Characterization of particle removal in an airlift pump with a U-bend

Abstract

This paper investigates the self-cleansing performance of an airlift pump with a u-bend. For this purpose, an experimental test model is used to assess the effect of air supply on the pump's ability to lift water and remove particles under different submergence ratios and particle concentrations. In addition, a simple yet accurate fluid mechanical model is used to rationalize the experiments with individual particles, and to predict the critical water velocity required for removal from the pipe bend. Our experimental results show that the airlift pump is self-cleansing for particle concentrations corresponding to as much as 70% of the cross-sectional area in the u-bend. Furthermore, the self-cleansing ability is relatively independent of the submergence ratio and almost entirely determined by the shear stress. However, the submergence ratio strongly affects energy use, and we find that submergence ratios around 0.75 provide a good compromise between energy use and particle removal efficiency.