Prediction And Control Of Aerodynamic Noise Of Centrifugal Fan

Centrifugal fan is a kind of fan widely used in various industrial fields,among which aerodynamic noise is the biggest main noise,accounting for about 50% of the total noise.The internal flow field of centrifugal fan is extremely complex,and numerical simulation of the internal flow field of centrifugal fan can provide information for in-depth analysis of the noise generation mechanism,noise reduction principle and method of centrifugal fan.With the increasingly serious environmental noise problem and the improvement of government noise emission standards,designers pay more and more attention to noise reduction and have higher requirements for the acoustic performance of centrifugal fans,so it is of great research significance for the prediction and control of aerodynamic noise of centrifugal fans.In this paper,numerical simulation and experimental measurement are used to study the aerodynamic noise prediction and control of centrifugal fans.Based on the transient data calculated by CFD,the information of internal flow field of centrifugal fan is converted into sound field information by FW-H equation,and the sound pressure data of noise monitoring points in the pipeline of centrifugal fan are obtained,and the sound pressure spectrum and total sound pressure level are obtained by Fourier transform.(1)Based on CFD numerical calculation method,the internal flow field of centrifugal fan is numerically simulated,and the corresponding flow field information is obtained.The flow field structure and flow loss of the fan are analyzed from multiple dimensions such as pressure,velocity,temperature,vorticity Q criterion and streamline.The complex flow area in the fan is highly coincident with the area where aerodynamic noise sources are concentrated under the broadband noise source model.(2)Based on the transient data calculated by CFD,the flow field information in the centrifugal fan is converted into sound field information by FW-H equation,and the simulation value of sound pressure data of each noise monitoring point in the pipeline is obtained.The sound pressure spectrum and total sound pressure level are obtained by Fourier transform and total sound pressure level calculation.The trend of noise spectrum obtained by experimental measurement and simulation calculation is consistent,mainly broadband noise,and discrete noise is obvious in low frequency band.There are peaks at the fundamental frequency,the second harmonic frequency and the third harmonic frequency,which may be caused by the leakage flow between the leading edge of the blade and the rotating shaft.(3)The noise in the inlet and outlet pipes of centrifugal fan is measured,and the accuracy of numerical simulation results is verified by comparing the measured results of aerodynamic noise with the predicted results.(4)The calculation model of adding muffler to centrifugal fan is established,and the noise reduction effect of muffler is analyzed from the aspects of noise reduction and insertion loss.The results show that the muffler has obvious noise reduction effect on the centrifugal fan,and a reasonable muffler is helpful to reduce the aerodynamic noise of the centrifugal fan.