O atom TALIF measurements in microdischarges upstream and downstream of an oxygen-enriched methane/air flame

Plasma-assisted combustion (PAC) can extend flammability and lean blow-off limits to enable low-NOx combustors, lower ignition thresholds, and mitigate combustion dynamics. When using Nanosecond Pulsed Discharges (NPD), one of the main pathways of combustion enhancement is through O-atom production by direct electron impact dissociation and dissociative quenching reactions of electronically excited molecular nitrogen. These O-atoms can also participate in NOx formation routes. In this work, we use two-photon-absorption laser-induced fluorescence (TALIF) to quantify O atom densities produced by a single microdischarge in isolated reactant and product regions of an oxygen-enriched laminar premixed methane/air flame. The single microdischarge is generated by nanosecond repetitively pulsed discharges operated in a dielectric barrier discharge configuration. The setup allows to image the discharge along the main axis of the microdischarge by utilizing indium tin oxide (ITO) transparent electrodes. Alternative approaches for calibrating O-atom TALIF signals were investigated, for comparison with the standard Xe TALIF method.