Fuel supply system for a combustion chamber using a fuel cartridge

Abstract

This fuel supply system (15) for a combustion chamber of an aircraft turbomachine includes a first fuel supply rail (17) and a second fuel supply rail (19), the first rail (17) comprising a starting injector (21), a cartridge (23) configured to hold fuel and a first pipe (25) configured to carry fuel from the cartridge (23) to the starting injector (21), the second rail (19) comprising a rated-speed injector (27), a second pipe (29), and a pump (31) configured to deliver fuel from a fuel tank to the rated-speed injector (27) via the second pipe (29). Figure for the abstract: Fig. 2

Description

Title of the invention: System for supplying a combustion chamber from a fuel cartridge Technical field

[0001] The present invention relates to the low and / or high altitude starting of aircraft turbomachines, in particular relatively small turbomachines.

[0002] In particular, the present invention relates to fuel supply systems for a combustion chamber of an aircraft turbomachine, in particular during a start-up phase of the turbomachine, also called ignition, or a cruising phase, also called nominal speed.

[0003] Generally speaking, the invention applies to any combustion chamber requiring starting by fuel injection. Previous techniques

[0004] During the rotational operation of a turbomachine, the start-up phase can be differentiated from the nominal speed of the turbomachine by the rotational speed of the turbine of the turbomachine as well as by the fuel flow rates injected into the combustion chamber, in particular for a start-up at high altitude, for example for an altitude greater than 3000 meters.

[0005] The injected fuel is for example a liquid fuel, such as kerosene.

[0006] For the start-up phase, particularly at high altitude, the injection flow rate of fuel consumption is very low, in the order of 20 to 90 liters per hour, while it is 200 to 700 liters per hour during nominal speed. These are orders of magnitude which vary according to the size of the engine.

[0007] [Fig.l] schematically shows a fuel supply system 1 for a combustion chamber according to the state of the art.

[0008] The current system 1 for supplying fuel to the combustion chamber comprises a first and a second rail 3 and 5 for supplying fuel to the combustion chamber, the two rails 3 and 5 being supplied by the same pump 7 connected to a fuel tank (not shown). The first rail 3 comprises one or more starting injectors 9 and is configured so that as soon as the pump 7 is started, the starting injector 9 is supplied and is configured to spray fuel into the combustion chamber. The second rail 5 comprises one or more nominal speed injectors 11 and a calibrated shutter 13. The calibrated shutter 13 is configured to pass fuel when the pressure of said fuel is greater than a predetermined calibration pressure. Thus, the nominal speed injector 11 is supplied when the pressure of the fuel at the outlet of the pump 7 is higher than the set pressure. Beyond said set pressure, both ramps 3 and 5 are therefore supplied.

[0009] Furthermore, with a view to their use respectively during a starting phase and a nominal speed, the starting injector 9 is configured to supply the combustion chamber with a low flow rate unlike the nominal speed injector 11. It is from the need to supply the two ramps 3 and 5 sequentially that the use of a calibrated shutter 13 and the achievement of a calibration threshold pressure arises to supply the second ramp 5.

[0010] This solution nevertheless has drawbacks, in particular a complexity of implementation, as well as the need to oversize the pump 7 in terms of power and size, the fuel having to be sent both to the starting injector 9 and having to have a pressure higher than the calibration pressure. Statement of the invention

[0011] The present invention therefore aims to overcome the aforementioned drawbacks and to provide a simpler fuel supply system for a combustion chamber with optimized dimensions.

[0012] The present invention relates to a system for supplying fuel to a combustion chamber of an aircraft turbomachine, comprising a first fuel supply rail and a second fuel supply rail, the first rail comprising a starting injector, a cartridge configured to contain fuel and a first pipe configured to transport fuel from the cartridge to the starting injector, the second rail comprising a nominal speed injector, a second pipe, and a pump configured to send fuel from a fuel tank to the nominal speed injector via the second pipe.

