连续高速分散混合器内的流体力学性能——Ⅱ.数值模拟

Hydrodynamic Characteristics in a Continuous Rotor-Stator Mixer——Ⅱ.Numerical Simulation

采用计算流体力学(CFD)方法研究连续高速分散混合器(CRS)的流体力学特性.采用FLUENT6.2软件,选用标准k-ε模型和滑移网格(SM)法,对CRS进行三维流动场的数值模拟.功率消耗的预测值与实验结果吻合良好,随雷诺数的增大功率准数NP基本不变,其模拟值为5.99,与实验的误差为13.7%.在中小流量下,水力学性能的模拟值与实验值吻合较好,但较高流量下由于液沫夹带而无法准确预测.模拟结果表明,CRS的最大泵送效率仅为13%,其功率消耗主要用于物料高效剪切混合;混合腔内的宏观流动场、剪切速率及湍流耗散率均呈非对称分布;对应转子不同的几何位置,定子槽内产生流型不同的漩涡,模拟结果与文献数据相吻合.研究结果可为工业CRS的优化设计提供参考.

The hydrodynamic characteristics in a continuous rotor-stator mixer （CRS） were numerically simulated by using computational fluid dynamics （CFD） package FLUENT 6.2 with the SIMPLE algorithm in this work. The standard k-ε model and sliding mesh （SM） method were used in the simulation. The power number Np was constant with variation of Reynolds number Re, and the calculated Np equaled 5.99, the calculation error was 13.7% compared with the experimental value. The hydraulic characteristics under the lower flow rate conditions predicted by CFD are in good agreement with experimental data, though they are unable to be predicted reasonably under the larger flow rates because of the liquid entrainment. The results show that the maximum efficiency of the pumping capacity of CRS is only about 13%, and the power consumption is mainly used for high shear mixing. The predicted flow field and the distribution of shear rate are asymmetric, and each stator slot has a different circulation and re-entrainment pattern as the rotor is passing by the stators, which is in agreement with the literature. The results are of reference to the optimum design of industrial CRS.