Device for controlling gas turbine engines

Claim 1

Electronic device for controlling gas turbine engines of the type comprising transducer means adapted to generate electrical signals proportional to parameters, such as engine speed, temperature and pressure, indicating the instantaneous operational conditions of the engine and a processor driven by the said signals, which controls a servo valve interposed in the fuel feed line to the combustion chamber, comprising: electromagnetic transducer means adapted to detect the engine speed; tachymetric circuit means driven by said transducer means and adapted to supply an output signal proportional to the engine speed; a main control circuit which compares the signal proportional to the engine speed with a reference signal set through a speed variator, said circuit being provided with a feedback ring operable from the outside and supplying a signal which controls the servo valve in the fuel feed line to the combustion chamber; a function generator circuit adapted to limit the energizing level of the servo valve whenever the signal from the main control circuit tends to rise above the limits set by the speed variator; sensing means adapted to supply a signal proportional to the gas temperature of the output from the turbine blades and at the exhaust from the turbine; a maximum temperature value selector circuit adapted to supply an output signal proportional to the highest temperature detected by the sensing means in a given time interval; an average value adding circuit supplying an output signal proportional to the average value of the temperature detected by the sensing means; a transducer adapted to supply a signal proportional to the pressure of the gas discharged from the compressor; a level correcting circuit driven by said transducer and adapted to generate a reference signal consisting of a constant term and a correcting term, substantially proportional to the pressure at the output from the compressor; a comparing circuit adapted to compare the temperature signal issuing from an OR circuit driven by the average adding circuit and by the maximum temperature selector, with the reference signal supplied by said level correcting circuit; an adjusting circuit and a maximum output limiting circuit driven by the signal issuing from said comparing circuit, adapted to supply a predetermined upper limit output signal when the signal proportional to the temperature is lower than the reference signal generated by said level correcting circuit, the said adjusting and limiting circuits being moreover adapted when the signal proportional to the temperature equals the reference signal to supply a predetermined lower limit output signal; maximum value selector means for the temperature signal adapted to select the highest level signal among the signals issuing from the adjusting circuit and an outer predetermined level supplied by a potentiometer; minimum value selector means adapted to select among the signals issuing from the main control circuit, function generator circuit and maximum temperature value selector circuit, the lowest level signal and adapted to supply a voltage proportional to the latter; voltage-current converting means driven by said minimum value selector means adapted to electrically drive the servo valve.