The Optimization Of Aeroengine Duct Geometry And Acoustic Liner

With continued rapid increase in air traffic, aircraft noise attractedever increasing attention from various stakeholders, and as a result, morestringent regulations on aircraft noise is gradually implemented. Thedevelopment and validation of numerical methods for noise predictionshas become an important issue for airframe manufacturers to designquieter aircraft. Although noise contribution from engines has beenreduced with the recent use of high bypass ratio turbofan engines, enginenoise, and fan noise in particular, is still an important noise source thatneeds to be addressed. Noise generated from rotor/stator interactions isone of the important fan noise sources and its propagation can beestimated using hybrid method–near field propagation and far fieldradiation. The former can be predicted by solving linearized Eulerequations (LEE), while the latter can be predicted using the FW-Hintegration method. A CAA method has been developed to estimate thefan noise propagation in engine intake by coupling the2.5D LEE in acomplex form and the TDIBC formulation proposed by Fung. Turbofanintake geometry and impedance parameters of the acoustic liner are optimized to achieve increased noise attenuation in the forward arc. Thenon-uniform mean flow was solved using RANS method. The analyticalsolution of Munt and the numerical results of far field SPL of anunflanged semi-infinite duct have been used in the valduation of the code,while the measured data of NASA Langley GIT experiment has beenused in the validation of TDIBC code. Multi-objective optimizationformulation based on response surface method using Kriging surrogatemodels is implemented with total pressure recovery (TPR) at fan face andsound pressure levels (SPL) at integral surface as the two objectivefunctions. Results showed that the proposed strategy can be effectivelyused to achieve overall optimum in terms of both aerodynamic andaeroacoustic characteristics by a combined optimization of geometry andliner paraemeters. The method proposed in this paper can be used in thelow noise design optimization of turbofan engines.