Wavelet packet analysis for the propagation of acoustic emission signals across turbine runners

Acoustic emission (AE) signals propagated across turbine runners incur attenuation due to propagation distance and structure interface. Wavelet packet transform (WPT) was used to analyze the attenuation characteristics of AE signals. A series of experiments had been carried out on an HLA286a-LJ-800 Francis turbine runner and AE signals were obtained from standard pencil lead break sources. The experimental results indicate that the WPT technique is an effective tool in extracting the attenuation characteristics. The feature packet can reflect the attenuation characteristics of signals across the runner. As a result, the pressure on data transmission and storage can be decreased by extracting feature packet coefficients using the wavelet packet technique, which indicates the feasibility to apply the AE technique to monitor the running state of turbine runners on site.