Vane arrangement for a gas turbine engine

Abstract

A method of manufacturing a vane arrangement for a gas turbine engine comprises providing an aerofoil having a hollow cavity with an open end and providing a support member having a stub with a through hole extending therethrough. The method comprises welding the aerofoil to the stub such that the open end of the hollow cavity of the aerofoil is aligned with the through hole of the stub so as to define a hollow region extending through the support member and stub to the cavity of the aerofoil. During welding a tool is positioned within the through hole and cavity and is aligned with an interface between the stub and aerofoil, the tool being configured to prevent weld splatter onto a surface of the cavity or through hole.

Claims

1. A method of manufacturing a vane arrangement for a gas turbine engine, the method comprising: providing an aerofoil having a hollow cavity with an open end; providing a support member having a stub with a through hole extending therethrough; and welding the aerofoil to the stub such that the open end of the hollow cavity of the aerofoil is aligned with the through hole of the stub so as to define a hollow region extending through the support member and stub to the cavity of the aerofoil; wherein during welding a tool is positioned within the through hole and cavity and is aligned with an interface between the stub and aerofoil, the tool being configured to prevent weld splatter onto a surface of the cavity or through hole.

2. The method according to claim 1, wherein the radius of a leading edge and/or trailing edge of the cavity and/or of the through hole is greater than or equal to 3 mm.

3. The method according to claim 1, wherein the tool comprises two opposing end members shaped to be received in a leading edge and trailing edge region of the cavity and through hole.

4. The method according to claim 3, wherein the end members are removable or include a removable portion.

5. The method according to claim 3, wherein the end members are made from or coated with a ceramic material.

6. The method according to claim 3, wherein one end member is positioned to be in a close fit with the leading edge and the other end member is positioned to be in a close fit with the trailing edge.

7. The method according to claim 6, wherein the end members comprise a radius section having a radius substantially equal to that of a leading and/or trailing edge of the cavity and/or the through hole.

8. The method according to claim 3, wherein the tool comprises an elongate member extending between the end members.

9. The method according to claim 8, wherein the elongate member comprises one or more arms that are moveable relative to each other so as to move the end members into contact with a surface of the cavity and through hole.

10. The method according to claim 8, wherein the tool comprises a handle connected to the elongate member for manipulating the tool.

11. The method according to claim 1, wherein walls of the aerofoil are thicker in a region proximal to the open end of the cavity than a region distal to the open end of the cavity.

12. The method according to claim 1, wherein walls of the stub are thicker in a region proximal to a surface to be welded to the aerofoil than at a position distal to the surface to be welded to the aerofoil.

13. The method according to claim 12, wherein the walls of the aerofoil and/or stub are tapered so as to increase the thickness of the walls towards a welded joint between the aerofoil and stub at least at the leading edge and/or trailing edge.

14. The method according to claim 1, comprising providing an aerofoil with an enclosed cavity and removing one end of the aerofoil to expose the cavity and define the open end of the cavity.

15. The method according to claim 14 comprising forming the aerofoil with enclosed cavity using diffusion bonding and hot creep forming.

16. The method according to claim 1, wherein the support member is a ring and, optionally, the stub of the ring is welded to a radially inner end of the vane.

17. The method according to claim 16, comprising providing a support foot having a stub with a through hole, and welding a radially outer end of the aerofoil to the stub of the foot using the tool of the method of any one of the previous claims.

18. The method according to claim 1, wherein the support member is a support foot and/or the vane arrangement is a fan outlet guide vane arrangement.

19. A method of manufacturing a vane arrangement, the method comprising providing a plurality of aerofoils comprising a cavity with an open end, and providing a support member comprising a plurality of stubs with through holes, and wherein an aerofoil is connected to each stub using the method according to claim 1.

20. A method of manufacturing a gas turbine engine comprising the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will now be described by way of example only, with reference to the Figures, in which:

(2) FIG. 1 is a sectional side view of a gas turbine engine;

(3) FIG. 2 is a perspective partial view of an aerofoil and a ring with a stub;

(4) FIG. 3 is a transverse cross section of one end of an aerofoil with enclosed cavity;

(5) FIG. 4 is an axial cross section of one end of an aerofoil with a cavity open at one end;

(6) FIG. 5 is a cross section of a leading edge of an aerofoil taken at a section D-D of FIG. 4;

(7) FIG. 6 is a plan view of a tool used during a process of welding an aerofoil to a stub;

(8) FIG. 7 is a side view of the tool of FIG. 6;

(9) FIG. 8 is a plan section view of the tool in a hollow cavity defined by an aerofoil and a stub;

(10) FIG. 9 is a partial side view of a tool within the hollow cavity defined by the aerofoil and stub; and

(11) FIG. 10 is a cross section of an end of an aerofoil welded to a foot.

