Abstract: A gas turbine engine turbomachine (10) comprises a turbine section (18) in which cooling air is supplied from a compressor section (14) via a pipe (68) to a chamber (60). The chamber (60) supplies the cooling air through passages (58) in the nozzle guide vanes (30) to impinge upon a stator disc (32). A valve (70) in the pipe (68) is used to switch the flow of cooling air on and off. The valve (70) is opened to allow the cooling air to cool the stator disc (32) to shrink the stator disc (32) to minimise clearance between a shroud (34) supported by the nozzle guide vanes (30) and the turbine blades (28) during one mode of operation. The valve (70)is closed to allow the stator disc (32) to expand to increase the clearance between the shroud (34) and the turbine blades (28).

Abstract: A turbine suitable for a gas turbine engine is provided with a stage of rotary aerofoil blades which is surrounded by a shroud ring made of silicon nitride. In order to minimize load transfer between the shroud ring and the turbine casing the shroud ring is radially supported by and radially spaced apart from the turbine casing by a woven wire mesh array.

Abstract: The low pressure turbine of a gas turbine engine has an array of rotor blades and a shroud which surrounds the blade tips. The shroud is made up of a plurality of segments which are pivotally mounted from the turbine casing at their midpoints. The upstream portions of the shroud segments are fixed to the casing so that localised cooling of the casing in the region of pivotal attachment of the shroud segments causes the shroud segments to tilt and thereby improve the gas seal between the tips of the rotor blades and the shroud segments.

Abstract: An air intake for a gas turbine engine compressor comprises an arcuate primary duct which is in communication with the compressor of the gas turbine engine and which is provided with frangible wall portion. The frangible wall portion provides a barrier between the primary duct and a secondary duct and is so positioned and adapted as to be impacted and penetrated by a foreign body, such as a bird, which is above a predetermined weight and which has been ingested through the inlet of the primary duct. After penetrating the wall portion the foreign body passes through the secondary duct and is discharged therefrom at a location remote from the primary duct.

Abstract: An axial flow turbine comprises an annular array of rotatable turbine blades which are surrounded by a shroud ring. An open honeycomb structure is attached to the shroud ring, the open cells of which honeycomb structure contain an abradable material. The honeycomb structure is totally covered by an impervious coating which contains a ceramic material. The impervious coating resists oxidation and/or erosion of the abradable material.

Abstract: A turbine suitable for a gas turbine engine is provided with a stage of rotary aerofoil blades which is surrounded by a shroud ring made of silicon nitride. In order to minimize load transfer between the shroud ring and the turbine casing the shroud ring is radially supported by and radially spaced apart from the turbine casing by an annular brush seal.