GB2107225A - Method of providing location means for gas turbine engine components - Google Patents

Abstract

The invention provides a method whereby vanes 10 or struts 10a are connected to their location rings or housings 24, by heating and applying gas pressure to superplastically extend the ring or housing into the end of the vane or strut and effect diffusion bonding between the end of the vane or strut and the ring or housing. <IMAGE>

Description

SPECIFICATION Method of providing location means for gas turbine engine components This invention relates to a method of providing components with means by which the components will be located in a gas turbine engine.

The invention has particular efficacy in the provision of location means for struts and vanes.

in known arrangements, vanes such as compressor guide vanes, are individually welded into annular flanged location rings. If the guide vanes are required to rotate about fixed axes, bosses are welded onto their radially outer ends and are used to locate the vanes in flanged rings.

Bearing housings have struts protruding radially outwardly which are welded to flanged rings. The flanged rings are in turn, bolted to other static parts of the gas turbine engine.

Making such assemblies as these described hereinbefore is costly, time consuming and difficult. Distortion is a common problem and is brought about by local heating, when welding of individual vanes or struts takes place.

The invention seeks to provide an improved method of providing a vane or strut with means whereby it may be located in a gas turbine engine.

According to the present invention, a method of providing a strut or vane with locating means for locating said strut or vane in a gas turbine engine, includes the steps of partly forming the desired shape of said location means from a metal which is capable of superplastic extension, arranging the strut or vane and partly formed location means in juxtaposition such that an end of said strut or vane is against a major surface of said location means, placing the assembly in a vacuum furnace and heating the whole to a temperature at which said location means is capable of superplastic extension and applying a gas pressure to said location means, to superplastically extend said major surface of said location means to complete its shape and contact said strut or vane end and continuing said pressure and heating so as to effect diffusion bonding between said strut or vane end and location means.

The invention will now be described, by way of example and with refrence to the accompanying drawings in which: Fig. 1 is a view representing both a strut and a guide vane.

Fig. 2 is a part view representing both an assembly of struts joining a bearing housing to location means and an assembly of guide vanes joining a platform and location means, in accordance with embodiments of the invention.

Fig. 3 is a view on line 3-3 of Fig. 2 and including a die structure.

Fig. 4 is an enlarged part view of Fig. 2.

Fig. 5 is a part view of a further embodiment of the invention.

Fig. 6 is a view on line 6-6 of Fig. 5 and includes a die structure.

Fig. 7 is a further embodiment representing both a strut and a guide vane.

Fig. 8 is a still further embodiment of the invention.

Fig 9 is a view in the direction of arrow 9 in Fig.

8 and includes a die structure.

Referring to Fig. 1. A guide vane 10 is viewed on its leading edge. Guide vane 10 is manufactured by forging a suitable blank of metal, of a kind which is compatible with the metal of other structures to which it is desired to diffusion bond guide vane 10.

Guide vane 10 has an excess of metal 12 provided at each end and has blending radii 14 at its junction therewith.

After forming of guide vane 10, the excess metal 14 is machined off along the dotted lines 16, thus providing a guide vane 10 with flared ends.

A number of guide vanes 10 are formed as described hereinbefore and then placed in a circular jig 1 8 of which only the upper portion is shown (see Fig. 3). Jig 1 8 consists of two portions 18a, 18b, in which guide vanes 10 are located in equi angular spaced relationships and an annular cover 20, also in two pieces 20a, 20b.

A gas inlet 22 is provided in cover 20.

A ring 24 is preformed and also placed in jig 18. Ring 24 is produced from a material which is capable of superplastic extension when appropriately treated and of being diffusion bonded to guide vanes 1 0.

The two portions 20a, 20b of cover 20 are placed over ring 24 and drawn together so as to trap the ring edges against jig portions 1 8a, 1 8b.

The assembly is then placed into a vacuum furnace (not shown) and heated to a temperature at which the material of ring 24 can be superplastically extended, provided the appropriate strain rate is applied.

The strain is applied by the injection of an inert gas e.g. argon via pipe 26, into space 28, whereupon the central portions of ring 24 extends radially inwardly, its thickness reducing as it does so. Eventually the ring contacts the ends of guide vanes 10. The heat and pressure is maintained, or modified if necessary, for a given time period, so as to achieve diffusion bonding of the ring 24, to the ends of each of guide vanes 10.

A similar operation is performed at the same time, in those inner ends of guide vanes 10 which are not shown. The end product is as shown in Fig.

2 i.e. an angular array of guide vanes 10 which have had flanged rings 24 and 30 superplastically formed and extended into their ends and diffusion bonded thereto for the purpose of locating guide vanes 10 in a gas turbine engine.

