Aircraft Engine Exhaust Nozzle System for Jet Noise Reduction

Conventional aircraft typically include propulsion engines that are under the wing or tail surfaces. Each propulsion engine system includes an engine housed in a nacelle with an inlet and a nozzle system. Primary component noise sources from the engine system include the noise associated with the fan, compressor, turbine, and combustor, and the noise associated with the high-velocity jet exhaust flow. There are many methods for reducing the various noise sources from the aircraft, including those noise sources from the engine system. One method includes the use of the aircraft itself as an acoustic shield for the noise sources associated with the engines. This approach requires a new configuration of aircraft with the engines installed on the upper surface of the wing or fuselage, or an aircraft that has a hybrid wing and fuselage. Of the engine noise sources, the jet exhaust is a particular challenge due to the fact that the noise sources are in the exhaust flow itself, and therefore originate throughout the jet exhaust flow as many as ten engine diameters downstream of the nozzle system exit plane. Therefore, it is desirable to have an improved aircraft nozzle system that is capable of much more noise reduction when installed on the upper surface of the aircraft.