A visualized study of the motion of individual bubbles in a venturi-type bubble generator

As an equipment for generating millimeter- or micrometer-sized bubbles, venturi-type bubble generator has a great potential application in online poison gas removal for molten salt reactor, water treatment, mineral flotation, flue gas desulphurization, even in drug delivery, etc. While the process of generating bubbles in a venturi tube is quite different from that in a conventional tube. A visualized study was carried out to illustrate the details of the transportation of individual bubbles in a venturi-type bubble generator. Sizes, velocity, acceleration of the bubbles were obtained by Digital Image Analysis (DIA) method. An extremely rapid deceleration and intense breakup process was observed nearby the entrance of the diverging section of the bubble generator. Bubbles with average diameter larger than 1.5 mm were usually split before collapse, while the smaller one collapsed directly without split. Within several millimeters, the velocity of the bubbles were almost reduced by half, which is believed to play a key role for triggering their collapse. Once a bubble was decelerated to its minimum velocity, it was collapsed promptly into many tiny bubbles around the position of 8-10 mm from the inlet of the diverging section. Increasing the liquid flow rate could intensify the collapse process, while its influence on the position of collapse was weak.