Measurement and modeling of turbulence in the gas/liquid two-phase zone during gas injection
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I.
INTRODUCTION
B U B B L Y plumes produced by the injection of gas into liquids are common to a number of industrial processes: bubble columns in chemical engineering, the destratification of lake water, and bottom-stirred metallurgical processes. Recently, great efforts have been made to understand various metal-refining processes involving plumes, such as ladle stirring and bottom stirring processes for oxygen-blowing converters and electric arc furnaces. Water models have proven to be invaluable to simulate injection into full-scale metallurgical vessels. Research with water models has yielded the following information: (1) Experimentally measured void fraction and bubble frequency distributions; tl-51 (2) Measured mean liquid patterns outside the two-phase region with laser Doppler anemometer (LDA) or other velocity-measuring tools; [6-8~ (3) Computer simulation of flow patterns with mathematical models which were originally developed for single-phase flOWS. [9-121 Since the most intensive mass and heat transfer occurs in the two-phase plume region, it is vital to acquire more knowledge of the behavior of both phases in this region. In the present work, an experimental technique developed by the present authors for the discrimination of gas and liquid velocities is utilized to measure the mean and turbulent components of the liquid velocity. ~j31 Without effective discrimination of the velocities, LDA or hotfilm anemometry data within the two-phase region cannot be interpreted properly. [141In the metallurgical literature related to water models of gas injection into liquid metals, no discrimination techniques have ever been reported. Thus, the present work provides the first opportunity to compare measured mean velocities and turbulent kinetic energy distriubtions with those that can be Y.Y. SHENG, Postdoctoral Fellow, and G.A. IRONS, Professor and Chairman, are with the Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada L8S 4L7. Manuscript submitted July 24, 1992. METALLURGICAL TRANSACTIONS B
calculated from the various models of turbulence that have been proposed.
II.
PHYSICAL MODEL
The water model was a one-tenth scale of a steelmaking ladle, which consisted of a cylinder 760-mm high and 500 m m in diameter. It was placed inside a rectangular box 560 x 560 m m 2 • 760-mm high, as shown in Figure 1. The outer box was also filled with water to minimize distortion due to curvature. Five horizontal slots were cut along one-quarter of the circumference to eliminate refraction of the laser beam for measurements off the centerline. Slots not in use were taped closed. The plumes were produced by a flush-mounted orifice (4-mm inner diameter) placed at the center of the bottom of the model. The sizes of bubbles in the plumes ranged from approximately 5 to 40 m m in diameter as measured with a video camera. The largest bubbles in the plumes were formed as a result of the coalescence of smaller bubbles. The gas flow rates used in the experiment ranged from 50 to 200 m L /
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