Patent GB-660317-A (GB)
Title: Tailpipe or afterburning control for turbojet engines
IPC: F02K1/16
Filed: 1949-04-27
Abstract: 660,317. Jet propulsion plant. BENDIX AVIATION CORPORATION. April 27, 1949 [May 8, 1948], No. 11222/49. Class 110(iii) [Also in Groups XI, XII and XXXV] In a gas turbine jetpropulsion plant the turbine exhaust is reheated before the variable area propulsion nozzle. The reheat fuel supply and the nozzle area are adjusted, in approximately the proper relationship, by a single control lever. The relationship is corrected by an overriding control which varies the propulsion nozzle area so as to maintain a certain relation between the airinlet and the turbine exhaust pressures with a secondary correction for the air-inlet temperature. A hand-lever 30; acting through a servomotor 31 moves a lever 72 coupled to the reheat fuel valve 70 and the gate valves 83, 84 of the variable area propulsion nozzle 22. The pivot 96 of the lever 95 in the operating link-work of the gate valves is moved by a reversing motor 126 through a rack-and-pinion gear 130 when a circuit is closed between a contact 120 and either of contacts 122, 123. The contact 120 is carried by a rod 105 connecting two bellows 103, 104. The bellows 103 is subjected to the air-inlet pressure brought by a pipe 102. The bellows 104 is subjected to the tail-pipe pressure at 101 brought by pipe 100 but this pressure is modified before passing to pipe 109 by means of a leak 117 and a valve 111 positioned by a device 114, 116, responsive to the air-inlet temperature. The servo-motor 31 comprises the lever 30, a frame 32 and toothed segment 34, all mounted on one axis. The segment 34 carries the output lever 72 and is moved by means of an electric motor 41 through a worm-and-rack gear 45. The alternative circuits of the motor are made by a contact on the hand-lever 30 and contacts 37, 38 on the frame 32. When the lever 30 is moved to one side it engages the frame 32 at one or other of the contacts and carries the frame with it. The springs 35, 36, permit the frame to move relative to the segment 34. A circuit of the motor being thus closed, the segment 34 is moved up to a position in which the springs 35, 36 are again balanced and both contacts 37, 38 on the frame are out of touch with the lever 30. The reheat fuel is injected into the tailpipe by nozzles 66 which are on the downstream side of jet-bars 67. The fuel spreads over the faces of the jet-bars and is carried off their edges by the gas stream. The reheat fuel is ignited by spurts of flame from burners 138 in the main combustion equipment 11. Fuel is supplied to these burners through a valve 140 when it is opened by a solenoid 142 in a circuit which includes an intermittent switch 143, a switch 143<SP>1</SP> normally closed but opened by a thermal device 145 at a high temperature and the contact 38. The valve 140 shuts when the follow-up motion of segment 34 opens the circuit at contact 38 or when the temperature in the tailpipe rises enough to operate switch 143<SP>1</SP>. The pressure drop across the reheat fuel valve 70 is varied by a device 51 in accordance with the air-inlet pressure and temperature to which a bellows 76 is subjected. The pressure in the chamber 53 is determined by a valve 55 connected to a diaphragm 52. The counter pressure in chamber 54 is determined by the relative values of two restricted orifices 58<SP>1</SP> and 79. Expansion of the bellows 76 increases the area of orifice 79 and thereby lowers the pressure in chamber 54. The valve 55 then moves to lower the pressure in chamber 53 and therefore the pressure drop across the fuel valve 70.