キャビテーション状らせん渦心に起因した曲がり吸出し管不規則水圧脈動の分析

概要

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To evaluate pressure surge caused by a spiral vortex core in an elbow draft tube, the technique for processing the ensemble-averaged pressure data measured at two points at an angle 0f 90 degrees in the cross section of an inlet cone is regarded as the minimum essential. However, this is not applicable to fluctuating pressure data having a random nature, which are sometimes observed in model testing of a Francis turbine. Thus, the present study aims to develop a new method based on spectrum analysis instead of Fourier analysis for the diagnosis of pressure fluctuations for those cases mentioned above. Experiments were conducted using an elbow draft tube having a long inlet cone under three kinds of swirl strength. The dominant frequencies derived from the cross spectrum of fluctuating pressure were classified and correlated with the behavior of the vortex core inside the tube, which was observed by using a high-speed video system.
社団法人日本機械学会の論文
1994-05-25