Abstract
In this article, the unsteady flow field in a radial diffuser pump has been investigated by laser Doppler velocimetry measurements at the design condition Qdes and also at three off-design conditions 0.5Qdes, 0.75Qdes, and 1.15Qdes. Both the upstream effect and the downstream effect originating from the unsteady interactions are quantitatively examined, and these effects are also compared with the turbulence effect. The analysis of the experimental results shows that the upstream effect is only limited to the impeller rear part for all examined flowrates. The downstream effect is comparable to the turbulence effect before the diffuser inlet throat at Qdes and 1.15Qdes. However, the turbulence effect dominates totally over the downstream effect at part-flow conditions 0.5Qdes and 0.75Qdes.