Patent GB-1103065-A (GB)
Title: Improvements in or relating to the control of the fuel supply to a gas turbine
Inventor: MATTHEWS ROBERT BARRY
IPC: F02C9/16
Filed: 1964-06-26
Abstract: 1,103,065. Gas turbine engine fuel systems. PLESSEY - UK Ltd. June 10, 1965 [June 26, 1964], No. 26624/64. Heading F1G. The invention relates to a fuel supply system of a gas turbine in which means are provided to limit automatically the fuel supply during acceleration so as to avoid compressor surge and overheating. Fuel is supplied from a pump to a throttle or metering valve through an automatic pressure drop adjustment valve which serves to maintain the pressure drop across the metering valve at a predetermined function of an operational datum. The metering valve is operated by compressor discharge pressure P 2  in such a direction as to increase its metering orifice with increase in discharge pressure P 2  with respect to intake pressure P 1 , while a further means which is subject to compressor discharge pressure acting against a vacuum capsule in the direction tending to reduce the metering orifice is connected through a lost motion device to the metering valve element so as to eliminate or reduce the influence of the intake pressure P 1  when the ratio P 2 /P 1  exceeds a predetermined value. In the embodiment shown fuel is supplied by centrifugal pump 1 through a pressure drop control valve 5 and metering valve 4 to the outlet 3 leading to the fuel burners. The pump 1 is driven by an air turbine 2. The metering valve 4 comprises a valve member 11 axially movable in a fixed sleeve 14, the valve member having a recess 12 which co-operates with a port 13 in the sleeve to provide a metering orifice. The valve member 11 is connected to a diaphragm 17 which separates two spaces 16 and 18. The valve member is acted on in an upward direction (which tends to reduce the area of the metering orifice) by a spring 19, and in a downward direction (which tends to increase the area of the metering orifice) by a spring 20. Compressor intake pressure P 1  is supplied to the space 16 below the diaphragm, also to the space 15 below the valve member 11, this pressure acting to move the valve member upwardly. Compressor discharge pressure P 2  is supplied to space 18 and acts on the diaphragm 17 and tends to move the valve member downwardly. An evacuated capsule 21 is mounted on a perforated partition 22 in the chamber 18 and a platform 23 bears against the upper end of the capsule, the platform being connected to a yoke member 24 which is connected to the valve member 11 through a lost motion device. The arrangement is such that up to a certain value of the ratio of P 2 /P 1  the lost motion device is ineffective but above a predetermined value of this ratio, the lost motion device becomes effective and the downward movement of the valve member (i.e. in the direction tending to increase the size of the metering orifice) is opposed additionally by the bellows 21 acting as a spring which assists the action of the spring 19. The fuel pressure upstream of the metering orifice is conveyed to the lower end of the valve member 6 of the pressure drop control valve while the pressure downstream of the metering orifice is conveyed 9 also acts against the upper end of the valve member 6. The control valve 5 shown tends to maintain the pressure drop at the metering valve substantially constant. In a second embodiment however the spring 9 is replaced by a bimetal to the upper end of the valve member. A spring spring 25, Fig.3 (not shown) the temperature of the liquid in which the spring is immersed being subject to the air intake absolute temperature T 1  so that the pressure drop at the metering valve is dependent on the air intake temperature.