FUEL SUPPLY CIRCUIT FOR A COMBUSTION CHAMBER OF A TURBOMACHINE

Abstract

The invention relates to a fuel supply circuit (1) for a combustion chamber (2) of a turbomachine (10), comprising: —a fuel supply pump (3) configured to provide a fuel flow at a predetermined flow rate, —a plurality of fuel injectors (4), and —a ramp (5) for connecting the pump (3) to the injectors (4), said circuit further comprising a device for the heat treatment of the fuel (6), having a chamber (60) connected to a fuel inlet (61) linked to the pump (3) and to a fuel outlet (62) linked to the ramp (5), wherein heating elements (60) are located in said chamber and are configured to heat the fuel flow to a predetermined temperature so as to cause coking of the fuel within the chamber (60) of the device (6).

Claims

1. A fuel supply circuit for a combustion chamber of a turbomachine, in particular for an aircraft, comprising: a fuel supply pump, said pump being configured to provide a fuel flow at a predetermined flow rate, a plurality of fuel injectors, a ramp for connecting the pump to the injectors, and a device for the thermal treatment of the fuel comprising a chamber connected, on the one hand, to a fuel inlet connected to the pump and to a fuel outlet connected to the ramp, heating elements being located in this chamber and being configured to heat the flow of fuel provided by the pump up to a predetermined temperature so as to cause a coking of the fuel within the chamber wherein said heating elements comprise at least one perforated metal tube which comprises fuel passage orifices and which is associated with a heating electrode for heating the tube and thus the fuel passing through the tube.

2. The circuit according to claim 1, wherein it comprises a conduit for bypassing said device, this conduit extending between the pump and the ramp and allowing a fuel flow to leave the pump and to supply the ramp without passing through said device.

3. The circuit according to claim 2, wherein the bypass conduit is equipped with a valve, for example a flap valve, which is configured to adopt, on the one hand, an open position in which the fuel flow passing through the conduit is maximum, and on the other hand, a closed position in which this flow is zero.

4. The circuit according to claim 1, wherein it further comprises a fuel metering unit which is connected to said device and which is configured to control said heating elements.

5. The circuit according to claim 3, wherein the circuit further comprises a fuel metering unit which is connected to said device which is configured to control said heating elements and said unit is configured to control the valve according to a parameter of the fuel flow provided by the pump, such as the pressure of the fuel flow.

6. The circuit according to claim 1, wherein each of said heating elements comprises metal tubes coaxially engaged in each other.

7. The circuit according to claim 1, wherein the or each tube comprises a wall formed by a metal mesh or metal screen.

8. The circuit of claim 7, wherein at least one seal and/or dielectric seal is arranged between said metal meshes or metal screens of the heating elements.

9. The circuit according to claim 2, wherein the device comprises means for cooling the fuel flow leaving the chamber or the bypass conduit.

10. The circuit according to claim 1, wherein the orifices of the tube or tubes have a diameter between 0.1 and 1 mm.

11. The circuit according to claim 1, wherein the heating elements are configured to provide a heating temperature of between 200 and 300° C., preferably of the order of 250° C.

12. A turbomachine, in particular for an aircraft, comprising a fuel supply circuit as defined in claim 1.

13. A method for supplying fuel to a combustion chamber of a turbomachine, in particular for an aircraft, by means of a fuel supply circuit according to claim 1, this method comprising a step of controlling the heating elements with a view to heating the fuel only when a parameter of the fuel flow provided by the pump is below a predetermined threshold.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] Further characteristics and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference is made to the attached drawings in which:

[0043] FIG. 1 is a schematic half-view in axial cross-section of a fuel supply circuit for a combustion chamber of a turbomachine;

[0044] FIG. 2 is a partial schematic view of a fuel supply circuit according to one embodiment of the invention, and shows a thermal treatment device and a bypass conduit;

[0045] FIG. 3 is a schematic cross-sectional view of a heating element of the device in FIG. 2;

[0046] FIG. 4 is a schematic cross-sectional view along the line IV-IV of FIG. 2;

[0047] FIG. 5 is another very schematic view of a circuit according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0048] In general, in the following description, the terms “longitudinal” and “axial” refer to the orientation of structural elements extending in the direction of a longitudinal axis X. This axis X may be coincident with an axis of rotation of a rotor of a turbomachine. The terms “radial” or “vertical” refer to an orientation of structural elements extending in a direction perpendicular to the axis X. The terms “inner” and “outer”, and “internal” and “external” are used in reference to a positioning relative to the axis X. Thus, a structural element extending along the axis X comprises an inner face oriented towards the axis X and an outer surface opposite its inner surface. In the present application, the terms “upstream” and “downstream” are defined with respect to the direction of flow of the gases in the turbomachine.