[0013] Generally speaking, the combustion start-up phase in a combustion chamber is only required once, lasts only a few seconds and uses only a small quantity of fuel. There is therefore an interest in relieving the pump of the start-up phase, and thus in sizing the pump to the exact requirement by dissociating the components supplying the two rails.

[0014] Thus, the system according to the invention makes it possible to do without a calibrated shutter on the second ramp, simplifies the architecture of the supply system by allowing correct sizing of the pump, allows a reduction in its mass, and an increase in its reliability.

[0015] The constraint linked to the start-up phase is removed at the pump level, the maintenance of combustion during the cruising phase can very well be ensured by a lower power pump: the flow rate will be greater in the second ramp but the spraying being aided by ventilation by an air flow in the combustion chamber, the pressure in the second ramp may be lower than in the state of the art, and therefore maintained with a smaller sized pump.

[0016] In one embodiment the cartridge comprises an expulsion means configured to expel fuel contained in the cartridge when said expulsion means is triggered.

[0017] Advantageously, the expulsion means comprises a spring as well as a piston, and / or a pressurized gas.

[0018] Advantageously, the first ramp comprises a trigger configured to trigger the expulsion means.

[0019] In a particular embodiment, the first pipe of the first ramp comprises a calibrated shutter.

[0020] Advantageously, the cartridge has a volume of between 5 and 50 centiliters.

[0021] Advantageously, the pump is electric or mechanically driven.

[0022] In particular embodiments, the cartridge is configured to be refillable with fuel in the event of a start failure and / or the first rail comprises at least two cartridges configured to contain fuel.

[0023] The present invention also relates to a turbomachine comprising a combustion chamber and comprising a system as defined above.

[0024] The present invention also relates to an aircraft comprising the system or the turbomachine as defined above.

[0025] The present invention also relates to a method for supplying fuel to a combustion chamber of a turbomachine of an aircraft for starting the turbomachine, with a system, a turbomachine or an aircraft as defined previously, the method comprising the following steps:

[0026] - Spraying of a fuel contained in the cartridge towards the chamber of combustion via the starter injector; and

[0027] - Ignition of the pump and spraying of fuel via the nominal speed injector, said fuel spraying via the nominal speed injector being initiated during the previous step of spraying a fuel contained in the cartridge. Brief description of the drawings

[0028] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0029] [Fig.l] is a schematic representation of a fuel supply system of a combustion chamber according to the state of the art;

[0030] [Fig.2] is a schematic representation of a fuel supply system for a combustion chamber according to the invention;

[0031] [Fig.3] is a schematic representation of a turbomachine according to the invention; and

[0032] [Fig.4] is a schematic representation of the steps of a method for supplying fuel to a combustion chamber according to the invention.

[0033] Detailed description of at least one embodiment

[0034] [Fig. 2] schematically shows a fuel supply system 15 for a combustion chamber of an aircraft turbomachine (shown in [Fig. 3]).

[0035] The fuel supply system 15 comprises a first fuel supply rail 17 and a second fuel supply rail 19 separate from the first rail 17 and supplied by different fuel sources.

[0036] The first ramp 17 comprises a starting injector 21, a cartridge 23 configured to contain fuel and a first pipe 25 configured to transport fuel from the cartridge 23 to the starting injector 21. The first ramp optionally comprises several starting injectors 21 depending on the size of the combustion chamber to be supplied or the type of turbomachine.

[0037] The cartridge 23 has for example a volume between 5 and 50 centilitres, preferably between 12 and 25 centilitres.

[0038] The starting injector 21 comprises a spraying device configured to spray a fuel into the combustion chamber, the starting injector 21 allowing combustion to be started in the combustion chamber. The injection flow rate of the starting injector 21 is low, for example between 20 and 90 liters per hour.

[0039] The presence of a low-flow starting injector 21 makes it possible to carry out a combustion start at high altitude, for example at an altitude above 3000 meters, during pressure and temperature conditions requiring a fuel injection different from an injection in a cruising phase. For a combustion start at low altitude, it is thus not necessary to use the first supply rail 17, the second rail 19 is sufficient under these pressure and temperature conditions.

