Patent GB-1347257-A (GB)
Title: Turbine engine control system
IPC: F02C9/32
Filed: 1970-05-26
Abstract: 1347257 Gas turbine control systems ULTRA ELECTRONICS Ltd 25 May 1971 [26 May 1970] 25240/70 Heading F1G [Also in Divisions G1 and G3] A system for controlling the flow of fuel to a gas turbine engine comprises a fuel flow metering valve 20, an operator controlled accelerator pedal for producing (from potentiometer 8) an electrical signal representative of a required gas generator speed, an operator controlled retard pedal for producing (from switch 9) an electrical signal representative of desired retardation, an operator controlled, idle switch 7 for producing an electrical signal representative of a desired gas generator idling speed, means 61 operative to sense gas generator speed-N gg  and to provide an electrical signal 25 representative thereof, means 31' operative to sense output shaft speed N os  and to produce an electrical signal 31 representative  thereof, means operative to sense gas generator turbine inlet temperature T 7  and to provide an  electrical signal 21 representative thereof, means operative to sense compressor inlet temperature T 2  and to provide an electrical signal 24 representative thereof, the metering valve being controlled by an electrical circuit responsive to a plurality of electrical signals including the required gas generator speed signal, the desired retardation signal, the desired gas generator idling speed signal, the gas generator speed signal 25, the output shaft speed signal 31, the gas generator turbine inlet temperature signal 21, and the compressor turbine inlet temperature signal 24. The circuit includes a lowest wins logic circuit 18 which selects whichever one of three fuel demand signals is representative of the lowest fuel demand and passes it to output stage 19 which controls the current in the operating solenoid of valve 20. The action under steady cruising is that fuel flow is controlled by a closed loop which renders gas generator speed N gg  equal to that demanded by the accelerator pedal position. At the same time the power turbine nozzles are controlled (see 25239/70 and 25274/70) by a loop so that compressor turbine inlet temperature T 7  is held to an "economy schedule" value determined as a function of N gg  and T 2  at generator 13. Automatic over-ride. If the shaft speed N os  exceeds say 3, 000 R.P.M. fuel is reduced automatically by block 26, and amplifier 22 controlling one of the fuel demand signals to block 18. If the fuel flow reduction is insufficient and N os  rises to say 3, 150 R.P.M. the nozzles are controlled on N os  instead of T 7  to provide further braking. Another over-ride occurs if the accelerator pedal is raised or depressed. In the latter case the nozzles are re-positioned. In the former (acceleration) case the nozzles are repositioned but in addition fuel flow increase is limited during acceleration by circuit blocks 12 and acceleration detector 14 to hold T 7  to a predetermined function of N gg  and T 2 , the detector providing one of the input signals to block 18. If the retard pedal is depressed N os  is limited to 3, 000 R.P.M. as above and the retard pedal position determines a datum value of N gg  in the range 55% to 80% maxm. which over-rides the accelerator pedal datum if it is lower.