625 ポンプ水路系で発生した複雑な脈動と振動現象

概要

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Significant pressure fluctuations were observed in suction water tunnels when an axial flow pump was operated without an actual head at some blade angles. To identify the causes, investigations were done by measuring acoustic natural frequencies and pressure fluctuations in the tunnels, lateral and torsional vibrations of the pump shaft, and pressure fluctuations of the oil in the hydraulic system to control the blade angle. Measurements were also taken by inserting air into the suction tunnels with a compressor and by setting air bags inside the tunnels. The results showed that acoustic resonance occurred in the tunnels, but it was not a simple resonance. The dominant frequency, which was neither the blade passing frequency nor its higher harmonics, depended on rotating speed in the reverse way : it decreased when rotating speed increased and vice versa. The pressure fluctuations and vibrations of the pump shaft had a strong relationship. However, they had different dominant frequencies and occurred at different blade angles. Several measurements were made in different seasons and it was found that the phenomena were season-dependent. The causes are discussed. It is believed that the excitation source was vortex shedding from the blades, which locked into the acoustic resonance in the water tunnels via vibration of the blades.
一般社団法人日本機械学会の論文
2003-09-15