METHOD AND DEVICE TO AVOID TURBO INSTABILITY IN A GAS TURBINE ENGINE
1-19. -19. (canceled)
(A1) A turbofan engine control system is provided for managing a fan operating line. The engine (10) includes a spool having a turbine housed in a core nacelle (12). A turbofan (20) is coupled to the spool (14). A fan nacelle (34) surrounds the turbofan and core nacelle and provides a bypass flow path having a nozzle exit area (40). A controller (50) is programmed to effectively change the nozzle exit area in response to an undesired turbofan stability margin which may result in a stall or flutter condition. In one example, the physical nozzle exit area is increased at the undesired stability condition in which the airflow into the engine creates a destabilizing pressure gradient at the inlet side of the turbofan. A turbofan pressure ratio, turbofan pressure gradient, low spool speed and throttle position are monitored to determine the undesired turbofan stability margin.
1-19. -19. (canceled)
20. A turbofan engine control system for managing a turbofan operating line comprising:
a spool including a turbine housed in a core nacelle; a turbofan coupled to the spool; a fan nacelle surrounding the turbofan and core nacelle and providing a bypass flow path having a nozzle exit area; and a controller programmed to effectively change the nozzle exit area in response to an undesired stability margin for the turbofan by lowering the turbofan operating line and increasing the turbofan stability margin, wherein the controller detects the undesired stability margin.
- View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
34. A method of managing a turbofan engine turbofan operating line, the method comprising the steps of:
detecting at least one of a turbofan pressure ratio, low spool speed, airflow direction and throttle position; determining the undesired turbofan stability margin from the detecting step; effectively increasing a nozzle exit area of a bypass flow path in response to an undesired turbofan stability margin; and lowering the turbofan operating line and increasing the turbofan stability margin as a result of the nozzle exit area increasing.
- View Dependent Claims (35, 36)