FUEL INJECTOR FOR A TURBINE ENGINE

Abstract

The invention relates to a fuel injector for a turbine engine, comprising a body having a fuel inlet opening into an upstream chamber and a fuel outlet connected to a downstream chamber, a metering valve being mounted between the upstream chamber and the downstream chamber, said valve being subjected to the action of an elastic return spring tending to return the valve to a closed position, the spring (11) and the valve being designed to allow the opening of the valve and to allow the passage of fuel from the upstream chamber to the downstream chamber, above a given fuel pressure in the upstream chamber, the return spring (11) extending along the axis (X) of movement of the valve, characterized in that the spring (11) has a first axial end and a second axial end, both annular, connected to one another by at least two helical parts (11c, 11d) elastically deformable in the axial direction (X).

Claims

1. A fuel injector for a turbine engine, the injector comprising a body having a fuel inlet opening into an upstream chamber and a fuel outlet connected to a downstream chamber, a metering valve being mounted between the upstream chamber and the downstream chamber, said valve being subjected to the action of an elastic return spring tending to return the valve to a closed position, the spring and the valve being designed to allow the opening of the valve and to allow the passage of fuel from the upstream chamber to the downstream chamber above a given fuel pressure in the upstream chamber, the return spring extending along the axis of movement of the valve, characterized in that the spring has a first axial end and a second axial end which are annular and are connected to one another by at least two helical parts which are elastically deformable in the axial direction.

2. An injector according to claim 1, characterized in that the helical parts are evenly distributed over the circumference.

3. An injector according to claim 1, characterized in that the helical parts have the same diameter.

4. An injector according to claim 2, characterized in that the helical parts have the same diameter.

5. An injector according to claim 1, characterized in that the number of turns ranges from 2 to 3.

6. An injector according to claim 3, characterized in that the number of turns ranges from 2 to 3.

7. An injector according to claim 1, characterized in that the spring is made in one piece from a metallic material, for example steel, titanium or a titanium alloy.

8. An injector according to claim 2, characterized in that the spring is made in one piece from a metallic material, for example steel, titanium or a titanium alloy.

9. An injector according to claim 3, characterized in that the spring is made in one piece from a metallic material, for example steel, titanium or a titanium alloy.

10. An injector according to claim 4, characterized in that the spring is made in one piece from a metallic material, for example steel, titanium or a titanium alloy.

11. An injector according to claim 5, characterized in that the spring is made in one piece from a metallic material, for example steel, titanium or a titanium alloy.

12. An injector according to claim 6, characterized in that the spring is made in one piece from a metallic material, for example steel, titanium or a titanium alloy.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0018] [FIG. 1] is a cross-sectional axial view of an injector according to one embodiment of the prior art,

[0019] [FIG. 2] is a front view of an injector according to one embodiment of the invention.

[0020] FIG. 1 shows an injector 1 according to the prior art. The latter comprises a body 2 comprising a main part 2a extending along an axis X and intended to be fixed by means of screws 3 to a stationary part 4 of the turbine engine, and an injection part 2b extending perpendicularly to the axis X, from a so-called lower end of the main part 2a. The terms high and low are defined in relation to FIG. 1 and are not necessarily related to the actual orientation of the injector 1 in the turbine engine.

[0021] The main part 2a of the body 2 comprises a recess delimiting an upstream chamber 5 into which a fuel inlet 6 opens, and a downstream chamber 7 connected to a fuel flow channel 8 opening at a fuel outlet 9.

[0022] The fuel flow channel 8 has an axial part 8a opening upwards into the downstream chamber 7 and a radial part 8b extending substantially perpendicularly to the axis X, opening outwards from the injector at the outlet 9 so as to form an injection nozzle.

[0023] The upstream chamber 5 and the downstream chamber 7 are separated from one another by a metering valve 10 which is movable between a closed position (visible in FIG. 1) in which it is biased upwards by a helical compression spring 11, and an open position in which it is moved downwards when the fuel pressure in the upstream chamber 5 is higher than a determined pressure. In this case, the pressure in the upstream chamber 5 exerts an axial force in the downward direction onto the metering valve 10 against the axial return force exerted by the spring 11.

[0024] The spring 11 has a first, lower, axial end 11a and a second, upper, axial end 11b. The first axial end 11a rests on a stationary element 12 mounted in the body 2 and forming the seat of the valve 10, in particular of the lower end 13 of the valve 10. The second axial end 11b of the spring 11 is supported by an annular collar 14 of the valve 10. The spring 11 consists of a single metal wire which is generally helical in shape and whose axial ends 11a, 11b generally extend in radial planes.

[0025] The lower part of the valve 10 has slots 15 whose geometries are such that the passage sections between the surfaces delimiting the slots 15 and the element 12 vary according to the axial position of the metering valve 10.

[0026] As mentioned above, the structure of such a helical compression spring 11 generates buckling stress and friction creating a hysteresis phenomenon that should be avoided.

[0027] For this purpose, the invention proposes to replace the spring 11 described with reference to FIG. 1 by a spring 11 whose structure is shown in FIG. 2. This spring has a first axial end 11a and a second axial end 11b which are annular and are connected to one another by at least two helical parts 11c, 11d which are elastically deformable in the axial direction. In the case of FIG. 2, the number of helical parts 11c, 11d is equal to two.

[0028] The helical parts 11c, 11d are evenly distributed around the circumference, i.e. diametrically opposed in pairs in the case of an even number of helical parts.

[0029] The number of turns of each helical part 11c, 11d is between 2 and 6, e.g. 3.5 turns in the case of FIG. 2, preferably between 2 and 3. The spring 11 is made in one piece from a metallic material, e.g. steel, titanium or a titanium alloy.

[0030] Each helical part 11c, 11d may have a round or polygonal, e.g. rectangular or square cross-section.

[0031] The different helical parts 11c, 11d have the same diameter.

[0032] The axial ends 11e of the helical parts 11c, 11d can be connected to the annular ends 11a, 11b of the spring 11 by areas with no break of slope, e.g. by inclined areas 16 or by curved areas 17, in order to locally limit the mechanical stresses.

[0033] Such a structure reduces buckling forces and friction so as to reduce hysteresis during operation and thus improve the operation and service life of the injector 1.