Behavior Of Bottom Injecting Bubbles In Liquid

Gas-liquid two phase flow widely exists in steel making industry. Research on the phenomenon of bubble formation and their rising velocity in liquid is very important in order to utilizing gas-liquid reactor efficiently. The phenomenon of bubble formation decides the primitive bubble size in the system, whereas the rising velocity decides the characteristic contact time between the two phases which governs the interfacial transports phenomenon as well as mixing. In view of their importance, Research on behavior of bubbles in liquid has theoretical and practical significance.Behavior of bottom injecting bubbles was studied through physical experiment and numerical simulation. A set of pressure equipment was established in the laboratory. Photographs and videos of bubbles’ shape and movement were obtained though a digital camera, then Ulead Video Studio software and Photoshop software were used to analyze the images in order to study bubble rising velocity and bubble size under different pressure. In numerical simulation, Volume of fluid (VOF) method was presented featuring an interface reconstruction technique based on piecewise linear interface calculation (PLIC), and continuum surface force (CSF) model of Brackill was adapted to deal with surface tension which exist in the gas-liquid interface. A mathematical model of two-dimensional bottom injecting bubbles was established to analyze bubble formation, movement, coalescence and breakup, and bubbles behavior under different conditions were studied.The physical experiment results indicate that the rising trajectory of bubble’s diameter between 4mm and 8mm is spiral, and the rising trajectory of bubble diameter above 8mm is nearly linear. Bubble shape is more stable at higher pressure, and spherical bubble could be formed. The rising velocity of bubble will increase when the gas flow rate and orifice diameter increase, while bubble’s velocity will decrease when the system pressure increases. Bubble’s size will decrease when the system pressure increases. Moreover, Pressure has a more significant effect on bubble’s size when the orifice diameter is bigger. The orifice diameter plays a decisive role in bubble’s size.The process of bubble formation at the orifice, bubble movement in liquid and bubble breakup at the liquid surface were obtained through numerical simulation. The increased contact angle delays bubble detachment time at the orifice. Bubble’s diameter and bubble’s velocity will increase when contact angle, surface tension, gas velocity and orifice diameter increase, while bubble’s diameter will decrease when liquid density increase. Bubble’s velocity will decrease when liquid viscosity increases. Liquid viscosity has a litter effect on the bubble’s diameter. Co-axial and oblique coalescence of two bubbles rising in liquid were simulated, and the following bubble catches the leading bubble, then the two bubbles collide and formed a big oval bubble. The simulation of two bubbles at the same height is different from the co-axial and oblique coalescence, and the two bubbles cannot collide. Surface tension can efficiently sustain bubble shape. When surface tension is small, a big bubble in liquid may breakup and formed several small bubbles.