Experimental and Numerical Simulation Study of Clocking Effects on Hydraulic Performance of Multi-stage Centrifugal Pump

Multistage centrifugal pumps are distinguished by their high head capacity, energy efficiency, and operational reliability. These pumps are extensively employed in boiler feedwater systems, petrochemical processing, fire protection infrastructure, and industrial process pressurization. To mitigate synchronous excitation vibrations from root imbalance, impellers are typically installed with circumferential phase differences, an approach that gives rise to the clocking effect. Hydraulic performance and transient flow patterns in the initial 3-stages of a multi-stage centrifugal pump are analyzed with respect to clocking effects at rated operating conditions. Nine clocking configurations were designed, and measurements of internal flow were conducted at three key locations within the pump. The relationships among pressure variation patterns, internal flow distribution, turbulent kinetic energy dissipation, and entropy-based energy loss were analysed. Quantitative results reveal that clocking has a notable impact on hydraulic performance, with efficiency variations of up to 14.3% at part-load and 9.1% at overload conditions. Additionally, impeller pressure fluctuations exhibited a 90° phase shift along with a principal frequency deviation of 59.17 Hz, directly linked to changes in stator–rotor interaction. These effects lead to observable improvements in internal flow behaviour. Among the nine clocking configurations, optimised impeller phase alignment reduced secondary flow structures, minimised wake-induced losses, and enhanced volumetric efficiency by up to 4.2%. These findings demonstrate that clocking optimisation is a viable strategy for enhancing flow stability and pump efficiency.