Spoke hub weld interface

Abstract

A turbine engine component comprises a hub portion comprising a plurality of circumferentially extending sectors 1. Each sector is joined to a circumferentially adjacent sector by two weld lines 5a, 5b. The weld lines comprise a first weld line on a first axial side of the hub portion and a second weld line on a second axial side of the hub portion opposite the first axial side. The first and second weld lines extend from a radially outermost side of the hub portion to a radially innermost side of the hub portion. The component may be a turbine mid structure or turbine rear structure. Each sector may have a spoke or strut 3 extending from the hub. The weld lines may be formed by electron beam welding. A method of forming the hub portion includes machining the ends of the weld lines.

Description

FIELD AND BACKGROUND

[0001] The present invention is concerned with an improved weld join interface for use in a turbine frame or case of a gas turbine engine and a method of manufacturing the turbine frame. For example, the invention may be applied in cases such as a low pressure turbine case, a high pressure turbine case or a high pressure compressor case.

[0002] The operation of a gas turbine engine is well known to a person skilled in the art who will also be familiar with the arrangement of a conventional turbine frame which comprises an inner circumferential case portion (a hub portion) connected to a plurality of struts.

[0003] Typically, the turbine frame and struts are made in a single piece casting. This is an expensive way of making the frame and casting the frame in one piece leads to low quality parts. It has therefore been discovered that it is desirable to make the turbine mid frame from a number of sectors which together make up the turbine frame. By casting sectors of the frame, the quality of each casting is improved due to their reduced size.

[0004] A turbine frame made of a number of sectors has been developed in the field. However, the known method is time consuming to manufacture as each sector must be joined to an adjacent sector by three separate weld lines. Furthermore, due to the configuration of the weld lines, a gap must be formed along the interface between adjacent sectors. This leads to stresses being induced in the weld joints. The reliability of the weld joints is therefore reduced. Furthermore, the integrity of the welds is further reduced as the start / stop of the weld (where the weld is most unstable) forms part of the final frame. Additionally, these weld joints do not provide easy access for non-destructive testing (NDT).

[0005] The inventors have developed a counterintuitive solution to address these problems. Specifically, the invention as set out herein counterintuitively increases the integrity of the weld joints and therefore increases the reliability of the turbine frame. Furthermore, the weld lines in the turbine frame of the present invention provide improved access for NDT.

[0006] An invention described herein is therefore concerned with an improved weld join interface for use in a turbine frame of a gas turbine engine. The invention may also be used in any compressor case, combustion, turbine case or turbine frame structure which consist of a centre huband radial outwards positioned spokes / struts / vanes in a gas turbine engine. SUMMARY

[0007] Particular aspects and embodiments are set out in the appended claims.

[0008] Viewed from a first aspect, there is provided a turbine engine component. The turbine engine component comprises a hub portion comprising a plurality of circumferentially extending sectors. Each sector is joined to a circumferentially adjacent sector by two weld lines. The weld lines comprise a first weld line on a first axial side of the hub portion and a second weld line on a second axial side of the hub portion opposite the first axial side. The first and second weld lines extend from a radially outermost side of the hub portion to a radially innermost side of the hub portion.

[0009] The turbine engine component may be a turbine rear structure or a turbine engine frame. By forming the hub portion of a plurality of sectors rather than from one piece, the manufacturing process is made more efficient. The present invention counterintuitively uses only two weld lines rather than three as is known in the art. Specifically, the present invention comprises two weld lines at each end of the circumferentially extending sectors which extend from the radially outermost side of the hub portion to the radially innermost side of the hub portion. The wording ‘extend from the radially outermost side of the hub portion to the radially innermost side of the hub portion’ is intended to mean that the weld line extends all the way to both the radially innermost and the radially outermost sides. This configuration differs from existing solutions where a third axially extending weld line is also used. The use of the axially extending weld line in prior art solutions means that radial extending weld lines in existing solutions cannot extend all the way to the radial outer surface of the hub. A gap must be left in order to hold a shield to prevent damage to the initial weld lines. This gap induces stress in the weld lines.

[0010] The firstand second weld lines may extend from outside the radially outermost side of the hub portion to inside the radially innermost side of the hub portion. Specifically, the start and stop portions of each of the weld lines may be outside the hub portion. During welding, the start and end of the weld is of poor quality and does not provide a stable joint. By starting and ending the weld radially outside the hub portion on radially extending flanges, the part of the weld with poor weld quality can be removed after the sectors are joined together.

