Effects of submergence ratio and particle size on flow regime transition and edge-density-based dynamics in a gas-liquid-solid airlift riser

초록

To interpret the relation between flow regime and transport capability of an airlift system, flow-visualization experiments were conducted in an airlift riser with an inner diameter of 25 mm, and effects of critical factors such as the submergence ratio and particle diameter were investigated. Both gas-liquid two-phase and gas-liquid-solid three-phase flows were covered. When the submergence ratio increases from 0.5 to 0.9, coherent slug flow structures are replaced with short and dispersed gas cavities. The slug flow structures are still recognizable when particles of 4.0 mm in diameter were lifted at low superficial gas velocities. Increasing the submergence ratio leads to increases in the velocity ratio of superficial liquid velocity to gas velocity and meanwhile the increase in pressure gradients, explaining why the highest lifting efficiency and the highest transport capability cannot be obtained synchronously. A dynamic characteristics analysis shows that flow regime reorganization was accompanied by attenuation of low-frequency periodic structures and fragmentation of recurrence patterns. At a submergence ratio of 0.9, the determinism for particles of 2.0 mm in diameter decreases by approximately 63.1% relative to the gas-liquid two-phase baseline. The residual correction analysis suggests that dynamic indicators can help interpret efficiency deviations beyond the liquid-lifting baseline, but cannot independently determine the lifting efficiency. © 2026 Elsevier Ltd.

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