Bubble Formation at a Submerged Orifice for Aluminum Foams Produced by Gas Injection Method
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THE process of bubble formation in liquid metals is always a problem in industries using liquid metal refining techniques.[1,2] Many investigations were employed to obtain the accurate prediction results of bubble size.[3,4] Generally, many factors affect the final bubble size, including gas flow rate, size and shape of nozzle, gas chamber volume and pressure, physical and chemical characteristic of gas and liquid, etc.[5–10] Since Hughes et al.[11] made an analogy between the gas circuit and the electric circuit to predict the bubble size and developed a coefficient Nc (capacity number) to represent the effect of gas chamber on the bubble formation, many publications[12–14] have proposed modified equations to predict the bubble size, in either water or liquid metal system. Besides, Davidson and Amick[15] and McCann and Prince[16] considered that the bubble formation patterns, i.e., double bubbling and bubble coalescence, should be taken into account to improve the prediction results. Gerlach et al.[17,18] and Martin et al.[19] simulated the bubble’s formation and detachment process dynamically, such as the shape, height, and volume of the bubble. Among various models for bubble formation process, Kumar’s two-stage model[20–22] simulated the growth and detachment of the bubbles clearly at both constant and inconstant flow and pressure. Wraith[23] investigated the influence of gas kinetic energy on the bubble formation and established a theoretical model to
XUELIU FAN, Master Degree Candidate, XIANG CHEN, Associate Professor, XINGNAN LIU, Ph.D. Student, HUIMING ZHANG, Master Degree Candidate, and YANXIANG LI, Professor, are with the Department of Mechanical Engineering, Tsinghua University, Beijing 100084, P.R. China. XIANG CHEN, Associate Professor, and YANXIANG LI, Professor, are with the Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084, P.R. China. Contact e-mail: [email protected] Manuscript submitted March 7, 2011. Article published online September 26, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
predict the bubble size. Gnyloskurenko and Nakamura[24] studied the contact angle during bubble formation in water and metal system successfully, although they did not mention any formula in their literature. Although some formulas and equations have been obtained to predict the bubble size, few publications have studied bubble size in the process of aluminum foam by gas injection directly. In this study, a theoretical model is developed for bubble formation in aluminum alloy melt with introduction of air. Some parameters affecting the bubble formation, such as gas flow rate, orifice diameters, and gas chamber pressure and volume, are investigated, and the average cell size in the foams can be predicted in the producing process of aluminum foam by the gas injection method.
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MODEL FOR BUBBLE FORMATION IN LIQUID
According to the literature,[2] the three bubbling regimes remain in liquid: static regime, dynamic regime, and turbulent regime and the transition between
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