Evaluation of the mean argon plasma conductivity and temperature at the exit of an atmospheric DC arc plasma torch

Abstract

A new long-life DC arc T-plasma torch [1] was studied. The well-known method of electric field strength measurements in a stabilized arc channel [2] was applied in a modified form as a consequence of the specific shape of the presumably diffuse anode spot attached to a gas vortex on the external surface of the anode unit. The electric field strength was determined assuming that the potential drop across the diffuse anode spot in the new plasma torch was small. This yielded a mean argon plasma conductivity σ ≤ 118 Ohm−1 cm−1 for arc current I ≤ 180 A which agrees with the independent experiment [2] thus affirming the correctness of the above assumption. The analysis of the known experimental and theoretical data on atmospheric argon plasma conductivity resulted in the selection of R.S. Devoto's theoretical dependence σ(T) [3] as the most reliable one for T = 800 − 20000 K at P = 1 atm, which allowed us to evaluate the mean argon plasma temperature at the exit of the plasma torch, namely, T ≤ 19 500 K.