Dynamics And Manipulation Of Bubble Formation In Slurry System In T-junction Microchannel

Microfluidic technology has attracted extensive attention over domestic and overseas in recent years due to its advantages of high safety performance,flexible and convenient operation,and low sample consumption.In this work,a high-speed camera was used to study the generation size,generation frequency,and generation dynamics of bubbles in the T-junction microchannel.The main results are as follows:The bubble generation frequency,bubble size of the channel in the glass bead slurry system in the T-junction microchannel were studied.The effects of dispersed phase and continuous phase flow rates,particle concentration on the bubble generation frequency,bubble size and pressure drop under the Taylor flow were studied.The results show that under slug flow,when the flow rate of the dispersed phase was constant,both the frequency of bubble generation and the pressure drop in the channel increased while the bubble size decreased with the increase of the flow rate of the continuous phase.When the flow rate of the continuous phase was constant,with the increase of the flow rate of the dispersed phase,the bubble generation frequency,bubble size,and pressure drop in the microchannels all increased.As the particle concentration was increased,the surface tension of the slurry would decrease,and the apparent viscosity would increase,thus the generation frequency and pressure drop of bubbles increased and the bubble size decreased.A prediction model of bubble generation size in slurry system in T-junction microchannel was proposed with good prediction accuracy.The dynamics of bubble formation in the shear-thinning slurry fluid was studied.The results show that the bubble generation process could be divided into three stages:expansion,squeezing and rapid pinch-off stages.In expansion stage,as the flow rate or concentration of the slurry increased,the maximum width of the bubble neck decreased,while the time of expansion was almost the same.In the squeezing stage and the rapid pinch-off stage,the variation of the minimum neck width of the dimensionless bubbles with the remaining time could be described by a power law relationship.As the continuous phases flow rates and slurry concentration increased,the power law indices of both stages increased.In addition,higher gas flow rate would lead to larger bubble size,generation frequency and pressure drop in the channel.Larger slurry flow rate could result in smaller bubble size but greater generation frequency and pressure drop.As the slurry concentration increased,the bubble size decreased,while the generation frequency and pressure drop increased.A prediction model of bubble size in shear thinning slurry in T-junction microchannel was proposed,which showed a good prediction performance.