Low field in the vaned diffuser of a centrifugal pump at different vane setting angles

Particle image velocimetry (2D-PIV) has been used for the investigation of the time and phase-averaged flow field inside the vaned diffuser of a centrifugal pump operating at the best efficiency point (BEP). Pump performances and the diffuser flow field were analyzed for three different vane setting angles. It was evidenced that flow coefficient at the best efficiency point decreases with the diffuser setting angle reduction. From 2D-PIV measurements in five different blade to blade planes, spanwise averaged flow angles and velocity distribution were computed. It was evidenced an influence of the diffuser setting angle on the spanwise distribution of the flow rate and of the absolute mass averaged flow angle at impeller discharge. An overturning at the diffuser discharge was also evidenced for the two highest setting angles. 2D-PIV flow fields are presented in three different pseudosecondary planes in order to enlighten the cross flows affecting the diffuser flow field. © 2012 American Society of Mechanical Engineers.