| The discipline of the multiphase flow in microchannels is the micro-chemical technology development foundation. At present, scholars have studied multiphase flow mainly in the T shaped, Y shaped and cross shaped microchannels, but shown less concern to focused microchannel. Research shows that the inlet fluid can be hydrodynamically focused into a thin stream. However, researchers only observed the apparent phenomenon of liquid-liquid flow, detailed data in the microchannel is not studied. Besides, gas-liquid two phase flow condition in focused microchannel is not reported yet. Based on this situation, a focused microchannel with a reducing channel is designed in this paper. Liquid-liquid and gas-liquid two phase flows in the microchannel are simulated with FLUENT. VOF model is used for the simulation.The insoluble liquid-liquid two phase flow simulation is made with n-hexane and water. Phase distribution, velocity distribution, pressure distribution data are gained. The influence of pressure ratio of water to n-hexane on phase, velocity and pressure distribution, flux, membrane thickness is studied. The research results shows that n-hexane and water formed membrane in the microchannel. The existence of a low pressure area around the reducing channel makes n-hexane cone shaped expanding in the cross crea. A greater inertia force than viscous force is the key to the formation of thin film of n-hexane. The n-hexane velocity increases with the increase of pressure ratio, while the flux and membrane decrease with that. When the pressure ratio is smaller than 0.25 or greater than 1.025, the two fluids cannot form membrane in the microchannel.The gas-liquid two phase flow simulation is made with air and water. Phase distribution, velocity distribution, pressure distribution data are anticipated. The development of gas-liquid flow in the cross crea is analyzed. The influence of pressure ratio of water to air on phase, velocity and pressure distribution, flux, membrane thickness is studied. The research result shows that air and water formed membrane in the microchannel. However, low pressure area around the reducing channel is not found which makes air cone shaped shrinking in the cross crea. Pressure distribution and viscous force have a major impact on the membrane formation of air and water. The air velocity, flux, membrane thickness decrease when the pressure ratio becomes smaller. Compared to n-hexane, the pressure ratio change has greater effect on air flux. When the pressure ratio is smaller than 0.6 or greater than 1.05, the two fluids cannot form membrane in the microchannel.Research finds that nanoscale fluid membrane can be obtained in the focused microchannel. This membrane can intensify fluid mix, mass transfer, heat transfer and reaction process. The data obtained in the microchannel can provide theoretical basis for microchannel design and multiphase experiment. |
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