Airworthiness Analysis Of Engine Jet Flow Noise In Flight State

With the rapid development of civil aviation industry,the number of aircraft is also growing,the problem of noise pollution caused by flight is becoming more and more serious,and noise airworthiness standards are becoming more and more stringent.Therefore,in order to achieve the purpose of reducing noise,it is necessary to study and analyze the mechanism and noise characteristics of jet noise,so as to make it of application significance in the top-level design of engine and noise airworthiness examination.In this paper,the large eddy simulation module in FLUENT,the acoustic module in ACTRAN and the static Stone algorithm are used to simulate the jet noise and analyze the noise characteristics.Firstly,the influence of pressure and temperature conditions on the sound field is demonstrated.Secondly,the propagation and attenuation characteristics of OASPL,PNL and dB noise values of jet noise at different direction angles are demonstrated.At the same time,the numerical simulation method is compared with the static Stone,and the effective sensory noise level under airworthiness conditions is calculated.The following conclusions are drawn:(1)It can be seen from the calculated flow field and sound field that the connotation pressure has a great influence on the flow field of the jet flow,and can convert the low-frequency large-scale eddy current to the high-frequency small-scale eddy current,and increase the jet noise attenuation speed.The value can reach 5dB,and the jet noise is within 15°of the vertical plane,and the total sound pressure level increases with the pressure.(2)From the comparative analysis of the far-field sound pressure level diagram of the jet,it can be seen that the high-frequency noise is significantly reduced as the noise propagation distance increases.(3)Comparing and analyzing the OASPL,PNL and dB distribution maps,the three models increase sharply and then decrease slowly with the increase of the angle,and the effective sensory noise level calculated by PNL is 94.6dB,which is smaller than the airworthiness noise of the whole machine.Airworthiness certification requirements.Secondly,through the numerical simulation and the absolute error analysis of the static Stone algorithm,it can be seen that the numerical simulation value is too small,and the absolute error is between 1-3 dB,which is an acceptable range.