Ignition of Methane-Air Mixture at Low Temperature Using Dielectric Barrier Discharge Plasma

摘要

This paper presents the results of low temperature (below 500 K) plasma assisted ignition study on premixed methane-air mixture. For the study, a coaxial reactor with provision to vary the discharge gap (D.G.) is used so that plasma discharge can be established for different reduced electric fields (E/N). Volumetric DBD is established in the gap using a 30 kV, nanosecond duration pulse generator whose pulse repetition rate (PRR) can be varied up to 3.5 kHz. This study investigates the effect of different E/N values on the low temperature plasma-combustion kinetics for a given electrical energy input. Gas chromatographic technique has been adopted for product species quantification. Low temperature ignition of methane-air premixed mixture of equivalence ratio in the range of 0.4-1.4 was observed when it passes through the plasma region with a 3 mm discharge gap. Ignition was observed at 1500 Hz or higher PRR which is much less than the reported PRR values in the literature. No ignition was observed when it passes through 2 mm or 1 mm discharge gaps studied. Voltage-current measurements have been done for the calculation of total energy loading into the reactor which increases with decrease in discharge gap. Low temperature plasma effect on methane reforming also has been studied. In the case of methane reforming, CH_4 conversion and H2 yield is even less than that of low temperature oxidation which suggests that plasma assisted combustion kinetics is highly active for the 3 mm discharge gap in the presence of O_2. Further studies on reduced electric field (E/N) estimation and plasma combustion kinetics simulation are required for better understanding of these experimental results.