Study on the pump cavitation characteristic through novel independent rotation of inducer and centrifugal impeller in co-rotation and counter-rotation modes

The influence of counter-rotation between the inducer and impeller, along with a newly introduced system for their independent rotation on the pump cavitation characteristics, has been studied experimentally. Remarkably, this pump allows users to select between co-rotation and counter-rotation modes, providing significant operational adaptability. The high-speed camera is used to analyze vaporization structures and closely monitor the stability of the head pressure delivered by the pump during the cavitation testing phase. For both co-rotation and counter-rotation modes, different types of cavitation within the inducer and between the inducer and the impeller at three varied flow rates have been studied using image analysis. The results reveal improved cavitation performance and comparable efficiency at consistent pressure–flowrate combinations, emphasizing the advantages of counter-rotation across the three tested flow rates. In counter-rotation mode, the tangential velocity of the flow at the output of the inducer is opposite to that of the co-rotation mode. Consequently, the tangential velocity of the flow entering the impeller is reduced, leading to enhanced flow stability and increased pump pressure. The findings from image analysis demonstrate that the structure of cavitation varies between co-rotation and counter-rotation modes. Reversing the rotation direction of the inducer not only improves the pump cavitation characteristics but also changes the vapor structure due to changes in the flow pattern.