Dynamics And Controllability Of Droplets Fusion Under Gas-liquid-liquid Three-phase Flow In A Microfluidic Reactor

Gas-liquid-liquid three-phase flow system has unique advantages in controlling reagents manipulation and improving reaction performance.There still remains lack of insight into the mechanism of droplet fusion,and the understanding of gas-liquid-liquid three-phase microfluidics are more stable than two-phase in reagent addition is still ambiguity.A microfluidic reactor with three T-junctions was employed to study the hydrodynamics of bubble/droplet formation process and the fused time rule.The mainly conclusions are as the following parts.1.The formation of the bubble can be divided into two stages: the growth stage and the collapse stage.The forces that dominate the formation of bubbles or droplet are different at different stages.The influence of fluid viscosity and flow rate on the size of bubbles is appreciably,and the interfacial tension has little effect on the size rule.The stability of bubble formation determines the uniformity of dispersed droplet size.2.The formation of the droplet can be divided into the growth stage and the collapse stage as well.The shedding of droplet is affected by the continuous phase shear force and the extrusion pressure of the gas-oil interface.The effect of low concentration surfactant on droplet size can be neglected.3.The formation of second dispersed aqueous phase at the third T-junction is accompanied by the droplets fusion process.The phase diagram of droplet fusion under different experimental conditions is obtained.The results show the prerequisite for droplet fusion is that the continuous phase between two droplets can be discharged rapidly,and the increase of gas phase flow can accelerate the discharge.The size of fused droplet is very uniform and the coefficient of variation is less than 1% in this work,which also indicates that the system is very stable.4.The droplet fusion in two phase and three phase systems is compared,the results show that the three phase microfluidic is easier to form droplet flow or slug flow than the two phase flow,and the flow range of directly adding reagent is wider.The droplet size is more uniform after fusion in three-phase flow,which is because the gas in the three phase has a strong compressibility,which can well reduce the external interference to the system and the droplets can still fusion under the condition of large flow injection.