Variable area nozzle assisted gas turbine engine restarting
An example turbofan engine restarting system includes a core nacelle housing, a compressor, and a turbine. The core nacelle is disposed within a fan nacelle. A bypass flowpath downstream from the turbofan is arranged between the two nacelles. A controller is programmed to manipulate the nozzle exit area of the bypass flowpath to facilitate startup of the engine. In one example, the controller manipulates the nozzle exit area using hinged flaps in response to an engine shutdown condition. The flaps open and close to adjust the nozzle exit area and the associated bypass flow rate, the mass flow rate of the air through the core nacelle and the rotational speed of the compressor rotor.
1. A turbofan engine restarting system, comprising:
a core nacelle housing a compressor and a turbine;
a fan nacelle housing a fan section that is arranged upstream from said core nacelle; and
a bypass flow path downstream from said fan section and arranged between said core and fan nacelles, said bypass flow path including an effective nozzle exit area that defines an axis;
a controller programmed to selectively increase and decrease said effective nozzle exit area to facilitate restart of said engine during flight in air; and
a starter for increasing a rotational speed of said fan section.
2. A method of restarting a turbofan engine comprising the steps of:
a) detecting a shutdown of a turbofan engine during flight in air;
b) selectively increasing and decreasing an effective nozzle exit area from a bypass flow path within the engine in response to the shutdown during a flight in air to establish a desired condition for a startup of the engine during the flight in air; and
c) increasing the rotational speed of a fan section of the engine using a starter.
3. A turbofan engine restarting system, comprising:
a core nacelle housing a compressor and a turbine;
a fan nacelle housing a fan section that is arranged upstream from said core nacelle; and
a bypass flow path downstream from said fan section and arranged between said core and fan nacelles, said bypass flow path including an effective nozzle exit area that defines an axis;
at least one nozzle flap disposed on said fan nacelle operative to control said effective nozzle exit area; and
a controller programmed to selectively increase and decrease said effective nozzle exit area to facilitate restart of said engine during flight in air, wherein said effective nozzle exit area is increased when said effective nozzle exit area is not a maximum effective nozzle exit area.
4. A method of restarting a turbofan engine comprising the steps of:
a) detecting a shutdown of a turbofan engine during flight in air;
b) selectively increasing and decreasing effective nozzle exit area from a bypass flow path within the engine in response to the shutdown during a flight in air to establish a desired condition for a startup of the engine during the flight in air;
c) actuating a plurality of individual flaps radially away from an axis of the turbofan engine to increase said effective nozzle exit area, and actuating the plurality of individual flaps radially toward the axis to decrease said effective nozzle exit area, wherein the increasing occurs when the effective nozzle exit area of the bypass flow path is not a maximum effective nozzle exit area of the bypass flowpath.