FUEL INJECTOR

Abstract

A staged fuel injector comprises a pilot inner air swirler arranged along a centre axis of the injector, a pilot fuel swirler arranged radially outboard of the pilot inner air swirler, a main inner air swirler arranged radially outboard of the pilot fuel swirler and a main fuel swirler arranged radially outboard of the pilot fuel swirler. A fuel feed arm is arranged in fluid communication with the pilot fuel swirler and the main fuel swirler for delivering fuel to the pilot fuel swirler and the main fuel swirler and a heat protective casing enclosing the fuel feed arm, the pilot fuel swirler and the main fuel swirler.

Claims

1. A staged fuel injector comprising a pilot inner air swirler arranged along a centre axis of the injector, a pilot fuel swirler arranged radially outboard of the pilot inner air swirler, a main inner air swirler arranged radially outboard of the pilot fuel swirler and a main fuel swirler arranged radially outboard of the pilot fuel swirler; a fuel tube arranged in fluid communication with the pilot fuel swirler and the main fuel swirler for delivering fuel to the pilot fuel swirler and the main fuel swirler and a heat protective casing enclosing the fuel tube, the pilot fuel swirler and the main fuel swirler, wherein walls of the pilot and main inner air swirlers extend axially, together terminating in a common radial plane with the heat protective casing and adjacent axially extending walls of the heat protective casing, the pilot inner air swirler, and the main inner air swirler are joined by a braze.

2. The staged fuel injector of claim 1, wherein the main inner air swirler branches at a downstream end to form an intermediate outer air swirler and a radially outer air swirler.

3. The staged fuel injector of claim 1, wherein the intermediate outer air swirler and the radially outer air swirler are integrally formed.

4. The staged fuel injector of claim 2, wherein the intermediate outer air swirler and the radially outer air swirler are formed from separate components which are joined by a braze.

5. The staged fuel injector of claim 1, wherein component and component sub-assemblies of the fuel injector are configured to be assembled, in sequence, in an upstream to downstream direction, the casing forming the most upstream end of the assembly, are assembled with braze between circumferentially facing surfaces of the components and are heated to complete the brazing process after assembly.

6. The staged fuel injector of claim 1, further comprising a gas turbine engine having a combustor and the combustor incorporates the staged fuel injector.

7. A method for manufacturing a staged fuel injector, the staged fuel injector comprising; a pilot inner air swirler, a pilot fuel swirler, a main inner air swirler and a main fuel swirler; a fuel tube for delivering fuel to the pilot fuel swirler and the main fuel swirler and a heat protective casing enclosing the fuel feed arm, the pilot fuel swirler and the main fuel swirler, wherein axially extending walls of the pilot and main inner air swirlers and the heat protective casing are configured, on assembly, to terminate in a common radial plane and are configured to receive a deposit of braze between adjacent surfaces of the axially extending walls when assembled, the method comprising; depositing braze on the adjacent faces of the axially extending walls, inserting the pilot inner air swirler into the heat protective casing with central axes of the pilot inner air swirler and heat protective casing substantially in coaxial alignment and ends of the axially extending walls substantially aligned in a common radial plane, arranging the pilot fuel swirler and the main fuel swirlers radially outboard of the pilot inner air swirler, with the main fuel swirler radially outboard of the pilot fuel swirler and each in substantially coaxial alignment with the pilot inner air swirler and heat protective casing and ends of the axially extending walls substantially aligned in the common radial plane, arranging the main inner air swirler between the pilot fuel swirler and the main fuel swirler in substantially coaxial alignment with the pilot inner air swirler and heat protective casing and ends of the axially extending walls substantially aligned in the common radial plane, thereby to provide an assembled staged fuel injector, applying heat to the assembled staged fuel injector sufficient to cause the braze to melt, and allowing the assembled staged fuel injector to cool thereby forming brazed joints between the adjacent surfaces of the axially extending walls.

8. The method of claim 7, wherein the main inner air swirler has a radially outer axially extending wall which is arranged, on assembly to sit adjacent an axially extending wall of the main fuel swirler at a location downstream of the common radial plane and a radially inner axially extending wall arranged on assembly to sit adjacent an axially extending wall of the primary fuel swirler at a location downstream of the common radial plane, wherein adjacent surfaces of axially adjacent surfaces of the axially extending walls are configured to receive a deposit of braze therebetween and braze is deposited therebetween prior to arranging the main inner air swirler between the pilot fuel swirler and the main fuel swirler.

9. The method of claim 7, further comprising thermally resizing of one or more of the pilot inner air swirler, pilot fuel swirler, main inner air swirler, main fuel swirler and casing as a preliminary step to assembling the assembled staged fuel injector.

10. The method of claim 7, wherein adjacent surfaces of the axially extending walls include a small basin configured to receive the braze.

