GB1605219A

GB1605219A - Stator vane for a gas turbine engine

Info

Publication number: GB1605219A
Application number: GB40245/75A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1975-10-02
Filing date: 1975-10-02
Publication date: 1984-08-30
Also published as: IT1068291B

Description

(54) A STATOR VANE FOR A GAS TURBINE ENGINE (71) We, RoLLs-RoYcE LIMITED. a British Company, of 65 Buckingham Gate, London SWIE 6AT, formerly ROLLS ROYCE (1971) LIMITED, a British Company of Norfolk House, St. James's Square, London, S.W.1Y 4JR, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a stator vane for a gas turbine engine.

Such vanes frequently comprise shrouds and/or platforms which define a portion of the gas flow annulus of the engine. Because they have been used to carry mounting loads and other loads, these shrouds and platforms have in the past tended to be of comparatively heavy construction, and have therefore been difficult to cool.

The present invention provides a stator vane in which the platform or shroud is provided with a relatively easily cooled gas contacting surface.

According to the present invention a stator vane for a gas turbine engine comprises an aerofoil portion adapted to direct a portion of the hot gas flow of the engine and mounted in the load-carrying platform of a root or tip platform or shroud, said load carrying platform supporting a gas contacting skin which defines part of the boundary of the gas flow annulus of the engine and which overlays the load carrying platform and is spaced therefrom so as to leave a gap, and passage means adapted to allow cooling fluid to flow into said gap.

Said skin may be made of a porous material so that cooling fluid may flow through it to provide film cooling on its exposed surface; thus the skin may be made of a laminated material each lamina having pores therein which are out of register with those in the adjacent lamina but are interconnected by passages within the laminate.

Said cooling fluid may be caused to flow into said gap in the form of jets which impinge on the undersurface of said skin to provide impingement cooling.

The aerofoil, the skin and the load carrying platform may be made as separate pieces which are subsequently joined together, or alternatively the load carrying platform may be a separate piece while the skin may be cast into the aerofoil.

The invention also comprehends a method of manufacturing such a stator vane in which the skin is formed from sheet material, the aerofoil section is cast so that it incorporates the skin, the load-carrying platform is cast separately, and the load-carrying platform is metallurgically bonded to said aerofoil and at least to the edges of said skin.

The invention will now be particularly described, merely by way of example, with reference to the accompanying drawings in which: Figure 1 is a partly broken away view of a gas turbine engine incorporating vanes in accordance with the invention Figure 2 is an exploded view of a vane of the engine of Figure 1, and Figure 3 is an axial section through the platform of the vane of Figures 1 and 2.

In Figure 1 there is shown a gas turbine engine comprising a casing 10 within which are located in flow series a compressor section, a combustion section, a turbine and a final nozzle. The casing 10 is broken away to expose to view the combustion chamber 11 and nozzle guide vanes 12 which direct hot gases from the combustion chamber onto the turbine rotor 13. Operation of the engine is conventional in that ambient air is taken into the compressor section and compressed before being mixed with fuel in the combustion chamber, and burnt to produce hot gases which then drive a turbine which is drivingly interconnected with the compressor to drive it. Residual hot gases from the turbine exhaust flow through the final nozzle to provide thrust.

Because the vanes 12 are exposed to the hot gases it is necessary to provide them with some form of cooling and Figures 2 and 3 show how the vanes are made to enable this cooling to be applied.

Figure 2 shows only the lower half of one of the guide vanes 12 and it will be seen that the vane includes an aerofoil portion 14 and a platform made up of a load carrying platform 15 and a skin 16 which are drawn exploded apart. The skin 16 is cast into the aerofoil 14 so as to retain it thereto while the platform 15 is provided with an aerofoil shape aperture 17 therein which is adapted to receive an aerofoil section extension 18 of the aerofoil 14. On the upper surface of the platform 15 there is provided a ridge 19 which extends round its periphery and is adapted when the vane is assembled to engage with the edge of the skin 16 so as to retain the skin and maintain it with a constant small separation between its lower surface and the corresponding upper surface of the platform 15. This separation or gap is more easily visible in Figure 3 where it is shown at 20.On its under-surface the platform 15 is provided with a pair of relatively massive locating flanges 21 and 22 which serve to transmit loads from the aerofoil 14 to mounting structure of the engine.

