Research on Perforated-Drainage-Based Active Flow Control for Gas Blockage Mitigation in Multiphase Mixed-transport Pumps

The helical axial multiphase pump is a key device in deep-sea oil extraction, where the internal gas-liquid two-phase flow is highly complex. Under high gas volume fraction conditions, intermittent gas blockage occurs, which directly compromises pumping efficiency. To address this issue, an active flow control strategy based on perforated drainage holes was employed. Using an orthogonal experimental design, in combination with numerical simulations and experimental validation, the effects of geometric parameters of the drainage structure on pump performance and gas blockage were systematically investigated. The results indicate that the inclination angle of the drainage holes exerts a stronger influence on pump performance than other structural parameters. At high gas volume fraction, the drainage structure significantly improves pump efficiency. An appropriate inclination allows the drainage direction to better align with the local streamlines, thereby reducing additional energy losses, alleviating gas accumulation near the hub on the suction-side blade trailing edge, and effectively dispersing bubble clusters. Conversely, excessively small angles fail to generate sufficient shear to disrupt gas aggregation, while overly large angles misalign with the flow, inducing separation and increasing energy dissipation. The optimal performance was achieved at an inclination angle of 20°, where the pump efficiency reached its maximum.