Rushton搅拌釜内的气含率分布及其流动特性的模拟  

Simulation for gas hold-up distribution and flow behavior in Rushton stirred tank

作　　者：李伟[1] 刘跃进[1] 孔丽娜[1] 韩路长[1] 

机构地区：[1]湘潭大学化工学院,湖南湘潭411105

出　　处：《化工学报》2011年第10期2691-2698,共8页CIESC Journal

基　　金：国家自然科学基金项目(20776121);湖南省高校环境友好催化与绿色化工工艺科技创新团队支持计划;湖南省高校绿色催化与反应工程重点实验室开发基金项目~~

摘　　要：利用雷诺应力模型结合多参考系法模拟了Rushton气液搅拌釜内的气液流动特性,得到了不同截面处气含率大小分布规律,并与γ射线CT实验所测得的结果做了比较,发现除排出流区CFD模拟值与实验值相差较大外,上循环区与下循环区都吻合得较好;结果表明排出流区的气含率最高,在搅拌桨高速旋转下,流体沿叶片端面急速排出,湍动也十分强烈。通过比较液相速度的径向分布侧形与轴向分布侧形可知:单相流的径向速度峰值更接近搅拌叶片的尖端,而两相流的径向速度峰值向外发生了平移;当达到临界状态后,自叶片端面向外的径向位置,通气量对液相速度的分布侧形几乎没有影响,但搅拌转速的影响却不能忽略;在叶片端面位置时,搅拌转速与通气量对径向速度的轴向分布影响较大,且通气量对液相径向速度变化的影响效果更加显著。Reynolds stress model was combined with the multiple reference frame （MRF） approach to simulate gas-liquid flow characteristics in a stirred vessel agitated by a Rushton turbine, and an array of gas hold-up distribution in different cross sectional places was obtained. The numerical simulation results were compared with the experimental data measured by a developed gamma ray computed tomography （CT） system. The CFD simulation results are in reasonable agreement with the experimental data except the discharge flow region. It is indicated that the gas hold-up distribution in the discharge flow region is higher than that in other regions. At high speed of rotary agitator, the fluid discharges rapidly along the surface of blade-tips, and the turbulent dispersion is extraordinarily intense. Radial and axial velocity distribution profiles of the liquid phase under different experimental conditions have been discussed. It is demonstrated that the maximum radial velocity of single-phase flow is closer to mixing blade-tips, while the maximum radial velocity of the two-phase flow has a small outward translation. After reached the critical condition, from the outward blade-tips to the wall, the velocity distribution profile of liquid phase is barely influenced by gas flow rate along radial position, but the influence of impeller rotation speed can not be neglected. On the blade-tip surface, both impeller rotation speed and gas flow rate have seriousinfluence on the axial distribution of radial liquid velocity, and the effect of gas flow rate is more significant than impeller rotation speed.

关 键 词：雷诺应力模型 气液流动 气含率分布 速度分布 

分 类 号：TQ028.8[化学工程]