Analysis Of Mixing Behaviors Of Unbalanced Split And Recombine Micomixer With D-shaped Sub-channels

With the rapid development of microfluidic system,the micromixer has gained more and more attention and application as an important component of microelectromechanical system and the pretreatment device of microfluidic chip.According to whether additional power source should be added,the micro mixer can be divided into active and passive class.Compared to active micro mixer,passive micro mixer which can improve the efficiency of fluid mixing simply by changing the shape of micro channel structure to form a chaotic convection do not need any additional power,hence passive micro mixer is the main direction of current research.It is the best choice to improve the mixing efficiency by optimizing the microchannel structure and changing the flow state of the mixed fluid.In order to further improve the mixing efficiency of micro mixers in microfluidic control system,a D-typed asymmetric separation and recombination micromixer was designed based on the theory of asymmetric separation and recombination and multi-direction vortex system.Provided by computational fluid dynamics software ANSYS CFX,the flow channel geometry parameters as well as the number of micro mixer mixing unit which could influence flow characteristics and mixing efficiency was studied at different Reynolds number(Re = 1 ~ 80).The results show that the optimal mixing unit of the micro mixer is 6,and the optimal direction of the reducing pipe is the opposite direction of the mixed flow of the main channel.At the same time,the D-typed mixed flow channel forms extending vortex and Dean vortex system during the process of mixture,and in the stands at the junction of fluid intense collision occurs,to realize the superposition and strengthening of vortex system.when Re < 30,and the width ratio C=1.2the optimum mixing efficiency is obtained.When 30 < Re and is less than or equal to 40,the mixing efficiency of the three micro mixers is slightly different.When Re>40,the maximum mixing efficiency is about 96% because the secondary flow produced in the micro mixer when C=1 is the most obvious.The micro mixer was made of PDMS and Pyrex glass by microcomputer electrical processing technology,in which PDMS was the flow channel and Pyrex glass was cover plate.At the same time,a test bed was set up to carry out a hybrid experiment of asymmetric d-type separation and recombinant micromixer.The image of mixed steady state is taken by CCD camera and analyzed and compared with the mixed state diagram under the condition of the numerical simulation.Studies have shown that among the D-typed hybrid flow passage the mixed fluid collides increasingly acutely with the increase of Re number and the mixed state in the diagram taken by CCD camera and the status in numerical simulation are presented with good similarity.At the same time,the efficiency and pressure drop of micromixer measured by the experiment keep good consistency with those in numerical simulation,further proved the accuracy of the numerical simulation method adopted in this paper.