided so as 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

[0001] DESCRIPTION

[0002] TITLE: Turbojet engine equipped with means to maintain its operation in the event of failure of its main fuel supply circuit

[0003] TECHNICAL FIELD

[0004] The invention relates to a fuel supply system equipping a single-engine aircraft turbojet, arranged to supply the engine even in the event of failure of a main supply circuit of this supply system.

[0005] STATE OF THE PRIOR ART

[0006] The invention relates to the fuel supply of an aircraft engine, such as a single-engine military aircraft, for which it is desired to maintain a fuel supply in the event of failure of a main fuel supply circuit equipping this engine.

[0007] In Figure 1, such a turbojet 1 extending along an axis of rotation AX comprises at its upstream AM an inlet sleeve through which the air is admitted to pass through a low pressure compressor 2 before being split into a central primary flow and a secondary flow surrounding the primary flow.

[0008] The primary flow is then compressed in a high-pressure compressor 3 before arriving in a combustion chamber 4, after which it is expanded through a high-pressure turbine 6 and a low-pressure turbine 7 before being discharged to the rear. The secondary flow is directed directly to the rear.

[0009] This turbojet is equipped downstream AV of the turbine 7 with an afterburner chamber 9, in which the secondary flow joins the primary flow, and in which fuel is injected to generate additional combustion to increase the thrust.

[0010] In the extension of the afterburner chamber, a nozzle 10 operated by jacks not shown makes it possible to direct the flow leaving the engine in order to increase the maneuverability of the aircraft and / or to modify the section of the neck of this nozzle to adapt it to the operating conditions.

[0011] Such an engine is equipped with a main fuel supply circuit comprising a pump and a regulator to supply injectors so as to supply fuel to the combustion chamber, but a failure in this main circuit can lead to engine shutdown.

[0012] To enable the engine to be restarted if such a failure occurs, one possibility is to provide redundancy in the main circuit. This implies an increase in the mass of the engine since it is then necessary to provide an additional pump and its mechanical drive system via a rotating shaft of the engine.

[0013] Another possibility is to provide redundancy for only some of the components in the main circuit, but this does not cover the case of a failure of the main circuit pump.

[0014] The aim of the invention is to provide a solution enabling such a motor to be restarted and put back into operation in the event of a failure of its main power supply circuit, without significant addition of mass.

[0015] STATEMENT OF THE INVENTION

[0016] To this end, the invention relates to a turbojet comprising:

[0017] - a combustion chamber and a nozzle;

[0018] - a main circuit including a main centrifugal pump and a main volumetric pump supplying fuel to the combustion chamber injectors, via a main regulator;

[0019] - an auxiliary circuit including an auxiliary volumetric pump for supplying pressurized fuel to the nozzle cylinders, via an auxiliary regulator; characterized in that it comprises a backup system connected to the auxiliary regulator and to the injectors to supply these injectors with fuel with the auxiliary pump to restart the turbojet engine in the event of a failure of the main circuit. This architecture allows the engine to operate in the event of a simple failure of the main supply circuit likely to cause the engine to shut down, without having to add a backup pump or a mechanical drive element for such a backup pump.

[0020] The invention also relates to a turbojet engine thus defined, in which the emergency system comprises a pressure limiter.

[0021] The invention also relates to a turbojet engine thus defined, in which the emergency system comprises an emergency regulator, and in which the pressure limiter is interposed between the emergency regulator and the auxiliary regulator to which this emergency system is connected.

[0022] The invention also relates to a turbojet engine thus defined, in which the emergency system comprises a controlled valve which is interposed between the auxiliary regulator and the pressure limiter to supply the pressure limiter when this valve is in an open state.

[0023] The invention also relates to a turbojet engine thus defined, in which the emergency system comprises a solenoid valve connected to the controlled valve to open or close it.

[0024] The invention also relates to a turbojet engine thus defined, in which the main volumetric pump is a gear pump.

