布置成涡结构微混合器内的流动与混合特性

Fluid flow and mixing characteristics in micromixer with vortex-generated structures

基于成涡结构强化混合原理设计了一种改进型的平面被动式微混合器。采用商业软件CFD-ACE+对该结构微混合器的混合特性进行了三维数值模拟和结构优化,进一步揭示该微混合器结构对通道内流体流动与混合特性的影响。结合混合通道内流体的浓度和流型分布的数值和实验结果可知,该新型微混合器在布置成涡结构的弯曲通道内形成了扩展涡、分离涡和Dean涡,实现了涡系的叠加和强化,加大了流体间的扰动,从而增加了流体的接触面积强化混合;在综合考虑流体混合强度和压降分布等因素下,成涡结构正向布置且缝宽比Wd/W=1/4,厚宽比B/W=3/10,布置角度θa=120°的该微混合器在较广Re范围内的混合效果显著。

A design for modified planar passive micromixer based on the concept of vortex-generated structure enhanced mixing is described in this work.By using computational fluid dynamics CFD-ACE＋,three-dimensional numerical simulation and structural optimization for mixing were performed in order to reveal the structural influence on the flow feature and mixing characteristics.Experimental data were used to validate the numerical analysis.The computational and experimental results for the concentration distributions and flow patterns demonstrate that the expansion vortices,separated vortices and Dean vortices appear in the curved channel of this modified micromixer,which is arranged to vortex-generated structures.The combination and enhancement of the vortex system increase the fluid disturbance,effectively improving the contact area of fluid and accelerating the mixing process.Based on comprehensive consideration of mixing efficiency and pressure drop distribution,the structural design adopts the vortex-generated structure with regular arrangement,and the gap width ratio Wd/W,thickness-width ratio B/W,and arrangement angle θa are equal to 1/4,3/10,and 120°,respectively.Significant mixing effect of fluid in the micromixer can be realized in a wide range of Reynolds number.