GB737354A - Improvements in or relating to a fuel control system for gas turbine engines - Google Patents

Abstract

737,354. Gas turbine plant. BENDIX AVIATION CORPORATION. Sept. 8, 1953 [Sept. 24, 1952], No. 24835/53. Class 110 (3). [Also in Groups XIII and XXIX] A fuel control system for a gas turbine engine having a governor-controlled metering valve 64 and a regulating valve 48 actuated by the governor and by a diaphragm 46 subject to the pressures before and after the metering valve so that the pressure difference across the latter is maintained as a function of engine speed, as described in Specification 655,311, has means sensitive to engine speed and air temperature at the inlet to the compressor so to govern the fuel flow during acceleration that compressor surge is not encountered and that the maximum safe turbine temperature is not exceeded and during deceleration that the burner is not extinguished. As in the above-mentioned Specification, a bleed from a chamber 44 to the downstream side of the metering valve for modifying the pressure difference maintained across the latter is controlled by a needle valve 110 actuated by a bellows 128, but in this case the bellows is responsive only to the ram pressure at the intake to the compressor. A second bleed, which also passes by way of the needle valve 110 to the downstream side of the metering valve, is taken from a chamber 144 in which a fuel pressure is set up proportional to the square of the engine speed by the rotating governor weights 90, 96, this bleed comprising conduits 38, 40 between which is a spring- loaded valve 142. The compression of the loading spring 210 is varied by a slidable abutment 206 actuated through a lever 186 having abutment with an adjustable flange 194 by a bellows 166 connected to a temperature sensing bulb 169 at the compressor intake. Also actuated by the bellows is a cranked lever 212 with adjustable abutments 230, 236 and operating a slidable stop 222 for the valve 142. The arrangement is such that during acceleration the valve 142 is opened at a certain engine speed dependent upon temperature, the higher the temperature the greater the speed, to increase the pressure in the chamber 44 whereby the opening of the valve 48 is increased. Thus the fuel flow is increased at a rate just insufficient to cause compressor surge until the valve 142 engages its stop 222, whereby the rate of increase of fuel flow is reduced to prevent excessive turbine temperature. As the required speed is reached the fuel flow is stabilized by the action of the metering valve 64. To compensate for the effect of fuel temperature on the bellows 166, bimetallic discs 180 are interposed between the bellows and a member 182 by which the levers 186, 212 are operated. In a modification, the slidable spring-abutment 206 and the stop 222 are integral with one another and are actuated by the bellows without the interposition of levers. Specifications 604,466 and 612,840 also are referred to.