The spout of air jets upwardly injected into a water bath
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I.
INTRODUCTION
A
gas-stirred melt can be considered to consist of three regions: a single-phase zone of recirculating liquid, a twophase zone of gas dispersed in liquid, and a spout where the gas discharges from the bath. Most of the theoretical and experimental work to date has been carried out on the liquid zone, the gas-liquid region close to the injection point, and the two-phase zone. Thus, our understanding of the process of bubble formation, the regimes of gas discharge, velocity/turbulence fields, and mixing of liquids has improved considerably in the past few years. However, the spout region of gas jets in liquids has received little attention, even though it has both theoretical and practical significance. In ladle furnaces, for example, the gas-liquid plume rising through the bath generates turbulence in the upper portion of the vessel, which enhances the kinetics of the reactions at the slagmetal interface. The turbulence in the spout region also increases the absorption of oxygen and nitrogen by the bath. Notwithstanding its importance, the spout region has been neglected in mathematical recirculatory flow models that have been developed for gas-stirred baths, since it has been generally assumed that the bath has a flat top surface; but this reduces the accuracy of the predictions of velocity and kinetic energy, particularly close to the spout region. Owing to its significance in practical gas-stirred systems, the spout of a submerged jet is the focus of the present study. This paper describes the experimental characterization of the spout and presents the resulting correlations of gas fraction with axial and radial position for different gas flow rates. The correlations have been incorporated into a mathematical model of turbuV. SAHAJWALLA, formerly Graduate Student, is Research Engineer with J.K. BRIMACOMBE, Stelco/NSERC Professor and Director of The Centre for Metallurgical Process Engineering, The University of British Columbia, Vancouver, BC. A.H. CASTILLEJOS, formerly Postdoctoral Fellow, The Centre for Metallurgical Process Engineering, is with Centro de Investigacion y de Estudios Avanzados del IPN, Carr. Saltillo, Monterrey Km, 13 Apdo., Postal No. 663, 25000 Saltillo, Coahuila, Mexico. Manuscript submitted November 10, 1988. METALLURGICAL TRANSACTIONS B
lent recirculatory flow in a gas-stirred liquid, the results of which will be presented in a forthcoming publication, together with the practical bearing of the spout on the gas-injection process. II.
PREVIOUS WORK
A comprehensive review of the literature has revealed that the spout has received little attention by previous researchers, as pointed out earlier. Gray et al. m have qualitatively described the formation of two important regions in the upper portion of a gas-stirred bath, namely, a disengagement zone and a splash zone. Splashing and spitting were studied by Paul and Ghosh ~2] for various tuyere arrangements in physical models of the LD and Q-BOP processes, and comparisons between them were drawn. The LD process was found to
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