Near-exit flow-field investigation in an inducer including laser-Doppler velocimetry

Abstract

The flow field was measured near the exit of an axial-flow spiral-inducer pump impeller at design and off-design conditions. Laser-Doppler velocimetry was employed to define the blade-to-blade velocity distribution inside and outside the rotating impeller passage near the trailing edge. The observed variation of velocity and flow angle revealed a strong secondary flow, of a double vortex form, at the design flow rate and a developing hub separation zone at lower flow rates. The observed rearrangement of the flow field between the closely spaced locations upstream and downstream of the trailing edge is believed to be linked to the developing recirculation zone. Distributed deviation angles are presented for the design flow rate and overall values for all flow rates.