GB840456A - Fuel control apparatus for gas turbine engines - Google Patents

Abstract

840,456. Gas turbine plant. BENDIX AVIATION CORPORATION. Oct. 24, 1957 [Dec. 5, 1956], No. 33282/57. Class 110 (3). [Also in Group XXIX] The pump 30 of a gas-turbine engine fuelsystem is provided with a by pass valve 84 to regulate the pressures in the pump outlet conduit 32, the valve being actuated by a spring loaded diaphragm 80; the chambers 72, 78 on opposite sides of which are connected, respectively, to the conduit 74, leading to a manifold 24 supplying the fuel nozzles, and to the pump outlet conduit 32. A pressure-regulator 40 consisting of a valve closure 94 integral with a spring-urged piston 86 has the opposite sides of the,latter connected across the pump 30 to control the pressure of fluid entering conduits 98 and 130. Conduit 98, which includes a restriction 100, opens to a chamber 102 that houses a piston 104, the position of which is determined by a leak-off valve 106 connected by an arm 108 to an engine-speed responsive member 50 ; a spring 112 is disposed between the arm 108 and the piston 104 whilst a rack 110 is moved by the latter. A pinion 114 co-operates with rack 110 to control the position of an acceleration fuel-flow cam 116, the position of which is also varied by an engine-temperatureresponsive device 58. A second engine-speedresponsive member 118 is connected to another leak-off valve 124 that is further controlled by the throttle lever 39 ; the valve 124 is associated with a spring-loaded piston 134 supplied with fluid from the regulator 40 via a restriction 132, the piston 134 setting the axial position of the closure 140 of a metering valve 142, the rotational position of which is determined by a device 144 responsive to compressor discharge pressure. Fuel flows from the metering valve 142 to the conduit 74 via a restriction 158 with which cooperates a check valve closure 154 having in parallel therewith a second restriction 160 with which is associated a valve closure 162 mechanically linked to the piston 104. A leak-off valve closure 166 controls the flow of fuel from the conduit 32 to a chamber 168 connected to the input of the restriction 160, the valve 166 being operated by a diaphragm 176 responsive to the pressure differences between the fluid in chambers 168 and 178, the latter being connected by a restriction 180 to the conduit 74. The position of the metering valve closure 140 is determined in accordance with engine speed and compressor discharge pressure modified during acceleration by the cam 116; during deceleration the closure 140 is moved by the throttle lever 39 and engine speed to the minimum axial position against a step 141, the compressor discharge pressure then controlling the fuel flow until the latter falls sufficiently to enable closure 154 to shut-off the restriction 158 whereupon the leak-off closure 166 opens when the pressure differential across diaphragm 176 falls below a given value and the fuel flow on deceleration is accordingly modified. The opening of the closure 166 is varied to maintain a constant pressure-drop across the restriction 160 and closure 162.