Numerical study on transient hydraulic excitation force characteristics of a water jet mixed-flow pump during rapid startup period

Mixed-flow pumps have been widely used in water jet propulsion field. To ensure reliability and operation efficiency, it is necessary to investigate the characteristics of hydraulic excitation force during transient operations. In this paper, the radial force of a water jet mixed-flow pump during rapid startup period was investigated numerically based on improved delayed detached eddy simulation (IDDES) and siding mesh method, the external characteristics were verified by test results. The spatial-temporal evolution of radial force was analyzed. The radial force during rapid startup presents transient and delay phenomenon, which shows disparity compared with quasi-steady state. The flow analysis and blade strip analysis show inlet recirculation significantly affects the radial force's evolution, the radial force is quite different from blade root to tip and the blade tip contributes most to the radial force delay phenomenon. By applying boundary vorticity flux (BVF) theory and separation vortex formation diagnosis, separation regions caused by the dissipation of inlet recirculation were effectively identified and the change trend is in line with the change of radial force, which explains how inlet recirculation results the delay of radial force on blade tip strip and the whole impeller blade.

Automated summary

In this paper, the radial force of a water jet mixed-flow pump during rapid startup period was numerically investigated. The spatial-temporal evolution of radial force and its transient and delay phenomenon were analyzed. The study found that inlet recirculation significantly affects the radial force evolution, and the blade tip contributes most to the radial force delay phenomenon.