A Study On Noise Reduction For The Non-Smooth Surface Cooling Fan

As an important part of the automotive engine cooling system,the cooling fan plays an important role in enhancing cooling and increasing the heat dissipation coefficient.However,the fan aerodynamic noise has become an important part of the car noise.As the noise laws become more stringent,the performance of automotive NVH becomes more important,and the noise problem of fans has also attracted the attention of many engineers.In this paper,the cooling fan was taken as the research object,and the lownoise blade structure was designed as the research target under the premise of ensuring the ventilation.According to the generation mechanism of fan noise,two different noise reduction ways were proposed,and the corresponding non-smooth blade structure was designed.CFD technology was used as a research method,the single-variable method was used to compare the non-smooth blade fans with different structures,and the effects of different structural parameters on fan flow and noise performance were analyzed.By reading a large number of domestic and foreign literatures,we have fully understood the structural characteristics and development status of the fans.In order to prove the correctness,feasibility and accuracy of the simulation algorithm,the corresponding fan bench test is very necessary.This paper gives a brief introduction to the test standards,test equipment and specific steps used for the bench test.During the simulation process,the original fan was simplified and 3D modeling was completed.The modeling and meshing process is done in Fluent software.The numerical simulation was used to simulate the flow field and sound field of the fan at four common speeds.Compared with the experimental data,the error of the flow value is within 2.5%,and the error of the noise data is within 3.5%,indicating the correctness of the simulation algorithm.The source of fan noise is analyzed.The generation principle of rotating noise and eddy current noise is discussed.The corresponding noise reduction ideas are proposed for both.The rectification of eddy current noise and the solution to the advance generation of turbulence are proposed.There are two different non-smooth blade designs for the guide vane and the serrated blade.The influence law of the structural parameters of the guide vane and the serrated blade was studied,and the different laws of the two were obtained.The setting of the guide vane and the zigzag structure has obvious noise reduction effect(rotation noise and eddy current noise are reduced)and the fan flow is increased,and the optimal noise reduction effect is most obviously 4.6 dB(A).Based on the above research,this paper also analyzes the characteristics of the fan including the groove type non-smooth blade and the different installation angles of the blade,which provides a way of thinking for the design method of low noise blade.