國立臺灣大學機械工程學研究所碩士論文 論文題目:風扇噪音場分析模擬(與減噪設計) 指導教授:顏家鈺 博士 作 者:徐逸亭 中華民國九十五年六月 科技的日新月異,電子產品不斷追求高性能、高能量、高處理速度的方向進展,但隨著人們對消費品質的要求提升,近年來,噪音的問題逐漸受到重視,乃成為設計或研發產品及工程上非常重要的一個課題。本研究主要在分析並用軟體模擬鋸子的噪音場,進而利用模擬的結果做減噪設計的改善。由噪音的原理我們可以知道,音是空氣中發生壓力變化而以音速傳播的現象,噪音的產生可由結構產生的結構噪音或氣流產生的氣動噪音所造成,結構振動使接觸物體面的空氣隨之振動,引起壓力變化產生噪音,所以結構振動的振動量與噪音的大小有極大的關係,改善結構振動所產生的噪音,可由軟體ANSYS作暫態振動的模擬,由軟體上的機構設計作改善,如:避免產生共振頻率…等等,進一步達到減噪設計的目的。一般鋸子的轉速都非常地高,所以為了避免散熱的問題,會在轉子的裝一個風扇解決散熱的問題,而風扇就是造成氣動噪音最大的來源,如果噪音的來源大部分是風扇所造成的氣動噪音,可由流力軟體Fluent裡頭的Ffowcs Williams-Hawkings Solution equation來分析噪音的暫態響應,也就是壓位準(Sound Pressure Level ,SPL)的頻譜圖,藉由軟體上的機構改善作模擬,達成減噪設計的改善
Computation of the Noise Intensity (and the Noise Reduction) of an Electrical Fan By Yi-Ting Hsu MASTER DEGREE OF ENGINEERING DEPARTMENT OF Mechanical Engineering NATIONAL TAIWAN UNIVERSITY June 2005 ADVISER: Dr. Jia-Yush Yen Reducing acoustic noise from rotating machinery is always desirable to all the applications. To estimate the noise level generated from rotating machinery, on the other hand, is very difficult. The computation often involved the interference between structural vibration and the induced air flow. The noise may result from both the flow field and the structural resonance. From the computation point of view, the moving part of the rotating machinery also requires additional treatment. This thesis addresses the modeling of the handsaw noise. The high speed handsaw uses a fan attached to the rotor to remove the heat accumulation. This thesis uses the Ffowcs-Williams/Hawkings formulation in Fluent to analyze the acoustic Sound Pressure Level (SPL). The analysis compares the simulation frequency spectrum with the experimental measurement and provides suggestions for noise reduction.