| 摘要 |
A turbine shroud 15 for a gas turbine rotor blade stage 7 comprises shroud segments 25 made of a low strength metallic alloy of the "MCrAlY" type which is very highly oxidation resistant at elevated temperatures. The shroud segments 25 are supported by a structure in the form of a carrier ring 29 consisting of an alloy which retains high strength at high temperatures, and shroud cooling air chambers 53 are defined between the shroud segments 25, strengthening ribs (54 Fig. 2 not shown) of the shroud segments, and throttle plates 58 which also form part of the support structure for the shroud segments. Cooling air from chamber 49 is metered into shroud chambers 53 through holes 57 in throttle plates 58 so that the pressure in chambers 53 is only just enough to ensure exhaustion of the cooling air through holes 55 into the turbine passage just downstream of the rotor blades 7. This ensures not only low consumption of cooling air but also that the shroud segments are thrust outwards against their seatings on the throttle plates 58 by the higher turbine gas pressures upstream, the ribs (54) defining load paths which give the segments adequate distributed support to prevent overstressing or overstraining of the low strength alloy. <IMAGE>
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