Simulation analysis of internal flow field characteristics of high-speed centrifugal pump as a turbine

The pump as turbine (PAT), utilizing high-speed centrifugal pumps, boasts technical advantages such as low cost, compact structure, and broad flow adaptability. The present work is a numerical simulation study of the internal flow fields of the volute, runner, and draft tube of a PAT using CFX flow field analysis software. The findings reveal that the maximum energy loss in the PAT runner amounts to 11.5%, accounting for 49.67% of the total loss. The energy loss in the volute section follows closely at 10.6%, constituting 45.79% of the total loss, while the loss in the draft tube is minimal at 1.05%. The PAT volute exhibits significant velocity variations at the inlet section, accompanied by rapid changes and suboptimal internal pressure distribution. Within each flow passage of the runner, the velocity distribution is uneven, with vortices present on the suction side of the blades. The pressure distribution at the center of the runner is nonuniform, characterized by large and multiple small vortices. In the draft tube, the pressure distribution is uneven, with vortex bands at the center causing some energy loss; however, the overall internal flow characteristics remain favorable.