Research On The Method Of Isoline Estimation Of Aircraft Engine Fan Noise

With the economic globalization,the amount of airplane transportation is increasing day by day.The noise level of the aircraft is one of the factors for the success of obtaining airworthiness visa.Therefore,the research on aircraft noise has always been the focus of manufacturers and researchers.China is in the initial stage of big aircraft research and development,more attention should be paid to aircraft noise.Fan component is one of the four most important noise sources of turbofan engine.With the increasing of bypass ratio,the contribution of fan noise to engine noise increases.Therefore,the prediction of fan noise is of great significance,so as not to waste money on airworthiness certification.Firstly,the basic knowledge of aero-engine noise was introduced,and the Boeing algorithm was combined with the aircraft B737-700 standard take-off flight path,and a series of corrections of noise source shift effect,geometric divergence attenuation and atmospheric sound attenuation were performed to obtain the fan dynamic noise prediction model during the take-off phase of the aircraft.The engine CFM56-7B was taken as an example to calculate the predicted value of the static sound pressure level of the fan,and the frequency characteristics and direction characteristics were analyzed.Then,the predicted value of the dynamic sound pressure level of the fan every 0.5 seconds from the slip point of the aircraft was calculated.The accuracy of Boeing fan dynamic noise prediction model was verified by comparing the real value of effective sensory noise level provided by European aviation safety authority with the predicted value obtained by modeling calculation.If the forecasting method is applied to the early stage of research and development,the research and development cost of the new aircraft will be significantly reduced,and the number of flight tests will be reduced,and the time of airworthiness examination will be greatly shortened.On the basis of this model,the fan noise isoline was drawn and analyzed by means of grid division,which could make up the blank in the drawing noise isoline of engine parts,and provide reference for airport sites selection,lands planning and flights arrangement.