The effect of initial NO content on spark breakdown in high-temperature air

A one and one-half-dimensional simulation of the streamer breakdown in long high-temperature air gaps is performed by using a detailed kinetic model for the ionization processes in heated air in a strong electric field. The breakdown threshold is calculated as a function of the initial gas temperature under the assumption of the "frozen" number of NO and under the assumption of the local-thermodynamic-equilibrium content of NO. The first assumption corresponds to rebreakdown within a post-arc channel cooled down to the temperatures T<3500 K whereas the second one corresponds to the breakdown of slowly heated air. A hysteresis effect in the breakdown threshold that can attain 35% is obtained.