11. The method of claim 10, wherein the small basin is in the form of an annularly extending recess in one or both of the walls to be joined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] An embodiment of the disclosure will now be further described with reference to the accompanying Figure in which;

[0032] FIG. 1a shows a perspective view from an upstream end of a staged fuel injector as known from the prior art;

[0033] FIG. 1b shows a schematic cross sectional view of the staged fuel injector of FIG. 1a;

[0034] FIG. 2 shows in cross section, an embodiment of a staged fuel injector in accordance with the present disclosure; and

[0035] FIG. 3 shows a sectional side view of a gas turbine engine as is known from the prior art.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.

[0037] FIG. 2 illustrates an embodiment of a staged fuel injector of the disclosure. The staged fuel injector is configured to be assembled and subsequently brazed in a single heating step.

[0038] As can be seen the staged fuel injector of the embodiment comprises a pilot inner air swirler 1 arranged on an axial centreline C-C of the staged fuel injector. At an upstream end, the radially outer wall la of the pilot inner air swirler 1 is received in a central aperture of an annular heat protective casing 3 which extends in a plane R-R which is substantially orthogonal to the axial centreline C-C. Within the radially outer wall, in an axial position adjacent a facing radial wall of the casing 3 is provided an annularly extending recess into which a braze material is provided prior to insertion of the pilot inner air swirler 1 into the central aperture of the casing 3.

[0039] Arranged radially adjacent and outboard of the pilot inner air swirler 1 is the pilot fuel swirler 5. Whilst other configurations of fuel swirler could be substituted without departing from the scope of the disclosure as claimed, the pilot fuel swirler 5 of the shown embodiment comprises a dual walled component, the walls together defining flow passages for fuel delivered to an inlet from a fuel feed arm feed 7 via a conduit 8. The walls of the pilot fuel swirler 5 may be configured and assembled in accordance with the method described in prior published patent U.S. Pat. No. 7,926,178. These walls may be brazed together prior to insertion in the staged fuel injector assembly, or may be brazed as part of a single heating operation used to braze components of the entire assembly together.

[0040] The radially outer wall 5a of the pilot fuel swirler 5 extends radially outwardly at an upstream end and turns back to extend axially and define an annular space. The radially outer wall enclosing the annular space serves as an inner wall 6b of a dual walled main fuel swirler which has a similar construction to the pilot fuel swirler 5. The walls of the main fuel swirler 6 may be configured and assembled in accordance with the method described in prior published patent U.S. Pat. No. 7,926,178. These walls may be brazed together prior to insertion in the staged fuel injector assembly, or may be brazed as part of a single heating operation used to braze components of the entire assembly together.

[0041] In the annular space there is inserted a main inner air swirler 2 which is bounded by radially inner and outer walls 2a, 2b which are connected by a radially extending wall 2c. The axially extending walls 2a, 2b fit snugly against walls 5a and 6b of the pilot and main fuel swirlers 5, 6. A separating wall 9 divides a downstream end of the main inner air swirler into two radially adjacent swirler passages 2 and 4. Between adjacent surfaces of the main inner air swirler walls 2a, 2b, 2c and the walls of the main and pilot fuel swirlers 5a, 6b, an annular gap is filled with braze. Braze may additionally be provided between the facing radially extending surfaces of these components.

[0042] Finally a radially outer wall 10a is positioned radially outboard of the main fuel swirler 6 defining a bounding wall of an outer air swirler 10. The outer air swirler 10 is optionally formed integrally with the main inner air swirler 2. A radially inner wall of the outer air swirler 10 may be brazed to a radially adjacent wall which may form part of the heat protective casing and is radially outboard of the main fuel swirler 6.

[0043] With reference to FIG. 3, a gas turbine engine is generally indicated at 310, having a principal and rotational axis 311. The engine 310 comprises, in axial flow series, an air intake 312, a propulsive fan 313, a high-pressure compressor 314, combustion equipment 315, a high-pressure turbine 316, a low-pressure turbine 317 and an exhaust nozzle 318. A nacelle 320 generally surrounds the engine 310 and defines the intake 312.

[0044] The gas turbine engine 310 works in the conventional manner so that air entering the intake 312 is accelerated by the fan 313 to produce two air flows: a first air flow into the high-pressure compressor 314 and a second air flow which passes through a bypass duct 321 to provide propulsive thrust. The high-pressure compressor 314 compresses the air flow directed into it before delivering that air to the combustion equipment 315.

[0045] In the combustion equipment 315 the air flow is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high and low-pressure turbines 316, 317 before being exhausted through the nozzle 318 to provide additional propulsive thrust. The high 316 and low 317 pressure turbines drive respectively the high pressure compressor 314 and the fan 13, each by suitable interconnecting shaft.

[0046] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. three) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan. The engine may be configured as a turbojet engine. The disclosure is applicable to any of this variety of engine configurations.

[0047] Within the combustion equipment sits a fuel injector which may, for example, have the configuration of a staged fuel injector in accordance with the disclosure described herein.

[0048] While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.