Patent GB-645942-A (GB)
Title: Means for effecting and controlling the supply of liquid fuel to a prime mover
Inventor: IFIELD RICHARD JOSEPH
IPC: F02C7/22
Filed: 1947-05-03
Abstract: 645,942. Gas turbine plant. LUCAS, Ltd., J. May 3, 1947, No. 11959. [Class 110(iii)] [Also in Groups XI and XXIX] A choke member regulating the fuel supply to a gas turbine is supplied with fuel by a centrifugal pump driven by the turbine and regulated by a servomotor controlled by a valve responsive to barometric pressure and by a diaphragm responsive to a fuel pressure difference, which diaphragm may further control the said valve or a second servomotor control valve or alternatively regulate the fuel supply to the choke. As shown, the choke 9, Fig. 1, and the centrifugal pump 2 are housed in a casing 1 having an inlet 4 to the pump and an outlet 8 to the burners. The choke 9 is connected to a servomotor piston 12 slidable in a cylinder 13 connected at its bottom end to a chamber 6 around the pump periphery via ducts 14, 7, at its top end to the seat of a leak-off valve 17 via a duct 15 and between its ends by a restricted orifice 18 in the piston. The valve 17 is mounted on a pivoted lever 19 coacting at one end with a bell crank lever 31 whose longer arm 26 is loaded by springs 27, 28 arranged to abut an adjustment screw 29 and the piston 12 respectively and by capsules 23, 24 in a chamber 21 communicating with the pump inlet through a duct 22. The capsule 23 is evacuated whilst the capsule 24 communicates with the atmosphere through a duct 25. The other end of the lever 19 coacts with a pin 35 carried by a spring-loaded diaphragm 33 which separates the chamber 21 from a chamber 32 communicating through a throttled duct 36 with the inlet side of the choke 9. A manually-actuated cam 40 controls the opening of a byepass duct 38 between the duct 36 and the chamber 21 to regulate the pressure in the chamber 32. Normally the valve 17 is closed and the fuel locked between it and the piston 12 holds the choke 9 against upward movement. In the event of a decrease of atmospheric pressure, e.g., through an increase in altitude of an aircraft, the capsule 24 contracts and the lever 31 acts upon the lever 19 to open the valve 17 to relieve the pressure above the piston 12 and so adjust the position of the choke 9 towards closure to accommodate for the reduced amount of fuel required. In the event of an increase in the turbine speed above a selected value the increased pump outlet pressure results in an increase in pressure in the chamber 32 and the movement of the diaphragm 33 and its pin 35 to act on the lever 19 to open the valve 17 and again reduce the opening of the choke and hence the speed of the turbine. In a modification, a double beat lift valve 43, Fig. 2, is disposed between the chamber 6 and the choke 9 and is operable by a spring-loaded diaphragm 44 adjustable by a manually-actuated cam 47 and subjected on opposite sides to the pressures on the upstream and downstream sides of the choke to maintain the flow of fuel thereto substantially constant. In this arrangement the manual adjusting arrangement for regulating the pressure in the chamber 32 is omitted and, if it is not desired to limit the maximum speed of the turbine, the diaphragm 33 and its associated parts may be omitted. In a further modification the adjustment of the pressure in the chamber 32 is achieved by a ported movable wall associated with the pump which taps the fuel from the pump at any radius thereof. The position of the wall being manually-adjustable by a rack and pinion. The capsules 23, 24 and the diaphragm 33 may, if desired, act on separate leak-off valves to control the servomotor piston 12.