GB696758A - Improved method of feeding liquid fuel to gas turbines and notably to jet turbine and propellor turbine engines - Google Patents

Abstract

696,758. Automatic control systems. SZYDLOWSKI, J. March 9, 1950 [March 19, 1949; Sept. 28, 1949], No. 5999/60. Class 38(iv) [Also in Groups XXVI, XXIX and XXXVII] A gas turbine engine fuel system comprising a valve which controls the fuel pump at an adjustable constant output pressure by opening or closing a main by-pass around the pump has the output pressure determined by the pressure between two restrictions in a second by-pass around the pump which also includes a valve responsive to engine combustion gas temperature. The combustion chambers 1a, Fig. 1, are supplied with fuel by a pump 3a through a hand-operated throttle valve 30 and a governor controlled valve 8a. The delivery pressure of the fuel is controlled by a valve 6a inserted in a main by-pass 7a around the pump. The valve 6a is attached to a diaphragm 43 which is loaded by a spring 31, the opposite end of which bears against a piston 32 sliding in a cylinder 33. The cylinder 33 forms part of a second by-pass which also includes two restrictions 34, 35 and a spring-loaded electrically-controlled valve 37a. When the temperature of the combustion gases exceed a selected temperature, the thermocouple 23a causes the relay 21a to be sufficiently energized to close the switch 19a. This in turn causes the winding 17a of the electrically-controlled valve 37 to be energized and the valve 37 to be opened. Fuel then flows through the second by-pass and causes a drop of pressure in the cylinder 33 which reduces the loading on the spring 31 with a consequent lowering of the controlled pressure in the pipe 5a. Less fuel is fed to the engine and the temperature of the combustion gases falls. The relay 21a is no longer sufficiently energized and the valve 37a is closed by the action of its spring. To allow a temporary increase of combustion gas temperature during take-off, a resistance 40 and a switch 41 is included in the circuit of the relay 21a and thermocouple 23a. By opening the switch the temperature at which the thermocouple operates the valve 37 is increased. The switch may be connected to throttle lever so that it may be opened only when the valve 30 is fully open. To prevent the time during which the switch 41 is open from lasting too long, the switch 41 may be a time switch as shown in Fig. 2. When it is desired to open the switch a lever 102 is moved counter-clockwise and this causes the rod 104 to be moved to the right and the switch 41 to be opened. The lever 103 is also moved and starts clockwork which rotates the wheel 101. The wheel 101 slowly raises the rod 104 and after a short time the rod is lifted off the cam on the lever 102 and is returned to the right by the spring 106. This causes the switch 41 to close and the lever 103 to return to its original position. Specifications 642,229, 686,908 and 693,217, [both in Group XXVI], are referred to. Reference has been directed by the Comptroller to Specification 638,494, [Group XXVI].