Abstract
A free-burning arc experiment was performed in a gas mixture composed of
CO2 /O2 /C5F10O (85% / 10% / 5%). An optical emission spectroscopy
diagnostic was developed to obtain spatially resolved arc spectra at a
high frame-rate. Spectral measurements are compared with simulated
spectra to estimate arc parameters including temperature and
composition. These techniques are used to characterize the arc and its
associated electrode jets over a range of conditions, in order to study
the influence of ablated Cu/W on arc characteristics. The observed
spectra indicate that the ablation of the contact tip primarily occurs
through vaporization rather than the expulsion of droplets. The metal
vapor content of the arc is investigated as the arc driving current is
varied, and a transition threshold for increased ablation at electrode
current densities above 50A/mm2 is determined. The
expansion angle of the electrode jet is estimated from the concentration
of metal vapor in the arcing region at different axial positions, using
a basic conical expansion model. The dependence of the measured voltage
on the arc composition is examined, and a positive correlation between
Cu content and arc voltage is identified. This trend is attributed to
the higher emissivity of the metal vapor, which suppresses the central
arc temperature and increases its resistivity.