Investigation on Bubble Breakup in a Venturi-Tube Bubble Generator under Low Gas Fraction Condition

In order to illustrate the mechanism and process of bubble breakup in a venturi-type equipment for generating bubbles, the transportation and breakup process of bubbles in a venturi-type bubble generator is analyzed in detail with the help of image and video processing softwares of PFV and Image-Pro Plus. It is found that two distinguished stages of bubbles exist in the generator; Bubbles will be decelerated rapidly at the entrance of the expansion section, during which three different kinds of deformation may occur to the bubbles. It is believed that the deceleration of bubbles has a significant effect on the bubble breakup process. The rapid deceleration of bubbles in the expansion section results in the increasing of the velocity difference and intensifies the interaction between the gas and liquid, leading to the bubbles with relatively large diameter breaking up into a great many tiny bubbles.