Stage-dependent evolution and gas-phase effects on tip leakage vortex dynamics in a three-stage multiphase pump

The tip leakage vortex (TLV) significantly governs hydraulic losses and flow instability in multiphase pumps, yet its behavior in multistage configurations under gas–liquid two-phase conditions remains poorly understood. This study investigates the spatial trajectory, spatial–temporal evolution, and vortex dynamics of the TLV across three consecutive impeller stages of a helico-axial multiphase pump, combining experimental validation with high-fidelity numerical simulations under pure water and 20% inlet gas volume fraction (GVF) conditions. Vortex structures are identified using the Q-criterion, and dynamic mechanisms are quantified via the relative vorticity transport equation. Under pure water conditions, the primary tip leakage vortex (PTLV) exhibits a stable “gradual” evolutionary pattern, with peak swirling strength escalating progressively from ∼300 s−1 in stage 1–900 s−1 in stage 3 as inter-stage pressure loading intensifies. At 20% GVF, TLV undergoes an “abrupt” evolutionary pattern: PTLV in stage 2 fractures at mid-chord, while stage 3 displays premature breakdown into a chaotic flocculent distribution, with energy dissipation rates approximately two to three times those observed in pure water. Vorticity transport analysis reveals that vortex stretching and Coriolis force jointly sustain vorticity generation under single-phase conditions, whereas gas-phase introduction reduces their contributions by ∼25% in stage 1 and nearly eliminates them by stage 3. Concurrently, viscous dissipation spatially expands throughout the blade tip region, with stage 3 dissipation intensities increasing by 130%–150% relative to pure water. These findings elucidate the cumulative inter-stage degradation mechanism of the TLV in multistage multiphase pumps and provide a quantitative framework for tip clearance optimization and operational stability enhancement.