DETAILED DESCRIPTION OF THE DISCLOSURE

(12) With reference to FIG. 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

(13) The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the air flow directed into it before delivering that air to the high pressure compressor 15 where further compression takes place.

(14) The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

(15) 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. two) 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.

(16) Fan outlet guide vanes (OGVs) 24 are provided in the bypass duct 22. The OGVs guide airflow from the fan 13 through the bypass duct. The OGVs extend from an inner ring that connects to or forms part of the core casing/a splitter 24 that splits airflow from the fan between the bypass duct and the core. The OGVs are connected to an outer casing 28 of the bypass duct.

(17) In the present example, the OGVs are arranged to transfer axial, radial and torsional loads. The OGVs are integrally formed with an inner ring and a hollow cavity is formed extending through the ring to a cavity of the OGV, such that the cavity of the OGV is open at a radially inner side of the ring. In this way, the aerofoil profile of the OGV can be greater (e.g. have a larger foot print) and/or the walls of the OGV can be thickened in a region proximal to the ring so as to cope with the transfer of torsional loads, without the need for an A-frame structure. Provision of a hollow region extending through the ring to the OGV means the aerofoil can be made larger in regions and/or the walls of the OGV can be thickened whilst having minimal weight and cost penalties. When the OGV is welded to the ring, the thickening of the walls of the OGV can improve the quality of the weld between the OGV and the ring.

(18) A method of manufacturing an OGV of the present example will now be described.

(19) Referring to FIG. 2, an aerofoil 30 with a hollow cavity 34 that has at least one end 38 is provided. A ring 50 is also provided. The ring 50 includes a plurality of stubs 48. The stubs 48 include a through hole 52. The through hole extends the entire way through the stub and ring, such that the through hole extends from a radially inner surface of the ring to a radially outer surface of the stub. In the present example, the through hole in the stub and the cavity of the aerofoil are complimentary in shape. In the present example, the shape and dimensions of the cross section of the cavity and the through hole are the same. Further, when the aerofoil is positioned on the stub, the dimensions and shape of the cross section of the aerofoil and the stub are substantially equal at the interface between the two.

(20) Referring to FIG. 3, the aerofoil 30 is made using two panels 32 that are diffusion bonded together and then hot creep formed to define a cavity 34 and the walls of the aerofoil. The ends 35 of the aerofoil are diffusion bonded such that the cavity 34 is enclosed.

(21) The panels 32 are tapered in thickness, such that the walls of the aerofoil have an increased thickness adjacent a position where the ends are diffusion bonded together. The tapering in thickness commences at a position spaced from the ends of the aerofoil, and more particularly spaced from a position 36 where the aerofoil will be subsequently trimmed to remove an end of the aerofoil. The spacing is such that the final trimmed aerofoil includes walls that have a thickness that increases in a taper towards a position of attachment with the ring. The tapering may be applied only in the regions of the leading and trailing edges, or may be applied across the entire cavity chord.

(22) Once the aerofoil with enclosed cavity is formed, an end of the cavity is removed (at the line indicated at 36 in FIG. 3). The aerofoil is cut at a position sufficiently spaced from the end of the aerofoil that the cavity 34 is opened by the removal of the end. Further, the aerofoil is cut at a position before the walls of the aerofoil start to move closer together to form the closed end. Referring to FIG. 4, the walls of the aerofoil taper to have an increased thickness adjacent the open end 38 of the cavity 34. In this example, the increased thickness of the walls reduces the chord length of the cavity at a position proximal to the opening of the cavity compared to a position distal from the opening of the cavity. Referring to FIG. 5, it can be seen that the cavity 34 is shorter in chordal length compared to a cavity of a more conventional vane, with the leading edge 40 of the cavity 34 being spaced further from the leading edge 42 of the aerofoil, than a leading edge 44 of a cavity of a conventional vane, i.e. the leading edge portion of the aerofoil is thicker than a conventional vane.

