Simulation of Bubble Behavior in a Water Physical Model of an Aluminum Degassing Ladle Unit Employing Compound Technique
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one of the most important dehydrogenation technologies of molten aluminum,[1,2] the rotating impeller degassing technique has been widely investigated in the degassing industry, which can improve the metallurgical quality of aluminum alloy significantly.[3,4] To further explore the factors that affect purification, water modeling and numerical simulation have been recognized as useful tools to clarify stirring phenomena occurring in the melting tank, based on the geometric similarity, kinematic similarity, and dynamic similarity.[5–8] Although the effects of rotor speed, gas flow rate, and type of rotor on the fluid flow and vortex formation were discussed based on Eulerian two-phase mode, the concrete shape of bubbles has not been studied. However, the morphology and distribution of bubbles are closely related to the degassing efficiency of the melt (according to the Fick¢s law,[9] boundary layer theory,[10] and surface renewal theory,[11] there are mainly three ways to improve the efficiency of
GUILI GAO, MING WANG, DEQUAN SHI, and YINGFANG KANG are with the School of Materials Science & Engineering, Harbin University of Science & Technology, Harbin 150040, P.R. China. Contact mail: [email protected] Manuscript submitted October 25, 2018. Article published online May 29, 2019. METALLURGICAL AND MATERIALS TRANSACTIONS B
purification: a. Increase the number of bubbles, b. decrease the bubble size, c. Prolong the bubble path). Hasan[12,13] made an experimental study on single bubble breakage in a stirred tank, qualitative and quantitative results were obtained for the effect of Reynolds number and mother bubble size on the breakage probability, breakage time, number of daughter bubbles, and the sizes of the daughter bubbles in 2017, and subsequently, trajectories of the bubbles were analyzed and quantified in 2018. Nevertheless, there are few studies with respect to their numerical simulations because of the large amount of computation. Ultrasonic degassing is an environmentally friendly and relatively inexpensive technique, in which high-intensity ultrasonic vibrations are used to generate alternating pressures.[14,15] The alternating pressure above the cavitation threshold can lead to numerous cavities in the liquid metal, thus strengthening mass transfer processes, which accelerates the diffusion of hydrogen from the melt to the existing bubbles.[16] The majority of investigations associated with ultrasonic degassing are based on the changes of frequencies and intensity vibrations through analyzing the effect of ultrasound on metallographic structure.[17,18] The ultrasonic-argon degassing is a highly efficient process both for hydrogen removal and microstructure refining.[19,20] In order to further investigate the impact of ultrasound in rapid degassing involving cavitation and bubble interaction, Liu et al.[21] proposed a water VOLUME 50B, AUGUST 2019—1997
modeling on the behavior of an argon bubble in ultrasonic field, indicating that the argon bubble can be broken up and refined by the ultrasound. Ma et al.[22] combined exp
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