This invention relates to an apparatus and method for changing an effective nozzle exit area of a turbofan engine.
A typical turbofan engine includes a core nacelle housing one or more spools supporting at least one compressor and turbine. One of the spools is used to rotationally drive a turbofan arranged upstream from the core nacelle. A fan nacelle surrounds the turbofan and the core nacelle. The core nacelle is supported by several bifurcations to centrally locate the core nacelle relative to the fan nacelle. In addition to supporting the core nacelle, the bifurcations are used to house various components, such as bleed air conduits and wires, for example. The bifurcations are typically fixed, closed structures.
A generally annular bypass flow path is arranged between the core and fan nacelles through which bypass air from the turbofan flows. The bifurcations are arranged in the bypass flow path. The bypass flow exits from a nozzle exit area at the rear of the engine. The nozzle exit area is typically fixed in a turbofan engine.
Non-turbofan aircraft turbine engines have been developed that change the effective nozzle exit area to affect the efficiency and operation of the engine. In military aircraft, for example, multiple circumferentially arranged flaps at the exit of the engine nozzle are rotated inwardly and outwardly in a radial direction to change the physical size of the nozzle's exit area. This arrangement adds additional weight and cost to the engine externals. Many flaps are required as well as associated actuators. Further, the moveable flaps are external and subject to damage from foreign objects.
What is needed is a turbofan engine capable of changing the effective nozzle exit area using existing engine structure and surfaces.