Patent GB-932749-A (GB)
Title: Improvements in afterburner fuel control mechanism for turbojet engines
IPC: F02C7/22
Filed: 1961-08-24
Abstract: 932,749. Gas-turbine jet-propulsion engines. GENERAL ELECTRIC CO. Aug. 24, 1961 [Sept. 13, 1960], No. 30559/61. Class 110 (3). [Also in Group XXIX] The total fuel supply to primary and secondary after-burners in a turbojet engine is controlled by a throttle valve 59 in accordance with a throttle control setting and compressor discharge pressure, the flow to the primary burners is controlled by a throttle valve 67 also in accordance with throttle control setting and compressor discharge pressure, and the flow to the secondary burners is controlled by a throttle valve 69 in a manner to maintain a constant pressure drop across the valve 67. Compressor discharge pressure is communicated to the interior of a bellows 133 which, together with an evacuated bellows 181, acts on a lever 175 pivoted at 177 and coacting with nozzles 170, 171 to control operation of a servo piston 165 which positions fulcrum points 161, 213 for levers 153, 207. The servo piston also actuates a roller 199 to vary the effect on the lever 175 of a spring 195 to obtain proportional control. Cams 131, 201, mounted on a shaft 51 actuated by the throttle control act on the levers 153, 207 which, through plungers 145, 209, actuate the control valves of servo pistons 135, 211 connected to the fuel valves 59, 67. Maximum and minimum flow stops 149, 151 are provided for the control valve of the servo piston 135. The pressure difference across the valve 59 is maintained substantially constant by controlling a throttle valve (not shown) in the air supply to an airturbine which drives a pump feeding fuel to the inlet 27 of the valve 59. This throttle valve is actuated by a servo piston 73 controlled by a valve 87 which is operated by a diaphragm 97 subject to the pressure difference across the valve 59. A lever 111 and link 113 provide a follow-up connection to the valve 87, and an anticipatory and stabilizing effect is provided by a further valve 117 controlling a diaphragm 119 which is connected to one end of the lever 111. An adjustable abutment 105 for a spring 103 loading the diaphragm 97 is of bi-metal construction to provide compensation for fuel temperature variations. The valve 69 controlling the flow to the secondary burners remains closed until, with increasing opening of the valves 59, 67, a point is reached at which the pressure difference across the valve 67 attains a certain value whereafter the valve 69 is opened by a servo piston under the control of a valve 219 to prevent further increase of pressure difference across the valve 67. The valve 219 is actuated by a diaphragm 221 subject to the pressure difference across the valve 67 and loaded by a spring of which an adjustable abutment 225 may incorporate a bi-metal element for fuel temperature compensation. On-off control of the after-burner fuel flow is effected by a cam 237 which is mounted on the shaft 51 and actuates a piston valve 239 which controls a servo piston 257 of a fuel shut-off valve (not shown) and, through a passage 247 controlled by the position of the servo piston 257, the motive fluid supply to the servo piston 73.