GB750472A - Co-ordinated fuel feed and exhaust jet control for jet engines - Google Patents

Abstract

750,472. Gas turbine jet propulsion plant. BENDIX AVIATION CORPORATION. April 10, 1951 '[April 20, 1950], No. 8335/51. Class 110(3) [Also in Group XXIX] In a turbojet engine of which the effective area of the jet is varied by mechanism having control means for preselecting the degree of actuation thereof energization of the mechanism is made dependent on the attainment of a certain engine operating condition, e.g. a predetermined engine speed. In the embodiment described fuel is fed by a pump 52 past a regulating valve 70 and a governor valve 75 to a conduit 66 leading to the burners of the engine. An engine-driven, centrifugal governor-pump 81 discharges through an orifice 79, adjusted by a needle valve 88 responsive to the temperature and pressure of air flowing to the engine or to ram pressure, to a chamber 74 bounded by a diaphragm 72 and having a restricted outlet 84. Since the diaphragm 72, which is attached to the stem 70<SP>1</SP> of the valve 70, is subject to the pressure rise across the pump 81, connected for air density by the needle valve 88, the valve 70 will take up a position of equilibrium in which the pressure difference across a second diaphragm 71, which is also the pressure difference across the governor valve 75, balances that produced by the pump 81. Hence, due to the centrifugal pump, the pressure difference across the governor valve 75 will be proportional to the square of the engine speed so that the flow past it will be proportional to engine speed. A mechanical governor 91 connected by a lever 93 with the valve 75 has a loading spring 97 adjusted, through linkage 98, 99, 111 and a cam 104, by a control lever 100. Also operable by the lever 100 is a cam 103 which has connection through linkage 105, 106 with a piston valve 34 slidable within a hollow servopiston 30 which adjusts tail gate valves of the jet through linkage 25, 23. The cams 103, 104 are so arranged that over the lower part of the power range of the engine movement of the lever 100 varies the loading of the spring 97 to alter the speed setting of the governor but does not affect the servo-piston 30 which maintains the tail gate valves in open position, and movement of the lever 100 to higher power positions results in closing movement of the tail gate valves without substantial increase in engine speed setting. To prevent over-fuelling of the engine during acceleration a stop 114, controlled by a diaphragm 121 subject to the pressure rise across the pump 81, limits the opening of the valves 75 when the governor spring 97 is compressed. At a certain engine speed the pressures acting on the diaphragm 121 overcome a spring 119 and allow the valve 75 to open to a greater extent, as is permissible at higher speeds, until the governor 91 becomes effective on the valve. To prevent, during acceleration, the tail gate valves of the jet from closing during acceleration before the engine speed has risen sufficiently a valve 125 controlled by a diaphragm 126 subject to the pressure rise across the pump 8 prevents the supply of motive fluid to the servo-piston 30 until a certain speed has been reached. The piston 30 then moves under the influence of pressure acting on the left-hand end thereof and in a chamber 33 until drain ports 31, 32 in the piston come into register with an annular recess 38 and ports 37 in the valve 34. Should, during acceleration, the tailpipe temperature become excessive a valve 134 operated by an electric actuator under the control of a thermocouple restricts the drain passage 42 from the servo-piston 30 thereby tending to equalize the pressures on opposite sides of the piston to prevent further closing movement of the tail gate valves until the temperature falls to a safe value. Specification 750,490 is referred to. Reference has been directed by the Comptroller to Specification 612,840.