Study on the Dynamic Structure and Unsteady Characteristics of Vortex Flow for Blade Tip Clearance Leakage of a Single-vane Spiral Centrifugal Pump

Numerical simulations based on the RANS equations and the SST k‑ω turbulence model were carried out to study the turbulence characteristics in the tip clearance region of a spiral centrifugal pump. Results indicate that reducing the tip clearance significantly improves pump head and efficiency. At the design flow rate, compared with the original 1.0 mm clearance model, the head increases by 2.6% and 4.5% for the 0.6 mm and 0.4 mm clearance models, respectively, while efficiency rises by 2.1% and 8.4%. As the clearance decreases, the leakage flow velocity declines. Attached leakage vortices are observed on the impeller blade suction surface near the tip clearance, and their influence range expands with higher leakage velocity. During impeller rotation, the flow in and around the clearance exhibits an unsteady evolution of a complex vortex system. The tip leakage vortex (TLV) gradually merges, expands, and moves away from the wall, while the decoupling vortex on the pressure surface continues to develop and eventually interacts with vortices in the blade outlet region, forming a multi-vortex structure. The production of turbulent energy is mainly dominated by the tangential velocity gradient. The rotating impeller intensifies the tangential flow, resulting in significant anisotropy of turbulence. This study demonstrates that appropriately controlling the size of the impeller tip clearance in screw centrifugal pumps can effectively improve vortex development and evolution within the pump, thereby enhancing both pump head and efficiency.