The numerical modeling of near, cathode erosion processes in electric-arc plasma generators

An electric-arc plasma generator with high-current arc that burns in hydrocarbon-containing gas (methane) at atmosphere pressure is simulated. In a hydrocarbon plasma at the near cathode region two streams are always found. The first, ion stream is directed to the cathode surface and moves under the effect of the electric field. The second, backward stream, resulting from diffusion of the carbon particles sublimating from the cathode surface is directed back to the plasma. If those streams are equal the regime of cathode material self-recovery is realized. This regime is important because it increases significantly the cathode lifetime. The flow structure inside the plasma generator was modeled using averaged Navier-Stokes equations and k-ε turbulence model. The thermal and ionization equilibrium hypothesis was used to model the multicomponent plasma. The influence of flow swirling, flow intensity and geometry of the plasma generator on carbon mass fluxes at the cathode surface was studied. The results of numerical simulation are in good accordance with experiment. This allows one to use the model proposed for research of the main characteristics of the cathode units and for development of a new ways of their further improvement