Patent GB-757004-A (GB)
Title: Improvements in or relating to a control system for turbo jet engines
Inventor: COAR RICHARD JOHN
IPC: F02K1/16
Filed: 1954-08-17
Abstract: 757,004. Gas turbine jet propulsion plant. UNITED AIRCRAFT CORPORATION. Aug. 17, 1954, No. 23895/54. Class 110(3) [Also in Groups XI and XXIX] A gas turbine jet propulsion engine with a reheat chamber in the jet pipe, a variable area propelling nozzle and means for igniting the fuel in the reheat chamber has the igniting means rendered inoperative by means tending to open the nozzle. The gas turbine jet propulsion engine 2 has a compressor 4 supplying air to combustion chambers 8 feeding a turbine 6 driving the compressor. The turbine 6 discharges into the atmosphere through a reheat chamber 10 and a variable area propelling nozzle 44. Fuel is supplied to the combustion chamber 8 through a speed governor 15 the setting of which is controlled by a lever 17. Fuel is supplied to the reheat chamber from a fuel tang 46 by means of a booster pump 48 and a fuel pump 50 which discharges through a control device 52 to the fuel nozzles 26. The fuel pump 50 is driven by an air turbine 58 supplied with air from the compressor discharge through an electrically controlled valve 68. The variable area nozzle 44 is operated by a piston 132 in a cylinder 130 to which compressed air is supplied through a control 76. Thermocouples 88 in the turbine discharge are connected to an an amplifier 86 which is then connected to the control device 52. When it is desired to operate the reheat, switch 94 is moved' to the "on" position. This energizes the amplifier 86, opens the normally closed solenoid operated valve 418, Fig. 2, in the control device 52, opens the motor operated valve 68, starts the booster pump 48 and opens the solenoid actuated valve 82 controlling the fuel supply to the igniter control 28. Fuel from the igniter control is injected into the combustion chambers 8 and the flame propagated through the turbine ignites the fuel in the reheat chamber 10. The opening of the motor operated valve 68 allows compressed air to be supplied to the turbine 58 which then supplies fuel to the control device 52. The control device 52, Fig. 2, meters the fuel as a function of compressor pressure rise and the turbine exhaust temperature. The fuel supply is controlled by a metering valve 402 which is carried by a diaphragm 438. Bellows 458, 460 attached to the diaphragm are connected to opposite sides of a fuel metering orifice 408. The spaces around the bellows are connected to the inlet and outlet of the compressor respectively. The pressure acting in the chamber around the bellows 460 is varied by means of a valve assembly 406 which has a valve 490 rotated by a shaft 512 to vary the restriction caused by orifice 504 and the contour 506 of the end of the valve in accordance with variations of turbine exhaust temperature. The opening of the valve 82 allows fuel to be supplied to the igniter control 28, Fig. 4, through conduit 80. The igniter control is connected to the fuel supply conduit 74 by a conduit 84. When the conduit 74 is under pressure fuel is supplied by conduit 84 and passage 160, Fig. 4, to act on piston 114 which moves against the action of the spring 128 and opens the valve 118. This allows fuel to flow through conduit 122 to the combustion chambers 8. The duration of opening of valve 118 is determined by the size of a restriction 158 which allows fuel to flow to and act on the piston 112 and move the valve to the closed position. The ignition of the fuel in the reheat chamber causes the ratio pressure of the turbine exhaust to compressor discharge pressure to rise. These pressures are transmitted through conduits 222 and 79 to the nozzle control 76. These, pressures act on two bellows 218, 220, Fig. 3, to operate a pilot valve 202 controlling the supply of pressure fluid to or from a space 190 at one end of a control piston 168. The increase of the pressure ratio causes the valve 168 to be moved to the left and this allows air from the compressor discharge to pass to the right hand end of cylinder 130 through conduit 262 to open the nozzle 44. The increase in pressure in the conduit 262 is transmitted through a conduit 98 to a normally closed pressure switch 96 in the supply to the normally closed solenoid operated shut-off valve 82 which opens the switch and thereby causes the valve 82 to close. When the switch 94 is turned to the "off" position, the amplifier 86 is de-energized, the valves 418 and 68 closed and the booster pump shut down.