Research On The Noise Characteristics Of Electric Aircraft Propeller

The propeller is the main noise source of propeller aircraft.The propeller noise will produce a lot of adverse consequences.First of all,the noise will affect the airport area environment.Secondly,the propeller noise will be transferred to the cabin and then affect the comfort of passengers.Third,sonic fatigue and structural vibration,induced by the propeller noise,have a great impact on aircraft safety.In this paper,a study on the aerodynamic noise characteristics of an electric aircraft propeller is carried out from two aspects of experiment and numerical simulation.In the aspect of numerical simulation,the finite element analysis software is used to establish the three-dimensional model of propeller,and the computational grid is divided by structured grid and unstructured grid.The noise calculation is divided into the part of the flow field calculation and the part of the calculation of the propeller sound field.First,using the large eddy simulation calculation to obtain the flow information of the propeller,and then considering the flow field calculation as the boundary conditions,ultimately through solving the FW-H equation to calculate the acoustic propagation characteristics,we will get the noise characteristics in different site conditions.In the aspect of aerodynamic noise experiment,the static noise test of the propeller and the flight noise test are completed in the room.The overall strength of the near field,far field and over flight noise in the time domain,the frequency domain and the sound pressure are obtained through the design experiment.The results show that: In the experiment of indoor propeller noise,the noise pressure level increases with the increase of rotating speed;the main part of the noise is broadband noise,discrete noise is not obvious.The 2 types of propellers produced by different manufacturers are similar in the time domain waveform and frequency domain waveform at the same speed,and the overall strength of the sound pressure is basically the same.It is proved that the noise characteristics of the two propellers are the same.The propeller blade static frequency(Blade Passing Frequency,BPF)is consistent with the experimental frequency domain.Through the comparison,it is found that the rotating noise is mainly distributed in the low frequency region,and the circular noise monitoring points show a certain regularity at different experimental speeds.According to the type of aircraft airworthiness certification and noise regulations(CCAR-36-R1)(hereinafter referred to as the 36)requirements,the maximum noise test over the noise level should be in accordance with documentation requirements.In this paper,the distribution law of sound pressure level in the near field is analyzed by applying the finite element method and the boundary element method.It is concluded that the blade tip vortex and the leading edge separation vortex form a large pressure fluctuation on the blade surface.