GB735159A - Improvements in or relating to fuel control systems for gas-turbine power plants - Google Patents

Abstract

735,159. Gas turbine plant. UNITED AIRCRAFT CORPORATION. Aug. 25,1953, No. 23457/53. Class 110 (3). [Also in Group XXIX] Means for controlling the fuel flow to a gas turbine plant comprises a governing valve 46 operable by fly-weights 140 to reduce fuel flow in response to increase of speed, and a control valve 50 and by-pass valve 98 responsive to operating conditions of the plant so as to limit the fuel flow to prevent excessive turbine temperatures from being attained. The valve 50 includes a ported sleeve 58 moved in a rotary sense within a fixed, ported housing 54 by a rack-and-pinion 64, 66 connected to opposed bellows 68, 72. The bellows 68 is subject internally to the pressure at the inlet of the compressor or to a pressure at a point downstream of the inlet, and the bellows 72 is evacuated so that the bellows 68 is responsive to absolute pressure. A plunger 62 within the sleeve 58 is actuated through a rack-and-pinion 86, 88 and cam 90 by a spring-load piston 82 subject to pressure generated by a turbinedriven centrifugal pump 40 in such manner that the opening of the valve 50 increases with increased turbine speed. The ports 56, 60 in the housing 54 and sleeve 58 are rectangular and the top of the plunger is flat so that the valve opening is a function of the product of compressor inlet pressure and turbine speed. The by-pass valve 98 is actuated by a diaphragm 106 subject on its lower face, by way of a passage 108, to the pressure before the valve 50, and on its upper face to the pressure after the governing valve 46 for which it has a connection 110 containing a valve 122 sensitive to the temperature of the air entering the compressor, a bleed 128 allowing movement of the valve 122 to affect the pressure above the diaphragm 106. The by-pass valve thus maintains a pressure difference across the valves 50, 46 as a function of air temperature at the compressor inlet. In a modification, applied to a compound turbine plant in which a low-pressure turbine drives a low-pressure compressor and a high-pressure turbine drives a high-pressure compressor the bellows 68 is subject to the delivery pressure of the high-pressure compressor and the bellows 72 to the inlet pressure of the low pressure compressor. The pump 40 may be driven by either the high or the low pressure rotor. In a further modification, in which the plunger 62 instead of being speed-responsive is adjusted according to the expression 1-Pi/P2, where Pi and P2 are respectively the compressor inlet and highpressure compressor discharge pressures, the rack that operates the cam 90<SP>1</SP>, Fig. 4, carries a slotted part 216 which engages a pin 214 on a rod 212 which is pivoted to the free end of a bellows 210 and is slidable in a sleeve 204 connected to a bellows 202. Both bellows are subject exteriorly to compressor delivery pressure admitted to a box 192 whilst the interior of the bellows 202 is subject to compressor inlet pressure and that of the bellows 210 to the pressure at the throat of a sonic nozzle 206 through which compressor delivery pressure is discharged to atmosphere.