A phenomenological model for plasma-assisted combustion with NRP discharges in methane-air mixtures: PACMIND

Abstract

The recent advances in plasma-assisted combustion must now be strengthened through high-fidelity numerical simulations. However, detailed plasma-combustion coupled simulations in complex geometry and turbulent flow involving hundreds of discharges are still unaffordable due to prohibitive computational costs. In this work, a Plasma-Assisted Combustion phenoMenological modelIng for Non-equilibrium Discharges (PACMIND) is proposed. The model aims to avoid computing in detail the plasma phase and consists of incorporating the leading order plasma effects on the reactive compressible Navier–Stokes equations. It consists of two ultra-fast effects with radical productions and gas heating, as well as a slower gas heating due to vibrational energy relaxation. Based on detailed kinetic simulations, the model has been applied to air and methane-air mixtures and contains respectively 5 species, 3 reactions and 12 species, 7 reactions. The model has been validated against experiments in air and detailed plasma-assisted combustion ignition simulations in methane-air at various equivalence ratios and reduced electric fields. Significant improvements regarding ignition delay times have been observed by comparison with an existing model. In addition, the model accounts for NOx production by plasma discharge and covers the full range of conditions encountered in a premixed flame. Hence, it opens the way to the simulation of realistic 3D turbulent configurations with minimal over-costs.