Effect of Balance Drum Clearance on the Flow in the last stage Impeller Back Sidewall gap

Abstract

In order to study the effect of balance drum clearance on flow distribution in back sidewall gap of last-stage impeller, numerical calculation of a multistage pump was carried out. The accuracy of the numerical calculation method was verified with the external characteristic test. The axial distribution of the radial velocity at the inlet and the bottom of the back sidewall gap at different angles was plotted. The results showed that the radial velocity near the impeller flows radially to the outlet of the impeller, and the radial velocity near the pump shell flows radially to the hub. Influenced by the high-turbulent energy fluid at the outlet of the impeller, there are obvious eddy current movement at the inlet of the back sidewall gap, and the radial velocity increases with the increase of the balance drum clearance. When the flow rate increases from 0.5Q to 1.5Q, the radial velocity decreases gradually at the same angle. The results can provide a reference for the pump design and optimization.