Patent attributes
A casing arrangement (20) for surrounding a rotary component (16) of a gas turbine engine (10) especially a turbine is disclosed. The arrangement (20) comprises an annular casing member (22A) surrounding a bladed rotary section, such as a turbine stage. An array of gas path liner segments are suspended from the casing at a nominal clearance gap form the tips of the rotary blades. Running clearance is determined by expansion and contraction of the casing which, in turn, is controlled by a supply of heat transfer fluid passed through heat transfer holes in the casing. The casing arrangement described includes a passive pressure bleed effective during engine deceleration to reduce a pressure differential driving the fluid flow in order to avoid too rapid contraction of the casing as a result of overcooling.