In order to enable the skin 16 to be cooled the platform 15 is provided with means for supplying compressed air to its undersurface and a plurality of impingement holes 23 which extend through the platform from its lower to its upper surface. These holes are so arranged that the compressed air flows in the form of a plurality of jets which impinge on the undersurface of the skin and consequently provide impingement cooling of the skin. It will be appreciated that since the skin does not bear any loads other than gas pressures it can be relatively thin and consequently the impingement cooling can be efficient.

In order to provide further cooling of the skin a plurality of film cooling holes 24 are provided which extend completely through the skin 16. These holes allow air which is impinged on the undersurface of the skin to flow to the gas contacting surface, there to form a film of cooling air. The holes are so arranged and disposed that a film of cooling air is provided wherever it is found to be necessary on the outer surface of the skin.

In addition to the cooling system for the platform described above, cooling air is supplied to the interior of the aerofoil to effect cooling of this portion. This cooling is not described in detail since it is irrelevant to the present invention, but it will be appreciated by those skilled in the art that there are a large number of possible ways of cooling this section.

As described above the platform of the vane is therefore cooled by supplying cooling air to the lower surface of the platform 15 which then passes through the holes 23 to impinge on the lower surface of the skin 16.

The spent air then flows through the film cooling holes 24 to film cool the surface.

To manufacture the vane described above it is proposed that the performed skin 16 be cast into the aerofoil 14. The platform 15 is cast separately, and then the aerofoil 14 is assembled with the platform so that the extension 18 extends into the aperture 17 and the skin 16 overlays the upper surface of the platform 15 with its edges engaging with the ridge 19. The extension 18 is then brazed or otherwise metallurgically bonded in the aperture 17 and the edges of the skin 16 are similarly bonded to the ridge 19, thus completing the lower platform region of the blade. It will be appreciated that an upper platform where necessary may be made in an exactly similar manner.

There are a variety of alternative constructions and methods of manufacture which are available. Thus the skin 16 could be made of one of a variety of materials known to be suitable for cooling, for instance it could be made of a laminated material comprising a plurality of laminae abutting face to face and having pores through each lamina which are out of register with those in the adjacent laminae but interconnected by passages within the laminate; such a material is disclosed in our British patent no. 1,175, 816.

Alternatively the skin could be an unapertured metal sheet; in this case alternative means must be provided for the efflux of cooling air from the gap 20.

In manufacturing the blade or vane it would be possible to make the aerofoil, the load supporting platform and the skin all separate and to join these together at a late stage of manufacture, alternatively the aerofoil and the load supporting platform could be made integral and the skin applied later, or the skin and load supporting platform could be made separately and joined at a later stage. the aerofoil being assembled still later.

It is also possible to manufacture the vanes in assemblies of two or three or more aerofoils, or even a complete annulus with separate aerofoils.

WHAT WE CLAIM IS: 1. A stator vane for a gas turbine engine comprising an aerofoil portion adapted to direct a portion of the hot gas flow of the engine and mounted in the load-carrying platform of a root or tip platform or shroud, said load-carrying platform supporting a gas contacting skin which defines part of the boundary of the gas flow annulus of the engine and which overlays the load carrying platform and is spaced therefrom so as to leave a gap. and passage means adapted to allow cooling fluid to flow into said gap.

2. A stator vane as claimed in Claim 1 and in which said skin comprises a porous material through which the cooling fluid may flow from the gap to provide film cooling on its exposed surface.

3. A stator vane as claimed in Claim 2 and in which said porous material comprises a material formed from a plurality of laminae abutting face to face, each lamina having

