GB740457A - Improvements relating to fuel supply systems for gas turbine engines - Google Patents

Abstract

740,457. Gas turbine plant. DOWTY EQUIPMENT, Ltd. Oct. 27, 1953 [Oct. 27, 1952], No. 26970/52. Class 110(3) [Also in Group XXIX] In a liquid fuel supply system for gas turbine engines of the kind having an engine-driven pump 3 of fixed displacement supplying burners 7 of the spill type and a servo-controlled throttle valve 11 in the spill line 8, the vent or leak-off valve 33 controlling the throttle valve 11 is operated by a spring-loaded pressure responsive device 25 exposed to the output pressure of a pressure proportioning device having an input connection 17 with the burner supply line, an output connection 24 to the pressure-responsive device, and a return connection 23 to the spill line 8, a variable restrictor being provided to vary the fractional proportion of output pressure to input pressure and thereby determine the degree of opening of the vent valve 33 and of throttle valve 11 and hence the governed speed of the engine. As shown the pump 3 draws its supply from a tank 1 and supplies the burners 7 through pipes 4, 6 excess fuel being returned by the spill pipe 8 to the valve 11 and hence by a pipe 10 to the tank and the pump inlet. In the inoperative condition and at starting, the pipe 6 is blocked by the land 13 of a control valve 5 so that fuel is circulated back to the pump inlet by a pipe 14, the latter being closed by a land 15 when the valve is moved to the right to open the pipe 6. The valve 5 slides in a sleeve 22 and the input and output connections of 17, 24 open into this sleeve between the land 13 and a further land 18, controlling a series of orifices 19, 20, 21 leading to the return connection 23. The input connection 17 has a normally-fixed restrictor 16. As more of the orifices 19, 20, 21 are exposed the pressure in the output connection 24 drops and the vent valve 33 tends to close. The pressure-responsive device 25 comprises a bellows 26 exposed internally to the output pressure and externally to the pressure in the spill line 8. The bellows is loaded by an adjustable spring 30 and operates the valve 33 through a thrust rod 32. The throttle valve 11 is operated by a servo-device comprising a spring-loaded diaphragm 38 connected directly to the fuel supply pipe 4 on one side and on the other 'side to the vent opening 34 controlled by the valve 33, the two sides of the diaphragm being connected by a restricted orifice 40. The minimum idling speed is determined by the spring 30 and the maximum governed speed by the adjustment of the restrictor 16. The orifices 19, 20, 21 may be opened step by step by a remotely controlled constant speed motor. The orifices may be replaced by a single slut. According to the Provisional Specification the restrictor 16 may be biassed by a capsule or the like responsive to engine intake pressure to compensate for the effect of altitude and ram pressure on the governed engine speed