[0040] The fuel is for example liquid, such as kerosene, or gaseous.

[0041] The second ramp 19 comprises a nominal speed injector 27, a second ca nalisation 29, and a pump 31 configured to send fuel from a fuel tank (shown in [Fig.3]) to the nominal speed injector 27 via the second pipe 29. The second ramp 19 optionally comprises several nominal speed injectors 27 depending on the size of the combustion chamber to be supplied or the type of turbomachine.

[0042] The nominal speed injector 27 comprises a spraying device configured to spray a fuel into the combustion chamber, the nominal speed injector 27 making it possible to maintain combustion in the combustion chamber in a nominal speed, in other words during operation of a turbomachine in a cruising phase of an aircraft. The injection flow rate of the nominal speed injector 27 is for example between 200 and 700 liters per hour, i.e. approximately 10 times greater than that of the starting injector 21.

[0043] In order to facilitate the expulsion of fuel from the cartridge 23 to the starting injector 21, the cartridge 23 comprises an expulsion means 33 configured to expel fuel contained in the cartridge 23 when said expulsion means 33 is triggered.

[0044] In one embodiment, the expulsion means 33 comprises a spring 35 and a piston 37 defining a chamber 38 in the cartridge 23 configured to contain fuel. Alternatively, the expulsion means 33 comprises a pressurized gas with or without a piston, the pressurized gas forcing the cartridge 23 to empty itself of fuel.

[0045] In one embodiment, the first ramp 17 further comprises a trigger 39 configured to trigger the expulsion means 33 in order to release the fuel towards the starting injector 21.

[0046] The trigger 39 is for example an electromagnetic lock which, when open, triggers the expulsion means 33 in order to release the fuel towards the starting injector 21.

[0047] In a particular embodiment, the first pipe 25 of the first ramp 17 comprises a calibrated shutter 41 in order to limit the release of fuel to a predetermined pressure, so that the fuel is not released without reason.

[0048] The calibrated shutter 41 can be positioned in addition to the trigger 39 in order to ensure that fuel does not escape unnecessarily from the cartridge 23. The calibrated shutter 41 can also be positioned as an alternative to the trigger 39.

[0049] In a particular embodiment, the cartridge 23 is configured to be refillable with fuel in the event of a start failure or for the purpose of reuse.

[0050] In another embodiment illustrated in [Fig. 3], the first ramp 17 comprises at least two cartridges 23 configured to contain fuel and both connected to the starting injector 21 via the first line 25. The second cartridge 23 allows for subsequent starting, or acts as a backup cartridge 23 if combustion has not started after the fuel from the first cartridge 23 has been injected.

[0051] [Fig. 3] schematically shows a turbomachine 43 of an aircraft comprising a system 15 for supplying fuel to a combustion chamber 45.

[0052] The turbomachine comprises a combustion chamber 45, an exhaust nozzle 47, a turbine 49, and a main compressor 51 supplying air to the combustion chamber 45 from an air inlet 53. The air flow entering the combustion chamber 45 helps to disperse the injected fuel and allows the combustion to be stabilized.

[0053] The turbomachine 43 also comprises an accessory box 55 and a central shaft 57 to which the accessory box 55, the main compressor 51 and the turbine 49 are connected.

[0054] The accessory box 55 is also connected to a generator 59, in other words an on-board alternator.

[0055] In a particular embodiment, the turbomachine 43 is an auxiliary power unit of an aircraft and optionally comprises a charge compressor 61 making it possible to direct air towards an air circuit 63 in the direction of the cabin of the aircraft.

[0056] The feed system 15 shown is similar and embodiment shown in [Fig.2]. The first ramp 17 also includes an optional second cartridge 23.

[0057] The turbomachine 43 further comprises a tank 65 configured to contain fuel intended to be sent into the combustion chamber 45 by the pump 31. The combustion chamber 45 further comprises an igniter 67, for example a spark plug in order to initiate the combustion of fuel in the combustion chamber 45.

