Numerical Study of the Arc Fluctuations in DC Plasma Torch
To study the effect of the arc length on the voltage, first a steady-state model was considered for a range of arc lengths and arc-root radii. The results of this model provided the relation between arc length and arc voltage for a set of arc root radii and given argon flow rate. Then, given voltage fluctuation profile, the unsteady, arc root attachment movement was simulated from the estimation which found from steady models. Results show that the effects of velocity and temperature fluctuations at the outlet of the torch (where the particles are injected) are not negligible and such fluctuations exceed 15% of their average values. This will in turn affect the particle heating history and will negatively impact the microstructure of the coating.