Influence Mechanism of Trimming Impeller Diameter in a Centrifugal Pump by Computational Fluid Dynamics Investigation

Trimming the impeller diameter of a centrifugal pump is the easiest and most economical way to adjust its efficient operating range based on its original performance. Three impellers obtained by trimming the diameter are investigated. Energy performance, internal flow field, and entropy production analysis have been discussed in different cases. The results show that trimming the impeller diameter causes a great change in the energy performance of centrifugal pumps. The turbulent kinetic energy (TKE) distribution and entropy production also change significantly. The best efficiency point (BEP) shifts to low flowrate with trimming impeller diameter. The BEP shift rate was 6.67% and 20% for trimming amounts of 5.15% and 10.29%, respectively. As the impeller diameter decreases, the backflow phenomenon that occurs at the diffuser inlet at low flowrate improves. The ratio of mechanical energy to kinetic energy and pressure energy is not constant for pumps with different impeller diameters. The energy performance changes are mainly caused by flow changes inside the impeller, chamber, and diffuser. The results could be referred to as the design and selection of centrifugal pumps.