GB795651A - Improvements in or relating to aircraft power plant installations incorporating gas-turbine engines - Google Patents

Abstract

795,651. Gas turbine jet propulsion plant. ROLLS-ROYCE, Ltd. March 31, 1955 [April 27, 1954], No. 12244/54. Class 110 (3). In a gas turbine engine jetpropulsion plant designed to operate efficiently at a constant value of N/#T 1 , where N is the actual rotational speed and T 1 the engine air intake temperature, in which during low-speed flight the engine speed is reduced, the jet nozzle is provided with means to inject air which has been compressed in the compressor system of the engine into the exhaust gas stream at or near the throat so as to reduce the effective area of the nozzle and thus tend to restore the turbine inlet temperature. An axial flow compressor comprising a stator casing 10 and a rotor 12 feeds air to combustion equipment 15 supplying combustion products to a turbine, comprising a stator 16, nozzle guide vanes 17 and rotor blades 19, driving the compressor through a shaft 14. The turbine exhausts through a jet-propulsion nozzle consisting of a short frusto-conical outer wall 26 forming an extension of the stator 16 and an inner frustoconical wall 27 formed as the periphery of a disc 28 attached to the downstream side of the turbine disc 18. A manifold 29 secured to the wall 26 is supplied with compressed air from the compressor discharge through a manifold 31, conduit 30 and control valve 32. The manifold is connected to the turbine exhaust passage by a ring of orifices 33 situated at the throat of the nozzle. The orifices 33 may be replaced by a circumferential slot or slots. The jets of air passing through the orifices reduce the effective area of the nozzle, the amount of the reduction being determined by the valve 32. In a modification, Fig. 2 (not shown), the invention is described with reference to a convergentdivergent propulsion nozzle suitable for supersonic aircraft speeds. When used in an engine having high and low pressure compressors on independent rotors, the air for reducing the area of the nozzle is taken from the discharge of the high-pressure compressor and used to control the rotational speed of the low-pressure compressor in the manner described in Specification 757,981.