[0011] Each circumferential end of each sector comprises two flanges: a first flange on the first axial side of the sector; and a second flange on the second axial side of the sector, opposite the first axial side. Each flange extends radially inwards and outwards of the hub portion. Thus, the weld line may start or end radially inside and radially outside of the hub. This part of the weld line can then be removed by machining once the parts are welded together. This is beneficial since the start or end of the weld line typically provides a poor quality weld. By starting and ending the weld line radially inside / outside the hub, the poor quality weld can be removed after welding so does not form part of the final part. The flanges are essentially protrusions which extend inside and outside of the hub.

[0012] Each flange may comprise a witness line extending from an inner radial side to an outer radial side of the hub portion. The witness lines may be used to ensure that the weld line is formed in the correct location and along the correct line.

[0013] Each sector may comprise at least one strut or spoke extending from the hub. When the turbine engine component is a compressor or turbine case, the component does not comprise struts.

[0014] The hub portion at each circumferential end of each sector may comprise a recess or cut out portion. Specifically, the ends of each of the sectors comprise a substantially ‘D shaped’ portion cut out.

[0015] The recesses in adjacent sectors form an opening in the hub portion extending through the radial depth of the hub portion. Specifically, when the ‘D shaped’ cut out portions are brought into abutment with one another, an opening or hole is formed which extends through the depth of the hub. When the weld line is formed, the weld joints extend through the axial sides of the hub until it reaches the opening. Thus a strong join is created between adjacent sectors.

[0016] As the two hub flanges typically are positioned collinear with the struts leading and trailing edges respectively, an axial length of the opening may be substantially the same as an axial length of the strut. The opening may be used to insert a shield when the welding is being carried out. This prevents damage to the weld on either side of the opening. The openings are larger than those in existing casings as they are required to receive a shield between the two welds and to allow non-destructive testing. The opening may additionally be used for inserting service tubes or electrical cables. The service tubes are used to supply bearings with oil and bearing seals with air. The electrical cables can used for engine monitoring systems (e.g. a shaft speed sensor).

[0017] In other examples, the axial length of the opening may be larger than the axial length of the strut. For example, the axial length of the opening may be determined based on the axial length and positioning of the flanges. Specifically, if the first and second flanges at the end of each sector are further apart, the opening will be larger. On the other hand, if the first and second flanges at the end of each sector are closer together, the opening will be smaller.

[0018] A circumferential width of the opening may be substantially the same as the axial length of the opening. Thus, shields can be easily inserted to protect the first weld line when the second weld line is being added.

[0019] The opening may be configured for use in non-destructive testing, NDT. In this way, the weld lines are easily accessible. Furthermore, the opening improves the simplicity of postwelding machining operations so that the geometry of the finished part can be accurately controlled. Specifically, the root side of the weld lines inside the opening can be machined.

[0020] The opening may be covered by a plate. The plate may be fixably attached to the opening or removably attached. The plate may be required when the invention is incorporated into a turbine rear structure. In this configuration, the surfaces are air-washed which requires the opening to be closed. The plate may also increase the structural integrity of the frame or casing.

[0021] The weld line may be formed by gas tungsten arc welding (GTAW), laser beam welding (LBW), plasma arc welding (PAW) or electron beam welding (EBW). The welding technique is chosen based on the required depth of the weld which is determined by the axial length of the flanges. For example, wider flanges require deeper welds which are best carried out by EBW.

[0022] In this example the turbine engine frame is formed of four sectors and each sector contains of two struts. In other examples, a different number of sectors may be used. For example, the number of sectors may be varied based on the number of struts / spokes. The frame or casing may comprise eight struts, each located in a separate sector. In other example, the sectors may vary in size around the circumference of the frame or casing and may therefore comprise different numbers of struts or spokes. The number of sectors (and welds) will be based on a cost trade, where the cost of cast sectors and cost for additional machining, welding, geometrical inspection and non-destructive test shall be considered.

[0023] Each sector may be joined to the circumferentially adjacent sector by only two weld lines. Specifically, each sector may be joined to the circumferentially adjacent sector by two radially extending lines. Thus, the sectors can more quickly and efficiently be joined together compared to the art where three weld lines are used.

