Investigating the flow characteristics of air-lift pumps operating in gas-liquid two-phase flow

Experiments were conducted to investigate the flow characteristics in the riser pipe and the suction pipe of airlift pump at a series of air flow rates and submergence ratios by using a high speed camcorder and a Laser Doppler Velocimetry system (LDV).A modified model was developed to predict the performance of airlift pump operating in gas-liquid two-phase flow.The results show that an unstable flow structure composed by a water falling film,a bubbly mixture,a water ascending film appearing alternately in riser pipe dominates the performance of airlift pump at large air flow rates.The bubbly mixture with a strongest capacity for pumping water first increases to its maximum and then slightly decreases.In suction pipe,the average velocity shows a flat profile and increases with increasing submergence ratio.Moreover,the predicted results of modified model are in good agreement with the experimental data in a margin of ± 12％.