用CFD研究搅拌槽内的混合过程

CFD STUDY OF MIXING PROCESS IN STIRRED TANK

在CFX软件的基础上开发了用于混合过程计算的程序 ,并在流动场计算的基础上对单层涡轮桨搅拌槽内的混合过程进行了初步的数值研究 .对速度场和浓度场联立求解与单独求解两种处理方法分别进行了计算 ,计算得到的浓度响应曲线与文献数据趋势一致 ,两种方法计算的混合时间变化规律一致 ,联立求解计算得到的混合时间略小于单独求解 ,但是联立求解的计算量非常大 .计算结果表明 :混合过程与计算采用的流动场密切相关 ;混合时间大小不仅与监测点位置有关 ,还与加料位置有关 ,在搅拌桨附近加料混合时间最小 ,在槽底部加料混合时间最大 .

A program for mixing calculation was developed based on the commercial CFD code CFX. It was used in the numerical study of mixing process of a single Rushton turbine in the stirred tank. Coupled and segregated solutions of momentum and mass equation were adopted. The calculated concentration response curve was consistent with the literature data. Both solutions predicted the same change of mixing time, but the value of mixing time from coupled solution was shorter than that from segregated solution. Coupled solution needed much more computational efforts than segregated solution. The mixing process relied on the flow field used for mixing calculation. The value of mixing time was dependent on the position of detection and feeding. When the tracer was fed near the impeller, the mixing time was the shortest. When it was fed near the bottom of the tank, the mixing time was the longest.