Research On The Motion Characteristics Of Two-Phase Flow With Nitrogen/Carboxymethyl Cellulose Sodium Solution In Microchannel

Microfluidic technology involves many disciplines such as fluid,mechanical,chemical and biomedical.It has been widely used in many fields such as chemical engineering,biomedicine and national defense.It has been a hot topic for scholars at home and abroad.The research focus of microfluidic technology includes the generation,manipulation(transfer,fusion and breaking)of microdroplets/microbubble and their dynamic properties.Non-Newtonian fluids are ubiquitous in daily life and industrial production.In this paper,we study the flow characteristics of non-Newtonian gas-liquid two-phase flow in microchannels,namely nitrogen/carboxymethylcellulose sodium(CMC)solution.The aim of this research is to provide theoretical basis and technical support for the practical application of microfluidic technology.The main work is as follows:The high-speed camera system was used to study the bubble generation process of nitrogen/different CMC solution in T-junction microchannels.The effects of flow velocity,gas-liquid flow velocity ratio and solution concentration on the dynamic characteristics of bubble were analyzed.The flow field characteristics of the gas-liquid two-phase flow in the microchannel are numerically simulated by computational fluid dynamics.The study found that three flow patterns were observed in the T-junction microchannels,namely the plug flow,the slug flow and the slug-annular flow.The gas-liquid flow velocity ratio increases,the size of the bubble increases,and the generation period of the bubble becomes longer.The flow velocity increases,the bubble size increases,but the bubble generation period shortens.The CMC solution concentration increases,the bubble size is reduced,and the generation period of the bubble is shortened.Experimental studies were carried out on Y-junction microchannels with Gas-liquid phase inlet angle ranging from 300 to 150°.The gas and liquid phases were selected as nitrogen and 0.2wt.%CMC solutions respectively.The influences of Gas-liquid phase inlet angle,flow velocity and gas-liquid flow velocity ratio on the dynamic characteristics of bubble were analyzed.It is found that there are five flow patterns of plug flow,droplet flow,slug flow,slug-annular flow and jet flow in different gas-liquid phase inlet angle.As the gas-liquid phase inlet angle increases,the bubble size decreases first and then increases.The increase of the flow velocity will enhance the influence of the inlet angle of the microchannel on the size of the bubble.The motion process of the bubble at the bifurcation of the three-branch microchannel was observed by using the high-speed camera system.The effects of bubble size,flow velocity and microchannel branch angle on the dynamic characteristics of the bubble at the microchannel bifurcation were studied.The numerical simulation of the motion process of the bubble was carried out.The results indicated that there are five modes of motion in the three-channel microchannel.The smaller the bubble size,the easier the bubble is discharged from the middle branch.The larger the flow velocity,the easier the bubble is discharged from the side branch.In the 600 three-branch microchannel,the bubble splitting is easy to occur,and the effect of the flow field on the motion of the bubble is more significant.