Correlation analysis of cavitation-induced pressure pulsation and vibration in a bulb turbine

Abstract

Cavitation is one of the primary factors leading to the destabilisation of tubular turbines. To enhance their stability, this study examines the effects of runner cavitation on draft tube pressure fluctuations and vibration in tubular turbines through experimental methods. With varying cavitation coefficients, a synchronous test system, including a high-speed camera, vibration acceleration sensors and pressure pulsation sensors, is applied to obtain cavitation images of the runner, and vibration and internal fluid pressure pulsation data of the draft tube. The results show that the correlated component of pressure pulsation signals during the cavitation process is the synchronous pressure pulsation of 16 fn. With the development of cavitation, the amplitude of synchronous pressure pulsation increases first and then decreases. Cavitation enhances the high-frequency vibration of the runner chamber wall and the RMS of the vertical vibration component IMF3 and the horizontal vibration components IMF2 and IMF4 are linearly negatively correlated with the cavitation coefficient. The associated component between cavitation-induced vibration and pressure pulsation signal is 16 fn and its harmonics. In the process of cavitation, pressure pulsation plays a leading role in vibration.