GB975916A - Gas turbine engine fuel systems - Google Patents

Abstract

975,916. Gas turbine engine fuel systems. JOSEPH LUCAS (INDUSTRIES) Ltd. June 5, 1962 [June 12, 1961], No. 21088/61. Heading F1G. A fuel system for a gas turbine engine comprises a pump, the output of which is dependent solely upon its speed, a throttle valve through which fuel from the pump can be supplied to the engine, a branch passage through which fuel can be spilled from the upstream side of the throttle valve, a centrifugally operable valve for at least in part controlling the spill through the branch passage, and a balancing valve for establishing a pre-determined relationship between the pressure at the downstream side of the throttle and the pressure in the branch pipe. In the embodiment shown there is provided an engine-driven gear pump 1 which supplies fuel through a line containing a throttle valve 2, a shut-off valve 3 and a pressurising valve 4 to a line 5 leading to the fuel burners. A line 6 leads to burners used at starting. A branch passage 7 leads from a point between the pump 1 and the throttle valve 2 and fuel may pass therethrough back to the suction side of the pump. Fuel in the passage 7 enters a bore 11 and discharges therefrom through spill ports 12 the effective area of the ports being controlled by a centrifugallyoperable valve member 10. The fuel spilling through the ports 12 passes to a balancing valve 9 which comprises a cylinder having disposed therein a piston valve 17 the position of which controls the area of a spill port 19. The lower side of the piston valve communicates with the fuel supply line between the throttle valve 2 and the pressurising valve 4 so that the piston 17 takes up a position dependent on the difference in pressure between that downstream of the throttle valve 2 and that downstream of the centrifugally-operable valve 8. An adjustable orifice 12a is disposed in parallel flow with the spill ports 12. The centrifugally-operable valve member 10 is acted on by a pair of centrifugal weights 13 mounted on a rotor 14, the weights acting on the valve member in opposition to a spring 15. The loading of the spring 15 is controlled by the position of the throttle valve 2 so as to increase with increasing throttle opening. A relief valve 1a is provided at the pump discharge. A check valve 20 may be disposed between the valve 8 and the balancing valve 9, a by-pass passage with a variable restriction 21 being disposed across the valve.