Rotating arc plasma characteristics in the presence of methane flame

Plasmas can ignite and stabilize flames under extreme conditions and have already been applied in practical combustors, but further studies are needed to elucidate the complex flame--plasma interactions. Here, we present the results of an experimental study on the interactions between a methane flame on a rotating arc plasma, with particular focus on the influence of flame conditions on plasma generation. A gas chromatograph, chemiluminescent NO$_{x}$ analyzer, optical emission spectrograph, and intensified charge-coupled device were used to monitor product gases (CO$_{2}$, H$_{2}$, CO, C$_{2}$, C$_{3}$, and NO$_{x})$ with and without the plasma and also plasma characteristics (arc length, angular speed, and peak voltage) under different flame equivalence ratios $\Phi$. The results confirmed that the rotating arc indeed stabilized the flame and extended both flammability limits. In addition, the rotating arc was pushed upward and out of the reactor for rich and lean mixtures. The highest NO$_{x}$ concentration was obtained at the lower flammability limit in the presence of the plasma, but at $\Phi$ = 1.0 without the plasma.