Laser Diagnostics of Combustion Enhancement on a CH₄/Air Bunsen Flame by Dielectric Barrier Discharge

We investigate plasma-assisted combustion for premixed CH₄/air Bunsen flames. Dielectric barrier discharge (DBD) is employed to produce non-equilibrium plasma for combustion enhancement. The transient planar laser induced fluorescence (PLIF) technique of CH and OH radicals is used to image reaction zones for enhancement measurement, and the emission spectra of the Bunsen flame are monitored to explore the kinetics mechanism. From the drift of radicals in PLIF images, the quantitative enhancement of plasma on the flame velocities of premixed methane/air flames is experimentally measured, and the data show that the flame velocities are increased by at least 15% in the presented equivalence ratio range. Furthermore, the well analyzed emission spectra of the Bunsen flame (300–800 nm) with/without DBD reveal that the emissions as well as the concentrations of the crucial radicals (like C₂, CH, OH etc.) in combustion all are intensified greatly by the discharge. In addition, the appearance of excited spectral bands of N₂ and N₂⁺ during discharge indicates that the premixed gas is also heated and ionized partially by the DBD.