【title】：Prediction of aft fan duct lining attenuation for a turbofan enginePrediction of aft fan duct lining attenuation for a turbofan engine
【作者】：Mendoza, Jeff M. (Honeywell Engines, Systems, and Services, Phoenix, AZ)^Schuster, Bill^Lan, Justin
【Corportate Author】：【Catalog】：7571 Acoustics (1975-)【Keywords】：DUCTED FAN ENGINES; ACOUSTIC LINERS; ACOUSTIC ATTENUATION; COMPUTATIONAL AEROACOUSTICS; DUCTED FLOW; ACOUSTIC DUCTS; DUCT GEOMETRY; TURBOFAN ENGINES; UNIFORM FLOW; NOISE REDUCTION; ACOUSTIC PROPAGATION; HELMHOLTZ EQUATIONS【Publish Year】：2003
【Language】：English【Record id】：2003-3241【File Size】：937K
【Come From】：In: 9th AIAA/CEAS Aeroacoustics Conference and Exhibit, Hilton Head, SC, May 12-14, 2003, Reston, VA, American Institute of Aeronautics and Astronautics, Inc., 12 p..【AAIA ID】：A0331354
【Abstract】：The aft-radiated fan noise generated by a turbofan engine is an important contributor to aircraft community noise levels. ^A common and effective way of reducing the contribution from this noise component is to incorporate acoustic lining in the aft fan duct. ^Predicting the sound reduction provided by such treatment is an important and challenging problem. ^In this paper, two analysis codes are used to predict the attenuation provided by an outer fan duct liner that was applied to a Honeywell TFE731-60 turbofan engine. ^The first analysis code, called DUCT, is based upon analytical results for wave propagation in simplified geometries. ^The second analysis code, called CDUCT, solves a parabolic approximation to the convected Helmholtz equation. ^In the CDUCT code, the level of modeling sophistication is increased, enabling the investigation of more complex duct geometry and mean flow, and providing the ability to define general nonuniform wall impedance. ^The two codes are first compared using a simple annular duct geometry with a uniform mean flow as a calibration case. ^Next, predictions are made for a more complicated geometry that is representative of the acoustically treated bypass duct that was tested during the NASA Engine Validation of Noise Reduction Concepts (EVNRC) program. ^Finally, predictions are made for several different lining configurations in order to examine the effects of lining placement on the acoustic performance of the duct. % ^(Author)
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