Experimental and numerical study on the bubble dynamics and flow field of a swirl flow microbubble generator with baffle internals

• A swirl flow microbubble generator with baffle internals was proposed. • The bubble size was more sensitive to the liquid phase than the gas phase. • A PBM based framework was developed for the micro sized bubble dynamics prediction. Microbubble generators have been widely applied in various fields. This paper explored the bubble generation performance and two-phase flow characteristics of a swirl flow microbubble generator with baffle internals. It showed that the bubble size evolution process in the generator was more sensitive to the liquid flow rate than the gas phase. A semi-empirical expression considering the dimensionless factors of gas-liquid flow rate ratio, Reynolds number, and Weber number predicted the Sauter mean diameter reasonably. Meanwhile, the hydrodynamic simulations were conducted for the generator by using various bubble breakage and aggregation kernels. The Lehr-Liao and Luo & Svendsen-turbulent model combinations were determined to predict the bubble dynamics performance well. The hydrodynamic simulations showed that the larger the liquid flow rate, the higher the turbulent dissipation rate, which resulted in a smaller bubble size. The work is helpful to the design and operation of the swirl flow microbubble generator.