Numerical simulation of methanol combustion in dry air with a spark-plug electric discharge ignition

Abstract

This study explores the complexities of plasma-assisted methanol combustion, at the molecular level. A methanol–air mixture is considered, assuming that species $N_2$, $O_2$, and ${\mathrm{CH}}_3\mathrm{OH}$ are initially in thermodynamic equilibrium, with initial densities of 77%, 18%, and 5% (molecular ratio 1525:381:100), respectively. The original mixture is homogeneously distributed in a 2D axial symmetric domain, concentric with the bottom spark-plug electrode and $r=20\mathrm{mm}$. The plasmo-chemical kinetic model comprises 112 species interconnected by 1081 physical and chemical processes, including cross-sections resulting from electron impact, covering excitation, ionization, dissociation, recombination, attachment, and detachment. Heat and mass transfers are also considered, along with fluid dynamics. By comparing simulations and analyzing reaction rates, the research sheds light on the contribution of reactive oxygen and nitrogen species (RONS) and key reagents such as H, OH, and $H_{2}O$ in methanol decomposition. Additionally, it highlights the role of the duty cycle in producing atmospheric pollutants (${\mathrm{NO}}_x$, CO, ${\mathrm{CO}}_2$, and ${\mathrm{CH}}_{2}O$). Through detailed analysis of reaction pathways, the study reveals crucial plasma-chemical processes and their implications for combustion and environmental pollution.