[0049] FIG. 1 shows an annular combustion chamber 2 of a gas generator of a turbomachine 10, preferably for an aircraft.

[0050] The combustion chamber 2 is located downstream of one or more compressors, e.g. low-pressure and high-pressure, and upstream of one or more turbines, e.g. high-pressure and low-pressure (not shown in FIG. 1).

[0051] The combustion chamber 2 is part of a turbomachine 10 having a longitudinal axis X which is in particular the axis of rotation of the rotors of the compressors and turbines.

[0052] The combustion chamber 2 is placed in an annular enclosure delimited radially by an external annular casing 21 and an internal annular casing (not shown).

[0053] The combustion chamber 2 comprises coaxial internal 22 and external 23 annular walls joined upstream by an annular and substantially transverse chamber bottom 24.

[0054] The combustion chamber 2 is supplied with compressed air by the high-pressure compressor via an annular diffuser (not shown in the Figure), and with fuel via a fuel supply circuit 1.

[0055] In FIG. 1, the fuel supply circuit 1 comprises: [0056] a fuel supply pump 3 configured to provide a fuel flow F1 at a predetermined flow rate, [0057] injection devices or injectors 4 opening into the combustion chamber 2, and [0058] a ramp 5 for connecting the pump 3 to the injectors 4.

[0059] One of the particularities of the invention is that the circuit 1 also comprises a fuel thermal treatment device 6. The device 6 is located downstream the pump 3 and upstream the ramp 5 and the injectors 4. The device 6 can be releasably attached to the external casing 23 by fasteners (such as bolts).

[0060] With reference to FIGS. 2 and 3, the device 6 comprises a chamber 60 connected, on the one hand, to a fuel inlet 61, and on the other hand, to a fuel outlet 62. The fuel inlet 61 and outlet 62 may be a flow conduit of the fuel. In the example, and not limitation, the chamber 60 has a general parallelepiped shape.

[0061] The chamber 60 comprises heating elements 63. These elements 63 comprise at least one tube 630 associated with at least one heating electrode 632 adapted to heat the tube 630. The electrode 632 may be arranged coaxially with the tube 630. The tube 630 comprises fuel passage orifices 634. In FIGS. 2 and 3, the chamber 60 comprises six cylindrical tubes 630 that are arranged longitudinally with respect to the axis X and parallel to each other. The tubes 630 of the chamber 60 may also be arranged vertically with respect to the axis X.

[0062] With reference to FIGS. 3 and 4, each tube 630 is formed of at least three sub-tubes 630′ which may be coaxial or concentric with each other. The sub-tubes 630′ may be perforated and comprise orifices 634′. In FIG. 4, the tubes 630 are coaxial and each tube 630 is formed of three concentric sub-tubes 630′. In particular, the sub-tubes 630′ allow for a plurality of levels of filtration and fuel deposition in the chamber 60.

[0063] In FIG. 3, the sub-tubes 630′ are connected to each other in a fuel-tight manner by a seal 636 which may be made of a dielectric material. For example, a ceramic seal 636 allows to withstand a strong thermal gradient. In the example, the electrode 632 is arranged generally in the centre of the tube 630. The electrode 632 may be connected to the sub-tubes 630′ by a metal seal 638.

[0064] The tube 630 can be made of a metallic material, such as stainless steel. The tube 630 or the sub-tubes 630′ may comprise walls made of metal mesh or metal screen.

[0065] In FIG. 2, the circuit comprises a bypass conduit 64 that extends between the inlet 61 and the outlet 62. The conduit 64 can be equipped with a valve 65, for example a flap valve, adapted to adopt an open position and a closed position. When the valve 65 is in the closed position, the passage of fuel through the bypass conduit 64 is blocked. The passage flow rate is zero. When the valve 65 is in the open position, the fuel can flow through the conduit 64. The passage flow rate is then maximum.

[0066] The device 6 may also comprise means for cooling 8 the outlet 62. In a non-limiting way, these means 8 can comprise a thermal exchanger, fins formed in projection on a conduit connecting the outlet of the device to the ramp, etc.

[0067] The circuit 1 may also comprise a metering unit 7 allowing generally to regulate the device 6 of the invention centrally and automatically.

[0068] Thus, with reference to FIG. 5, the circuit 1 may comprise the following elements listed here in the direction of flow of the fuel from upstream to downstream: [0069] the pump 3 ensuring the supply of the fuel, for example from a reservoir arranged upstream of the pump 3, [0070] the metering unit 7 of the fuel total flow comprising a regulator 71 of the fuel flow and/or a self-cleaning filter 70 arranged upstream of the regulator 71, [0071] the fuel thermal treatment device 6, and [0072] a ramp 5 for connecting the device 6 to the injectors 4 arranged and opening onto the combustion chamber 2.

