Modeling plasma-assisted methane ignition using plasma energy fraction manifolds in a phenomenological model

The present work advances a phenomenological plasma-assisted combustion model by implementing spatiotemporally varying plasma energy fractions for fast gas heating, vibrational energy excitation, and fast chemical dissociation of gas species. This is achieved through a 2D manifold of plasma energy fractions generated for varying reduced electric fields (E/N, ranging from 50 to 500 Td) and the thermochemical state of the gas mixture, represented by a progress variable (ranging from 0 to 1). Additionally, a spatiotemporally evolving plasma power density obtained from 2D detailed plasma simulations is utilized in the model to describe the evolution of plasma discharge. Further, a spatially varying electric field between the pin-pin electrodes from the detailed solver is adopted to accommodate the electric field gradients in space to compute E/N and subsequently, the plasma energy fractions. This enhanced model will be validated against experimental ultra-fast gas heating and O₂ dissociation during plasma discharge, and the experimental pressure wave and heated channel radius. The present model will then be used to investigate ignition kernel evolution for a methane-air discharge across a pin-pin discharge configuration, and the plasma discharge will be compared against the results from detailed 2D plasma simulations.