Researches On Nosie Reduction Design Of Aerodynamic Noise For Electronic Devices

With the high-power, high-density electronic devices gradually coming into theworking site and residential place, large-size, high-speed fan used more widely to dealwith the problem of heat dissipation, but it brought more and more noise problems,people are increasingly concerned about the noise of the electronic equipment. Thenoise reduction design of electronic equipment have not been given sufficient attentionat the initial stage, designers generally design it with their own experience, then productmodel machine to test, and repeatedly revise until the completion. But this method istime-consuming and costly. With the emergence of high-performance computers andthe development of numerical simulation methods, people can already do research inaerodynamic noise by numerical simulation methods, thus this article will use thenumerical simulation of the aerodynamic noise to research the noise sources ofelectronic equipment, the generation mechanism of noise and the noise reductiondesign.(1) Summarize the basic types of sound sources for aerodynamic noise and theacoustic calculation, then analyze the common sources of aerodynamic noise forelectronic equipment; Study the scope of application for several different aerodynamicnoise numerical simulation method, analyze the impact of the turbulence model incalculation accuracy, and study the approach for rotating regional then verify thecorrectness of the simulation method.(2) Analyze the impact factors of axial fan and propose the method of notequidistant blades to reduce aerodynamic noise and explain its principle; Study theinfluence of blade tip spacing of noise; research the obstructions at fan inlet how toinfluent noise and propose one design technology of current collector which based onrectification; Analyze the variation of sound pressure level with the fan speed andsummarize reasonable design rule and select basis for axial fan.(3) Study the influence of three kinds of gas flow inlet to centrifugal fan noise, theresults show that the cone cylindrical entrance can effectively reduce the aerodynamicnoise; Propose a improved design for volute tongue which can change fan’s export airflow distributions, cut down reflux phenomenon and reduce aerodynamic noise;analyze the reason of blade tip vortex and designed a rotating ring to reduce the bladetip vortex shedding noise of centrifugal fan.(4) Study the sources for noise of flow resistance in electronic equipment andanalyze the structural parameters and location for flow resistance how to influentaerodynamic noise; summarized how much can the pressure level of flow resistanceimpact the whole noise of electronic equipment.