Effects of air-injection configuration on flow characteristics and lifting performance of an airlift system

Description

To investigate the influence of air injection configurations on the flow behavior and lifting performance of airlift systems, computational fluid dynamics (CFD) simulations were conducted for gas-liquid two-phase flow in a riser. A system with a riser diameter of 213 mm, length of 9.95 m, and submergence ratio of 0.9 was analyzed. Two injection strategies were considered: an injection-chamber-assisted configuration and a direct-injection configuration. The chamber-assisted design included uniformly distributed circular orifices, transverse slots, and longitudinal slots, while the direct-injection case examined the effects of orifice diameter and number, and injection angle. Performance was evaluated using liquid lifting rate, lifting efficiency, gas volume fraction, and flow field characteristics. Results indicate that the injection chamber significantly enhances gas distribution uniformity and inlet flow conditioning, leading to improved lifting performance and operational stability compared with direct injection. Among chamber configurations, uniformly distributed circular orifices provide the best performance due to more homogeneous gas dispersion and stronger gas-liquid interaction, followed by transverse slots, while longitudinal slots promote gas accumulation and reduce efficiency. For direct injection, a clear coupling between orifice diameter and number is observed: moderate enlargement of orifices reduces flow resistance and improves axial transport, whereas excessive enlargement weakens radial mixing. The effect of injection angle is limited, with 45° inclination providing only slight improvement over 90° injection. Transient results further show that gas gradually migrates upward under jet momentum and buoyancy, resulting in a dynamically evolving gas supply region and time-dependent flow behavior.

Institutions

• Jiangsu University

  Jiangsu, Zhenjiang

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