Experimental investigation on cavitating flow induced vibration characteristics of a low specific speed centrifugal pump

Abstract: Cavitation, one of the unexpected flow instabilities inside centrifugal pumps, is detrimental to the stable operation of centrifugal pumps. With absolute static pressure at the impeller suction decreasing, cavitation may easily occur at the blade leading edge. Furthermore, with static pressure decreasing continuously, cavitation region inside blade channels expands towards the blade trailing edge, and cavitation bubbles travel with the main flow collapsing at high static pressure region. During the collapsing process, unsteady impact forces acting on the blade surfaces and shock waves would be generated resulting in vibration energy of the pump increasing rapidly. Besides, due to the continuously impingement effect of the burst cavitation bubbles, cavitation erosion would develop on the blade surfaces. So it is essential to detect cavitation during pump operating to avoid the unexpected effects. In the present study, visualization of cavitating flow and the corresponding induced vibration characteristics are combined to investigate the influence of cavitating flow on vibration energy of the model pump. Emphasis is laid upon the low frequency signals. The present paper attempts to illustrate the influence of cavitation on the entire frequency band signals. Besides, the correlation between cavitation evolution and vibration energy characteristics would also be clarified. Finally, a comprehensive understanding of cavitation induced vibration would be carried out to establish an effectively way to detect cavitation in centrifugal pumps.