(23) Once the cavity 34 has been opened at a spanwise end of the aerofoil, the cavity is shaped (e.g. using a milling cutter) to increase the radius of a leading and trailing edge of the cavity 34. In the present example, the radius R is increased to approximately 3 to 5 mm. The radius of the leading edge and trailing edge of the cavity is increased in a region where the walls of the aerofoil taper to increase wall thickness; the added material provided by the thicker walls provides flexibility for selecting the desired radius. In the present example, the radius is increased in a portion of the tapered region proximal the cavity opening 38 (e.g. half of the tapered region has an increased radius). In this way, the cavity 34 of the aerofoil is still smaller in the region of the tapered portion of the walls, than a cavity of a conventional vane (the leading edge of the cavity at the increased radius portion is indicated at 46).

(24) Referring to FIGS. 6 to 9, the aerofoil 30 with an open hollow cavity is welded to the stub 48. The aerofoil is placed on and in alignment with the stub 48, such that an interface is defined between the aerofoil and stub. The aerofoil and stub are then welded together to define a joint (i.e. a welded joint 68) between the aerofoil and the stub. During the welding process a tool 54 is positioned within the through hole and cavity and is aligned with the interface between the stub and aerofoil. The tool is configured to prevent weld spatter onto a surface of the cavity or through hole. Minimising weld spatter reduces the risk of formation of potential stress raising features or failure locations. As will be described later, the tool of the present example is also configured so that the tool can be adjusted for a close fit with the leading edge and trailing edge of the through hole and cavity, which can improve the quality of the weld. Once the aerofoil is welded to the stub, the tool is removed from the arrangement.

(25) The tool 54 includes two end members 56. The end members are provided at opposite ends of the tool. The end members are shaped to be received in the region of the leading and trailing edge of the hollow region defined by the cavity and the through hole in a position adjacent the interface between the two. The end members include a radius portion that has the same radius as the leading edge and trailing edge of the hollow region, so in this example 3 to 5 mm. In the present example, the end members 56 are coated with a ceramic coating or provided as solid ceramic tips, so that it is possible to reuse the tool in subsequent welds.

(26) The tool includes an elongate member 58 that extends between the two end members 56. The elongate member may be a plate. One end member is provided at each longitudinal end of the elongate member. The end members may be removably mounted to the elongate member, such that the end members can be replaced if/when they suffer damage or are substantially worn.

(27) The elongate member is adjustable. In this example, the elongate member includes two arms 60 that are moveable relative to each other. The arms 60 are connected via a fastener 64 that is received in a slot 62. The position of the fastener within the slot determines the length of the elongate member. In alternative embodiments other methods of connecting and/or moving the arms may be provided, by way of example only a sprung mechanism or rack and pinion type mechanism may be used. The adjustable nature of the elongate member means that the length of the elongate member can be adjusted so as to achieve a close fit within the hollow cavity.

(28) The described method of connection permits the aerofoil portion of the vane to be increased in wall thickness and/or outer aerofoil cross section in a region proximal to joints with inner and/or outer ring members or supports (e.g. foot members) for improved transmittal of torsional loads. The provision of a hollow region extending through the hub to the cavity of the aerofoil means that the weight penalty of having increased wall thickness can be reduced.

(29) The use of the described tool during the welding process can eliminate or significantly reduce spatter on the walls of the hollow region. The radius applied to the leading edge and trailing edge of the cavity and through hole provides a controlled surface where the aerofoil and/or stub changes from solid to hollow. Further, when the tool is a close fit to the leading edge and trailing edge, the risk of voids forming in the weld may be further reduced.

(30) In the present example, a radially outer spanwise end of the OGV is connected to a foot 70 which can be bolted or otherwise connected to the outer casing of the engine, e.g. to a mounting ring. The foot may comprise a hollow stub. The aerofoil 30 may be connected to the foot in a similar manner to that previously described for connecting the inner spanwise end of the OGV to the stub of a ring. In this way, the aerofoil can be connected to the foot with a hollow region extending through the foot to the cavity of the aerofoil. In the present example, the hollow region extends through the foot, aerofoil and ring.

(31) The above method has been described in relation to OGVs, but it may also be applied to other vane types.

(32) In the present example, the stubs are provided on a ring that is defined by a single annulus member, but in alternative embodiments the ring may be defined by a plurality of arcuate members.

(33) In the present example the aerofoil is manufactured using diffusion bonding and hot creep forming, but in alternative embodiments the aerofoil may be made using any other known manufacturing methods. In further alternative embodiments, an aerofoil and support member with a hollow cavity that extends through the support member to the aerofoil may be manufactured without the need to weld the aerofoil to the support member, for example using additive layer manufacturing techniques.

(34) It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.