Velocity and turbulence measurements in a cylindrical bath subject to centric bottom gas injection
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I.
INTRODUCTION
M A N Y theoretical investigations have been undertaken to predict fluid flow behavior in metallurgical reactors subject to gas injection) ~-Sj The flows are usually highly turbulent and the two-equation turbulence models such as the k-e model are usually used to calculate the mean and turbulence components. Fluid flow behavior in the recirculation region can be predicted with sufficient accuracy, 161while theoretical results obtained in the bubbling jet have not received experimental confirmation. 17,81 The present study was made to offer fundamental data and empirical correlations for examining the validity of theoretical predictions. The velocity and turbulence components in the axial, radial, and tangential directions in a cylindrical water bath agitated by centric bottom air injection were measured using a two-dimensional laser Doppler velocimeter (LDV) system.
II.
EXPERIMENTAL APPARATUS AND PROCEDURE
A. Experimental Apparatus Figure 1 shows a schematic of the experimental apparatus. Two cylindrical vessels with inner diameter D of 126 and 200 mm, made of transparent acrylic resin, were used to examine the effect of bath size on the liquid velocity. These vessels were separately used. The bath height, Hw, in the smaller vessel is 233 ram, and the height of the larger vessel is 300 mm. The inner diameter of the nozzle, d,, is 1, 2, or 5 mm. Measurements MANABU IGUCHI, Associate Professor, is with the Department of Materials Science and Processing, Faculty of Engineering, Osaka University, Suita, Osaka, 565 Japan. TSUNEO KONDOH, formerly Graduate Student, Osaka University, is Researcher, with Sumitomo Metal Industries, Ltd. Wakayama, Japan. ZEN-ICHIRO MORITA, Professor Emeritus, and KEIJI NAKAJIMA, Senior Researcher, are with Iron and Steel Research Laboratories, Sumitomo Metal Industries, Ltd., Amagasaki, Hyogo 660, Japan. KAZUHARU HANAZAKI, Senior Researcher, is with Sumitomo Metal Industries, Ltd., Kashima, lbaragi. TOMOMASA UEMURA, Professor, is with Kansai University, Suita, Osaka, Japan. FUJIO YAMAMOTO, Professor, is with Faculty of Engineering, Fukui University, Fukui 910, Japan. Manuscript submitted December 21, 1992. METALLURGICAL AND MATERIALS TRANSACTIONS B
were made mainly for d, = 2 mm. Air was injected through a single-hole centric bottom nozzle into a water bath using a compressor equipped with a filter. The air flow rate was adjusted from 10.0 to 160.0 c m 3 / s with a mass flow controller. Further information on the experimental conditions is described in the figures.
B. Measurement of Mean Velocity and Turbulence Components The coordinate system is shown in Figure 2. The axial, radial, and tangential coordinates are denoted by z, r, and 0, and the velocity components in these directions are represented by u, v, and w, respectively. The three velocity components were measured using a twodimensional LDV system. A small amount of ordinary dairy milk was used to feed seeding particles. Since the flow is highly turbulent, the output signal of u, for example, changes with time,
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