立式双桨搅拌槽内液-液分散特性的CFD-PBM模拟

CFD-PBM SIMULATION OF LIQUID-LIQUID DISPERSION IN DOUBLE-LAYER STIRRING TANK

将破碎核函数应用于群体平衡模型(PBM)中,并与计算流体力学(CFD)方法进行耦合,开展了不同类型搅拌桨组合下搅拌槽内液滴尺寸分布和液-液分散特性的模拟研究。结果表明:推进桨(TXL)可促进流体的轴向混合,涡轮桨(RT)有利于流体分散,不同搅拌桨组合下的流场特征存在显著的差异;相同转速下抽吸桨(PM)+TXL组合桨拥有较小的功率消耗,而RT+RT组合桨的功率消耗较大;挡板的存在能够有效促进液滴破碎,且挡板对PM+RT组合桨搅拌下分散性能的影响显著大于另外两种搅拌桨组合。基于本研究结果,在双层桨搅拌槽的工业应用中,应首先考虑挡板的应用,在对液滴分散性能要求较小时,应优选带轴流型的PM+TXL组合桨;在对液滴分散性能有较高的要求时,应优选带档板的PM+RT组合桨。

The fragmentation kernel function was applied to the population balance model(PBM)and coupled with computational fluid dynamics(CFD)method to simulate size distribution and liquid-liquid dispersion characteristics of droplets in the stirring tank under different types of impeller combinations.The results showed that the propeller(TXL)could promote the axial mixing of the fluid,while the turbine paddle was beneficial to the dispersion of the fluid.Meanwhile,there were significant differences in the flow field characteristics under different impeller combinations.At the same rotating speed,the suction(PM)+TXL combined oars had smaller power consumption,while the RT+RT combined oars had larger power consumption.The presence of baffles could effectively promote droplet breaking,and the stirring performance of the PM+RT combined oars was largely enhanced by the baffle.Moreover,simulation results showed that the dispersed phase was rapidly broken into small-sized droplets in the first few minutes,and then the droplet diameter became stable with the evolution of the operating time.Based on the results of this study,the application of baffle should be considered first in the commercial application of double impeller stirring tank.When the droplet dispersion performance was not required,the PM+TXL combined impeller with axial flow type should be preferred;when high droplet dispersion performance was required,the PM+RT combined impeller with baffle plate should be preferred.