Abstract: Isolated mixing region often appears in the high-viscosity fluid with laminar flow in a stirred vessel, reducing fluid mixing efficiency. Diminishing or eliminating isolated mixing region improves the mixing efficiency and reduces mixing energy consumption. Experimental and computational studies were carried out to compare the flow field structures with rigid Rushton turbine impeller (rigid RT impeller) and rigid-flexible Rushton turbine impeller (combination RT impeller). Analyses were carried out on axial, radial and tangential velocity vector plots, velocity contours and velocity distribution scatter plots at the same time power consumption (3 kW·m^-3）with these two impellers. Results show that the energy concentrates at the tip of rigid RT impeller and the fluid velocity away from the impeller is small, even at 0 m·s^-1, while for combination RT impeller, the energy distributes well in the stirred tank so that the fluid gains certain velocity everywhere. The numerical simulation results agree with experimental results. The combination RT impeller improves mixing efficiency by eliminating isolated mixing regions, while rigid RT impeller presents a poor mixing efficiency since isolated mixing regions always exist.

Key words: mixing, chaos, stirred vessel, rigid-flexible impeller, numerical simulation

摘要： 高黏度流体处于层流状态时，普遍存在的混合隔离区，降低了流体的混合效率。减小或消除隔离区，是实现流体高效混合的基本途径。采用实验研究与数值模拟相结合的方法，对刚性六直叶涡轮桨（刚性桨）和刚柔组合六直叶涡轮桨（组合桨）的流场结构进行研究，对比分析了两种桨叶在相同功耗（3 kW·m^-3）时的轴向、径向和切向的速度矢量图、速度云图以及速度分布散点图。结果表明，刚性桨的能量集中在桨叶尖端部分，远离桨叶区域的流体速度很小甚至为0 m·s^-1；而组合桨可将能量从桨叶尖端扩散至全槽，使槽内流体均具有一定的流速，提高了混合效率，且显色实验与数值模拟结果一致，组合桨体系的混合隔离区在短时间内就可消除，混合良好，而刚性桨体系的混合隔离区始终存在，混合效果不佳。

关键词: 混合, 混沌, 搅拌槽, 刚柔组合桨, 数值模拟