초록 ▼

To enable shroud segments in a gas turbine rotor blade stage to operate at high temperatures with an adequate margin of safety, the shroud segments are mounted and cooled such that they are thrust outwards against seatings on surrounding high strength support structure by the gas pressure in the tur

To enable shroud segments in a gas turbine rotor blade stage to operate at high temperatures with an adequate margin of safety, the shroud segments are mounted and cooled such that they are thrust outwards against seatings on surrounding high strength support structure by the gas pressure in the turbine passage, the shroud segments being provided with strengthening ribs or the like so that the outward thrust is transferred to the support structure through a plurality of load paths distributed over the outer sides of the shroud segments as necessary to avoid overstressing.

대표청구항 ▼

1. A turbine shroud assembly for a gas turbine rotor stage, comprising a shroud ring comprising a plurality of shroud segments consisting of a metallic alloy, supporting structure circumferentially surrounding said shroud ring and to which said shroud segments are retained, at least said support

1. A turbine shroud assembly for a gas turbine rotor stage, comprising a shroud ring comprising a plurality of shroud segments consisting of a metallic alloy, supporting structure circumferentially surrounding said shroud ring and to which said shroud segments are retained, at least said supporting structure consisting of a metallic alloy which retains its high strength at elevated temperatures, the supporting structure having a high strength at its normal operating temperature and the shroud segments having a substantially lower strength than the supporting structure at their normal operating temperature, retaining means provided on said supporting structure and said shroud segments for retaining said shroud segments to said supporting structure, means defining shroud chamber means between said shroud segments and said supporting structure, means for supplying cooling air to pressurise said shroud chamber means, and means for exhausting said cooling air from said shroud chamber means to a location downstream of said rotor stage; said means for supplying cooling air to said shroud chamber means being adapted for metering said cooling air during operation of said turbine such that the total pressure forces acting outwardly on said shroud segments due to turbine gas pressure are substantially greater than the total pressure forces acting inwardly on said shroud segments due to cooling air pressure in said shroud chamber means, said shroud segments thereby experiencing an outward thrust, said shroud segments having means defining a plurality of load paths in addition to said retaining means distributed over said shroud segments so as to transfer said outward thrust to said supporting structure without overstressing said shroud segments. 2. A turbine shroud assembly according to claim 1 in which said means for supplying cooling air to pressurise said shroud chamber means is adapted to meter said cooling air during operation of said turbine such that the pressure in said shroud chamber means is only just sufficient to ensure exhaustion of said cooling air to said location downstream of said rotor stage. 3. A turbine shroud assembly according to claim 1 in which said shroud chamber means are defined between said means defining a plurality of load paths. 4. A turbine shroud assembly according to claim 3 in which said means defining said plurality of load paths comprise rib portions extending across said shroud segments to strengthen same. 5. A turbine shroud assembly according to claim 1 in which said supporting structure includes a surface for reacting said outward thrust from said shroud segments and sealing therewith, which surface is substantially cylindrical about the rotational axis of the turbine. 6. A turbine shroud assembly according to claim 1 in which said means for supplying cooling air to pressurise said shroud chamber means comprises a plurality of holes extending through said supporting structure. 7. A turbine shroud assembly according to claim 1 in which said shroud segments have a unitary, load-bearing structure. 8. A turbine shroud assembly for a gas turbine rotor stage, comprising a shroud ring comprising a plurality of shroud segments consisting of a metallic alloy, each said shroud segment having opposed edge portions defining groove features, supporting structure circumferentially surrounding said shroud ring and to which said shroud segments are retained, at least said supporting structure consisting of a metallic alloy which retains its high strength at elevated temperatures, the supporting structure having a high strength at its normal operating temperature and the shroud segments having a substantially lower strength than the supporting structure at their normal operating temperature, retaining means provided on said supporting structure and said shroud segments for retaining said shroud segments to said supporting structure, means defining shroud chamber means between said shroud segments and said supporting structure, means for supplying cooling air to pressurise said shroud chamber means, and including metering means for metering of said cooling air and means for exhausting said cooling air from said shroud chamber means to a location downstream of said rotor stage; said supporting structure also including plate members defining a surface for reacting said outward thrust from said shroud segments and for sealing therewith, said plate members having holes therein for said metering of said cooling air, a ring portion outboard of said plate members, and hook means extending from said ring portion to define tongue features thereon, which tongue features engage said groove features, whereby said shroud segments are retained to said supporting structure; wherein said plate members are sandwiched between said shroud segments and said ring portion of said supporting structures, said plate members spanning the distance between said opposed edge portions of said shroud segments such that at least some of the inward pressure forces on said plate members due to said metering of cooling air are transmitted through said opposed edge portions of said shroud segments for reaction against said tongue features, said means for supplying cooling air to said shroud chamber means being adapted for metering said cooling air during operation of said turbine such that the total pressure forces acting outwardly on said shroud segments due to turbine gas pressure are substantially greater than the total pressure forces acting inwardly on said shroud segments due to cooling air pressure in said shroud chamber means, said shroud segments thereby experiencing an outward thrust, said shroud segments having means defining a plurality of load paths in addition to said retaining means distributed over said shroud segments so as to transfer said outward thrust to said supporting structure without overstressing said shroud segments. 9. A turbine shroud assembly according to claim 8 in which said shroud segments have a unitary, load-bearing structure.