Method and system to increase stall margin

摘要

A method and system are provided to bias a control subsystem of a gas turbine engine having a fan and compressor. The method includes the steps of measuring an operating parameter of the engine and differentiating this parameter over time to obtain a derivative thereof. A bias signal is generated in a predetermined bias schedule in response to the parameter derivative, and provided to the control subsystem for biasing the subsystem. The bias signal has a zero value for values of the parameter derivative from zero to a first value thereof at a first time. The bias signal has a maximum value for values of the parameter derivative between second and third values thereof corresponding with second and third times. And, the bias signal returns to a value of zero after a fourth time greater than the third time. In an exemplary embodiment, the operating parameter is fan speed, and the bias signal is provided to at least one, and preferably both, control subsystems of variable guide vanes regulating flow to the fan and a variable area exhaust nozzle regulating discharge flow area.