GB751003A - Improvements in or relating to fuel control systems for gas turbine power plants - Google Patents

Abstract

751,003. Gas turbine plant. UNITED AIRCRAFT CORPORATION. Jan. 6, 1953, No. 437/53. Class 110(3) [Also in Group XXIX] A fuel control system for gas turbine power plants comprises a throttle valve 90 between a source of fuel supply and the combustion chambers and also means 200 responsive to a variable of power plant operation such as the outlet pressure of the compressor of the engine for regulating the flow of fuel from the throttle valve to the combustion chambers,. the throttle valve itself being controlled by a pilot valve 112 responsive to a controlling signal which is a function of a number of variables of power plant operation for example, engine speed, compressor inlet temperature, exhaust pipe temperature, and altitude. In Fig. 2, fuel supplied to a line 50 is pressurized by a pump 56 to a value determined by a relief valve 64. The pump delivery divides along two pipes 60, 62 the fuel in the pipe 60 being further pressurized by a pump 76 to a value determined by a relief valve 80. The delivery of the pump 76 divides along two pipes 84, 86, the fuel in the pipe 86 passing through the throttle valve 90 and thence via a pipe 92 and a manually operated shut-off valve 312 to the combustion chambers. A check valve 70 opens if the pumps 56 fail. The fuel system is provided with combined filter and filter by-pass units 52, 68, 87. A regulating valve 100 maintains a constant pressure difference across the throttle valve 90. The latter comprises a valve member 128 carried by a spring-loaded diaphragm 123 forming a wall of a chamber 122 connected to the pilot valve 112 by a pipe 120. The valve 112 is operated by the proportional solenoid 34 to the coils 30, 32 of which the controlling signal is supplied. In this case a speed signal produced by an engine driven generator and modified by the setting of a throttle unit is fed to an electronic unit where it is combined with signals corresponding to other engine operating variables. The valve seat or sleeve 130 is continuously rotated by gears 132, 134 to prevent sticking and has ports 110, 118 connected respectively to the lower and high pressure sides of the throttle valve 90. The opening movement of the throttle valve 90 is limited by an adjustable stop 140 and the closing movement by a mechanism 142 comprising a stop in the form of a ported piston 158 carrying a pin 156 cooperable with a cam slot in a member 154. The member 154 is adjustable horizontally in response to the movements of two oposed bellows 144, 148. The bellows 144 is evacuated and the bellows 148 is exposed internally to compressor outlet pressure through a pipe 157. Fuel is admitted by a pipe 150 to the space between the bellows to damp their movement. The vertical datum position of the cam member 154 may be adjusted by a sleeve 164. Before the valve member 128 contacts the stop or piston 158, a bleed valve 172 is opened to prevent an excessive pressure developing in the chamber 122. The means 200 for regulating the flow of fuel from the throttle 90 to the combustion chambers comprises a by-pass valve 234 to allow fuel to pass back through a pipe 236 to the intermediate pressure pipe 62. The valve 234 is operated by a piston subject to the pressure in an annular chamber 230 the pressure in which is controlled by a pilot valve 220 acted on one end by a bellows 212 subject internally to compressor outlet pressure and on the other end by a spring-loaded bellows 216 subject internally to atmospheric pressure. The valve 234 follows up the movements of the pilot valve. A shut-off 312 between the throttle 90 and the combustion chambers has a lost-motion connection with a rack 310 operated by a pinion 308 connected to a throttle lever 300 which also controls a potentiometer 302 which establishes a signal fed to the signal combining electronic unit. When the shut-off valve 312 is closed a port 352 leading to a dump valve is open. On opening the valve 312, a high pressure fuel supply port 350 is connected to the port 352 to close the dump valve.