燃焼ガスプラズマ境界層内での微細アークの変動限界と大電流巨大アークへの遷移機構

抄録

Current transport in the boundary layer of combustion gas plasma flow on a cold electrode changes from diffuse mode to micro-arc (about 1A/Arc) and then to high-current big-arc (about 100A/Arc) mode with the increase in mean current density. This study intends to clarify the big-arc formation mechanism and to extract the pure effects of basic factors, particularly electrode temperature and bulk plasma temperature, based on the statistical analysis at the arc transition state. While the critical current density for the transition from diffuse to micro-arc mode largely increases with the increase in electrode temperature, its effect on the transition from micro-arc to big-arc mode is not so significant. It is the bulk plasma temperature that changes the critical micro-arc current for the transition to big-arc mode. Micro-arc currents fluctuate and some micro-arcs with arc current beyond the critical value will grow up to big-arcs breaking through the thermal boundary layer. Most of the micro-arcs with arc current below the critical value remain as micro-arcs adjacent to the electrode wall.