Screw-type Centrifugal Pump Performance Improvement by Utilising Restraint of Back Flow

Abstract

Authors have been investigating the various characteristics as for a screw-type centrifugal pump, for example pressure fluctuation in the impeller, flow pattern in a volute casing and pump performance in air-water two-phase flow. During these investions, it was found from numerical results that three back flow regions existed in this pump. Among them, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. The important factor for higher pump performance was to reduce the influence of this back flow. The trial was carried out by the restraint of the back flow in order to investigate its influence. A wall was attached at the trailing edge of the impeller blade. Its effects on the flow patterns and the pump performance were discussed and clarified by comparing the calculated results under the conditions between with and without the wall. From the obtained results, it was found that the wall avoided the congestion of solids and worked well for the suppression of this back flow. In addition, the improvement in pump performance was realized by this trailing-edge type wall. The pump head and the efficiency at BEP were improved by 10% and 3%, respectively.