Mechanism and modeling of Taylor bubble generation in viscous liquids via the vertical squeezing route

Abstract

Bubble formation routes are vital to the application of microreactors, but a systematic understanding of the vertical squeezing remains lacking. Accordingly, this study focuses on the vertical squeezing bubble generation mechanism in viscous liquids in a T-junction microchannel. The results show there are the retraction, expansion, shrinking, and necking formation stages in the vertical squeezing route. A new formation stage, the retraction stage, is seen compared with horizontal squeezing. The influence of operating conditions on the generation mechanism was investigated from the gas–liquid interface behavior and force analysis, and the different formation mechanisms of satellite bubbles in the necking stage for two different squeezing routes were revealed. In addition, the complex bubble generation frequency rules were unified using a dimensionless frequency parameter. Finally, models for the generation frequency and bubble size were proposed. This work could provide some choice and design for the fundamentals of microreactors.