Calculation of combined diffusion coefficients in N₂-Ar-Cu mixtures

The diffusion process is a significant factor in high-voltage circuit breaker arcs simulation, due to the great influence of metal vapours and wall ablation. The combined diffusion coefficient method has been demonstrated as an accurate and simple treatment of diffusion process in two-gas mixtures. However, in many cases, the high voltage arc plasma consists of more than two gases. Recently, an extension of the classic combined diffusion coefficient method to allow the application of three-gas mixtures has been presented. In this paper, all four combined diffusion coefficients, which are combined ordinary diffusion coefficient, combined pressure diffusion coefficient, combined electric field diffusion coefficient and combined temperature diffusion coefficient, of N2-Ar-Cu mixtures are calculated using the derivation newly presented. These four coefficients describe diffusion due to composition gradients, pressure gradients, applied electric fields and temperature gradients, respectively. The results of different proportion mixtures at temperatures up to 30 000K and at atmosphere pressure are presented and compared with previous papers to validate this derivation. The method and results presented in this paper can be applied to the simulation of high voltage circuit breaker arcs.