GB664807A - Fuel feeding system for gas turbine engines - Google Patents

Abstract

664,807. Gas turbine plant. BENDIX AVIATION CORPORATION. June 23, 1949 [Aug. 3, 1948], No. 16727/49. Class 110(iii) [Also in Groups XXIX and XXXIII] A fuel supply system for a gas turbinecomprises a fuel supply passage with a throttle valve to regulate the fuel flow and means operated automatically in response to engine speed to supply fuel to the burners additional to that metered across the throttle valve when the engine speed attains a predetermined value. The fuel supply to the gas turbine is controlled by a throttle valve 70 operated by an allspeed governor the governed speed of which is pre-set by the pilot's throttle lever acting through a link 32 and levers 31 and 76 on the governor spring 73. The pressure drop across the valve 70 is controlled by a valve 37 operated by the diaphragm 36 and the engine driven speed governor 61. The force exerted on the valve spindle 38 by the governor weights 61<SP>1</SP> is balanced by the pressure drop across the diaphragm 36 so that this pressure drop is proportional to the square of the speed. This pressure drop is proportional to the pressure drop across the valve 70 which therefore also varies as the square of the speed. To enable the fuel supply to be varied with changes of altitude, a control bleed 90 between the chambers 34, 35, a passage 91, a chamber 92, a valve chamber 93, a needle valve 96 and a passage 94 pre provided. The valve 96 is actuated by a bellows 98 responsive to changes in density at the compressor-intake. Assuming that the engine is running at constant .speed, a decrease of density would cause the bellows 98 to expand and the valve 93 to open which will result in a decrease in the pressure drop across it. Since the flow through this valve is the same as that through the bleed 90, a similar decrease in pressure drop will occur across this bleed, which means a decrease in the pressure drop across the diaphragm 36 and a resulting drop across the throttle valve 70. The spring 40 ensures a minimum pressure drop across the valve 70 for idling purposes. The pressure drop between the discharge of the fuel pump 42 and the burner manifold is maintained constant by a diaphragm 50 controlling a byepass valve 45 between the delivery and suction sides of the pump. A valve 100 is provided to supply additional fuel to the burner manifold when a predetermined turbine speed is reached. This valve is operated by a diaphragm 101 actuated by the pressure drop across the diaphragm 36. The speed at which the valve opens may be varied by adjusting the loading of the spring 106 by means of a screw 107. A modification in which the quantity of additional fuel varies with the air density is also described. In this arrangement, the valve 100 is used to control the flow of fuel from the chamber 102 to the conduit 112, and an adjustable stop is provided to prevent further opening of the valve when a predetermined speed is reached.