Numerical analysis of cavitating flow characteristics in impeller of residual heat removal pump

Abstract

In order to investigate internal cavitating flow characteristics of the impeller in residual heat removal pumps, the three-dimensional cavitating flow in a residual heat removal model pump is numerically calculated by using the homogeneous mixture cavitation model based on the Rayleigh-Plesset equation and the shear stress transport SST k-ω turbulence model. The hydraulic performance curves, distributions of vapor volume fraction at NPSHA and the blade load profiles at the design flow rate are obtained. The numerical results show that the distribution of vapor volume fraction becomes non-axisymmetric with the decreasing of NPSHA, even some blade passages are blocked when NPSHA drops to 2.63 m. Vapor volume fraction distribution varies across blade span; the shorter the distance to the hub is, the higher the vapor fraction on the blade suction side is. Additionally, the cavity in the impeller shows a quasi-steady characteristic before the head starts to be deteriorated rapidly. Due to a sudden change in the primary flow direction near the eye of impeller, the blade load on the blade pressure side shows a sudden increasing and drop effect.