[0025] The invention also relates to a turbojet engine thus defined, in which the emergency system comprises a switch connected to the afterburner regulator and to the injectors to supply the injectors from the auxiliary pump through the afterburner regulator to restart the engine in the event of failure of the main circuit.

[0026] The invention also relates to a turbojet engine thus defined, in which the switch is connected to the afterburner regulator by a conduit equipped with a non-return valve to stop the supply of the afterburner regulator by the auxiliary circuit when the afterburner pump is activated.

[0027] The invention also relates to a turbojet engine thus defined, in which the emergency system comprises a pressure selector connected to the main regulator and to the pressure limiter for activating the emergency system when the pressure of the main regulator is lower than the pressure of the pressure limiter.

[0028] The invention also relates to a turbojet engine thus defined, in which the pressure selector comprises an outlet connected to variable geometries of the turbojet engine.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a longitudinal sectional view of a known afterburning turbojet engine;

[0031] Figure 2 is a schematic representation of the fuel supply systems of a military engine;

[0032] Figure 3 is a schematic representation of the fuel supply circuits of a military engine according to the invention;

[0033] Figure 4 is a schematic representation of a regulator in the case where the auxiliary volumetric pump is of the variable displacement type;

[0034] Figure 5 is a schematic representation of the fuel supply circuits of a military engine according to a second embodiment of the invention in a normal operating configuration;

[0035] Figure 6 is a schematic representation of the fuel supply circuits of a military engine according to a second embodiment of the invention in a main circuit failure restart configuration;

[0036] Figure 7 is a schematic representation of the fuel supply circuits of a military engine according to a second embodiment of the invention in an operating configuration after restart following a failure of the main circuit. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0037] A military engine comprises, as shown in Figure 2, a main fuel system 11, an afterburner fuel system 12 and an auxiliary fuel system 13.

[0038] The main circuit 11 is intended to supply fuel to a main combustion chamber of the engine, and to supply variable geometries of the engine with the energy necessary to operate them. These variable geometries are, for example, fixed compressor blades having a variable pitch operated hydraulically.

[0039] This main circuit 11 comprises a main centrifugal pump 14 mounted in series with a main volumetric pump 16 to supply a hydromechanical main regulator 17 which itself supplies injectors 18 of the main combustion chamber of the engine.

[0040] The main pump 14 is a centrifugal pump, so that it delivers a fuel flow proportional to the square of its rotational speed. Pump 16 is here a gear pump, it is a positive displacement pump, so that it delivers a flow which is proportional to its rotational speed. These two pumps are driven by a rotating shaft of the engine, via a gearbox generally designated AGB (Auxiliary Gear Box).

[0041] The positive displacement pump 16 is sized to provide a fuel flow sufficient to allow the engine to start, i.e. when its rotation speed is low.

[0042] The flow delivered by the pumps 14 and 16 feeds the regulator 17 which is controlled to regulate the supply flow of the injectors 18 to a desired value depending in particular on the pilot's commands, so as to obtain a desired thrust value.

[0043] This flow also feeds variable geometries 19 of the engine which are for example fixed blades with variable compressor pitch, the pitch of which is hydraulically operated with a circuit carrying fuel. The afterburner circuit 12 makes it possible to supply fuel to the afterburner chamber of the engine, which is intended to be activated punctually during a flight.

[0044] This post-combustion circuit 12 comprises a centrifugal post-combustion pump 21 located downstream of the main pump 14 and upstream of the post-combustion regulator 22. It is also driven by a rotating shaft of the engine. This pump 21 supplies post-combustion injectors 23 via a post-combustion regulator 22 which is also controlled to regulate the supply flow rate of the injectors 23.

[0045] The main circuit 11 and the afterburner circuit 12 are so-called low-pressure circuits. They deliver fuel to the injectors at a pressure of around 70 bars.

[0046] The auxiliary circuit 13 provides power to the cylinders of the engine outlet nozzle, to modulate the orientation of this nozzle in order to increase the maneuverability of the aircraft during its flight and / or to modify the section of its neck to adapt it to the operating conditions.

