Patent GB-672208-A (GB)
Title: Apparatus for controlling the flow of fuel to a turbo-jet-engine
IPC: F02C7/22
Filed: 1948-08-13
Abstract: 672,208. Gas turbine plant. PACKARD MOTOR CAR CO. Aug. 13, 1948 [Aug. 28, 1947], No. 21449/48. Class 110(iii) A gas turbine fuel system comprising a metering valve controlling the supply from a fuel pump to the engine and a byepass valve controlling the flow of fuel to the metering valve has a manual control for adjusting the metering valve through the range from a stop position through an idling position to the maximum speed position, an all-speed governor for adjusting the metering valve. from the idling to the maximum speed position and means operated by the manual control at the idling position to render the all-speed governor operative. The fuel supply to a gas turbine jet propulsion engine is controlled by a unit 12, Fig. 1, which comprises a main fuel pump 55, Fig. 2, a metering valve 57 and a byepass valve 63. The metering valve 57 may be controlled by the manual lever 21, Fig. 1, through linkwork 20 or by an electronic speed governor 30 through an electric motor 34. The engine is controlled from rest to the idling speed by the lever 21 but when the lever reaches the idling speed position 25 it engages the contact 45 and power is supplied to the electronic speed governor 30. So long as the manual lever remains at the position 25, the engine is controlled by the governor 30 to the speed pre-set by the lever 37. If the lever 21 is moved past the idling position 25, the power supply to the governor 30 is cut off and the control of the engine is solely by the manual lever 21. The valve 57 is operated by the motor 34 through worm gearing which rotates a nut screwed on to a threaded extension of the valve spindle and by the lever 21 through a pinion which engages a rack rotatably mounted on the nut. To prevent overloading of the motor 34 when the valve 57 reaches the limits of its travel, two limit switches operated by the valve spindle are adjustably mounted on the valve body. The byepass valve 63 is provided to vary the pressure drop across the metering valve 57 with speed and altitude and for this purpose is arranged to be .operated by the pressure rise across the compressor. The discharge of the compressor is connected to one side of the diaphragm 74, the other side of which is connected to the atmosphere. Variations of ,pressure rise cause the diaphragm to operate a rod 73 which allows the valve 63 to open or close and control the fuel now from 'the chamber 70 to the chamber 64. The chambers 70, 64 are connected to the discharge and suction sides respectively of the main fuel pump 55. The chamber 72 is connected to the discharge side of the' metering valve 57 so that any variations of pressure drop across this valve will also control the amount of fuel byepassed. A temperature responsive device 81 has a movable element 82 which opens the valve 63 when a critical temperature is reached. In the event of failure of the fuel pump 55, the pressure in the chamber 70 falls, the valve 63 moves to the right under the action of the spring 80 and rod 73 and fuel is supplied direct to the metering valve from the .chamber 64. A pressure responsive device may be connected to the control 83 of a booster pump 51 so that when the pressure in the chamber 70 falls, a second stage of the pump may be put into operation. This pressure responsive device may be embodied in the temperature responsive device 81. A modification in which an auxiliary valve is mounted in the byepass valve 63 and the auxiliary valve is arranged to open when the pressure in the chamber 70 falls is also described.