螺槳鳴音之量測與預測

Prediction and Measurement of Propeller Singing

In this paper, an analysis model is proposed to predict the propeller singing, which generally occurs when the vortex shedding frequencies at the blade trailing edge and some natural frequencies of the blade are nearly equal. A set of vibration and acoustic data taken during a sea trial of a bulk carrier was used to demonstrate this phenomenon. Numerical analyses, using finite element and boundary element methods, were performed to calculate the natural frequencies, mode shapes, and the radiation efficiency of the propeller blade. Together with a theoretical model describing the interaction of vortex shedding and blade vibration for predicting the response of the blade due to vortex excitation, the possible mode associating with singing can be deduced. In comparison with measured data, good agreement is shown between the frequency of the predicted mode that show both high response level and high radiation efficiency and the measured singing frequency. 本文提出一套有效之分析模式來預測螺槳鳴音之現象，該現象一般發生在當螺葉尾緣之渦洩頻率與螺葉本身之自然振頻偶合之情況下。文中之實船量測，係以一艘實際發生螺槳鳴之散裝貨輪為例，於出海試車時將量測到之振動與噪音資料，透過三維之頻譜圖，將鳴音於螺槳軸在轉速遞增與遞減之軸轉速變化情況下，展現其特性。此外，本文亦以有限元素法配合邊界元素法分別計算該實船螺葉之自然振頻、模態及幅射率，同時輔以一理論推導計算出螺葉洩與振動互制之反應，最後再將上述所有結果與實船量測資料做比較，結果顯示本文所提出之方法，可實際用以監定與預測螺槳鳴音之現象與能發生之模態。