[0047] Auxiliary circuit 13 is a so-called high-pressure circuit because it is dedicated to supplying the nozzle cylinders. It delivers a supply at a pressure of around 200 bars, at lower flow rates than those of the low-pressure circuits.

[0048] This auxiliary circuit 13 comprises a volumetric auxiliary pump 24 located downstream of the main pump 14, just like the post-combustion pump 21, and which supplies the cylinders 25 of the nozzle via an auxiliary regulator 26.

[0049] This pump 24 is a volumetric pump which may possibly be of the variable displacement type, and it is also driven by a rotating shaft of the motor.

[0050] The auxiliary regulator 26 is controlled to deliver the appropriate pressures and flow rates to the various cylinders of the nozzle to give it an orientation corresponding to set values ​​and / or to modify the section of its neck. According to the invention, a backup system T1 is provided connected to the auxiliary regulator 26 and to the injectors 18, to supply the injectors 23 with fuel in the event of failure of the main circuit 11, for example at the level of the main pump 14 or the main regulator 17.

[0051] As seen in Figure 3, the emergency system T1 comprises an emergency regulator 28, a pressure limiter 29, a controlled valve 31 and a solenoid valve 32.

[0052] The emergency regulator 28 is connected to the auxiliary regulator 26 by the pressure limiter 29 and by the controlled valve 31 which is controlled by the solenoid valve 32 to be closed during normal operation and opened in the event of failure of the main circuit 11.

[0053] The valve 31 comprises a body 33 in which a piston 34 slides, separating this body 33 into a control chamber 36 and a passage chamber 37 which can be opened or closed. A spring 38 housed in the control chamber continually tends to move the piston 34 towards the passage chamber 37 to keep it closed.

[0054] The passage chamber 37 is continuously connected to a high pressure outlet of the regulator 26 and it is also connected to the pressure limiter 29 when the valve 31 is in the open state.

[0055] The control chamber 36 is supplied via a high pressure outlet of the regulator 26 which is terminated by the solenoid valve 32. In normal operation, the solenoid valve 32 is kept closed, so that the pressures are substantially identical in the two chambers 36 and 37 of the valve 31, which then remains closed under the effect of the spring 38.

[0056] When a fault is detected in the main circuit 11, the solenoid valve 32 is commanded to open and discharge the flow passing through it to a return circuit. This has the effect of dropping the pressure in the control chamber 36, causing the piston 34 to move away from the chamber 37 to open it. This opening allows fuel to pass through the valve 31, from the regulator 26 to the pressure limiter 29 which supplies the regulator 28 located downstream thereof, which makes it possible to supply the injectors 18.

[0057] Thus, in operation, a failure of the main circuit can lead to a shutdown of the engine, its injectors 18 then no longer being supplied with fuel. In this case, the auxiliary volumetric pump 24 being operational, it continues to deliver a flow: the opening of the solenoid valve 32 then makes it possible to open the valve 31 to supply the limiter 29 and the emergency regulator 28, so as to supply fuel to the injectors 18 from the pump 24. Under these conditions, including if the engine is running at a low speed, the auxiliary pump 24 being of the volumetric type, it generates a sufficient flow to restart this engine.

[0058] In practice, prior to the opening of the solenoid valve 32, various actuators and solenoid valves of the auxiliary regulator 26 are controlled to block the cylinders of the nozzle in a reference position, and to no longer supply them. The cylinders will then be in the fallback position and cannot be activated. Thus, when the solenoid valve 32 is open, the auxiliary pump 24 is entirely dedicated to supplying fuel to the injectors 18, and the nozzle which cannot be operated occupies a reference configuration.

[0059] Once the engine has been restarted, the auxiliary pump provides 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, since it is supplied by the afterburner circuit 12 which is separate and independent from circuits 11 and 13.

