View Video Presentation: https://doi.org/10.2514/6.2022-2257.vid

Magnetically-guided atmospheric arc devices were applied to provide plasma-excitation to premixed methane-air flames. Researchers have recently applied similar technology to study vortex generation for aerodynamic flow control, and the scaling and driver circuits used for those devices has been leveraged in the presented work. To provide a plasma-exited volume, an arc is produced in the gap of coaxial electrodes placed within the field of a strong rare-earth magnet. Due to drift motion in the magnetic field, the charged particles experience Lorentz force which causes the arc filament to sweep about the center of the coaxial electrodes. To observers, this takes on the apparent form of a plasma “disc” at the tip of the coax. The technique is applied to flame holding by integrating flow channels in the dielectric spacers of the coax, through which fuel and oxidizer are injected and mixed in the rotating plasma filament. The use of zero-voltage-switching circuits operating in the 70-80 kHz range to introduce plasma power in the flame zone is reported, with these circuit modules being powered by low voltage DC supplies (e.g., 24 V). The enhanced mixing effect of the plasma-excitation technique was demonstrated through high-speed imaging and schlieren. Gas analyzers were used to measure the reduction in the unburnt CO level above the lean flame zone when the plasma system was engaged. The methodology for sizing the coaxial plasma burners for natural gas combustion is presented. An array of plasma-assisted burners is demonstrated using this technique, with lean methane flow rates (fi = 0.76) corresponding to available heat release between 46 and 138 kW.