Vertical Entrance Microchannel Gas-Liquid Two Phase Simulation

Due to scale characteristics, microchannel becomes the focus of the international forefront research area. It has been widely used in energy and power industry, chemical industry, biological and pharmaceutical industry. Compared to conventional bubble generate methods, bubble formation in microchannel has it unique advantage, regularity generation and high frequency during formation process. From current research method, the traditional means of experimental confined due to testing restrictions, and only can apply to qualitative analysis of quantitative descriptions of the phenomenon. The numerical method can descript detail physical phenomena in the solution and analysis. Simulation method has been used as the complementary method of experiment.Affected by some factors, such as the channel geometry, fluid boundary condition and material properties, bubble formation process is complex. The bubble generate mechanism in co-flow microchannel, T junction microchannel and flow focusing microchannel, due to channel geometry limiting the interface shape, has been researched widely and makes some conclusion. But the break-up mechanism of vertical entrance microchannel is not clear. Because the gas-liquid interface changes adaptively with the current flow condition, meanwhile the fluid flow influenced by the interface. So the flow condition is more complex.In the dissertation, VOF numerical method was used to study the gas bubble and gas slug break-up process in vertical entrance microchannel. Through the research on geometry model simplification, grid-scale sensitivity analysis, solving control parameters and solving model selection analysis, finally obtain ultimate experience on accurately simulating vertical entrance microchannel gas bubble and slug generate process. To verify the reliability of simulation result, made comparison with simulation and equipment results. The numerical simulation of vertical entrance microchannel on the bubble, gas slug formation mechanism studied in detail:according to flow regime of the bubbly flow, select the low and high gas-liquid flow ratio respectively, discussing formation of bubbles about different period. Finally draw the conclusion that the most important factors affecting bubble formation is the liquid shear effort on the gas phase; according to the flow regime of the slug flow, select the same gas and liquid flow ratio with different flow velocity, discussing the gas slug formation process. Finally draw the conclusion that gas slug generation mainly affected by liquid penetrating the slug neck.