The temporal dynamics of the spatial distribution of atomic hydrogen and oxygen in a lean methane-air flame, forced by a nanosecond repetitively pulsed discharge-induced plasma, are investigated via femtosecond two-photon absorption laser-induced fluorescence technique. Plasma luminescence that interferes with the fluorescence from H and O atoms was observed to decay completely within 15 ns, which is the minimum delay required for imaging measurements with respect to the discharge occurrence. During discharge, H atoms in the excited state rather than the ground state, produced by electron-impact dissociation processes, are detected at the flame front. It was found that the temporal evolution of H and O fluorescence intensity during a cycle of 100 µs between two discharge pulses remains constant. Finally, the decay time of O-atoms produced by the discharge in the fresh methane-air mixture was about 2 µs, which suggests a faster reaction between O-atoms and methane than in air.
|Original language||English (US)|
|Journal||Journal of Physics D: Applied Physics|
|State||Published - Apr 23 2021|
Bibliographical noteKAUST Repository Item: Exported on 2021-05-27
Acknowledgements: This research work was sponsored by the National Science Foundation for Young Scientists of China (Grant No. 12004147), the King Abdullah University of Science and Technology (KAUST), the Knut and Alice Wallenberg Foundation, the European Research Council (ERC) through the advanced grant TUCLA (No. 669466), the Swedish Research Council (VR), the Swedish Foundation for Strategic Research (SSF, ITM17-0309), and the Swedish Energy Agency through the Centre for Combustion Science and Technology (CECOST).