Gas turbine control

Claim 1

A control system for a gas turbine engine having a compressor-combustor-turbine gas generator, a power turbine energized by the gas generator having a variable nozzle, servo means for varying the nozzle, and a settable engine power level control, the system including input means responsive respectively to engine inlet air temperature, the power level control setting, gas generator speed, and gas generator motive fluid temperature, each responsive means generating an electrical signal representing the value of the respective condition responded to: the system comprising, in combination, fuel loop control means responsive to the gas generator speed signal, the power level control signal and the inlet air level signal to maintain gas generator speed at a constant idle speed through a predetermined low end of the power level signal range, means responsive to the inlet air temperature signal for generating an acceleration reference temperature signal increasing with inlet air temperature only up to a predetermined value of inlet air temperature; a nozzle reference temperature signal generating means responsive to the acceleration ration reference temperature signal and to the gas generator speed signal effective to generate a nozzle reference temperature signal increasing with gas generator speed and with the acceleration reference temperature signal; and signal generating means responsive to the inlet air temperature signal and the power level control signal coupled to the nozzle reference temperature circuit so as to reduce the nozzle reference temperature signal at idle gas generator speed as a function of the inlet air temperature and power level signals at the predetermined low end of the power level signal range below a predetermined ratio of power level signal to inlet air temperature signal; so that the nozzle reference temperature signal increases at constant gas generator idle speed over the said low end as maintained by said fuel loop control means and then increases with gas generator speed up to maximum rated speed; the servo means being responsive to the nozzle reference temperature signal and the motive fluid temperature signal for varying the power turbine nozzle.

Claim 11

A system for providing a turbine motive fluid temperature reference signal and a gas generator speed reference signal for control of a gas-coupled gas turbine engine, the signals being provided to control fuel flow to the engine and area of a power turbine nozzle, the system comprising, in combination, means for mixing a signal indicative of engine inlet temperature and a signal responsive to gas generator speed to provide a motive fluid temperature reference signal increasing with both of the said signals; means for mixing a signal indicative of engine inlet temperature and an engine power demand signal to provide a control signal increasing with both of the said signals; fuel loop control means responsive to the gas generator speed signal, the power demand signal and the engine inlet temperature signal to maintain gas generator speed at a constant idle speed through a predetermined low end of the power level signal range, means for mixing a signal indicative of engine inlet temperature with the motive fluid temperature reference signal to provide a crossover signal increasing with both of the said signals, means responsive to the control signal and the crossover signal effective to limit the motive fluid temperature reference signal so as to prevent the crossover signal from exceeding the control signal; and means responsive to the control signal and to the crossover signal effective to generate a gas generator speed reference signal proportional to a datum speed value plus a value proportional to the positive difference between the control signal and the crossover signal, so that the motive fluid temperature reference signal increases with the power demand signal and the speed reference signal remains constant when the control signal is less than the crossover signal, said motive fluid temperature reference signal increase and said constant speed reference signal occurring under constant gas generator idle speeds produced by said fuel loop means through said predetermined low end of the power level signal range, and the motive fluid temperature reference signal increases with gas generator speed and the speed reference signal increases with the engine power demand signal when the control signal exceeds the crossover signal.

Claim 12

A system for providing a turbine motive fluid temperature reference signal and a gas generator speed reference signal for control of a gas-coupled gas turbine engine, the signals being provided to control fuel flow to the engine and area of a power turbine nozzle, the system comprising, in combination, means for mixing a signal indicative of engine inlet temperature and a signal responsive to gas generator speed to provide a motive fluid temperature reference signal increasing with both of the said signals; means for mixing a signal indicative of engine inlet temperature and an engine power demand signal to provide a control signal increasing with both of the said signals; fuel loop control means responsive to the gas generator speed signal, the power demand signal and the engine inlet temperature signal to maintain gas generator speed at a constant idle speed through a predetermined low end of the power level signal range, means for mixing a signal indicative of engine inlet temperature with the motive fluid temperature reference signal to provide a crossover signal increasing with both of the said signals, means responsive to the control signal and the crossover signal effective to limit the motive fluid temperature reference signal so as to prevent the crossover signal from exceeding the control signal; and means responsive to the control signal and to the crossover signal effective to generate a gas generator speed reference signal proportional to a datum speed value plus a value proportional to the positive difference between the control signal and the crossover signal, so that the motive fluid temperature reference signal increases with the power demand signal and the speed reference signal remains constant when the control signal is less than the crossover signal, said motive fluid temperature reference signal increase and said constant speed reference signal occurring under constant gas generator idle speeds produced by said fuel loop means through said predetermined low end of the power level signal range, and the motive fluid temperature reference signal increases with gas generator speed and the speed reference signal increases with the engine power demand signal when the control signal exceeds the crossover signal.

