Influence of Reduced Electric Field (E/N) on Plasma-Assisted Low-Temperature Oxidation

This paper presents a study on the effect of a reduced electric field (E/N) on a premixed methane–air mixture oxidation at low temperature (less than 600 K). A coaxial reactor designed and built for the experiments has the flexibility to be configured for various discharge gaps and pressure conditions such that the discharge can be operated at various E/N. Volumetric dielectric barrier discharge plasma was established using 30 kV nanosecond pulses with repetition rates up to 3.5 kHz. A gas chromatographic technique was employed for product species characterization and quantification. The underscoring feature was the low-temperature ignition for 3 mm discharge gap cases, but no ignition was observed for 2 and 1 mm discharge gaps at atmospheric pressure. The effect of pressure on the low-temperature oxidation was also systematically examined. Discharge gaps of 3 and 2 mm followed a similar trend with pressure variation. Maximum combustion efficiency was observed for approximated E/N values close to 200 Td, whereas no conversion was observed after an E/N value of 350 Td for both discharge gaps. Electron energy branching calculations using BOLSIG+ and a plasma kinetics simulation using ZdPlaskin software were done to support the observations made during the experiments.