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

Cavitation is one of the main causes of deteriorating stability of bulb turbines. To enhance their stability, this study examines the effects of runner cavitation on draft tube pressure fluctuation and vibration in bulb turbine 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, 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 16f_n With the development of cavitation, the amplitude of synchronous pressure pulsation increases first and then decreases. Cavitation enhances the high-frequency vibration on the wall of runner chamber. The root mean square (rms) of the vertical vibration component IMF3, the horizontal vibration components IMF2, IMF4 are linearly negatively correlated with the cavitation coefficient. The associated component between cavitation-induced vibration and pressure pulsation signal is 16f_n and its harmonics. In the process of cavitation, pressure pulsation plays a leading role in vibration.