Staggered impeller configuration effects on energy transfer and pressure stability in two-stage centrifugal pumps for pumped-storage applications

The two-stage double suction centrifugal pump (TSDSCP), a pivotal component in pumped-storage hydropower systems, is widely employed across various sustainable energy sectors. Its operational stability is paramount, as it significantly affects the system's energy conversion efficiency and ensures the long-term reliable operation essential for the viability of these green energy solutions. The study specifically focused on the impact of the staggered arrangement of double suction impellers on the pressure pulsation within TSDSCP. Two impeller configurations, symmetrical and staggered, were experimentally established to evaluate the pressure pulsation behavior under different staggered conditions. The staggered impeller configuration was found to slightly increase efficiency by 0.04 % under design working conditions, marginally reducing the head by 0.6 m, and decreasing power consumption by 1.53 kW. These outcomes indicate that the impeller configurations have a relatively small impact on energy conversion efficiency and head. Notably, the amplitude of pressure pulsations was observed to be lower in the staggered impeller setup across the suction, vane, and pressure chambers when compared to the symmetrical arrangement. Specifically, at the design flow condition, the dominant frequency amplitude (DFA) in the suction chamber was reduced by 70 %, and under low flow conditions, a 39 % decrease was noted. A significant decrease in pressure pulsation was observed at the blade exit, especially at 0.6Q operation, where the DFA was diminished by 35.3 %. Employing the Stress-Blended Eddy Simulation (SBES) model for numerical calculations, further analysis of the wake-jet structure and the flow distribution at the entrance of the volute indicated that the staggered impeller enhances the uniformity of flow discharge and mitigates pressure pulsations caused by rotor-stator interactions. When the flow rate is low, the spinning vortex intensity in the staggered impeller's volute is lower, which in turn causes the pressure pulsations to be even less. Staggered impeller configuration greatly improves pump flow stability, leading to more stable operation, according to experimental and numerical studies.