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A 3-D DNS and experimental study of the effect of the recirculating flow pattern inside a reactive kernel produced by nanosecond plasma discharges in a methane-air mixture

par Castela, Maria;Stepanyan, Sergey;Fiorina, Benoît;Coussement, Axel ;Gicquel, Olivier ;Darabiha, Nasser;Laux, Christophe
Référence Proceedings of the Combustion Institute, 36, 3, page (4095-4103)
Publication Publié, 2016-07-21

Article révisé par les pairs

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Résumé :

Three-dimensional (3D) direct numerical simulation and experimental Schlieren results were used to study a non-equilibrium plasma discharge in a lean CH4-air mixture. The impact of gas flow recirculation on the temporal evolution of species and gas temperature in the vicinity of the discharge zone was examined. The results showed that the formation of a fresh gas counterflow with stagnation plane at the center of the discharge and parallel to the electrodes changed the topology of the hot kernel from an initial cylindrical shape to a toroidal one. This phenomenon leads to an increase of the area/volume ratio of the reactive kernel that may result under certain conditions in kernel extinction. Also the importance of considering this 3D gas flow recirculation was revealed to correctly predict the temporal evolution of the hot kernel. Particularly the temperature and species concentrations in the central region of the discharge returned to fresh gas conditions shortly after the end of the pulse in the order of 150 μs. This result is particularly important for ignition by Nanosecond Repetitively Pulsed discharges since the gas conditions at the beginning of each successive pulse depend greatly on the time interval between pulses thus on the pulse frequency.