Patent GB-684836-A (GB)
Title: Improvements in or relating to a control system for gas turbine engines
IPC: F02C9/16
Filed: 1949-05-31
Abstract: 684,836. Gas turbine plant. GARRETT CORPORATION. May 31, 1949 [Sept. 4, 1948], No. 14578/49. Class 110(iii) A gas turbine control system comprises a valve for controlling the rate of fuel flow to the engine, diaphragm means having a motion transmitting connection with said valve, an adjustable spring acting on the diaphragm to move the .valve in one direction and engine speed responsive means having a mechanical connection with the valve for moving it against the action of the spring in response to an increase of engine speed so as to produce a decrease in the amount of fuel supplied to the engine. The fuel supply to the gas turbine plant shown is controlled by a speed governor 52 which operates a valve 46 regulating the fuel flow through a by-pass 41, 42 connecting the delivery and suction sides of the fuel pump 26. The speed at which the turbine is controlled is regulated by adjustment of the load applied to the valve 46 by the spring 64. This load may be modulated by the pressure drop across an orifice 124 of air taken from the compressor discharge which acts on diaphragms 74, 75. The outlet side of this orifice may be connected through pipes 125 and 127 to the supply duct 113 of a useful power air turbine 112 in which case the speed of the turbine 11 will be modified according to output of the plant. When there is no load on the plant, the pressure in the duct 113 will be atmospheric and the pressure drop across the orifice 124 at a maximum. This pressure drop is applied to the valve 46 and by-passes sufficient fuel to cause the turbine to idle. This idling speed may be varied by adjustment of the valve 131. When it is desired to obtain the maximum speed from the turbine, the flow through the orifice 124 is stopped by means ot a shut ott valve 130. A selector valve 129 allows the pipe 127 to be vented to atmosphere or connected to the duct 113. When this pipe is vented to atmosphere, it is only necessary to close the valve 130 to bring the plant from idling to maximum speed. A shut off valve 80 opened by energising a solenoid 79 is arranged on the suction side of the main fuel pump. This solenoid is de-energised if the speed of the turbine exceeds a predetermined value by a governor 77 acting through a switch 78 and if the temperature of the gases exceed a predetermined figure by a thermostat 84 acting through a switch 85. A switch 137 operated by a diaphragm 135 responsive to the pressure at the compressor outlet is also provided in the solenoid circuit so that fuel is not supplied to the combustion chamber until the air supply is adequate. To start the engine, a switch 145 is moved into engagement with contacts 147, 148. This causes the relay 144 and ignition devices 23 to be energised and the solenoid circuit to be prepared for energisation. The relay 144 closes a switch 143 in the starter motor circuit. The motor 133 rotates the turbine-compressor unit and when the speed is sufficiently high, the pressure at the compressor discharge closes the switch 137 and energises the solenoid which opens the valve 80. After starting, the switch 145 is moved to a position in which the contact 148 only is engaged.