Airlift Pump With a Gradually Enlarged Segment in the Riser Tube

Abstract

Airlift pump is a type of deep well pumps. Sometimes, it is used for removing water from mines or pumping slurry of sand and water or other solutions. The performance of airlift pump is affected by two sets of parameters; the geometrical and operational parameters. This work suggests a way to reduce the acceleration loss followed the expansion of air phase in the riser tube of the airlift pump, and consequently minimize transition to annular flow regime that is characterized by poor pumping performance. The method is to gradually enlarge the riser tube at some points after the air injection zone. Enlarging the riser tube can be considered as an alternative way in the cases where increasing airlift tube diameter is restricted by, e.g., the design of air injection system. A numerical model of the airlift pump based on the concept of momentum balance was developed and validated against available experimental data. Parametric predictive studies on model airlift pumps with different riser tube configurations, based on position, degree of expansion ratio and length of tube graduation section, were carried out. The numerical results showed that gradually enlarging the riser tube diameter at a position near the air injection zone would significantly improve the airlift pump discharge rate. Having the enlarged section set at a certain position and increasing the degree of expansion of the gradually enlarged tube section, the predicted results illustrated an improvement in the pump discharge rate but limited by the value of tube expansion ratio. The length of the enlarged tube section is shown not to considerably contribute to the improvement in the pump output rate when gradually enlarging the riser tube.