Comprehensive performance comparison and applicability analysis of bidirectional flow passage pump device based on hub ratio under multi-operating conditions

To investigate the applicability of modified pump unit designs in actual pumping station projects, this study employs a combined approach of numerical simulation and model testing. It compares the hydraulic performance of pump units with different hub ratios, analyzes the patterns of internal flow losses under various configurations, and proposes operational conditions for different hub ratios in practical pumping station engineering. Research indicates that the hub ratio significantly influences the pump unit's high-efficiency range, hydraulic loss distribution in the discharge flow path, and cavitation performance. At a hub ratio λ=0.4, the pump unit exhibits the widest high-efficiency range, shifted toward higher flow rates by approximately 20% Q d . Pump units with smaller hub ratios demonstrate higher hydraulic efficiency under low-head, high-flow conditions. At a hub ratio λ=0.467, the pump unit's high-efficiency zone shrinks and shifts toward lower flow rates by approximately 15% Q d , while cavitation performance improves under high-head, low-flow conditions. Hydraulic losses in the pump assembly primarily occur in the discharge flow passage and guide vane assembly. Under design conditions, hydraulic losses in the discharge flow passage account for approximately 73.43% of total hydraulic losses, while those in the guide vane assembly constitute about 22.01%. Entropy production analysis based on the turbulent dissipation theory shows that the larger the hub ratio, the smaller the high entropy production regions at the outlet guide cone and the diffuser, thereby reducing the hydraulic loss in the outlet passage.Therefore, the selection of the hub ratio must be comprehensively determined based on the actual operating conditions of the pump station (head and flow requirements). The findings of this study provide a theoretical basis for the optimized design of bidirectional flow passage pump units.