Jet Noise Prediction And Analysis Applied For Take-off Stage

With the problem of global aviation noise becoming more and more serious,aviation noise has received great attention from society,and the standard of international noise airworthiness has gradually become more stringent.In the process of the takeoff stage,jet noise is the most prominent aircraft noise among the sources of noise,meanwhile,take-off noise is also one of the most important noise evaluation parameters of aircraft airworthiness approval.Consequently,the take-off jet noise research can provide data for noise airworthiness approval and noise suppression technology support and guidance.This paper is based on the theoretical knowledge of acoustics,noise airworthiness standards and the mechanism of jet noise.And it has applied ST2 JET prediction algorithm for calculating jet noise with correction,combined with the takeoff profile.With the help of program design and platform development,the aircraft take-off jet noise prediction algorithm is obtained with a platform which allows the users to input data and obtain the predicted jet noise data in tables or in charts.According to the calculated noise prediction data,the prediction results are analyzed by noise characteristics,airworthiness analysis,noise suppression analysis and correction analysis.With the consideration of the Kepler effect,geometric divergence effect and atmospheric absorption effect,the take-off jet noise prediction algorithm has been applied for type A engine model,type A chevron model and type B engine model,and it is found out that the spectrum characteristics and time characteristics of the predicted jet noise under the airworthiness condition have the similar trend,which first increase and then decrease with the increase of time and frequency,and which concentrate on the middle and posterior part of 10-dB period with the lower frequencies.With the comparison analysis on predicted effective perceived noise level data,it is concluded that the effective perceived noise level of the chevron model is smaller than that of the original model by about 1 EPNdB.