Study On Axial Compressor Noise Prediction Method Basing On CFD/CAA

While high bypass ratio turbofans engine used widely,the noise level of fan and jet decreases dramatically,and the proportion of compressor noise increases gradually.Especially when the aircraft approach,the noise level of compressor is comparable to that of fan.Noise design for compressor has become one of the important measures to improve engine noise performance.Therefore,researching on noise prediction methods,understanding the aerodynamic and acoustic characteristics of compressors and exploring the internal relationship between them,is the premise of compressor noise reduction design.In this paper,taking QF-1 compressor used in NASA test as the research object,calculated the ground test sound pressure level of the compressor by the method combining computational fluid dynamics and computational aeroacoustics.And finally,basing on compressor ground test noise,the noise radiation characteristics of the compressor in flight state was obtained through sound propagation correction.The main work was done as follows:(1)Researched on the theory and method of numerical calculation of compressor flow field and sound field.Introduced several fluid and acoustic models,including the direct numerical simulation model,Reynolds time average turbulence model,large eddy simulation turbulence model,Lighthill acoustic analogy model and Moring acoustic analogy model.Compared and analyzed the advantages and disadvantages of these models combination in acoustic calculation.Studied the requirements and strategies of compressor geometric model establishment,computational domain selection,mesh generation and boundary condition setting.As well as summarized the tools and operation flow of the hybrid numerical method for compressor acoustic filed calculation.(2)Researched on the method for correcting compressor noise from static state to flight state.For this purpose,the basic requirements of aircraft noise qualification were analyzed,and the calculation model of aircraft approach flight path was deduced.Moreover,the spherical diffusion model of noise,the Doppler Effect correction model and the atmospheric absorption and attenuation model were studied.(3)Analyzed Compressor flow field characteristics and static acoustic field characteristics.According to the characteristics of flow field,the types of compressor noise sources and the locations of noise sources were analyzed.The noise radiation characteristics of compressor under several operating conditions are analyzed,including directivity of discrete tone,total noise level,and spectrum characteristics of one-third octave bandwidth.Comparing the calculated value with test value,the rationality and validity of the hybrid numerical method were verified,and it can be used for noise assessment of compressors.(4)Calculated and analyzed compressor noise in flight state.Firstly,the approach flight path of Boeing 737-300 aircraft was calculated.And then basing on the flight path parameters,the static compressor noise was corrected to flight state.The results show that the noise radiation of the compressor is more significant at medium rotational speeds.