Numerical Simulation and Flow Diagnosis of Axial-flow Pump at Part-load Condition

The paper demonstrates the flow behavior in a high specific speed axial-flow pump at part-load condition by numerical methods. The unsteady Reynolds averaged NavierStokes equations (URANS) with the filter-based model were solved by using the computational fluid dynamics code ANSYS CFX and the hydraulic performance of axial-flow pump was estimated. At part-load condition numerical results show that parameters of hydraulic performance predicted by the filter-based model are proved to match with the experiment results better than that of the standard k-epsilon model. Furthermore, we analyzed the internal flow field within the axial-flow pump in fully developed stall and in deep stall, respectively, and compared the obtained typical flow features with the flow visualization experimental results in (I. Goltz, 2003). The boundary vorticity flux (BVF) was introduced to diagnose the internal flow field inside blade passage at part-load condition and to find out the root of the instability vortices. Based on the BVF diagnosis, the differences about the numerical results of flow fields in deep stall were further analyzed between the standard k-epsilon model and the filter-based model. It show that the filter-based model is more practical to capture the unsteady flow structures than the standard k-epsilon model.