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. vane includes an aerofoil portion 14 and a platform made up of a load carrying platform 15 and a skin 16 which are drawn exploded apart. The skin 16 is cast into the aerofoil 14 so as to retain it thereto while the platform 15 is provided with an aerofoil shape aperture 17 therein which is adapted to receive an aerofoil section extension 18 of the aerofoil 14. On the upper surface of the platform 15 there is provided a ridge 19 which extends round its periphery and is adapted when the vane is assembled to engage with the edge of the skin 16 so as to retain the skin and maintain it with a constant small separation between its lower surface and the corresponding upper surface of the platform 15. This separation or gap is more easily visible in Figure 3 where it is shown at 20.On its under-surface the platform 15 is provided with a pair of relatively massive locating flanges 21 and 22 which serve to transmit loads from the aerofoil 14 to mounting structure of the engine. In order to enable the skin 16 to be cooled the platform 15 is provided with means for supplying compressed air to its undersurface and a plurality of impingement holes 23 which extend through the platform from its lower to its upper surface. These holes are so arranged that the compressed air flows in the form of a plurality of jets which impinge on the undersurface of the skin and consequently provide impingement cooling of the skin. It will be appreciated that since the skin does not bear any loads other than gas pressures it can be relatively thin and consequently the impingement cooling can be efficient. In order to provide further cooling of the skin a plurality of film cooling holes 24 are provided which extend completely through the skin 16. These holes allow air which is impinged on the undersurface of the skin to flow to the gas contacting surface, there to form a film of cooling air. The holes are so arranged and disposed that a film of cooling air is provided wherever it is found to be necessary on the outer surface of the skin. In addition to the cooling system for the platform described above, cooling air is supplied to the interior of the aerofoil to effect cooling of this portion. This cooling is not described in detail since it is irrelevant to the present invention, but it will be appreciated by those skilled in the art that there are a large number of possible ways of cooling this section. As described above the platform of the vane is therefore cooled by supplying cooling air to the lower surface of the platform 15 which then passes through the holes 23 to impinge on the lower surface of the skin 16. The spent air then flows through the film cooling holes 24 to film cool the surface. To manufacture the vane described above it is proposed that the performed skin 16 be cast into the aerofoil 14. The platform 15 is cast separately, and then the aerofoil 14 is assembled with the platform so that the extension 18 extends into the aperture 17 and the skin 16 overlays the upper surface of the platform 15 with its edges engaging with the ridge 19. The extension 18 is then brazed or otherwise metallurgically bonded in the aperture 17 and the edges of the skin 16 are similarly bonded to the ridge 19, thus completing the lower platform region of the blade. It will be appreciated that an upper platform where necessary may be made in an exactly similar manner. There are a variety of alternative constructions and methods of manufacture which are available. Thus the skin 16 could be made of one of a variety of materials known to be suitable for cooling, for instance it could be made of a laminated material comprising a plurality of laminae abutting face to face and having pores through each lamina which are out of register with those in the adjacent laminae but interconnected by passages within the laminate; such a material is disclosed in our British patent no. 1,175, 816. Alternatively the skin could be an unapertured metal sheet; in this case alternative means must be provided for the efflux of cooling air from the gap 20. In manufacturing the blade or vane it would be possible to make the aerofoil, the load supporting platform and the skin all separate and to join these together at a late stage of manufacture, alternatively the aerofoil and the load supporting platform could be made integral and the skin applied later, or the skin and load supporting platform could be made separately and joined at a later stage. the aerofoil being assembled still later. It is also possible to manufacture the vanes in assemblies of two or three or more aerofoils, or even a complete annulus with separate aerofoils. WHAT WE CLAIM IS:

1. A stator vane for a gas turbine engine comprising an aerofoil portion adapted to direct a portion of the hot gas flow of the engine and mounted in the load-carrying platform of a root or tip platform or shroud, said load-carrying platform supporting a gas contacting skin which defines part of the boundary of the gas flow annulus of the engine and which overlays the load carrying platform and is spaced therefrom so as to leave a gap. and passage means adapted to allow cooling fluid to flow into said gap.

pores therein which are out of register with those in the abutting laminae but which are interconnected by passages within the laminate.

4. A stator vane as claimed in any preceding claim and in which said passage means causes the cooling fluid to flow into said gap in the form of jets which impinge on the undersurface of said skin to impingement cool it.

5. A stator vane as claimed in any preceding claim and in which the aerofoil, the skin and the platform comprise separate pieces joined together.

6. A stator vane as claimed in any of claims 1-4 and in which said skin is cast into said aerofoil and the load carrying platform is metallurgically bonded to the skin and aerofoil.

7. A stator vane as claimed in any preceding claim and in which a plurality of said aerofoil sections are associated with a single said platform or shroud.

8. A method of making the stator vane of Claim I and comprising the steps of forming said skin from a sheet material, casting said aerofoil section so that it incorporates said skin, separately casting said load carrying platform and metallurgically bonding said load carrying platform to said aerofoil and at least to the edges of said skin.

9. A stator vane substantially as hereinbefore particularly described with reference to the accompanying drawings.

it). A gas turbine engine having a stator vane as claimed in any of Claims 1 to 7 or Claim 9.