Numerical study on the stall behavior of a water jet mixed-flow pump

Water jet mixed-flow pumps have been widely used in the field of marine propulsion. To ensure that the pumps work at stable conditions, flow instabilities were analyzed under low flow-rate conditions, where unstable flow most likely occurs. A numerical simulation was performed with the realizable k-epsilon turbulence model. This model exhibits better agreement with the experimental data of the performance curve compared with the standard k-epsilon turbulence model. Performance and internal flow analyses in the diffuser and impeller channels were conducted separately. Results show that the performance curve of the pump model with and without guide vane presents a positive slope at 28–59 % of the designed flow rate where stall occurs. Furthermore, the stalled flow in the impeller channels, rather than the reverse flow in the diffuser channels, causes the positive slope of performance. The stalled flow is located at the leading edge of the blade tip. It develops from the suction side to the pressure side of the blade. In addition, the stall zone extends gradually from three to five impeller passages with decreasing flow rate. The results can serve as references to improve the performance instabilities of water jet mixed-flow pumps.