風扇噪音分析與有孔平板受風扇噪音激振的聲場分析

陳廷彰(Ting-Chang Chen)

指導教授 ： 黃以玫

國立中央大學/工學院/機械工程學系/碩士(2008年)

摘要

本篇文章主要研究風扇葉片旋轉時所產生的氣動噪音。首先由Ffowcs Williams與Hawkings的氣動聲學理論，計算出風扇噪音的聲壓。接著討論風扇置於四邊均為簡支邊界之有孔平板下方，此一平板將受風扇噪音激振產生振動，為求取四邊簡支有孔平板受風扇噪音激振之運動方程式，本文利用“Ectoplasm”的概念，以漢彌爾頓定理作為基礎，推導得板之運動方程式，並可由此計算有孔平板之自然頻率及其受聲場激振所得之振動位移，在有孔平板之另一面的聲場則會因平板板面振動而產生輻射聲壓，聲波也可從平板之孔洞繞射而出，進而在平板另一面空間中形成繞射聲場，本文引入克赫積分及格林函數來處理有孔平板輻射與繞射的問題，以求出有孔平板另一面之完整聲場。

關鍵字

輻射聲壓 ； 氣動噪音 ； 風扇噪音 ； 繞射聲壓

並列摘要

This thesis focuses on the investigation of the noise produced by rotating fan blade. In order to calculate the sound pressure due to a rotating fan, the theory introduced by Ffowcs Williams and Hawkings is used. Furthermore, the sound from the fan is applied to a holed plate and causes the vibration of the plate. For deriving the equation of motion of the holed plate, the technique of " Ectoplasm " as well as Hamilton ’s principle are adopted. The nature frequencies, of holed plate, and the dynamic responses due to the fan are then solved. In the corresponding acoustic field, both the radiated sound from the vibrating plate and the diffraction sound through the holes on the plate are investigated. Finally, parametric studies are also presented.

並列關鍵字

Ectoplasm ； FW-H ； Lighthill ； Acoustic Analogy ； fan

參考文獻

Beslin, O., and Guyader, J. L., 1996, “The Use of an “ECTOPLASM” to Predict Free Vibration of Plates with Cut-Outs”, Journal of Sound and Vibration, Vol. 191(5), pp. 935-954.

Beslin, O., and Guyader, J. L., 1997, “The Use of “ECTOPLASM” to Predict Radiation and Transmission Loss of a Holed Plates in a Cavity”, Journal of Sound and Vibration, Vol. 200(4), pp. 441-465.

Boltezar, M., Kuhelj, M.and Kuhelj, A., 1998, “The Influence of Uneven Blade Spacing on The SPL and Noise Spectra Radiated From Radial Fans”, Journal of Sound and Vibration Vol. 216 (4), pp. 697–711

Fahy, F., 1985, Sound and Structural Vibration : Radiation, Transmission and Response, Academic Press, London, Britain.

Hawkings, D. L. and Lowson, M. V., 1974, “Theory of Supersonic Rotor Noise”, Journal of Sound and Vibration, Vol. 36, pp. 1-20