Regular Article

Prediction of operational characteristics of a dc non-transferred arc plasma torch using similarity criteria

¹ Karunya University, Coimbatore 641114, India
² Institute for Plasma Research, HBNI, Gandhinagar, Gujarat 382428, India
³ Bharathiar University, Coimbatore 641046, India

^a e-mail: gravi@ipr.res.in

Received: 24 March 2017
Received in final form: 17 June 2017
Published online: 10 October 2017

Abstract

The operational characteristics of a dc non-transferred arc plasma torch have been predicted using the techniques of dynamic similarity. The torch used has a distinct design incorporating both axial plasma generating gas and a shroud gas that initially forms a cold boundary layer but eventually takes part in the plasma formation. The current–voltage characteristics are correlated with electrode heat losses and plasma power for different gas flow conditions using the techniques of dynamic similarity. It is shown that this torch can operate in various power levels at high electro-thermal efficiencies. Unique dimensionless numbers are created for its wide operating regimes. The voltage and operational characteristics are predicted using these numbers for a number of experimental conditions, which are in good agreement with actual experimental results. Predictions are made on the limits of operational characteristics of this torch and class of torches at higher powers.