Effect of swirl flow on the bubble motion and spatial distribution in a venturi tube

Abstract

In the process of carbon dioxide capture by chemical absorption, swirl flow plays a positive role in enhancing mass transfer. To leverage the advantages of swirl flow in enhancing mass transfer and overcome the drawback of bubbles easily aggregating in swirl flow, a tangential inlet venturi tube is designed. This study utilized dual-perspective high-speed imaging technology to achieve clearer measurements of the spatial positions of individual bubbles and the spatial distribution of bubble clusters. By measuring the three-dimensional motion trajectories of individual bubbles in still water and at low Re, the positive effect of swirl flow in expanding the distribution range of bubbles is observed. By measuring the three-dimensional motion trajectories of bubbles of different sizes at the same Re, it is observed that smaller bubbles are less likely to be captured by the vortices. And the spatial distribution of the bubble cluster in the diffuser section is analyzed by extracting grayscale values and correlating them with the flow field using Computational Fluid Dynamics (CFD) method. Experimental results indicate that as the bubble size decreases, the number of grayscale peaks gradually increases, indicating an expansion of the spatial distribution range of the bubble cluster in the diffuser section. CFD results reveal the presence of two vortices that continuously rotate around the central axis in the diffuser section. However, these vortices attract but did not confine small-sized bubbles. The bubbles are distributed around the vortices and moved along with the rotational motion of the vortices, allowing the bubble cluster to maintain a larger spatial distribution level within the swirl flow.