Modeling of the Plasma Flow and Anode Region Inside a Direct Current Plasma Gun
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Rodolphe Bolot, Christian Coddet, Alain Allimant, and Dominique Billie`res (Submitted April 29, 2010; in revised form July 29, 2010) This study is devoted to the modeling of the arc formation in a direct current plasma gun newly commercialized by Saint-Gobain Coating Solutions (Avignon, France). The CFD computations were performed using the FLUENT code. The electromagnetic coupling was implemented on the basis of a three-dimensional model using additional scalars for the electromagnetic equations and user-defined functions to set up the problem. Whereas most of earlier models include the arc region only, the CFD domain was extended to the gas injection region (i.e., upstream part of the gun, including the gas diffuser), thus allowing a better description of the swirl injection on the plasma flow. Similarly, whereas numerous earlier works include the fluid domain only, the present model takes the fluid/solid coupling problem in the anode into account. In particular, the thermal and the electromagnetic equations are solved not only in the fluid parts but also in the tungsten and copper parts of the anode. This change was found to be important because the internal surface of the anode is no more a boundary of the domain. Thus, its temperature (and electric potential) becomes variable and is thus not necessarily imposed. Finally, the implemented model provides interesting results describing the arc behavior inside the plasma gun.
Keywords
CFD modeling, DC arc, MHD model, plasma gun
1. Introduction Important efforts have been undertaken during the last 12 years for the conception of new generation plasma torches. Multiple cathode systems such as the Triplex gun from Sulzer-Metco (Winterthur, Switzerland) (Ref 1, 2) or the Axial III system from Mettech (North Vancouver, Canada) and multiple anode torches such as the Delta gun from GTV (Luckenbach, Germany) have been commercialized. The main benefits of this new generation of torches concern (1) their ability to provide an improved stability of the arc and (2) their elevated power allowing increased deposition rates. Saint-Gobain Coating Solutions, a business unit of Saint-Gobain group, is present as provider of thermal spray equipments and materials (ceramic powders, Rokide This article is an invited paper selected from presentations at the 2010 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray: Global Solutions for Future Applications, Proceedings of the 2010 International Thermal Spray Conference, Singapore, May 3-5, 2010, Basil R. Marple, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2011. Rodolphe Bolot and Christian Coddet, University of Technology of Belfort-Montbe´liard, LERMPS, Site de Se´venans, 90010 Belfort Cedex, France; and Alain Allimant and Dominique Billie`res, Saint-Gobain Coating Solutions, Avignon, France. Contact e-mail: rodolphe. [email protected].
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