A Computational Study of Induction Stirred Ladles
thesisposted on 12.12.2019 by Joshua D Vandenoever
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A numerical simulation was developed to capture the phenomena of electromagnetic stirring in a metallurgical ladle. Electromagnetic stirring requires an external magnetic field to be imposed on the molten steel bath, which is governed by the principles of magnetohydrodynamics. Electromagnetic stirring benefits over traditional stirring methods by offering non-invasive stirring, melt homogeneity, and ease of configuration alterations. Insight to the electromagnetic stirring phenomena is limited experimentally due to the high temperatures of the molten-steel bath. This investigation will include two numerical simulations, the first of which is to generate a magnetic field to properly stir the steel bath. The second incorporates the generated magnetic field and solves the fluid flow due to the magnetohydrodynamics interactions. The results of these numerical simulations will help to provide further understanding of the electromagnetic stirring method. This simulation was used to analyze the molten-steel bulk velocity, vortex formation, flow development time, slag-eye size, and wall shear stress in a metallurgical ladle.
The transient development of the bulk velocity in an EMS ladle was compared with the literature study completed by Sand et al. 2009. The comparison of the developed bulk velocity resulted in a percentage difference of 0.98% and an absolute difference of 0.007 [m/s]. Both numerical models, in the current work and the literature study, obtained a developed flow within 25 seconds of stirring. For the parametric studies, it was found that the addition of a circumferential taper angle to the geometry reduced the bulk velocity and slag-eye size formed compared to a cylindrical ladle. The electric current amperage of the external magnetic field coil system was determined to precisely adjust the bulk velocity. A 150 [A] reduction in amperage results in a ~20% loss in the bulk velocity magnitude. The locations of the high shear stress regions were determined which remained near the stirring unit.
From this study, it is recommended to use a magnetohydrodynamics package offered within a multiphysics numerical solver since the FLUENT® MHD module inherently under-predicts the velocity as well as the issue of the numerical instabilities of the Lorentz force calculations.