磁性微混合器混合性能的实验研究

自装配磁性微混合器是利用聚合的磁流体在旋转磁场作用下的运动,来破坏流体的层流状态,产生混沌对流而加强流体间的混合.利用Micro-PIV对不同磁场强度、旋转频率和流量下的混合效率进行了实验研究,结果表明:在保证外磁场能带动磁流体聚合链运动的前提下,磁场强度对混合效率的影响不大;而外磁场的旋转频率对混合效果有较大的影响,当旋转频率较低时混合效率随旋转频率升高而提高,而当旋转频率超过临界频率时,由于粘性拖曳力克服了磁场力,磁性颗粒的聚合被破坏,使混合效率反而下降.为磁性微混合器的设计提供基础.

Experimental research on mixing efficiency in magnetic micro-mixer

The movement of the aggregated magnetic fluid, which is cased by the rotation of the external magnetic field,will break the laminar flow in order to result in the chaos and improve the mixing efficiency. Micro-PIV experiments with varying magnetic field,rotation frequency and flow rate were carried out. The experimental results show no obvious effect of the external magnetic field when the external magnetic field is strong enough to rotate the aggregated chain. However,the rotation frequency influence the mixing efficiency greatly, the mixing efficiency increase with the increasing of the rotation frequency when the rotation frequency is below a critical value ,and the mixing efficiency will decrease with the increasing of the rotation frequency when the rotation frequency being above the critical value, because the viscous dragging force dominate over the magnetic force,and the aggregated chains are broken. It is helpful to design magnetic micro-mixer.