Abstract: In order to study the influence of cavitation on the internal flow of hydraulic turbine in a multistage centrifugal pump, a three-stage centrifugal pump was selected as the research object. Based on Zwart cavitation model and KNG k-ε turbulence model, three-dimensional numerical simulation of different cavitation numbers was carried out under rated flow conditions turbulence model. The internal flow law of the main flow components was analyzed, and suggestions for reducing cavitation were put forward. The results show that a small amount of cavitation is generated after cavitation inception, which changes the inlet and outlet circulation of the last stage impeller, resulting in a 2% increase in head and a 3% increase in shaft power. There are airfoil cavitation and vortex cavitation in the last stage impeller. Excessive distortion at the blade tail can induce airfoil cavitation, and excessive inlet flow relative to the flow angle causes vortex cavitation. Cavitation occurs first at the outlet of the tailrace chamber, and the flow state inside the chamber is affected by the uneven flow rate. The flow on the left side of the chamber is more chaotic, while the right side is more regular. This study provides a reference for inhibiting the cavitation phenomenon of multistage centrifugal pumps as hydraulic turbines and improving the stability of turbine operation.

Key words: multistage centrifugal pump as hydraulic turbine, airfoil cavitation, vortex cavitation, flow angle, numerical simulation