Patent GB-1347258-A (GB)
Title: Turbine engine control systems
IPC: F02C9/22
Filed: 1970-05-26
Abstract: 1347258 Gas turbine control systems ULTRA ELECTRONICS Ltd 20 May 1971 [26 May 1970] 25274/70 Headings F1G and FIT [Also in Divisions G1 and G3] A control system for a gas turbine engine 1 having vanes or nozzles 2 directing the flow of gas from a compressor turbine wheel 1f on to a power turbine wheel 1g so as to maintain a required temperature in the combustion chamber lc according to a preset fuel economy schedule comprises hydraulic actuators for the nozzles Figs. 3a, 3b (not shown) actuated by solenoid valves 41, 46, 52 in a control circuit receiving input signals representative of the position of an accelerator control member, and of the position of a retard control member, a signal representing compressor speed N gg , a signal representing the speed of the turbine output shaft Nos, a signal representing combustion chamber outlet temperature T 7 , a signal representing compressor inlet temperature T 2  and start-up or idling signal. The signal at input A representing the fuel economy schedule is a function of Ngg, T 2  and T 7  and is derived from a fuel control system (see Specification 1347257); and controls the engine during steady state cruising where the compressor speed error Nge is less than 10% N gg  max. and the accelerator pedal depression is greater than 15% full travel, by means of inhibit switches 53, 57 which prevent the blocks 54, 55 from passing signals into summing amplifier 48. Control signals from economy logic block 42 are passed through amplifier 48 and lowest-wins logic block 43 to enable AND gate 50 which energises the solenoid of nozzle locking valve 52 so that nozzle positions do not change. If the signal at A is sufficiently large indicating that the ratio T 7  /#* (#*=T 2 ‹R/520 for T 2  <520‹R and = 1 for T 2 >520‹ R) is not equal to the economy schedule value of N gg /#*<SP>¢</SP> then the level detector 49 gives a zero output and the valve 52 is deenergised, the nozzles are then driven to reduce the error to zero i.e. to maintain T 7  /#* on the economy schedule, by actuation of valve 46 controlling actuator position. During acceleration or deceleration where Nge exceeds 10% Ngg max., switches 47, 53 are closed and switch 57 is open so that the only signal passed into summing amplifier 48 comes from a nozzle position control loop including nozzle position potentiometer 56 feeding a signal to block 55 which receives a nozzle position datum at input 60, the nozzle actuator being moved to a transient position by actuation of valve 46. If the accelerator pedal is in an idling position and compressor speed N gg  is within 10% of its idling value switches 47, 57 are closed, switch 53 is open, so amplifier 48 is controlled by block 54 to actuate valve 46 to bring output shaft speed Nos to 750 R.P.M. Below a predetermined compressor speed of 42% N gg /#*<SP>¢</SP>the signal at point C is zero, so gates 44, 50 are disabled and the actuator for the nozzles moves to a "start" mode. Above 42% gates 44, 50 are primed for control as outlined above. A block 39 provides an over-ride control to limit output shaft speed Nos to 3, 250 R.P.M. A "retard" signal at point B acts to move the nozzles to a "retard" position for regenerative braking.