GB1175037A - Gas turbine jet propulsion engine - Google Patents

Abstract

1,175,037. Jet propulsion engines. ROLLSROYCE Ltd. Sept.11, 1968, No.43258/68. Headings F1J. [Also in Division G3] A gas turbine jet propulsion engine comprises conduit means in which are arranged in flow series combustion equipment and variable area nozzle means; means for measuring the dynamic pressure in the conduit means upstream of the combustion equipment; and means, acted upon by the measuring means, for controlling the nozzle area. The engine shown comprises front nozzles 14, 15 and rear nozzles 22, 23, all rotatable to vary the efflux direction. The nozzles 14, 15 receive air from the L.P. compressor 3, and their thrust can be increased, e.g. for vertical take-off, by supplying fuel to injectors 16, 17 from a vapour core centrifugal pump 34 having an inlet throttle 36 controlled by at least one engine variable and pilot's lever 39. The area of each nozzle 14, 15 is adjustable by a ram 18 connected by pipes 49 to the high and low-pressure sides of a swash-plate pump 48. For this purpose, the inclination of the swash-plate 47 is adjustable by a piston 40 subject on one side 43 via a duct 45 to a high-pressure, e.g., that of the fuel supply to the main combustion equipment 5, and subject on the other side 44 to a variable pressure intermediate the high-pressure in the duct 45 and a low-pressure in a chamber 50 connected to a low-pressure source. This variable intermediate pressure is established by a potentiometer comprising a fixed restriction 46<SP>1</SP> and a variable restriction 51, the latter being controlled by a valve rod 52 which is rotated to avoid stiction and is adjusted axially by a bell crank 53, 54 bearing against a roller fulcrum 62 and pivotally connected to the casing through a link 60. The bell crank 53, 54 is acted on by opposed diaphragms 63, 64, both of which are acted on one side by the total pressure of the air at a point 73<SP>1</SP> immediately upstream of the region of the fuel injectors 16, 17, communicated via a duct 73 to a chamber 66. The other side of diaphragm 64 is acted on by the static pressure at the point 73<SP>1</SP>, communicated via a duct 74 to a chamber 67, while the other side of diaphragm 63 is acted on by the pressure in a chamber 65, established by a potentiometer 68, 69 connected between the chamber 66 and a duct 70 open to atmosphere. The net force on diaphragm 64 therefore represents the dynamic pressure at the point 73<SP>1</SP>, while the net force on diaphragm 63 represents the dynamic pressure at the fuel nozzles 16, 17 (once this dynamic pressure is a fixed fraction of the total pressure when the fuel nozzles are choked). Accordingly, the control of the area of the nozzles 14, 15 maintains the ratio of these two dynamic pressures at a constant value.