为了研究 T 型微通道入口角度对非牛顿微液滴制备影响，采用流体体积(VOF)模型对聚丙烯酰胺水溶液微液滴形成过程进行数值模拟，开展高速数码显微实验对数值模拟结果进行验证。结果表明:在相同工况条件下，非牛顿微液滴生成频率随着分散相入口角度的增大呈先增大后减小的趋势，相对长度呈现先减小后增大的趋势。在入口角度小于 90°时，随着入口角度的增加，微通道内两相平均压差、液滴断裂时刻两相压差最低值随之升高，在入口角度大于 90°时，上述压差则随着入口角度的增加而降低。考虑两相体积流量比与连续相毛细数并引入关于分散相入口角度的修正系数，提出聚丙烯酰胺水溶液微液滴相对长度预测公式，为剪切变稀流体微液滴制备提供参考。
Effects of T-junction microchannel entrance angles on the preparation of shear-thinning fluid microdroplets
In order to study the effect of T-junction microchannel entrance angle on the preparation of non-Newtonian microdroplets,the fluid volume model was used to simulate microdroplet formation processes of polyacrylamide aqueous solution,and the accuracy of the numerical simulation results was verified by high-speed digital microscopic experiments.The results show that under the same operating conditions,the frequency of non-Newtonian microdroplet generation tends to increase and then decrease with the increase of dispersed phase inlet angles,while the relative length tends to decrease and then increase.When the inlet angle was less than 90°,the average pressure difference between the two phases in the microchannel and the lowest pressure difference at the time of droplet breakup increased with the increase of the inlet angle,and the above pressure difference decreased with the increase of the inlet angle when the inlet angle was higher than 90°.A formula for predicting the relative length of microdroplets of polyacrylamide aqueous solution was proposed considering two-phase flow ratios and the continuous phase capillary numbers,together with the correction coefficient of dispersed phase inlet angles,which provides reference for the preparation of shear-thinning fluid droplets.
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