[0058] In one embodiment, the pump 31 of the supply system 15 is mechanically driven by the accessory box 55.

[0059] In another embodiment, the pump 31 of the power supply system 15 is electric and supplied with electricity by the generator 59 or by an electrical energy storage, typically a battery, which can be recharged by the generator 59. This solution allows a significant weight saving at the level of the pump 31 and the generator 59. The pump 31 simply having to be sized for the needs of the nominal speed injector 27, the generator 59 can also be sized solely for this need.

[0060] The steps of a process are shown schematically in [Fig.4] for supplying fuel to a combustion chamber 45 of a turbomachine 43 of an aircraft for starting the turbomachine 43, with a supply system 15 as described previously.

[0061] To implement the method for supplying fuel to the combustion chamber 45, and when no combustion is present in the combustion chamber 45, a step 69 of spraying the fuel contained in the cartridge 23 towards the combustion chamber 45 is first carried out by means of the starting injector 21. In particular, the spraying step 69 comprises, for example, a step 71 of activating the trigger 39 configured to trigger the expulsion means 33, itself making it possible to expel the fuel more easily from the cartridge 23 towards the combustion chamber 45. During this step 69, a step 73 of creating a flame with the igniter 67 must be carried out if combustion is desired.

[0062] In a particular embodiment, the fuel present in the cartridge 23 is different from the fuel contained in the fuel tank 65. A different fuel in the cartridge 23 makes it possible, for example, to enrich the air / fuel mixture in order to facilitate the start of combustion in the combustion chamber 45.

[0063] Then, a step 75 of igniting the pump 31 and thus of spraying fuel via the nominal speed injector 27 is carried out, said spraying of fuel via the nominal speed injector 27 being initiated before the previous step 69 of spraying a fuel contained in the cartridge 23 is completed, so as not to stop the combustion.

Claims

Claims

1. A system (15) for supplying fuel to a combustion chamber (45) of an aircraft turbomachine (43), comprising a first fuel supply rail (17) and a second fuel supply rail (19), characterized in that the first rail (17) comprises a starting injector (21), a cartridge (23) configured to contain fuel and a first pipe (25) configured to transport fuel from the cartridge (23) to the starting injector (21), the second rail (19) comprising a nominal speed injector (27), a second pipe (29), and a pump (31) configured to send fuel from a fuel tank (65) to the nominal speed injector (27) via the second pipe (29).

2. The system of claim 1, wherein the cartridge (23) comprises an expulsion means (33) configured to expel fuel contained in the cartridge (23) when said expulsion means (33) is triggered.

3. A system according to claim 2, wherein the expulsion means (33) comprises a spring (35) as well as a piston (37), and / or a pressurized gas.

4. System according to one of claims 2 and 3, in which the first ramp (17) comprises a trigger (39) configured to trigger the expulsion means (33).

5. System according to any one of claims 2 to 4, in which the first pipe (25) of the first ramp (17) comprises a calibrated shutter (41).

6. A system according to any one of claims 1 to 5, wherein the cartridge (23) has a volume of between 5 and 50 centiliters.

7. A system according to any one of claims 1 to 6, wherein the pump (31) is electric.

8. System according to any one of claims 1 to 7, wherein the cartridge (23) is configured to be refillable with fuel in the event of a start failure and / or wherein the first rail (17) comprises at least two cartridges (23) configured to contain fuel.

9. Turbomachine (43) comprising a combustion chamber (45) and characterized in that it comprises a system (15) according to one any of claims 1 to 8.

10. Method for supplying fuel to a combustion chamber (45) of a turbomachine (43) of an aircraft for starting the turbomachine (43), with a system (15) according to any one of claims 1 to 8, characterized in that it comprises the following steps: - Spraying a fuel contained in the cartridge (23) towards the combustion chamber (45) via the starting injector (21) (step 69); and - Ignition of the pump (31) and spraying of fuel via the nominal speed injector (27) (step 75), said spraying of fuel via the nominal speed injector (27) being initiated during the previous step (69) of spraying a fuel contained in the cartridge (23).

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