Study on flow dynamics in a horizontal axial flow pumping station under off-design conditions

Large axial flow pump systems are widely used in inter-basin water transfer, farmland irrigation, and urban flood control. However, they often face challenges associated with off-design conditions during operation, leading to significant flow losses and pressure pulsations. To gain deeper insights into flow characteristics under off-design conditions, this study systematically investigates the flow losses and pressure pulsation energy characteristics of a horizontal axial flow pumping station using entropy production theory and the energy flow density method. The results indicate that under low-flow conditions, noticeable flow separation and horn-like vortex structures appear inside the impeller. Additionally, the energy loss of the pumping station under off-design conditions reaches 3.77 times that under the design condition at a low flow rate and 1.24 times at a high flow rate. In the main flow regions, the blade leading and trailing edges are identified as high-loss zones. Moreover, pressure pulsations are particularly intense under low-flow conditions, where the energy flux density and peak-to-peak value at the outlet rim side are respectively 52.69 times and 10.93 times those under the design condition. To ensure the safe and efficient operation of the pumping station, it is recommended to minimize operation hours under low-flow conditions.