Tip leakage vortex characteristics and phase distribution in a helico-axial multiphase pump at different flow rates

This study investigates tip leakage vortex (TLV) characteristics in helico-axial multiphase pumps at 20% inlet gas void fraction across three flow rates (Q/Qdes = 0.9, 1.0, 1.1). Numerical simulations using the SST k-ω and Eulerian-Eulerian models, validated by high-speed photography, reveal critical coupling among operating conditions, vortex dynamics, and gas–liquid phase distribution. With increasing flow rate from 0.9 to 1.1 Qdes, TLV penetration depth increases by 35% (measured by radial displacement), while peak vorticity intensifies from 22,500 s−1 to 24,500 s−1 at the leading edge. The vortex core migrates toward the impeller hub, with the radial position shifting from r* = 0.990 to r* = 0.983 at mid-chord, developing pronounced three-dimensional characteristics at Q/Qdes = 1.1. Vorticity concentrates at the leading edge (λ = 0.15–0.25) with peak values exceeding 24,000 s−1, then decays exponentially to below 5,000 s−1 by mid-chord (λ = 0.5), while turbulent kinetic energy peaks at 1.5–1.6 m²/s² in the mid-chord region (λ = 0.4–0.6). Gas holdup distribution exhibits strong spatial correlation with low-pressure regions, with maximum gas holdup increasing from 0.25 to over 0.4 as flow rate increases, gas volume fractions reaching 0.6–0.75 near the leading edge, and normalized gas phase deviation exceeding 300% at high flow rates, forming a coupled phenomenon where pressure depression promotes gas concentration and subsequently influences vortex structural evolution. These findings reveal TLV-induced gas accumulation is 15–20% higher than previous single-phase studies predicted, with critical implications for multiphase pump efficiency optimization.