Abstract:

In order to reduce the mixing isolation zone, increase the chaotic mixing zone and enhance the fluid chaotic mixing process, based on the self-similarity of fractal theory, a stirring impeller with fractal-arranged perforated holes to enhance the fluid chaotic mixing behavior was proposed. The power consumption characteristics, velocity distribution, shear strain rate distribution, isolation zone structure and Poincare section during the fluid mixing process were investigated by using computational fluid dynamics (CFD) combined with experiments. The results showed that FAPT impeller could effectively reduce the power consumption and power number compared with RT at the same Reynolds number, and the power consumption and power number could be further decreased with the increase of fractal iteration number of perforated holes. Compared with RT system, the power number of FAPT-1 system was reduced by 6.57%—12.50%, the power number of FAPT-2 system was reduced by 10.95%—19.32%, and the power number of FAPT-3 system was reduced by 15.25%—24.66%. FAPT impeller could enhance the shear effect on the fluid, increase the shear strain rate of fluid, reduce the isolation zone, shorten the mixing time, and improve the fluid mixing efficiency compared with Rushton turbine under the same power consumption, and this effect was more obvious with the increase of fractal iteration number of perforated holes.

Key words: fractal-arranged perforated impeller, mixing, flow field, computational fluid dynamics

摘要：

为减小混合隔离区、增大混沌混合区、强化流体的混沌混合过程，基于分形理论的自相似特性提出一种具有分形排布式穿流孔的搅拌桨强化流体的混沌混合行为。采用计算流体力学（CFD）和实验相结合的方法探究了流体混合过程中的功耗特性、速度分布、剪切应变率分布、隔离区结构以及Poincare截面。研究结果表明，在相同Reynolds数下，与Rushton桨相比，分形排布式穿流搅拌桨（FAPT）能够有效降低搅拌功耗和功率准数，而且随着穿流孔分形迭代次数的增加，搅拌功耗和功率准数进一步降低。其中，FAPT-1体系的功率准数降低6.57%~12.50%，FAPT-2体系的功率准数降低10.95%~19.32%，FAPT-3体系的功率准数降低15.25%~24.66%。在相同功耗下，与Rushton桨相比，FAPT桨能够增强对流体的剪切作用，增大剪切应变率，减小混合隔离区，缩短流体的混合时间，提高流体的混合效率，而且随着穿流孔分形迭代次数的增加这一效果更为明显。

关键词: 分形排布式穿流搅拌桨, 混合, 流场, 计算流体力学