湍流分散体系中液滴破碎频率模型的黏性修正

Modified viscosity model of droplet breakage frequency for turbulent liquid-liquid dispersions

在分析研究分散相黏度对液滴变形和破碎影响的基础上,提出了一个改进的液滴破碎频率模型并拓展了液滴破碎判据标准.同时通过MonteCarlo模拟的随机方法,得到了湍流搅拌槽中液-液分散体系的液滴直径分布和Sauter平均直径d32.通过与文献中关于d32的实验结果比较发现,该模型预测的Sauter平均直径更接近实验值,对于黏性分散相改进的液滴破碎频率模型要优于Coulaloglou和Tavlarides提出的模型.计算结果表明对于黏性分散相液滴,其黏度限制了液滴变形,使得液滴破碎频率被大大减少,液滴直径明显增加,液滴直径分布向右偏移.

A new droplet breakage criterion and a modified model of droplet breakage frequency which account for the effect of dispersed phase viscosity on drop deformation and breakage were presented. By the stochastic approach of Monte Carlo simulation the drop size distribution and Sauter mean diameter d32 in turbulent agitated liquid-liquid dispersions were obtained. The calculated results showed that predicted values of d32 were in better agreement with the experimental ones reported in literature, so the modified droplet breakage frequency model is superior to that proposed by Coulaloglou and Tavlarides in the case of viscous dispersed phases. The calculated results also showed that for viscous dispersed phases the viscosity of dispersed phase would restrict droplet deformation and drop breakage frequency would be decreased considerably. Consequently drop sizes would increase obviously and drop size distributions would also be shifted to the right.