Arrangement for maintaining clearances between a turbine rotor and casing

Claim 1

In a gas turbine engine having a rotor, a casing surrounding the rotor, a combustion chamber within the casing, and a compressor, an arrangement for maintaining minimal clearances between the radially-outermost surfaces of the turbine rotor and the turbine casing surrounding the rotor, the arrangement comprising: (a) an annular sleeve surrounding the turbine rotor and fixed with respect to the turbine casing, the sleeve being elastically deformable in a radial direction, (b) a wear ring carried by the deformable sleeve, the wear ring being composed of segments arranged end-to-end circumferentially, the adjacent ends of the segments being spaced apart at all operating conditions of the turbine, (c) duct means for conducting air from the outlet of the compressor, the deformable sleeve being mounted on the duct means and the duct means forming part of the combustion chamber of the engine, one wall of the duct means having a forked section, (d) an annular perforated sleeve surrounding and connected to the deformable sleeve, air from the duct flowing through the perforations in the perforated sleeve and thereby being directed against the deformable sleeve, (e) means for directing air from the duct against the wear ring, (f) an annular deflector connected to the perforated sleeve, the deflector defining an end of the duct and being loosely retained within the forked section of the duct, and (g) layers of thermal insulation on the duct means and on the surface of the wear ring facing the rotor blades, the insulation being of ceramic material.