Abstract: To analyze the effect of dsfferent impeller type on inner flow in impeller, two low-specific-speed high-speed complex impellers with eight blades are investigated whose types are closed and semi-open. Using the Spalart-Allmaras turbulence model and the Reynolds-Averaged Navier-Storkes equations, the three-dimensional turbulent flow fields in impellers are analyzed numerically. And the experimental studies on the cen-trifugal pump are carried out. The simulation results show that there all exists back flow region in impellers, the back flow region is few and the relative flow in clearance is alone the circumferential orientation in the half-open impeller, the static pressure in impellers rises gradually from blade inlet to outlet whose contours are almost alone the circumferential orientation, the static pressure of blade tip is bigger than that of blade root in the same radius of the blade in half-open impeller, and the static pressure coefficient at outlet of closed impeller is larger. The experimental results show that the efficiency of the half-open impeller is higher and the back flow has important influence on the performance of pump.

Key words: Centrifugal impeller, High speed, Low specific speed, Numerical simulation, Turbulence flow