Thermal-Chemical Instability in Plasma-Assisted Combustion*

In the flow of weakly ionized plasma, the transition from a diffusive volumetric discharge to a contracted localized filament is called plasma thermal instability. Traditionally, plasma thermal instability is controlled by the well-known thermal-ionization mechanism. However, endothermic/exothermic chemical reactions may bring new couplings between the reactive flow of weakly ionized plasma and chemical kinetics. In this work we developed a one-dimensional numerical model and studied the dynamics of thermal-chemical instability in a reactive mixture. Several key parameters including flow speed, gas pressure, initial temperature and mixture compositions are identified and discussed for their influence on triggering the thermal-chemical instability. This work will fill the knowledge gap in understanding the chemical kinetic effect on plasma instability in combustible mixtures and provide support for the future development of volumetric plasma ignition for ultra-lean combustion in advanced engines.