Airlift pumps provide reliable means of artificially lifting of liquids or liquid-solid mixtures from deep wells or vessels. This paper presents a numerical investigation into the effects of air injection strategy, single-stage vs. multistage air injection, on the airlift pump performance. A numerical model of airlift pump, based on the concept of momentum balance, was developed and validated against available experimental data. Predictive studies on model airlift pump with different arrangements of injected compressed air were numerically carried out. Numerical results showed that applying the commonly used single-stage air injection causes a steep change in the pump output-input characteristic curve followed by a fast decay after the optimum point. Injecting the compressed air in a number of air injection stages, on the other hand, was shown to increase the range of bubbly-slug flow regime as well as the pump operating window close to the optimum conditions. Improvement in the pump performance at higher degrees of air input mass flow rates is expected when employing multistage air injection.

airlift pumps, two-phase flow, multistage air injection