Computational Fluid Dynamics–Population Balance Model (CFD–PBM) Study on the Performance and Bubble Evolution of an Air–water Airlift Pump

To investigate the coupled effects of submergence ratio and gas flow rate on the lifting performance and bubble evolution of a straight-pipe air–water airlift pump, a three-dimensional transient computational fluid dynamics model built upon the Eulerian–Eulerian two-fluid framework incorporated with a Population Balance Model (PBM) was developed and validated against experimental measurements. Over the ranges of submergence ratio of ۰.۳–۰.۷ and gas flow rate of ۲۰–۵۰ m³·h⁻¹, the variations in liquid flow rate, gas holdup, Sauter mean diameter, and mass lifting ratio were systematically examined. The results indicate that liquid flow rate generally increases with gas flow rate and submergence ratio, although its marginal increment diminishes significantly under high gas flow rate conditions. Gas holdup increases monotonically with gas flow rate, but such an increase fails to yield a continuous enhancement in liquid lifting capacity. The Sauter mean diameter initially decreases and subsequently increases with gas flow rate, reflecting the competing effects of bubble breakup and coalescence. The mass lifting ratio declines progressively with increasing gas flow rate but rises gradually with submergence ratio. Overall, submergence ratio serves as the fundamental driving force for system operation, whereas gas flow rate modulates two-phase transport by regulating the bubble swarm structure and the gas–liquid interfacial state. Proper matching of operating parameters is therefore critical for the synergistic optimization of lifting capacity and gas utilization efficiency.

کلیدواژه ها:

Air lift pump ، Computational fluid dynamics-Population balance model (CFD -PBM) ، Gas-liquid two-phase flow ، Submergence ratio ، Gas flow rate ، Bubble size evolution