Patent GB-914188-A (GB)
IPC: B64C11/30
Abstract: 914,188. Automatic control systems for gasturbines. SZYDLOWSKI, J. March 25, 1960 [March 27, 1959; Aug. 13, 1959], No. 10730/60. Class 38 (4). [Also in Group XXXIII] A gas-turbine drivably connected to a variable-pitch propeller, or to a helicopter rotor, is controlled by a system wherein an engine-speed control lever acts on a speed governor to adjust the turbine fuel supply, a pitch-control lever varies the propeller pitch or rotor general pitch and a temperature regulator over-rides the pitch control when the gas temperature at the exit from the turbine tends to exceed a predetermined value so as to maintain the exit temperature constant. As shown, Fig. 1, a turbo-propeller engine comprises a compressor 1, a turbine 2 and a variable-pitch propeller 3 adjusted by an electric motor 4. The engine is controlled by a throttle 5 and a pitch-control lever 6 moving, respectively, along guides 5a, 6a. engine-speed control system.-Fuel from a tank 8 is fed to the engine through a line 9 by a pump 7. A cock 10 in the line 9 is controlled by the throttle 5 and has a by-pass 11 with an adjustable idling-speed jet 12. A fuelflow control device 17 is controlled by a mechanical speed governor 18 coupled to the engine by a transmission 19. A speed-setting lever for the governor is connected to the cock 10 by a linkage 21 and the complete assembly is controlled by the lever 5 which also actuates switches 51, 52. Flame-out cocks 25, 26 are operated through a linkage 27a by a lever 27. Propeller-pitch control system.-Variation in propeller pitch is effected by the electric motor 4 which is controlled by a temperature regulator 30 embodying a potentiometer 31 which is set to the reference temperature. One or more thermocouples 33, positioned inside the exhaust nozzle of the turbine, provide the regulator 30 with the actual temperature of the exhaust gases. Variation in propeller pitch caused by the motor 4 are transmitted to the lever 6 by a cable system 36. A pulley 38 in the cable system carries a cam 40 which operates switches 41-44. The switch 41 cuts-off the supply to the motor 4 at maximum reverse pitch, the switch 42 closes when the propeller is at zero-thrust pitch, the switch 43 cuts-off the supply to motor 4 at a preset pitch and the micro-switch cuts-off the supply to the motor 4 when the propeller is feathered. The pitchcontrol lever 6 is fitted to a shaft 45, carrying a disc 35, with slight friction and is drivingly connected with the shaft by springs 46. The lever 6 has an extension 48 which operates switches 49, 50 connected respectively in the low and high-pitch circuits of the motor 4. Electro-mechanical system .-The power supply is derived from a bus-bar 53, Fig. 2, and the main starting circuits 55 are energized through the switch 52. The thermocouples 33 are connected through a cold junction 80 to a summator 81, housed in the temperature regulator 30, wherein the actual temperature is compared with the reference temperature set by the potentiometer 31; a follow-up potential is derived from a resistance-capacity network 83. The summator, through an amplifier 84, controls flip-flops 85, 86 energizing relays A-D of a switch box 87. The relays through switches 41-44 control relays 72, 74 to energize the propeller pitch motor 4 so as to prevent the exhaust-nozzle temperature exceeding the reference value. On control lever 5, a switch 51 is a safety contact for the cock 10 and the switch 52 controls the energization of the starting circuits 55. In a modification, Figs. 15, 16, (not shown), the control system is applied to a gas-turbine drivably connected to a helicopter rotor. Specification 860,283 is referred to.