Optical diagnostics for determining gas temperature of reactive microdischarges in a methane-fed dielectric barrier discharge

The gas temperature of reactive microdischarges has been extensively investigated in a methane-fed dielectric barrier discharge (DBD) configured by a two parallel plate reactor with 0.5 mm gap spacing. Emission spectroscopy of the rotational bands of CH(2Δ→2Π) coupled with heat transfer experiments have been employed for this purpose. Stationary and space-averaged gas temperature between the discharge gap was estimated from the heat transfer experiment; thus heat capacity and enthalpy gained by the feed gas stream resulted in a ≈20 K temperature increase. The rotational temperature showed fairly good sensitivity to the inlet gas temperature variation in the range 370-670 K. However, the local gas temperature increase inside the microdischarges represented an additional 100 K above the average gas temperature, indicating one order of magnitude higher value than the theoretically expected gas temperature increase (5-10 K) for a single microdischarge. High-frequency operation (80 kHz) is responsible for memory effect, thus such a high gas temperature increase was the result of multiple microdischarges rather than a single one.