Ab initio modelling of thermal plasma gas discharges (electric arcs)

Abstract

The fundamental physical mechanisms of electric arc discharges were described first by J.Stark in 1903. Nevertheless, a quantitative prediction of the fundamental discharge parameters was practically impossible up to now. One fundamental modelling problem was the description of the non equilibrium layers (plasma sheaths) in front of the electrodes. Additionally, such electric discharges are dissipative self organizing systems. Their properties emerge from the complex interaction of their parts. A concept of a complete self consistent quantitative prediction of such electric arcs was developed. In this ab initio model, the properties of arc discharges are computed in detail. A variation of the discharge parameters gas, pressure, current and cathode diameter establishes the quantitative predictability of the fundamental arc behaviour for a discharge pressure range of 0.1 to 8 MPa and arc currents above 1 A for argon, xenon and mercury fillings. An experimental validation is provided. Especially the high precision of the cathode layer model becomes evident leading to a first positive model assessment. By a numerical coupling of the partial systems models, a complete quantitave predictability of this type of electric gas discharges is established.