[0024] According to a second aspect, there is provided a method of forming a hub portion of a turbine engine component. The method comprises forming a plurality of circumferentially extending sectors and welding a first sector of the hub portion to a second sector. Welding the first sector to the second sector comprises forming a first weld line on a first axial side of the hub portion and forming a second weld line on a second axial side of the hub portion opposite the first axial side, wherein the first and second weld lines extend from a radially outermost side of the hub portion to a radially innermost side of the hub portion. The method additionally comprises machining the ends of the first and second weld lines.

[0025] The first and second weld lines may be formed from outside the radially outermost side of the hub portion to outside the radially innermost side of the hub portion. Specifically, the start and stop portions of each of the weld lines may be outside the hub portion. During welding, the start and end of the weld is of poor quality and does not provide a stable joint. By starting and ending the weld radially outside the hub portion, the part of the weld with poor weld quality can be removed after the sectors are joined together.

[0026] The plurality of circumferentially extending sectors may be formed by casting, forging or may be additively manufactured. The use of forgings in any form and laser direct energy deposition (L-DED) will require machining to produce the final surfaces.

[0027] The circumferential ends of each of the sectors are machined before welding. This is because some types of welding, such as electron beam welding, only allow tolerances of about 0.1mm.

[0028] During machining prior to welding, machining stock is removed from each of the circumferential ends of each of the sectors. This is to ensure the required tolerances and surface texture for the weld.

[0029] After forming the first and second weld lines, the first and second weld lines may be machined. This is to remove the weld bead which is often full of small cracks, particularly after electron beam welding, so can lead to a reduction in strength of the weld.

[0030] Each circumferential end of each sector may comprise a cut out portion, wherein the cut out portions in adjacent sectors form an opening in the hub portion and wherein the method further comprises machining inside the opening after welding. In this way, the weld bead on the root side of the weld can be removed. This improves the structural integrity of the weld.

[0031] Other aspects will also become apparent upon review of the present disclosure, in particular upon review of the Brief Description of the Drawings, Detailed Description and Claims sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Examples of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0033] Figure 1 shows a cross-sectional view of a sector of a turbine engine frame with weld lines according to existing examples;

[0034] Figure 2 shows a cross-sectional view of a sector of a turbine engine frame with weld lines according to the present invention;

[0035] Figure 3 shows a perspective view of a sector of the turbine engine frame with two flanges at each end according to the present invention;

[0036] Figure 4 shows a perspective view of four sectors of a hub of the turbine engine frame welded together before welding is carried out;

[0037] Figure 5 shows a perspective view of four sectors of a hub of the turbine engine frame welded together after welding and post-welding machining is carried out;

[0038] Figure 6 shows a zoomed in perspective view of the weld lines between two adjacent sectors of the turbine engine frame according to the present invention after welding and postwelding machining is carried out; and

[0039] While the disclosure is susceptible to various modifications and alternative forms, specific example approaches are shown by way of example in the drawings and are herein described in detail. It should be understood however that the drawings and detailed description attached hereto are not intended to limit the disclosure to the particular form disclosed but rather the disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention.

[0040] As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”.

[0041] It will be recognised that the features of the above-described examples of the disclosure can conveniently and interchangeably be used in any suitable combination. It will also be recognised that the invention covers not only individual embodiments but also combinations of the embodiments that have been discussed herein. DETAILED DESCRIPTION

[0042] The present invention is concerned with an improved turbine engine frame for a gas turbine engine and a method of manufacturing such a turbine engine frame.

[0043] Figure 1 shows a cross-sectional view of a sector 1 of a turbine engine frame for a gas turbine engine. This arrangement is found in the art. The sector comprises a hub 2 and a spoke or strut 3. The sector 1 is attached to adjacent sectors by three weld lines 5a, 5b, 5c.

[0044] Weld lines 5a and 5b are along radially inwardly extending portions 6 of the hub 2. Each of weld lines 5a and 5b comprise a start / stop zone 7. The outer radial side of the hub 2 comprises the third weld line 5c. The third weld line 5c also comprises start / stop zones 7.

