GB2195403A

GB2195403A - Improvements in or relating to sealing and cooling means

Info

Publication number: GB2195403A
Application number: GB08622435A
Authority: GB
Inventors: Michael John George; Robert Charles Tonks
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1986-09-17
Filing date: 1986-09-17
Publication date: 1988-04-07
Also published as: FR2603967A1; GB8622435D0; JPS6385203A; DE3730411A1

Description

GB2195403A 1

SPECIFICATION

1 Improvements in or relating to sealing means This invention relates to sealing means positioned between two or more members and is particularly applicable to the cooling of sealing means between adjacent vanes or blades of a gas turbine engine.

In a gas turbine engine, it is normally necessary to provide sealing means between the parts of adjacent vanes which form part of the flow annulus, ie between the root plat- forms and/or between the outer platforms of a blade or vane.

A well known sealing means comprises a flat strip of metal which is positioned along the inter platform gap and extends into a re- cess in each of the platforms as shown in Fig. A.

In operation, the high gas pressure acting on the strip forces it against the wall of each recess continuously along its length to provide an air-tight seaL It has been found, however, that due to the presence of the recesses and the sealing strip it is difficult to provide adequate cooling in the region of the interplatform joint; this can result in the platforms overheating and distorting which might lead to the escape of high pressure working fluid from the flow annulus-a clearly undesirable result.

It is an object of the present invention to provide a sealing means which reduces and possibly eliminates the above mentioned problems.

The invention will now be described by way of example with reference to the following drawings, in which:

Figure A illustrates the prior art.

Figure 1 is a diagrammatic view of a gas turbine engine showing an embodiment of the present invention.

Figure 2 is an enlarged pictorial view of part of the embodiment shown in Fig. 1.

Figure 3 is an isometric view of a preferred design of sealing strip.

Figure 4 is an isometric view of a second design of sealing strip.

Figures 5 and 6 are respectively cross sectional views in the direction of arrows A-A and B-B of the sealing strips shown in Figs. 3 and 4 positioned in the grooves at the inter platform gap.

Figures 7 and 8 are plan and side views respectively of yet a further design of sealing strip.

Figure 9 is a view in the direction of arrow B in Fig. 2.

Figure 10 is an enlarged view of region Z in Fig. 9.

Referring to Fig. 1, a gas turbine engine shown generally at 10 comprises an intake 12, compressor section 13, combustion sec- 130 tion 14 and turbine section 15 terminating in an exhaust nozzle 16. A broken away portion of the casing around the turbine section 15 shows diagrammatically the turbine vanes in- corporating the present invention.

Fig. 2 is an enlarged pictorial view of the broken away portion shown in Fig. 1 and illustrates two vanes 17 and 18, each of which comprises an aerofoil shaped section 19, an outer platform 20 and an inner platform 21. The outer platforms 20 and the inner platforms'21 of the two vanes 17, 18 are integrally joined to each other to form a segment 22. The end faces 23, 24 of the inner plat- form 21 and/or outer platform 20 are provided with a generally axially extending recess 25, which forms part of the sealing means. Each recess 25 co-operates with a second recess 25 formed in the end faces 23, 24 of the next adjacent segment 22 (best seen in Figs. 5 and 6) to provide a void 26 in which sealing member 27 is positioned. The sealing member 27, best seen in Figs. 3 to 7, cornprises a flat strip of material having longitudi- nal and transverse slots 28, 29, 30 cut into its upper and side surfaces 31, 32 respectively.

Referring now particularly to Figs. 3 to 6, the longitudinal slot 28 is provided along the mid portion of the strip whilst a plurality of transverse cooling slots 29 are provided across the surface of the strip 27 such that they communicate at a first end with the longitudinal cooling slot 28 and at a second end with a cooling slot 30 which extends downwardly over the side surface 32. The slots 28, 29, and 30 collectively provide a flowpath for cooling air to pass from the bottom surface 33 to the top surface 31. Referring briefly to Fig. 4, it will be appreciated that an alternative design of seal 27 may be manufactured in which the slots 30 provided on the side surfaces 32 are omitted, this design, whilst being capable of providing an effective cooling/sealing strip under normal operating circumstances can suffer from reduced airflow problems under certain circumstances which will be described in detail below.