[0060] In this operation, the pressure limiter 29 makes it possible to compensate for the pressure difference between the auxiliary circuit 13 (high pressure), and the nominal supply pressure for the injectors 18 (low pressure). The pressure limiter 29 receives high-pressure fuel at the inlet, and it delivers fuel at the outlet at a low pressure corresponding to that of the circuit 11.

[0061] When the auxiliary volumetric pump 24 is a fixed displacement pump, the architecture of the emergency regulator 28 is of the same type as that of the main regulator 17. If the volumetric pump 24 is of variable displacement, it can deliver a flow rate and a pressure not dependent solely on the engine speed. The regulator 28 then advantageously comprises, as shown in FIG. 4, means for delivering a predetermined flow rate and output pressure, i.e. independent of the displacement setpoint of this pump 24.

[0062] This regulator 28 then comprises a variable restriction 41 receiving the fuel from the pressure limiter 29, this variable restriction 41 being controlled via the pressure difference of a metering valve 42 which it supplies. As visible in Figure 4, the metering valve 42 is itself controlled by a servovalve 43 to deliver, via a sealing valve 44, a more or less high flow rate to the injectors 18.

[0063] The variable restriction 41 is then connected upstream and downstream of the metering valve 42, so as to adapt the restriction that it introduces, to the pressure difference between the inlet and the outlet of the metering valve 42 controlled by the servovalve 43.

[0064] Under these conditions, when the servovalve 43 is commanded to increase the flow rate, it moves the metering valve 42, to increase its output flow rate. Under these conditions, the pressure difference between the inlet and the outlet of the metering valve 42 decreases, which controls the variable restriction 41 to reduce the restriction that it generates in order to increase the pressure upstream of the metering valve 42, so as to reestablish an appropriate pressure difference between the upstream and downstream of this metering valve 42. In other words, the variable restriction 41 makes it possible to adapt the pressure at the terminals of the metering valve 42 to regulate the flow rate to be injected.

[0065] The valve 44 is supplied by the metering valve 42 and is connected to the injectors 18. In normal operation, the pressure limiter 29 is cut off by the valve 31. The emergency regulator 28 is then returned to the low pressure from the centrifugal pump 14. The pressure at the injectors 18 being higher than the low pressure, the slide of the valve 44, aided by a spring, ensures the seal between the main circuit and the emergency system. In this first embodiment, any variable geometries 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 main circuit 11.

[0066] According to a second embodiment corresponding to figures 5 to 7, the emergency regulator is arranged to restart the engine by first requesting the auxiliary volumetric pump 24 by blocking the cylinders 25, and then to use the post-combustion centrifugal pump 21 in order to make the cylinders 25 maneuverable again, to restore almost normal operation of the engine.

[0067] In this second embodiment, the main circuit 11, the post-combustion circuit 12 and the auxiliary circuit 13 have the same arrangements and the same components as in the example of FIG. 2, the circuits 11 and 12 also being low pressure circuits, the auxiliary circuit 13 also being a high pressure circuit.

[0068] As seen in Figure 5, the backup system, marked 46, is connected to the auxiliary regulator 26, to the post-combustion regulator 22, to the variable geometries 19, and to the combustion injectors 18.

[0069] The emergency system 46 comprises, as in the case of Figure 3, a valve 31 connected to an output of the auxiliary regulator 26, a solenoid valve 32 and a pressure limiter 29. Activation of the solenoid valve 32 makes it possible to open the valve 31 to supply the pressure limiter 29 with the output of the auxiliary regulator 26. This emergency system 46 further comprises a pressure selector 47, and a switch 48.

[0070] The pressure selector 47 has one of its inputs connected to an output of the pressure limiter 29 and its other input connected to an output of the main regulator 17, and the output of this selector 47 is directly connected to the variable geometries 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 that of the regulator 17. Under these conditions, the selector 47 selects the regulator 17 as the power source for supplying the variable geometries 19, and the injectors 18 are also supplied by this regulator 17 because they are directly connected to its output. The switch 48, which is here a distributor slide, is continually returned by a spring to its so-called normal position, in which this switch connects the output of the afterburner regulator 22 to the afterburner injectors 23 to supply them.

