Arc Plasma Torch Modeling
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JTTEE5 18:728–752 DOI: 10.1007/s11666-009-9342-1 1059-9630/$19.00 ASM International
Arc Plasma Torch Modeling J.P. Trelles, C. Chazelas, A. Vardelle, and J.V.R. Heberlein (Submitted February 10, 2009; in revised form April 18, 2009) Arc plasma torches are the primary components of various industrial thermal plasma processes involving plasma spraying, metal cutting and welding, thermal plasma CVD, metal melting and remelting, waste treatment, and gas production. They are relatively simple devices whose operation implies intricate thermal, chemical, electrical, and fluid dynamics phenomena. Modeling may be used as a means to better understand the physical processes involved in their operation. This article presents an overview of the main aspects involved in the modeling of DC arc plasma torches: the mathematical models including thermodynamic and chemical nonequilibrium models, turbulent and radiative transport, thermodynamic and transport property calculation, boundary conditions, and arc reattachment models. It focuses on the conventional plasma torches used for plasma spraying that include a hot cathode and a nozzle anode.
Keywords
arc reattachment, chemical equilibrium, electrode, local thermodynamic equilibrium, nonequilibrium, plasma jet, plasma spraying, plasma torch, thermal plasma
1. Introduction Thermal plasma processes have proven their technological advantage in a wide variety of fields for over 40 years. The features that make thermal plasmas attractive are a high energy density (~106-107 J/m3) that comes with high heat flux density (~107-109 W/m2), high quenching rate (~106-108 K/s), and high processing rates. Direct current (DC) arc plasma torches are, generally, the primary component of these processes that include plasma spraying, ultra fine particle synthesis, metal welding and cutting but also, extractive metallurgy, waste treatment, and biogas production. These torches operate as thermal, chemical, and electrical devices in processes that achieve material modifications which often cannot be achieved, or are not economically feasible, with other devices. A distinctive example of an application that relies on DC arc plasma torches is plasma spraying that has become a well-established and widely used technology to manufacture coatings resistant to wear, corrosion, and temperature and generate near-net shapes of metallic and ceramic parts. For instance, plasma-sprayed coatings make possible turbine blades to withstand temperatures up to 1200 C and provide unparalleled wear resistance to prosthetic implants. The continuous development of
J.P. Trelles, Process Technology Modeling, Intel Corporation, Hillsboro, OR; C. Chazelas and A. Vardelle, ENSIL, Universite´ de Limoges, Limoges, France; and J.V.R. Heberlein, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN. Contact e-mail: [email protected].
728—Volume 18(5-6) Mid-December 2009
thermal plasma-based technologies stresses the need for a better understanding of the operation of arc plasma torches. The appa
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