Claim 13

A system for providing a turbine motive fluid temperature reference signal and a gas generator speed reference signal for control of a gas-coupled gas turbine engine, the signals being provided to control fuel fow to the engine and area of a power turbine nozzle, the system comprising, in combination, means for mixing a signal indicative of engine inlet temperature and a signal responsive to gas generator speed to provide a motive fluid temperature reference signal increasing with both of the said signals; means for mixing a signal indicative of engine inlet temperature and an engine power demand signal to provide a control signal increasing with both of the said signals; fuel loop control means responsive to the gas generator speed signal, the power demand signal and the engine inlet temperature signal to maintain gas generator speed at a constant idle speed through a predetermined low end of the power level signal range, means for mixing a signal indicative of engine inlet temperature with the motive fluid temperature reference signal to provide a crossover signal increasing with both of the said signals; means responsive to the control signal and the crossover signal effective to limit the motive fluid temperature reference signal so as to prevent the crossover signal from exceeding the control signal; and means responsive to the control signal and to the crossover signal effective to generate a gas generator speed reference signal proportional to a datum speed value plus a value proportional to the positive difference between the control signal and the crossover signal, so that the motive fluid temperature reference signal increases with the power demand signal and the speed reference signal remains constant when the control signal is less than the crossover signal, said motive fluid temperature reference signal increase and said constant speed reference signal occurring under constant gas generator idle speeds produced by said fuel loop means through said predetermined low end of the power level signal range, and the motive fluid temperature reference signal increases with gas generator speed and the speed reference signal increases with the engine power demand signal when the control signal exceeds the crossover signal; the last-named means including a first resistor, means for maintaining a current through the first resistor providing a potential drop equal to the said positive difference, a second resistor, means for maintaining a current through the second resistor proportional to that through the first resistor, and means responsive to the potential drop in the second resistor to generate the said signal value proportional to the positive difference.

Claim 14

A system for providing a turbine motive fluid temperature reference signal and a gas generator speed reference signal for control of a gas-coupled gas turbine engine, the signals being provided to control fuel fow to the engine and area of a power turbine nozzle, the system comprising, in combination, means for mixing a signal indicative of engine inlet temperature and a signal responsive to gas generator speed to provide a motive fluid temperature reference signal increasing with both of the said signals; means for mixing a signal indicative of engine inlet temperature and an engine power demand signal to provide a control signal increasing with both of the said signals; fuel loop control means responsive to the gas generator speed signal, the power demand signal and the engine inlet temperature signal to maintain gas generator speed at a constant idle speed through a predetermined low end of the power level signal range, means for mixing a signal indicative of engine inlet temperature with the motive fluid temperature reference signal to provide a crossover signal increasing with both of the said signals; means responsive to the control signal and the crossover signal effective to limit the motive fluid temperature reference signal so as to prevent the crossover signal from exceeding the control signal; and means responsive to the control signal and to the crossover signal effective to generate a gas generator speed reference signal proportional to a datum speed value plus a value proportional to the positive difference between the control signal and the crossover signal, so that the motive fluid temperature reference signal increases with the power demand signal and the speed reference signal remains constant when the control signal is less than the crossover signal, said motive fluid temperature reference signal increase and said constant speed reference signal occurring under constant gas generator idle speeds produced by said fuel loop means through said predetermined low end of the power level signal range, and the motive fluid temperature reference signal increases with gas generator speed and the speed reference signal increases with the engine power demand signal when the control signal exceeds the crossover signal; the last-named means including a first resistor, means for maintaining a current through the first resistor providing a potential drop equal to the said positive difference, a second resistor, means for maintaining a current through the second resistor proportional to that through the first resistor, and means responsive to the potential drop in the second resistor to generate the said signal value proportional to the positive difference.