GB1156462A - Fuel Systems for Gas Turbine Engines - Google Patents

Abstract

1,156,462. Gas turbine engine fuel systems. JOSEPH LUCAS (INDUSTRIES) Ltd. Nov. 4, 1966 [Oct.7, 1965], No.42563/65. Heading F1G. A gas turibe engine fuel system comprises a throttle 14 controlled by a manual lever 21 and also by a means 39 responsive to a pressure which varies with that in the engine intake, a cam 44 connected to the throttle and acting through a spring 46 upon a valve 48, which is arranged to modify the response of the means 39 to the pressure, and a means 50 responsive to changes in engine speed and acting on the valve 48 in opposition to the spring 46. The arrangement is such that manual opening of the throttle 14 increases the load exerted by the spring 46 to actuate the valve 48 to modify the response of the means 39 so as to tend to close the throttle, the resultant force on the throttle causing its opening rate to be controlled until the engine speed increases to an extent to actuate the valve again, whereupon equilibrium conditions are obtained to maintain the engine speed at a new value. Fuel is delivered by a swash-plate pump 10 via the throttle valve 14. The pressure drop across the valve 14 is maintained constant by a valve 16 subject to the pressure drop and acting to control the escape of fuel from a servo-mechanism 17 which controls the pump stroke. The means 39 comprises a piston subject to the fuel pressure upstream of the throttle 14, directly on one side of the piston and via a restirctor 40 on the other side. The pressure downstream of the restrictor 40, and hence the position taken up by the piston 39 in opposition to a spring 43, is varied by a valve 37 connected between the restrictor and the pump inlet passage 11. The valve 37 is actuated by an evacuated bellows 35 opposed by the spring 43 and acted on by a pressure intermediate atmospheric pressure and the engine intake pressure and derived from the latter pressures by a potentiometer 33, 34. The means 50 responsive to engine speed comprises an evacuated bellows acted on by a pressure proportional to the pressure rise across the engine compressor (and therefore proportional to engine speed) derived by a potentiometer 54, 55 connected between the inlet and outlet of the compressor. The linkage connecting the manual lever 21 and the piston 39 to the throttle 14 is preferably such that it can occupy a position in which the manual lever 21 has no effect on the throttle 14 and a further position in which the piston 39 has no effect on the throttle. This linkage is described in Specification 1, 128, 524.