[0045] In order to weld the sector 1 to an adjacent sector, the sectors 1 are brought into abutment with one another. The radially inwardly extending portions 6 of the adjacent sectors 1 are welded together by, for example, electron beam welding. Further tabs (not shown) extend radially inward of the radially inwardly extending portions 6. The weld lines 5a, 5b are started on these tabs in the start stop zones 7.

[0046] The third weld line 5c is made along the outwardly facing abutment line between the sectors 1 by laser beam welding. The third weld line 5c is started and ended in the start / stop zones 7 on tabs (not shown) extending in an axial direction from either side of the hub. Usually, the third weld line 5c is made first, the weld 5c is allowed to shrink, then first and second weld lines 5b, 5c are made.

[0047] In order to avoid interference between weld lines 5a and 5b and weld line 5c, a shield is used under the third weld line 3c. The electron beam weld lines 5a, 5b stop before the radially outer surface of the hub 2. Thus, a gap 8 is formed between the radially outermost part of the welds 5a, 5b and the weld 5c. This gap weakens the join between adjacent sectors.

[0048] Figure 2 shows a cross-sectional view of a sector 1 of a turbine engine frame for a gas turbine engine according to the present invention. The sector comprises a hub 2 and a spoke or strut 3. The strut has a leading edge 13 and a trailing edge 14. As can be seen from this figure, only two weld lines 5a and 5b are used to connect the sector 1 to an adjacent sector. The weld lines 5a, 5b extend from a start / stop zone 7 radially inside the hub 2 to a start / stop zone 7 radially outside the hub 2. The weld lines 5a, 5b are made by electron beam welding.

[0049] Figure 3 shows a perspective view of a sector of the turbine engine frame with two flanges at each end.

[0050] As can be seen from these figures, the sectors 1 are formed with flanges 9 extending radially inwards from the innermost surface of the hub 2 and radially outwards from the outermost surface of the hub 2. When adjacent sectors 1 are welded together, the weld line extends along the length of these flanges 9. In between these flanges 9, a recess or cut out portion 11 is formed at the circumferential end of each sector 1. As all sectors can be unique, if required, there are options to add additional local features (openings or bosses), to fulfill requirements related to interfacing parts. As shown in this example, it is possible for each sector to have a further opening 15 extending through the hub portion 2, to allow for routing of an extra service line. Before welding sectors together, the ends of the flanges 9 are machined to ready them for welding.

[0051] Figure 4 shows a perspective view of four sectors 1 brought in abutment with one another and welded together to form a turbine frame 10. In other examples, other numbers of sectors may be used. For example, more than four sectors may be used to form a turbine frame.

[0052] As can be seen from this figure, due to the cut out portions or recesses 11 at the circumferential end of each sector, an opening 12 is formed which extends through the hub 2. During welding, a shield (not shown) is placed in this opening 12 to protect the weld line on the other side of the opening 12. The opening 12 is sized so that it can receive the shield. Once the sectors 1 have been welded together, the flanges 9 are removed from the radially inner side and the radially outer side of the hub 2 by machining. The root side of the weld inside the opening 12 is also machined to remove the weld bead.

[0053] Figure 5 shows a perspective view of four sectors 1 of a hub of the turbine engine frame 10 welded together after machining is carried out. During machining, the flanges 9 are removed so that the inner and outer radial sides of the ends of each sector 1 sit flush with the rest of the sector 1.

[0054] Figure 6 shows a zoomed in perspective view of two adjacent sectors joined together. The opening 12 can be seen in this figure extending through the hub 12. This shows the weld line after machining when the flanges 9 have been removed. The weld line is formed from the first and second axial sides of the hub. The weld lines 5a, 5b extend through the flanges 9 into the opening 12.

[0055] A method of manufacturing the turbine engine frame hub according to the present invention will now be described.

[0056] The method comprises forming each of the sectors 1 by casting, additive manufacturing e.g. Laser powder bed fusion (LPBF) or forging methods. The circumferential ends of each of the sectors are machined before welding. This is because some types of welding, such as electron beam welding, only allow tolerances of about 0.1mm.

[0057] The sectors 1 are then welded together. The weld process comprises welding a first sector to an adjacent second sector by forming a first weld line 5a on a first axial side of the hub portion and forming a second weld line 5b on a second axial side of the hub portion opposite the first axial side. A shield is placed inside the opening 12 to protect the weld lines 5a, 5b when welding is being carried out on the other side. The weld lines 5a, 5b penetrate through the flange 9 into the opening 12. The first and second weld lines 5a, 5b extend from a radially outermost side of the hub portion 1 to a radially innermost side of the hub portion.

