Non-thermal ignition enhancement by magnetically stabilized gliding arc plasma discharge

Non-equilibrium plasma assisted ignition was studied through the development of a well defined system to elucidate non-thermal enhancement pathways. A counterflow diffusion flame ignition apparatus using 20% methane diluted in nitrogen versus air was integrated with a non-equilibrium magnetically stabilized gliding arc plasma discharge device to allow for measurement of the ignition temperatures with and without plasma activation of the air stream. For strain rates between 200 and 350 s-1, up to a 200 K decrease in ignition temperature with plasma activation compared to only heated air at the same strain rates was observed. Modeling of the counterflow burner with heated air and a range of NO addition (100 - 100000 ppm) allowed for the identification of two ignition regimes, kinetic and thermal, depending upon the strain rates in the system. The importance of heat release and thermal feedback in addition to the kinetic enhancement by NO was realized, especially at higher strain rates. The counterflow diffusion flame ignition modeling of heated air agreed qualitatively and quantitatively with the experimental results, while the modeling with calculations of NO production to mimic the NEMSGAPD showed only qualitative agreement to the experimental results. The discrepancy between the nonequilibrium magnetically stabilized gliding arc plasma discharge experimental and computed results opened up the possibility of other enhancement mechanisms including ions and excited species which were not included in this study.