Turbulent flow of liquid steel and argon bubbles in slide-gate tundish nozzles: Part II. Effect of operation conditions
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I. INTRODUCTION
THE tundish nozzle has an important influence on steel quality through its effect on the flow pattern in the mold, since the nozzle governs the speed, direction, and other characteristics of the jet entering the mold. There is great incentive to understand and predict the flow through the tundish nozzle, because its geometry is one of the few variables that is both very influential in the process and relatively inexpensive to change. Most previous studies have employed water models and plant trials to investigate how nozzle design and operation conditions affect flow in the mold and associated phenomena. Mills and Barnhardt[1] conducted experiments in freezing-water models to study the effect of nozzle design on the alumina entrapment mechanism inside the mold cavity. They found an improved flow pattern inside the mold cavity with the use of four-port nozzles rather than bifurcated nozzles. Tsai[2] measured pressure below the slide gate in water experiments and found that proper argon injection might avoid a partial vacuum and, hence, reduce air aspiration. Dawson[3] investigated inlet curvature and abrupt changes of the nozzle bore using water modeling and steel casting experiments. He found that these geometry changes should be avoided to eliminate flow separation in the nozzle and related problems. Tsukamoto et al.[4] investigated the effects of the inside and bottom shape of the submerged entry nozzle (SEN) on preventing uneven flow and on decreasing the alumina clogging at the lower part of the SEN, by using a water HUA BAI, Senior Research Engineer, is with the Dow Chemical Company, Freeport, TX 77541. BRIAN G. THOMAS, Professor, is with the Department of Mechanical and Industrial Engineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801. Manuscript submitted May 26, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS B
model. Gupta and Lahiri[5] performed water modeling experiments for nozzles with different port angles and bore diameters in free-fall and submerged jets. Honeyands et al.[6] performed water modeling experiments for SENs with various bore diameters, port angles, and heights and measured the jet angle and the effective port area. Sjo¨stro¨m et al.[7] performed an experimental study of argon injection and the aspiration of air into a stopper rod using liquid steel, and found that air aspiration could be reduced by increasing the argon flow rate or pressurizing the stopper. Previous mathematical modeling work to investigate how nozzle design and operation conditions affect the nozzle flow pattern and jet properties has been confined mainly to single-phase flow modeling.[8–11] Hershey, Najjar, and Thomas performed an extensive parametric study on singlephase flow in a bifurcated SEN. They found that the SEN port angle was the most influential variable controlling the jet angle entering the mold, and the jet always left the mold at a steeper downward angle than the SEN port angle. Shorter, thicker, and narrower ports forced the flow to conform more closely to the shape
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