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 anactual head at some blade angles. To identify the causes, investigations were done by measuring acoustic natural frequencies andpressure fluctuations in the tunnels, lateral and torsional vibrations of the pump shaft, and pressure fluctuations of the oil in thehydraulic system to control the blade angle. Measurements were also taken by inserting air into the suction tunnels with acompressor and by setting air bags inside the tunnels. The results showed that acoustic resonance occurred in the tunnels, but itwas 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 pressurefluctuations and vibrations of the pump shaft had a strong relationship. However, they had different dominant frequencies andoccurred at different blade angles. Several measurements were made in different seasons and it was found that the phenomenawere 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.
社団法人日本機械学会の論文
2003-09-16