FRVT - Capítulos de Libros Internacionales

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Author: search.filters.author.Mancinelli, Beatriz

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    On the Double-Arcing Phenomenon in a Cutting Arc Torch.
    (2011) Prevosto, Leandro; Kelly, Héctor; Mancinelli, Beatriz
    Transferred arc plasma torches are widely used in industrial cutting process of metallic materials because of their ability to cut almost any metal and the very high productivity that can be achieved with this technology (Boulos et al., 1994). The plasma cutting process is characterized by a transferred electric arc that is established between a cathode, which is a part of the cutting torch, and a work-piece (the metal to be cut) acting as the anode. In order to obtain a high-quality cut, the plasma jet must be as collimated as possible and also must have a high power density. To this end, the transferred arc is constricted by a metallic tube (a nozzle) with a small inner diameter (of the order of one millimeter). Usually, a vortex-type flow with large axial and azimuthal velocity components is forced through the nozzle to provide arc stability and to protect its inner wall. In such case the hot arc is confined to the center of the nozzle, while centrifugal forces drive the colder fluid towards the nozzle walls, which are thus thermally protected. The axial component of the gas flow continuously supplies cold fluid, providing an intense convective cooling at the arc fringes. In addition, the vortex flow enhances the power dissipation per unit length of the arc column, resulting in high temperatures at the arc axis. Since the nozzle is subjected to a very high heat flux, it is made of a metal with a high thermal conductivity (copper is broadly used). The arc current is of the order of ten up to a few hundred amperes, and the gas pressure is several atmospheres. Arc axis temperatures around 15 kK are usual, but larger values, close to 25 kK or even higher, have been reached.
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    Numerical Modelling of a Cutting Arc Torch
    (Jan Awrejcewicz. INTECH, 2014-02-14) Mancinelli, Beatriz; Minotti, Fernando Oscar; Prevosto, Leandro; Kelly, Héctor
    Plasma cutting is a process of metal cutting at atmospheric pressure by an arc plasma jet, where a transferred arc is generated between a cathode and a work-piece (the metal to be cut) acting as the anode . Small nozzle bore, extremely high enthalpy and operation at relatively low arc current (≈ 10 ÷ 200) A are a few of the primary features of these torches. The physics involved in such arcs is very complicated. The conversion of electric energy into heat within small volumes causes high temperatures and steep gradients. Dissociation, ionization, large heat transfer rates (including losses by radiation), fluid turbulence and electromagnetic phenomena are involved. In addition, wide variations of physical properties, such as density, thermal conductivity, electric conductivity and viscosity have to be taken into account.