The Computation And Optimization Of Fan And Bypass Duct Noise Of Aircraft Engine

The noise of aircraft engine is an important factor in the design ofcivil aircraft, as noise is part of the air worthiness regulations adoptedby major administrations. The overall aircraft noise includes the noisecoming from the engine and the airframe. Although the engine noisehas been reduced significantly by the use of high bypass ratio turbofanengines, it is still one of the major sources of the overall aircraft noise,in both take-off and landing stages. High bypass ratio turbofan enginehas much bigger fans and therefore reduced jet speed, which makesengine fan noise an increasingly important factor in reducing theoverall aircraft noise levels.In this thesis CFD method is used first to calculate the mean flowfield of engine intake, then2.5D linearized Euler equations is derivedto calculate the noise propagation in the engine intake and bypass duct.Runge-Kutta integration is used for time marching and six-ordercompact schemes and artificial selective damping are used in spatialdiscretization. FW-H integration is used to calculate the noise levels atcertain observer points located in far field.Based on the results from CAA calculations, a preliminary optimization was carried out on the internal intake shape of enginenacelle using combined DoE and Kriging optimization method. Thestudy provided an optimized intake geometry while maintaining thetotal pressure recovery value at engine fanface. The results showed theeffectiveness of using Kriging-based optimization with CAA methodsfor the design of low noise geometry for high bypass ratio turbofan, andthe framework can be extended into other areas where noise is one ofthe objectives.