Numerical Modeling of the Gas Breakdown Development in the Space?Charge Layer inside the Nozzle of a Transferred Arc Torc

B MANCINELLI; L. PREVOSTO,; F. O. MINOTTI

Journal of Physics: Conference series

IOP

Año: 2012 p. 1 - 5

1742-6596

Double–arcing is a phenomenon that occurs when a transferred arc, flowing inside anelectrically insulated nozzle, breaks into two separate arcs: one that connects the cathode withthe nozzle, and another that connects the nozzle with the anode. Experimental evidencesuggests that the reason for double–arcing is a Townsend like breakdown occurring in the thinspace–charge layer, which separates the plasma from the metallic nozzle, due to the highvoltage drop across it. Breakdown phenomena in a gas between metallic electrodes have beenextensively studied; however the present case involves breakdown of a high–temperature gasbetween one electrode (the nozzle) and a plasma boundary. A 1–D model of the gas breakdowndevelopment in the space–charge layer contiguous to the nozzle of a cutting arc torch operatedwith oxygen is reported. The dynamics of the discharge is analyzed. The kinetic schemeincludes processes of ionization of heavy particles by electron impact, electron attachment,electron–ion recombination and ion–ion recombination.