An advantage of the method is that it obviates the necessity which previously existed, of removing large amounts of metal in machining operations. The only operation necessary after diffusion bonding the assembly, is to trim the flanges of rings 24 and 30 and drill bolt hole therein.

The method also enables retention of the blending radii 14 (Fig. 4) and thus still avoids stress concentrating features and, in operation, flow turbulence.

Referring to Fig. 3a. An alternative method of providing a closed space 28a is the welding of metallic, annular cap 32 to a ring 24a which has preformed flanges 34, 36. Gas is introduced as hereinbefore described and after completion, cap 32 is machined off for re-use, by trepanning.

Should guide vanes 10 need support against buckling, when diffusion bonding pressure is applied, the spaces between them can be filled with a ceramic slurry 38. When the slurry dries, it will support the guide vanes 10. When the superplastic forming and diffusion bonding operations are complete, the ceramic can be removed.

Referring to Figs. 5 and 6. An outer ring 24b and an inner ring 30a have been superplastically extended so as to envelop respective ends of guide vanes 10. Diffusion bonding has then been achieved between all areas of contact between rings 24b and 30a and guide vanes 10.

A possible disadvantage of the latter arrangement, is the loss of blending radii. This however, can be rectified by the arrangement shown in Fig. 7. Each vane has a shaped, thickened portion 38 at each end (only one being shown). The thickened portion 38 is joined to its respective vane end via a blending radius 14a. On assembly, each ring (not shown in Fig. 7) is superplastically extended so as to envelop thickened ends 1 4a and then diffusion bonded thereto.

In Figs. 8 and 9, the means for locating each of vanes 10 in gas turbine engine structure, consists of a hollow boss 40. In operation, boss 40 will rotatably fit in a prepared recess in a ring (not shown). Means not shown, but which are known, will be connected to each boss 40 for the purpose of achieving the rotation and thus enable variation of the thrust area of a set of guide vanes 10.

As can be seen in Fig. 9, blending radii 1 4b are formed by providing a complementary radius 42 around the lips of the aperture 43 in die 44 in which vane 10 fit, and superplastically extending the material of boss 40 onto its surface.

Referring now to Fig. 10. A shaft 50 rotates in a ball bearing 52, which in turn is located in a bearing housing 54.

Bearing housing 54 consists of inner ring 30b in which bearing 52 resides, an outer ring 24c via which the assembly is located in gas turbine engine structure, and a number of equi angularly arrayed struts 1 Oa which join inner and outer rings 30b and 24c.

The joining of inner and outer rings 30b and 24c, by struts 1 0a may be achieved as described hereinbefore.

No data is included herein, with respect to temperatures, times or pressures which it will be necessary to achieve, in order to superplastically extend and diffusion bond, the various parts. The data used will depend on the material of the parts and is available to the skiiled man in various publications.

Claims (7)

1. A method of providing a strut or vane with locating means for locating said strut or vane in a gas turbine engine, including the steps of partly forming the desired shape of said location means from a metal which is capable of superplastic extension, arranging the strut or vane and partly formed location means in juxtaposition such that an end of said strut or vane is against a major surface of said location means, placing the assembly in a vacuum furnace and heating the whole to a temperature at which said location means is capable of superplastic extension and applying a gas pressure to said location means, to superplastically extend it to complete its shape and move said major surface to contact said strut or vane end and continuing said pressure and heating so as to effect diffusion bonding between said strut or vane end and location means.

2. A method of providing a strut or vane with locating means as claimed in claim 1 including the step of partly forming the location means by forming a ring from strip material.

3. A method of providing a strut or vane with locating means as claimed in claim 1 or claim 2 including the step of forming the strut or vane with thickened ends which blend into the strut or vane via blending radii, then machining said thickened ends away, leaving said radius portions so as to provide a vane with flared ends.

4. A method of providing a strut or vane with locating means as claimed in claim 1 or claim 2 including the step of superplastically extending the locating means to the extent that the locating means envelops said vane end or ends.

5. A method of providing a strut or vane with locating means as claimed in any previous claims, including the step of superplastically forming the locating means into an annular structure having radial flanges.

6. A method of providing a strut or vane with locating means as claimed in claim 6 including the step of arranging first and second rings centrally in adis, spaced from each other by a plurality of equi angularly arranged in a vacuum furnace and heating it to a temperature at which said rings may be superplastically extended, applying a pressure via an inert gas so as to extend said rings against the walls of the die to form radial flanges and to extend a major surface of each ring against respective strut or vane ends and maintaining said temperature and pressure until said rings and struts or vanes are diffusion bonded together.

7. A method of providing struts or vanes with location means for locating them in a gas turbine engine, substantially as described in this specification, with reference to the drawings.