[0073] We will now describe a method for supplying fuel to the turbomachine combustion chamber 2 by means of the supply circuit 1 equipped with the device 6 of the invention.

[0074] With reference to FIGS. 2 and 5, the device 6 is supplied with a first fuel flow F1 provided directly by the pump 3 with or without regulation by the metering unit 7.

[0075] The first flow F1 splits into a second fuel flow F2 or a third fuel flow F3 at the level of the inlet 61 of the device 6. The second flow F2 passes through the bypass conduit 64 to the outlet 62 of the device when the valve 65 is in the open position. The third flow F3 passes through the chamber 60 to the outlet 62 when the valve 65 is in the closed position. The third flow F3 is heated by the heating elements 63 to generate fuel deposits within the chamber 60.

[0076] The open and closed positions of the valve 65 can be controlled by the metering unit 7, more specifically by the regulator 71, depending on a measurement parameter of the fuel flow. This parameter, such as a pressure or a flow rate, can be measured by a sensor. This sensor is configured to measure the pressure and/or the flow rate of the fuel flow either at the outlet of the pump 3 or at the inlet of the device 6 (i.e. the first flow F1).

[0077] Similarly, the metering unit 7, preferably the regulator 71, can also control the heating elements 63. This control of the elements 63 may be realized to heat the fuel when a parameter of the fuel flow provided by the pump 3 is below a predetermined threshold. This threshold may be a predetermined pressure level of the first flow F1 that is measured by the sensor.

[0078] When the turbomachine is operating (for example at full throttle, in the climb phase or during the “Cruise” mode), the valve 65 adopts the open position and the second flow F2 passing through the conduit 64 is maximum. The first measured flow F1 is thus higher than the predetermined threshold. This allows to supply fuel to the ramp 5 and the injectors 4 via the bypass conduit 64 and thus bypassing the chamber 60 of the device.

[0079] When the turbomachine is going to be stopped or in idle operation (during the approach phase of the aircraft, for example), the valve 65 adopts the closed position and the second flow F2 passing through the conduit 64 is zero. The first measured flow F1 is thus below the predetermined threshold. This allows the ramp 5 and the injectors 4 to be supplied after the third flow F3 has been heated in the chamber 60. In fact, the fuel passes through the tubes 630, the orifices 634, 634′ and the sub-tubes 630′ to be heated and freed of these reaction compounds (dissolved oxygen and sulphur-type precursors).

[0080] Preferably, the tube or the tubes 630 are heated to a temperature between 200 and 300° C., more preferably 250° C., to form the coke deposit by oxidation of the fuel. This device of the invention does not allow the tube or the tubes to be heated to a temperature higher than 400° C., in particular to avoid the pyrolysis of the fuel.

[0081] Besides, the consumption of the compounds may be generated by an electric current of the order of 5 kW in the tube or the tubes 630 through the associated electrode 632.

[0082] Specifically, the flowing of the electric current causes a local heating (e.g., to 250° C.), so as to force the fuel and these compounds to precipitate on the surface of the tube or the tubes 630 and form a coking or fuel clogging on the walls of the tube or tubes 630. In this configuration, the large oxidation surface of the fuel allows that the device does not clog up quickly. This is not the case, for example, with injectors that comprise one or more small diameter pipelines in which a coking can easily clog the injectors.

[0083] At the level of this outlet 62, the means 8 allow to cool the flow F3 leaving the chamber 60. This allows to limit the excessively high fuel temperatures at the inlet to the ramp 5 and the injectors 4 when the heating elements are used.

[0084] When the chamber 60 comprises multiple tubes 630, each tube 630 may operate independently of each other or simultaneously. In the event that the tubes 630 operate independently, the chamber 60 may comprise at least one valve and a guide element for guiding the flow of fuel entering the chamber 60 toward the active tube or tubes 630.

[0085] In this description, the device for thermal treatment of the fuel is described in a turbomachine, in particular an aircraft. The device of the invention can also be adapted in hydromechanical systems of turbomachine other than the aeronautical field.

[0086] Furthermore, it is understood from the present description that the efficiency of the device within the supply circuit is dependent on various parameters, such as the number and the dimensions of the heating elements.

[0087] The fuel thermal treatment device according to the invention provides several advantages which include in particular: [0088] causing the formation of fuel coke deposits upstream of the injectors, [0089] easily attaching and detaching from the supply circuit, [0090] optimizing the service life of the injectors by preventing the formation of coking, [0091] limiting the maintenance cost of the injectors and the combustion chamber, and [0092] easily adapting to the existing gas generators.

[0093] Overall, this proposed solution is simple, effective and economical to build and assemble on a turbomachine, while providing an optimal fuel supply and an improved service life of the injectors in a combustion chamber.