An experimental and numerical investigation into flow phenomena leading to wastewater centrifugal pump blockage

The work covered in this project had the objective of investigating key factors in single vane pump impeller blockage using both Computational Fluid Dynamics (CFD) and experimental analysis. CFD has been used to highlight flow features leading to such blockage while experiments provided some insight into the significance of certain key parameters, namely radial and tangential velocities within the fluid domain. This was achieved by testing a large variety of centrifugal wastewater pumps in a purpose built test rig. The test rig was designed and built for this study based on previous research on smaller pumps by Mcevoy et al. (1). A suitable test material was used to test blockage performance of the pumps at three different flow rates, Best Efficiency Point (BEP), BEP +30% and BEP-30%. Average blockage performance across the product range was found to vary inversely with duty flow rate, with average Blockage Index (BI) across the tested range varying from 64% at lower flow to 92% at high flow. A pump which had varying blockage performance with duty flow rate was chosen for further study with CFD. An analysis of the CFD results showed a significant correlation between pump blockage performance and radial velocity components within the fluid domain, specifically in the impeller region. BI within this pump varied from 73% to 100% with increasing flow rate while the local radial velocity (v_rad) at the impeller leading edge, where blockage was most prevalent, varied from 1.4 m/s to 6.2 m/s. The results of this study highlight large scale flow components and their effect on blockage performance