In Fig. 5, the sealing member 27 can be seen positioned in the void 26 with its longitudinal and transverse cooling slots 28, 29 on the low pressure LP side of the void. A plurality of air holes, 33,34 provided at the inter platform gap 36 on both the high and low pressure sides allow high pressure air to load the sealing member 27 against the low pressure side of the void's surface 35 and effectively provide a seal at the inter platform gap 36. It will be appreciated that the sealing member 27 allows a controlled portion of air to pass through the cooling slots 28, 29 and 30 as shown in Figs. 5 and 6, such that the area of the platform 20 and 21 in the region of the sealing member 27 is cooled together with the sealing member 27. Cooling air is 2 GB2195403A 2 allowed to escape from the longitudinal slot via the air holes 34 on the low pressure side of the inter platform gap 36.

Referring now briefly to Fig. 6, it will be appreciated that the alternative design of sealing strip 27 already shown in Fig. 4 may be used in the same manner as that described above. The lack of transverse cooling slots 30 on the sidewall might however lead to cooling problems should the sealing member 27 be displaced sideways in the void 26 such that its side faces 37 and 38 come into contact with the bottom portions 39 or 40 of the recesses 25 as little or no air will be able to pass into the slots 29. This problem is particularly acute if the bottom portions 39, 40 are flat as shown dotted at 41 in Fig. 6. Due to the problem outlined above, this design would not be a preferred solution to the problem.

Referring now to the remaining figures, but particularly to Fig. 7, it will be seen that the transverse slots 29 may be arranged at a skew angle 0 to the sealing. strips longitudinal axis 42, Figs. 9 and 10 illustrate a sealing member 27 inserted in a segment 22 which has its joining surfaces arranged for convenience at a scew angle 0 to the engine 10 or segment 22 longitudinal centreline 43. The angle 0 is ar- ranged to be the same as the angle 0 such that each transverse slot 29 is orthogonal to the centreline 43. A sealing member 27 arranged in the above mentioned manner has the advantage of being able to supply the same amount of cooling air to either of the two segment recesses 25 between which it is sandwiched. This avoids overheating and prolongs the life of the segments 22.

Referring briefly back to Fig. 7, it will be appreciated that if additional cooling is required at. any particular point along the segment 22, the frequency of the transverse slots 29 may be increased as shown in region P.

An example of a material suitable for use as a sealing member 27 subject to temperatures of up to 600'C is NIMONIC 75, it will however be appreciated that other materials may be used.

Claims

1. A sealing member for use between spaced apart components each of said components being provided with one or more end portions each having at least one recess which includes two sidewalls, said recess cooperating with a corresponding recess in an adjacent end portion to form a void in which the sealing member is inserted, the sealing member comprising a strip having a first side, a second side and two edges, in which the first side is provided with a plurality of slots for the passage of cooling fluid.

2. A sealing member according to claim 1 in which the slots comprise a first slot which extends generally along the strips longitudinal axis and a plurality of second slots which extend generally transversely to the first slot and which act to provide a flow passage between the edges of said strip and said first slot.

3. A sealing member accoraing to claim 2 in which the strips edges are provided with third slots which communicate at a first end with the second slots and at a second end with the second side of the strip.

4. A sealing member according to any one of the preceeding claims in which pressurised fluid acts on the second side of the strip and urges said first side of said strip against adjacent sidewalls of said components.

5. A sealing member according to any one of claims 1 to 3 in which pressurised fluid is passed through the slots to effect cooling of the sealing member and the components in the region of the recesses.

6. A sealing member substantially as herein described with reference to Figs. 1 to 10 of the accompanying drawings.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC113 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

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