Patent Application
20080112804
The present application relates generally to gas turbine engines and more particularly relates to seals between ceramic matrix composite vanes and the metallic components of a gas turbine engine.
In a gas turbine engine, air is pressurized in a compressor, mixed with fuel in a combustor, and ignited for generating hot combustion gases that flow downstream into a turbine so as to extract energy therefrom. The turbine generally includes a number of turbine nozzles with each of the nozzles having a number of circumferentially spaced apart nozzle vanes supported by integral outer and inner bands.
Overall engine efficiency is related to the temperature of the combustion gases. As a result, ceramic matrix composite (“CMC”) materials have been used to form the nozzle vanes because of their high temperature capabilities. Although the CMC vanes may not require cooling, the attachments to the vane, such as the strut and the metallic bands, do require cooling. In order to minimize the parasitic losses and improve the efficiency of the overall turbine engine, the amount of cooling air used to cool the metallic attachments should be minimized. Specifically, effective sealing will minimize the cooling air leakage and thereby improve the efficiency of the turbine engine. Effective sealing design also will prevent the ingestion of hot gas into the metallic attachment section of the turbine and thereby increase the life of the metallic components.
Thus, there is a need for improved sealing methods between a CMC vane and the associated metallic components. The seals preferably will be easy to install, have an adequate lifetime, provide increased efficiency, and substantially prevent the leakage of the cooling air.
The present application thus provides a ceramic matrix composite nozzle assembly. The ceramic matrix composite nozzle assembly may include a ceramic matrix composite vane, a number of metallic components positioned about the ceramic matrix composite vane, and a number of metallic seals positioned between the ceramic matrix composite vane and one or more of the metallic components.
The metallic seals may include an exterior seal, an interior seal, and/or a horizontal seal. The metallic seals may include a number of shims, a cloth and a crimped metal shim, a shim and a metal cloth sandwich, and/or a metallic foil. The metallic seals may include a compliant material.
The metallic components may include an inner diameter band and an outer diameter band and the metallic seals may be attached to the inner diameter band and the outer diameter band. The metallic components may include a strut casing and the metallic seals may be attached to the strut casing. The ceramic matrix composite nozzle assembly may have a number of ceramic matrix composite vanes.
The present application further describes a ceramic matrix composite nozzle assembly. The ceramic matrix composite nozzle assembly may include a ceramic matrix composite vane, an inner diameter metallic band and an outer diameter metallic band positioned about the ceramic matrix composite vane, and a number of metallic seals positioned between the ceramic matrix composite vane and the inner diameter metallic band and the outer diameter metallic band. The metallic seals may include a cloth and a crimped metal shim, a shim and a metal cloth sandwich, and/or a metallic foil.
The present application further describes a ceramic matrix composite nozzle assembly. The ceramic matrix composite nozzle assembly may include a ceramic matrix composite vane, a strut casing positioned about the ceramic matrix composite vane, and a number of metallic seals positioned between the ceramic matrix composite vane and the strut casing. The metallic seals may include a cloth and crimped metal shim, a shim and a metal cloth sandwich, and/or a metallic foil.
These and many other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description of the invention when taken in conjunction with the drawings and the appended claims.
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Referring now to the drawings, in which like numbers refer to like elements throughout the several views,
As is known, the vanes 110, 120 may be positioned between a pair of bands, an inner diameter band 130 and an outer diameter band 140. A strut casing 150 is positioned within the vanes 120 from the outer diameter band 140 to the inner diameter band 130. A pair of cloth seals, a first set of cloth seal 160 and a second set of cloth seal 170 may be positioned between the strut casing 150 and the outer diameter band 140 as well as underneath the inner diameter band 130. The inner diameter band 130 of the CMC nozzle assembly 100 is positioned on a diaphragm 180 of the turbine 10.
The exterior seal 200 may take a number of different embodiments.
In use, the seals 200, 300, 350 may be installed at the interface of the bands 130, 140 and the vanes 110, 120. Because the seals 200, 300, 350 are substantially compliant, the seals 200, 300, 350 can accommodate some dimensional variations in the vanes 110, 120. The compliant nature of the seals 200, 300, 350 also results in better seal effectiveness. The cooling air pressure generally pushes the seals 200, 300, 350 against the vanes 110, 120. The seals 200, 300, 350 thus perform better at high differential pressures. The seals 200, 300, 350 generally rest on the vanes 110, 120. As a result, the seals 200, 300, 350 exert minimum force on the vanes 110, 120.
An alternative design would include only the use of the shims 240 or the use of the foil 260 without the metallic cloth 220, 230. This design may not require active cooling. An alternate seal design would include coating the seals, either shims 240 or cloths 220, 230 or both, with thermal barrier coatings or similar coating for protection against high temperature and for increased life. The seals, shims or cloth or both, also may be coated with a wear or oxidation resistant coatings as well.
It should be apparent that the foregoing only relates to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
