An Investigation of Axial Pump Backflow and a Method for its Control

Abstract

The flow field within an axial flow inducer pump near the blade leading edge was explored by laser-Doppler velocimetry to extend the previous studies of the recirculation zone which is observed at low flow rates. Although a considerable region of upstream reverse flow and swirl was observed, the recirculation zone within the impeller was of limited axial extent and was confined to the pressure side of the passage. In an attempt to reduce the flow reversal, a series of perforated disks were placed in front of the inducer. The optimum disk geometry produced minor changes in the pump performance. LDV measurements of the flow field ahead and behind the disk showed considerable reduction of the swirl velocity under reverse flow conditions, with the observed upstream swirl opposite to the inducer rotation.