| A strategy is developed to numerically study thermal plasma arc columns under high-current conditions. Necessary assumptions are made to focus the investigation on the interactions between gas flow, energy transport and the electromagnetic field. In order to study the macroscopic behavior of a thermal plasma under the conditions of local thermodynamic equilibrium, coupled Navier-Stokes and Maxwell's equations are derived. While the air plasma studied is assumed to be a multi-species ideal gas, the thermodynamic properties (specific heat and enthalpy) and transport properties (electrical conductivity, thermal conductivity, viscosity, and total volumetric radiation emission coefficient) are obtained using molecular theory.; A commercially available, finite-volume based computational fluid dynamics code FLUENT is adapted through the use of user-defined subroutines to include the electromagnetic field and its coupling with plasma flow and heat transfer. One of Maxwell's equations--the current continuity equation--is solved in conjunction with the Navier-Stokes equations, while the magnetic field is obtained using the Biot-Savart equation. The non-linearity of the physical properties as functions of temperature and pressure are treated in the programs to ensure solution convergence. The coupling between the fluid field and electromagnetic field is modeled through source terms--an ohmic heating term in the energy equation and a Lorentz force in the momentum equation.; In order to validate the code, a two-dimensional, axi-symmetric, steady-state, vertical arc column at low current ({dollar}<{dollar}100 A) is modeled without considering the influence of the magnetic force (Lorentz force). The effects of current level, cathode diameter and natural convection are studied. At high current levels ({dollar}>{dollar}100 A), the self-induced magnetic field can no longer be ignored. Therefore, a three-dimensional arc column at high current is modeled and again compared with the literature. The comparison between the results from the current study and those from the literature were satisfactory, providing validation of the code.; To study the effects of both internal and external effects on a high current arc, a parametric analysis is carried out on a wall-stabilized three-dimensional arc column to investigate the influences of geometric configuration, ambient pressure, gravitational field and various boundary conditions. When the arc column is exposed to a transverse external magnetic field, the arc is bent toward the direction of the magnetic force. The corresponding plasma flow pattern is also altered.; Transient analysis is performed in an open-ended arc chamber where a three-dimensional air arc column is under the influence of a transverse external magnetic field. It is found that the arc starts to bend under the magnetic force while the arc voltage increases as a result. Eventually, arc interruption is predicted when the arc voltage undergoes a rapid increase.; The effects of gas ablation from sublimation materials on a high current arc column are studied by modeling the mixing of the sublimated gas (hydrogen) and air plasma. The gassing velocity is a function of heat transfer to the material, and therefore is a function of time and position. It is found that gassing in the arc chamber increases the arc voltage rapidly.; The current numerical tool developed is shown to be a useful tool in applications involving thermal plasma, such as current interruption technology in switchgear applications and thermal plasma technology. Further development of the model would enable additional real arcing phenomena to be studied. |
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