Abstract: A gas turbine engine power unit (10) comprises a gas generator (11) having a valve (21) located at its downstream end. The valve (21) receives the exhaust efflux of the gas generator (11) and directs it either to a plurality of turbochargers (32) to boost the output power of the unit (10) or to a plurality of heat exchangers (39) to provide regeneration of the unit (10). The valve (21) comprises a rotary portion (20) which rotates within a static portion (28) to provide alignment of apertures within both portions (20,28) to facilitate the direction of the gas generator (11) exhaust efflux.

Abstract: A low drag surface comprises at its upstream edge, an intermittent linear vortex producing means which extends transverse to the flow over the surface and produces a succession of rolling vortices extending transverse to said flow. The vortices move across the surface and reduce drag in the manner of roller bearings. In preferred embodiments the vortex producing means is mechanical, in the form of an oscillating part or fluid dynamic, in the form of a nozzle arrangement.

Abstract: A turbofan gas turbine engine comprising in axial flow series a fan, a booster compressor and a core engine is provided with a diffuser. The diffuser is positioned axially between the booster compressor and the compressor of the core engine to efficiently diffuse the air from the fan to the compressor of the core engine. The diffuser comprises a plurality of circumferentially arranged geodesic pipe diffusers, the pipe diffusers extend axially and radially and the outlets of the pipe diffusers are displaced circumferentially by an angle of between 20.degree. and 60.degree. with respect to the inlets of the pipe diffusers.The geodesic pipe diffusers allows the airflow between the fan and the core engine to be diffused adequately without compromising the efficiency of the core engine, or the high mass flow rate of the fan and also minimizes the length, weight and drag of the gas turbine engine.

Abstract: A common mechanism enables both throat area change in either a fan duct or an exhaust gas duct and flow deflection at the nozzle of the duct.

Abstract: In order to damp possible vibration of a rotor blade for a gas turbine engine, the blade has a hollow tip portion with an internal surface extending across the direction of the centrifugal field on the blade. A weight comprising e.g. Silicon Nitride or Carbide is caused by centrifugal force to bear on this surface. Relative motion and hence friction between the weight and the surface serves to damp vibration of the blade.

Abstract: A turbine suitable for a gas turbine engine is provided with a bearing support member which is interconnected with the turbine casing by means of an annular array of aerofoil guide vanes. The whole assembly of support member and aerofoil guide vanes is maintained in a state of tension. The degree of tension in the assembly is controlled so as to be substantially constant throughout the normal operating cycle of the turbine.