Mechanistic study of the regulatory effects of key discharge parameters on plasma-assisted microscale methane combustion

Conventional power supplies are limited in micro-power systems by low energy density and short endurance. Plasma-assisted combustion (PAC) can improve microscale combustion, but the coupling between discharge and combustion remains unclear. Here, a multiphysics PAC model is developed by coupling COMSOL-based discharge simulation with three-dimensional FLUENT combustion simulation, in which spatially and period-averaged reactive-species mole fractions are imposed as inlet species boundary conditions. The model clarifies how key discharge parameters regulate microscale PAC performance. Dielectric-property optimization is critical for discharge enhancement: increasing relative permittivity from 2.30 to 4.20 or reducing dielectric-layer thickness from 1.50 mm to 0.75 mm increases average electron density by about 69%, while the incremental changes in the simulated combustion-related indicators become modest as the relative permittivity increases from 3.75 to 4.20. Enhanced discharge promotes key active species such as H radicals, shortens the Chemkin-calculated ignition delay by 25%, shifts the flame front upstream by 6.5 mm, and increases peak temperature by 60 K. When argon is used as the carrier gas, increasing its blending ratio from 0.1 to 0.4 increases the electron density by 31.5% at 18 kV, whereas the corresponding increase is 20.3% at 20 kV, indicating a nonlinear discharge response. Under the investigated combustion conditions, argon blending reduces wall-temperature non-uniformity by 13.5% and increases methane laminar flame speed by up to 5.6 cm/s. Under fuel-rich conditions, however, excessive blending may suppress flame speed, possibly because of competitive side reactions. These results provide theoretical guidance for designing stable micro-combustors.