[0058] Once the weld lines 5a, 5b have been made, the method additionally comprises machining the flanges 9 of the sectors 1 (discussed above). Furthermore, the root end of the weld inside the opening is also machined to remove the weld bead.

[0059] As would be understood by the skilled person, the invention could also be used in a turbine rear structure / turbine exhaust casing. The invention may also be used in any compressor case, turbine case, combustion or turbine frame structure.

[0060] The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and / or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Claims

1. A turbine engine component comprising:a hub portion comprising a plurality of circumferentially extending sectors, wherein each sector is joined to a circumferentially adjacent sector by two weld lines, wherein the weld lines comprise:a first weld line on a first axial side of the hub portion; anda second weld line on a second axial side of the hub portion opposite the first axial side, wherein the first and second weld lines extend from a radially outermost side of the hub portion to a radially innermost side of the hub portion.

2. The turbine engine component of claim 1, wherein the first and second weld lines extend from inside the radially outermost side of the hub portion to outside the radially innermost side of the hub portion.

3. The turbine engine component of claim 1 or 2, wherein each circumferential end of each sector comprises two flanges:a first flange on the first axial side of the sector; anda second flange on the second axial side of the sector, opposite the first axial side, wherein each flange extends radially inwards and outwards of the hub portion.

4. The turbine engine component of claim 3, wherein each flange comprises a witness line extending from an inner radial side to an outer radial side of the hub portion.

5. The turbine engine component of any preceding claim, wherein each sector comprises at least one strut or spoke extending from the hub.

6. The turbine engine component of claim 5, wherein the hub portion at each circumferential end of each sector comprises a recess.

7. The turbine engine component of claim 6, wherein the recesses in adjacent sectors form an opening in the hub portion.

8. The turbine engine component of claim 7, wherein an axial length of the opening is substantially the same as an axial length of the strut.

9. The turbine engine component of claim 8, wherein a circumferential width of the opening is substantially the same as the axial length of the opening.

10. The turbine engine component of claims 7 to 9, wherein the opening is configured for use in non-destructive testing, NDT.

11. The turbine engine component of any of claims 7 to 10, wherein the opening is covered by a plate.

12. The turbine engine component of any preceding claim, wherein the first and second weld lines are formed by laser beam welding.

13. The turbine engine component of any of claims 1 to 11, wherein the first and second weld lines are formed by electron beam welding.

14. The turbine engine component of any preceding claim, wherein the turbine engine component is a turbine mid structure.

15. The turbine engine component of claim 1 to 13, wherein the turbine engine component is a turbine rear structure.

16. The turbine engine component of any preceding claim, wherein the turbine engine component is formed of two or four sectors.

17. The turbine engine component of any preceding claim, wherein each sector is joined to the circumferentially adjacent sector by only two weld lines.

18. A method of forming a hub portion of a turbine engine component, the method comprising:forming a plurality of circumferentially extending sectors;welding a first sector of the hub portion to a second sector, wherein welding the first sector to the second sector comprises:forming a first weld line on a first axial side of the hub portion;forming a second weld line on a second axial side of the hub portion opposite the first axial side, wherein the first and second weld lines extend from a radially outermost side of the hub portion to a radially innermost side of the hub portion, wherein the method additionally comprises:machining the ends of the first and second weld lines.

19. The method of claim 18, wherein the first and second weld lines are formed from outside the radially outermost side of the hub portion to outside the radially innermost side of the hub portion.

20. The method of claim 18 or 19, wherein the plurality of circumferentially extending sectors are formed by casting.

21. The method of any of claims 18 to 20, wherein the circumferential ends of each of the sectors are machined before welding.

22. The method of claim 21, wherein during machining, about 3mm of is removed from each of the circumferential ends of each of the sectors.

23. The method of any of claims 18 to 22, wherein after forming the first and second weld lines, the first and second weld lines are machined.

24. The method of any of claims 19 to 23, wherein each circumferential end of each sector comprises a recess, wherein the recesses in adjacent sectors form an opening in the hub portion and wherein the method further comprises machining inside the opening after welding.

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