Investigation on Cavitation Characteristics in Hydraulic Turbines Based on Frequency Bandwidth Analysis of Wavelet Packet

The characteristics of wavelet basis that is applicable for the processing of cavitation acoustic emission signal are summarized based on the analysis of the characteristics of the acoustic emission signal emitted by cavitation in hydraulic turbines.Besides,local decomposition of wavelet packet are proposed and employed in signal processing to improve the efficiency of decomposition.Aided with the pictures of cavitation,taken in the cavitation tests on the model turbine,with different cavitation coefficients,the ultrasonic signal of cavitation corresponding to each cavitation coefficients are analyzed via the time-frequency distribution and energy distribution.The relationships between the amplitude modulation in time domain as well as energy distribution in frequency domain and cavitation coefficients are achieved via model tests.The effect of frequency bandwidth analysis of wavelet packet has been proved.