Patent GB-655311-A (GB)
Title: Fuel feeding system for gas turbines, jet propulsion engines and like power plants
IPC: F02C7/22
Filed: 1947-12-09
Abstract: 655,311. Gas turbine plant; stuffing-box substitutes. BENDIX AVIATION CORPORATION. Dec. 9, 1947, No. 32485. Convention date, Dec. 13, 1946. [Classes 110(iii)] and 122(v)] A fuel system for. a gas turbine power plant .having a fuel supply conduit in which is located a variable metering restriction the area of which is controlled by a valve connected to an engine driven centrifugal governor and a regulating valve which controls the pressure drop across the restriction, .has the regulating valve mechanically connected to a second centrifugal governor also driven by the turbine. The fuel supply to the engine is controlled by a metering and power device consisting of a lower regulating section 27, Fig. 2A, and an opper governor section 28 Fig. 2B. The lower regulating section comprises a byepass valve 33 which maintains the pressure in the chamber 31 above the metered fuel pressure in the chamber E and a regulating valve 51. The valve 33 is controlled by a spring - loaded diaphragm 39 enclosing a chamber 41 connected to the chamber E through a duct 43<SP>1</SP> and to the fuel discharge side of the metering unit by a duct 43. A relief valve 46 mounted in the valve 33 limits the maximum pressure that can be reached in the chamber 31. The regulating valve 51 is connected to a diaphragm 60 forming a flexible wall between the chambers C and D and to one arm 98 of a lever the other end of which is loaded by a sleeve 94 actuated by a pair of governor weights 100. As the chamber C is connected to the discharge side of the governor control valve 70 through a passage 163. altitude control valve 159 and jet 161, the diaphragm 60 will, by operating the regulating valve 51, tend to keep the pressure drop across the governor control valve 70 constant for a given setting of that valve and the altitude control valve 159. Further, as the force exerted by the diaphragm 60 is opposed by the force exerted by the governor weights 100, and the pressure in chamber C, the pressure maintained in the chamber D above that in the chamber E will be substantially proportional to the square of the turbine speed. A spring 67 ensures a minimum pressure drop across the governor valve 70 to prevent instability of the governor at low powers. The governor section, Fig. 2B, comprises a governor valve 70 operated by a second pair of governor weights 93 the spring-loading on which may be varied by the pilots control lever 115, Fig. 3. The governor spring 85 abuts at one end against a sliding sleeve 84 and at the other end against a bushing 86 carried by a member 87 rotatably mounted on a rod 89 which is axially. movable in a sleeve 90 operated by the governor weights 93. The pilot's control lever 115, Fig. 3, is connected to the governor spring compressing sleeve 84 by means of a hollow link 116, a lever 117 secured on one end of a shaft 118 and a yoke 119 secured on the opposite end and having fingers 119<SP>1</SP> which engage the flange 84<SP>1</SP> of the sleeve 84. The sleeve 84 is carried by a cylindrical fixed support 82. The lever 117, Fig. 3, carries a pivot pin 120 which engages an elongated slot in the link 116 and is held by a spring- loaded sliding pin 122<SP>1</SP>. When the lever 115 is held in the idling position by a detent engaging a recess 125<SP>1</SP>, the force in the governor spring 85 is only opposed by the force in the spring 139. By adjusting the screw 121, the idling speed may be varied. A recess 126<SP>1</SP> corresponds to the minimum fuel flow position. When the lever .115 is in this position fingers 127 of the yoke 119 engage the sliding bushing 81 and compress the spring 80, thus opening the valve 70 to pass sufficient fuel for starting purposes. An adjustable stop limits the travel of the valve 70. Under these conditions, the governor weights have no controlling action. A shut off valve 130 mounted in the discharge conduit is closed by the lever 115 when it is moved past the minimum fuel flow position, movement of the lever 115 to increase the load moves the valve 70 to increase the fuel flow, this results in a drop in pressure across the diaphragm 60 whereupon the regulating valve 51 opens and further increases the fuel supply. The turbine then speeds up until the governor weights 93 balance the setting of the governor spring 85 and the weights 100 the pressure drop across the diaphragm 60. Since the pressure drop across the altitude control valve 159 and jet 161 is equal to the pressure drop across the governor valve 70 any drop in pressure across the valve 159 due to the opening of the valve 159 by the bellows 146 will cause a drop in pressure across the governor valve resulting in a lower rate of fuel supply to the burners. The valves 70 and 51 have a number of openings 71, 52 to prevent instability of control due to a suction action. Fig. 6 shows a fuel system controlled by the metering and power device described and comprises a boost pump 101, feeding an engine driven fuel pump 30 through a cockpit control valve 102 together with an auxiliary or emergency system having an auxiliary fuel pump 171 controlled by a valve 173. Two non-return valves 174, 175 are fitted to prevent one' system interfering with the other. The engine may be started on the emergency or the main fuel system and the sequence of operation of the various valves is fully described in the Specification To ensure against leakage of fuel along the shaft 102, Fig. 2B, a seal is provided comprising a bushing 106 which is urged by a spring 106<SP>1</SP> against the inner surface of a sealing and bearing ring, 107. A retainer 108, secured to the housing 92, has a flange engaging the opposite side of the ring 107 and enclosing a packing ring 109.