Numerical investigation of the double-arcing phenomenon in a cutting arc torch.
Date
2014
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Abstract
A numerical investigation of the double-arcing phenomenon in a cutting arc torch is reported.
The dynamics of the double-arcing were simulated by using a two-dimensional model of the gas
breakdown development in the space-charge layer contiguous to the nozzle of a cutting arc torch
operated with oxygen. The kinetic scheme includes ionization of heavy particles by electron impact,
electron attachment, electron detachment, electron–ion recombination, and ion–ion recombination.
Complementary measurements during double-arcing phenomena were also conducted. A marked rise
of the nozzle voltage was found. The numerical results showed that the dynamics of a cathode spot at
the exit of the nozzle inner surface play a key role in the raising of the nozzle voltage, which in turn
allows more electrons to return to the wall at the nozzle inlet. The return flow of electrons thus closes
the current loop of the double-arcing. The increase in the (floating) nozzle voltage is due to the fact
that the increased electron emission at the spot is mainly compensated by the displacement current
(the ions do not play a relevant role due to its low-mobility) until that the stationary state is
achieved and the electron return flow fully-compensates the electron emission at the spot. A fairly
good agreement was found between the model and the experiment for a spot emission current growth
rate of the order of 7 x 104 A/s.
Description
Keywords
Double-arcing., Cutting arc torch., Plasma.
Citation
JOURNAL OF APPLIED PHYSICS.
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