Modeling of a Dielectric-Barrier Discharge-Based Cold Plasma Combustion Ignition System

We present a computational modeling study of plasma phenomena in a dielectric-barrier discharge (DBD) for automotive combustion ignition applications. The study was performed using a self-consistent, two-temperature plasma model with finite-rate plasma chemical kinetics for methane-air combustion mixture. The structure of a DBD discharge and the yield of active combustion enhancing radicals from the discharge is quantified for positive and negative pulsing, and a comparison is made with a single electrode corona discharge. The DBD plasma develops as a streamer discharge with individual streamers preferentially emerging from sharp features on the bare electrode of DBD which quickly propagates to the opposite dielectric surface where it is quenched. The dielectric barrier therefore self-limits the discharge resulting in a total radical yield that saturates in time. The corona on the other hand provides a radical yield that can continuously increase in time. The negative polarity pulsing of the DBD results in a more intense plasma with a higher radical yield compared to a positive polarity pulse. Simulations are also performed for a long 1-μs duration afterglow period once the active pulse is terminated. The active combustion enhancing radicals are found to remain relatively stable in density over this duration, indicating that ~100-kHz pulse repetition rates can sustain or even gradually increase the radical densities over long durations of transient time.