GB879982A - Improvements in liquid fuel supply systems - Google Patents

Abstract

879,982. Fluid-pressure servomotor-control systems. DOWTY FUEL SYSTEMS Ltd. Jan. 30, 1958 [Oct. 30, 1956], No. 33116/56. Class 135. [Also in Group XXVI] A liquid fuel supply system for supplying fuel to a gas-turbine engine includes a fuel pump connected to deliver fuel to the engine, an acceleration control operative on the fuel pump during engine operation to continuously adjust its output controllably to a fuel-flow capable of permitting safe engine acceleration, and an all-speed governor selectively responsive to any speed within a range of engine speeds to control a by-pass valve to by-pass fuel controllably from the fuel flow adjusted under control of the acceleration control in order to tend to maintain any selected engine speed. The variable displacement pump 1 delivers fuel past a metering valve into a delivery line connected to a by-pass valve 52, the metering valve being controllably positioned by differential pressure on servo piston 18, under the control of a vent valve 14, hinged at 13, which is spring connected to the metering valve and responsive to compressor delivery pressure acting in bellows 7. A servomotor controlling the pump displacement comprises a servo piston 46 acting on the displacement changing lever 44 of the pump, pressure beneath this piston being controlled by a vent valve 25, hinged at 24, which is responsive to the pressure drop across the metering valve 5 applied to diaphragms 21, 22, and is also responsive, through spring-loaded cup 33, lever 32, track 37 of this lever, guided cam follower 31 and cam 30, to engine speed and compressor ram entry temperature, which two variables are transformed by a function generator 28 into cam movement through cam-shaft 29. Another servomotor, controlling independently the by-pass valve 52, comprises a servo piston 53 of this valve, and means for varying the pressure beneath this piston comprising an allspeed governing device 57 having a vent control valve 56, hinged at 62, and responsive to compressor delivery pressure in bellows 64a and to a pressure signal derived from engine speed which is applied to diaphragms 60, 61. A pilot's control lever 66 acts through spring 63 on the hinged vent valve 56. The pressure signal on diaphragm 61, which is supplied through restrictor 69, is modified by a maximum engine speed governor 71 acting on a further vent control valve 70. The leverage exerted by bellows 7, bellows 64a, and cam 30 on their respective vent valves is adjustable by screw devices 12, 66a, and 38, respectively. In order to prevent an insufficient fuel flow to maintain combustion when reducing speed by altering the setting of the all-speed governor, a throttle valve 73 is provided in series with the by-pass flow into valve 52. Specification 834,916 is referred to.