Research on Characteristic of the Vibration Spectral Entropy for Centrifugal Pump

Hydraulic instability caused by flow separation, vortex, second flow, and other unstable flow conditions leads to operational instability, consumption of additional energy, and pump damage. Evaluating the degree of hydraulic instability and addressing the problem at an early stage are highly important. This study focuses on developing a measurement and evaluation method for hydraulic instability by nonintrusive vibration techniques. At the onset of hydraulic instability, the spectral structure of the vibration signal significantly changes, especially for some broadband characteristics. Spectral entropy is regarded as an indicator of hydraulic instability and is capable of evaluating the spectral structure of the signal. The spectral entropy of vibration is efficient and reflects the development of cavitation. Moreover, the positive slope area in the head-flow characteristic indicates the emergence of hydraulic instability. The spectral entropy is highly suited for online tests because of its dimensionless nature, and as compared with the root mean square value, a common dimensionless parameter, spectral entropy can highly coincide with energy characteristic.