[0072] When a malfunction is detected on the main circuit 11, the solenoid valve 32 is commanded to open in order to pressurize the pressure limiter 29 so that it is then this limiter 29, supplied by the auxiliary pump 24 which becomes the power source for the variable geometries 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 the situation in Figure 6.

[0073] Prior to the activation of the solenoid valve 32, the cylinders 25 are blocked at a reference position, and are no longer supplied by the regulator 26, so that the latter is available to supply the injectors 18 so as to restart the engine.

[0074] When the switch 48 is in the emergency position, on the one hand it connects one of the outputs of the limiter 29 to an input of the post-combustion regulator 22, and on the other hand it connects the output of this regulator 22 to the combustion injectors 18, instead of connecting it to the combustion injectors 18.

[0075] In this situation which corresponds to figure 6, the injectors 18 are supplied by the auxiliary pump 24, successively through the auxiliary regulator 26, the pressure limiter 29, and the post-combustion regulator 22.

[0076] Once the engine has been restarted and reaches a sufficient speed, the afterburner pump 21 can then be activated to ensure a nominal supply of the injectors 18, while releasing the auxiliary circuit 13 which can again be controlled to supply the cylinders 25 of the nozzle, as well as the cylinders of the variable geometries 19 in the event of a failure of the main circuit resulting in a reduction in the output pressure of the main pump 16.

[0077] As can be seen in the figures, the conduit connecting the switch 48 to the regulator 22 is equipped with a non-return valve 49, here a ball valve, to stop the supply of the regulator 22 from the auxiliary circuit 13 as soon as the pressure of the regulator 22 becomes higher than that of the circuit 13 when the post-combustion pump 21 is activated.

[0078] In this situation which is illustrated in figure 7, the engine is validly supplied with fuel by the afterburner circuit 12, and its nozzle as well as its variable geometries 19 are maneuverable thanks to the auxiliary circuit 13, despite the failure of the main supply circuit 11.

[0079] In this configuration, the invention allows the use of the turbojet in all flight conditions, except for the use of the afterburner circuit.

Claims

CLAIMS 1. Turbojet comprising: - a combustion chamber and a nozzle; - a main circuit (11) including a main centrifugal pump (14) and a main volumetric pump (16) supplying fuel to injectors (18) of the combustion chamber, via a main regulator (17); - an auxiliary circuit (13) including an auxiliary volumetric pump (24) for supplying pressurized fuel to the cylinders (25) of the nozzle, via an auxiliary regulator (26); - an afterburner circuit (12) including a centrifugal afterburner pump (21), an afterburner regulator (22) and afterburner injectors (23) supplied by the afterburner pump (21) through the afterburner regulator (22); characterized in that it comprises a backup system (27; 46) connected to the auxiliary regulator (26) and to the injectors (18) to supply these injectors (18) with fuel with the auxiliary pump (24) to restart the turbojet engine in the event of failure of the main circuit (11).

2. Turbojet according to claim 1, in which the emergency system (27; 46) comprises a pressure limiter (29).

3. Turbojet according to claim 2, in which the emergency system (27) comprises an emergency regulator (28), and in which the pressure limiter (29) is interposed between the emergency regulator (28) and the auxiliary regulator (26) to which this emergency system (27) is connected.

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

5. Turbojet according to claim 4, in which the emergency system (27; 46) comprises a solenoid valve (32) connected to the controlled valve (31) to open or close it.

6. Turbojet according to claim 1, in which the main positive displacement pump (16) is a gear pump.

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

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

9. Turbojet according to claim 7, wherein the emergency system (46) comprises a pressure selector (47) connected to the main regulator (17) and to the pressure limiter (29) to activate the emergency system when the pressure of the main regulator (17) is lower than the pressure of the pressure limiter (29).

10. Turbojet according to claim 9, in which the pressure selector (47) comprises an outlet connected to variable geometries (19) of the turbojet.

Images