Generation of micro-nano bubbles by self-developed swirl-type micro-nano bubble generator

The fabrication of bubble generator with high micro-nano bubble generation efficiency has always been challenging. Strong turbulence is considered to be beneficial. Herein, we developed a swirl-type micro-nano bubble generator by equipping a variable-pitch spiral cavitation reactor to enhance the shear breakage effect of bubbles. The variable-pitch spiral guide vanes and central column were innovatively installed into the cavitation reactor to generate swirling liquid flow so as to intensify gas-liquid contacting and mixing. The effect of geometric parameters on the flow field structure was investigated through numerical simulations and the optimum structure was obtained. Then the lab-scale swirl-type micro-nano bubble generator was manufactured to conduct flow tests. The bubbles with size down to 0.301 μm were generated. In addition, the bubble generator displayed superior oxygen enrichment capacity, which was higher than that of the traditional venturi tube. The insights from this study provide a guideline for the development of efficient micro-nano bubble generators.