GB1427328A - Fuel control systems for combustion engines particularly gas turbine engines - Google Patents

Abstract

1427328 Gas turbine engine fuel systems LUCAS INDUSTRIES Ltd 27 June 1973 [20 June 1972] 28833/72 Heading F1G A fuel control system for a combustion engine, particularly a gas turbine engine, comprises an epicyclic gear arrangement 13 including a member (a planet gear carrier 12) driven, in use, at a speed proportional to the engine speed N, an output member (a sun gear 14) drivingly connected to a centrifugal fuel pump 16; and a reaction member (an annulus gear 17), a variable delivery hydraulic pump 19 drivingly connected to the reaction member, means responsive to the speed of the output member for varying the delivery of the hydraulic pump, a variable-area nozzle 30 through which fluid from the hydraulic pump is directed on to a pelton wheel 32 so as to assist rotation of the output member, and means 31 for varying the nozzle area in accordance with engine operating variables. The means 31 is movable in response to electrical signals from a control unit 36 which is responsive to engine speed N, fuel flow Q, the setting # of the engine control lever 37 and also to other engine variables such as compressor inlet and delivery pressures P 1 , P 2 and compressor inlet temperature T 1 . If the engine speed increases, for example thereby producing an initial increase in the speed of the fuel pump 16, the resultant increase in the fuel flow Q causes, via control unit 36, a reduction in the area of nozzle 30, thereby reducing the driving effect of the pelton wheel 32 and so tending to restrict further increase of the fuel pump speed. The reduction in the area of the nozzle 30 causes an increase in the pressure upstream of the nozzle and acting on a valve 23 in opposition to the force produced by a governor 22, whereby a port 26 is opened to apply pressure to a piston and cylinder unit 27 to tilt a swash-plate 29 to reduce the stroke of pump 19, whereby the pressure falls until the valve 23 regains an equilibrium position in which the port 26 is closed. The pressure fall further reduces the driving effect of the pelton wheel 32 whereby the speed of pump 16 and hence the fuel flow falls, causing a decrease in engine speed and a consequential increase in the area of the nozzle 30 until the engine speed stabilizes at the desired value. A centrifugal pump 33 scavenges liquid from the inside of housing 10.