Effects of guide vane angle on internal flows and vortex characteristic of reactor coolant pump passage under flow coastdown

Abstract

In order to explore the effects of guide vane angle on internal flows of reactor coolant pump during flow coastdown, the law of vortex evolution and vortex intensity change in the impeller and guide vanes was analyzed. Based on the second generation vortex identification method: Q criterion, the unsteady evolution law and vortex intensity change of impeller guide vane during flow coastdown were analyzed by numerical simulation. The results show with the flow coastdown, fluctuation law of pressure and velocity in the impeller keeps consistent, while the pressure gradually approaches the outlet pressure and the speed decreases. When the vortex identification’s threshold value is Q=24000 s-2, the vortex area in impeller is small and vortex structure is clear. In a rotation period, the shape and area of vortex structure at the inlet with different guide vane angles are the same. The outlet’s vortex structure is affected by dynamic-static interference, resulting the vortex structure is the same but the vortex area is different. The law of guide vane placement angle changes from “convex-vortex” to “concave -vortex”, and vortex area decreases gradually. In the guide vane, horseshoe vortex is dominant, and structure of blocked vortex and shear layer decreases during flow coastdown.