Numerical modelling of high-pressure arc discharges: matching the LTE arc core with the electrodes

Abstract

A widely-used approach to simulation of high-pressure arc discharges is based on the system of magneto-hydrodynamic equations written in the approximation of local thermodynamic equilibrium (LTE). In this work, boundary conditions on the surface of the electrodes are formulated with the use of equations of balance of energy in the non-equilibrium near-electrode layers that separate the LTE bulk plasma and the electrodes. As an example, numerical simulations of a free-burning arc in atmospheric-pressure argon plasma in the current range from 20 to 200 A are reported. Simulation results are in a reasonably good agreement with those given by more sophisticated models and with the experiment. Simulations performed for cathodes of slightly different geometries have predicted a strong effect produced by details of the cathode geometry over the distribution of the current density along the cathode surface and therefore over the plasma temperature; an interesting and potentially important result worth of further numerical investigation and experimental verification.

Computing anode heating voltage in high-pressure arc discharges and modelling rod electrodes in dc and ac regimes

“…Therefore, the computed values of the anode heating voltage may be used for analysis of arc plasma-anode interaction in other situations. In particular, in [19] these data are used for simulation of interaction of an atmospheric-pressure argon arc with the arc current 20 to 200 A, described in the LTE approximation, with a planar water-cooled copper anode. Figure 2.…”

“…Note that the data given in table 1 have been derived from simulations performed in the range of current densities j up to 10 7 A m 2 , as seen in …gure 2. This range is appropriate for most applications; for example, the computed maximum value of current density at the surface of a planar copper anode of a 200 A atmospheric-pressure Ar arc is about (1:25 1:6) 10 6 A m 2 depending on the model [6,19]. On the other hand, the current density on anodes of very-high pressure high-intensity discharge lamps may reach values of several times 10 7 A m 2 [13].…”

“…The latter may be considered as an experimental validation of both the approach and the computed values of the anode heating voltage. This allows one to employ these values for analysis of interaction of high-pressure plasmas with anodes in other situations, e.g., for simulation of interaction of an LTE arc plasma with a planar water-cooled anode as was done in [19].…”

Моделирование Плазмы Короткодугового Ксенонового Разряда Сверхвысокого Давления

“…Будем полагать, что плазма находится в условиях локального термодинамического равновесия [1,2] и что в плазме присутствуют атомы тория, эмитированные торированным катодом. Геометрия разряда такова, что для описания пространственных распределений характеристик плазмы оказывается удобным использование эллиптических координат [19], где поверхности τ совпадают с эквипотенциальными поверхностями (с поверхностью электродов в том числе), а поверхности σс силовыми линиями электрического поля.…”

“…Разряды высокого и сверхвысокого давления в инертных газах, на основе которых созданы в том числе и ксеноновые короткодуговые лампы, изучены достаточно хорошо [1,2]. Исследованы их оптические, спектроскопические, светотехнические и электрические характеристики.…”