Speaker
Description
A one-dimensional fluid plasma model is developed to study an ablating arc discharge using graphite electrodes in atmospheric pressure conditions. The plasma physics and chemistry are coupled with the plasma-wall interactions, e.g. sheath, electron emission, evaporation, and deposition. In the plasma model, chemical, thermal, and velocity nonequilibrium are accounted for and equilibrium effects are observed as a consequence of large intermolecular collision frequency. A cathode deposit model is developed to estimate the size of the cathode deposit based on the principle of energy minimization, i.e. there is an optimal deposit area (or deposit temperature) which minimizes the energy loss on the deposit due to evaporation and radiation for a given electron current. The numerical results show good qualitative agreement with previous experimental results, showing the transition between high and low ablation modes. In our numerical simulations, it is found that the radiative heat transport between the electrodes plays an important role in determining the anode temperature, which is a potential mechanism for the enhanced ablation characteristics observed in experiments.
