Comparison of the Shutdown Transitions of the Full-Flow Pump and Axial-Flow Pump

In this study, a comparative analysis of the shutdown transitions of a full-flow pump and an axial-flow pump was carried out through numerical simulation and model tests. The UDF method was used to achieve control of the impeller rotational speed during shutdown. The results show that during the shutdown transition, the rate of decline of rotational speed, flow rate, and torque of the axial-flow pump are greater than those of the full-flow pump, so the axial-flow pump stops faster than the full-flow pump. The axial force of the axial-flow pump is significantly lower than that of the full-flow pump, and the maximum value of the radial force of the axial-flow pump is approximately 1.14 times that of the full-flow pump. Due to the influence of the clearance backflow vortex, the impeller inlet and outlet of the full-flow pump generate clearance backflow vortices in the near-wall area, resulting in the overall flow pattern of the impeller chamber being worse than that of the axial-flow pump and the hydraulic loss being greater than that of the axial-flow pump. The runaway speed and flow rate of the axial-flow pump are higher than those of the full-flow pump. Due to the influence of the clearance backflow, the range of the high entropy production rate at the suction side of the impeller of the full-flow pump is always larger than that of the axial-flow pump. The research results in this paper can provide theoretical support for the selection and operation of pumps in large low-head pumping stations.