台阶式并行微通道内液液两相流流型及其转变机理

利用高速摄像仪研究了台阶式并行微通道内液液两相流流型及其转变机理。以甘油水为分散相、含3% Span 85的环己烷为连续相，观测到了滴状-滴状流、过渡-滴状流、喷射-过渡流和喷射-喷射流4种流型；以两相流量为坐标轴绘制了流型图，并获得了流型转变线；分析了流型的转变机理。考察了分散相黏度对流型及其转变的影响机制。随着分散相黏度的增大，流型转变线整体向下移动，滴状-滴状流区域变小，喷射-喷射流区域变大。最后，运用介尺度概念分析了并行微通道内液液两相流非均匀结构的动态效应。

Study on the flow patterns and transition mechanism of the liquid-liquid two-phase flow in a step-emulsification microdevice with parallel microchannels

The flow patterns and transition mechanism of liquid-liquid two-phase flow in a step-emulsification microdevice with parallel microchannels are studied by using a high-speed camera system. The aqueous glycerol solutions are used as the dispersed phase, and cyclohexane with the surfactant of 3% Span 85 as the continuous phase. Four flow patterns are observed under different two-phase flow conditions: dripping-dripping, transition-dripping, jetting-transition, jetting-jetting. The diagram of flow patterns is constructed with the flow rates of the two-phase as the coordinate axes, and the transition lines of the adjacent flow patterns are obtained. The transition mechanism of flow patterns is analyzed. The influences of the viscosity of the dispersed phase on the flow patterns and their transitions are investigated. The flow patterns of the liquid-liquid two-phase flow are mainly affected by the hydrodynamic feedback effect in the chamber, the operating conditions and the physical properties of fluids. As the flow rate of the dispersed phase increases, the flow pattern in the microchannel changes from the dripping to the transition flow, and finally into the jetting. With the increase of the flow rate of the continuous phase, the flow rate of the dispersed phase that changes the flow patterns increases. As the viscosity of the dispersed phase increases, the transition lines of flow patterns move downward, the region of the dripping-dripping becomes smaller, and the region of the jetting-jetting becomes larger. Finally, using the concept of mesoscale, the dynamic effects of the non-uniform structure of liquid-liquid two-phase flow in parallel microchannels are analyzed.