双层涡轮桨搅拌槽内混合过程的数值模拟

Numerical Simulation of Mixing Process in Stirred Tanks with Dual Rushton Turbines

采用FLUENT软件对双层六直叶涡轮桨搅拌槽内的混合过程进行了数值模拟,选用RNG标准κ-ε模型及多重参考系法(MRF),通过改变网格策略,增加网格数量,并降低浓度收敛残差的方法,将速度场与浓度场方程分开求解,预测了不同的加料点、监测点位置及操作条件对混合时间的影响规律。模拟结果表明:搅拌功率的模拟值与实验值吻合良好,但由于模型基于各向同性的假设,且双层六直叶涡轮桨两桨之间子域的存在,混合时间的模拟结果与实验值有较大的误差。

The mixing process in a stirred tank of 0. 476 m diameter with dual six-blade Rushton turbine （DT-6） was numerically simulated using computational fluid dynamics （CFD） package FLUENT 6.0. The RNG κ-ε turbulent model and multi-reference frame were used in the simulation. By changing the meshing technology, increasing the number of mesh and decreasing the residual discrepancy, the effects of tracer feeding and detecting positions on mixing time were investigated. The momentum and mass equations were computed separately. The shaft power predicted by CFD is in a good agreement with experimental results. Although the mixing time predicted by CFD is better than that reported in literatures, it is still about two times higher than that obtained by experiment.