Numerical modelling of unsteady heating and melting of the anode by electric arc. Part 1. Mathematical model and computed characteristics of the arc column

Abstract

The two-dimensional mathematical model in the approximation of a partial local thermodynamic equilibrium of plasma and the technique for numerical computation of the unsteady electric arc characteristics, including the conjugate heat exchange of the electric-arc plasma flow with the treated product (anode) are considered. The results of overall testing of the numerical algorithm point to the correctness of the model and computational technique. The results of the computation of the arc characteristics from the conventional ignition moment until the passage to stationary regime are presented. It is found that a single thermal torus, which scatters fairly quickly in the ambient medium, forms around the arc column.

Numerical modelling of unsteady heating and melting of the anode by electric arc. Part 2. Numerical characteristics of the anode weldpool

“…Since on the melt surface, as a rule, ∂T/∂r < 0, the Marangoni force acting on a unit surface of the melt F Mr = Г T ∂ ∂ T r ∂ ∂ has the positive sign and, consequently, in the given case it contributes to the melt flow in the positive direction along r, that is from the near-axial region to the weldpool periphery. By the moment of time t = 10 ms, the arc characteristics have already passed to the stationary regime (see [2]), however, the maximum temperature of the anode surface amounted to 804 K, and only by the time t = 80 ms it reached the melting temperature value, remaining invariable until t = 150 ms due to the consideration of the latent heat of melting. As a result, within the framework of the above-accepted assumption, at the given external parameters of the discharge, the process of the anode "numerical" melting starts in 200 ms after the arc initiation.…”

“…The computations were done in the time interval t = 1−20 s, the external parameters of the problem are invariable (see [2]). …”