Multiscale numerical study of Plasma-Assisted combustion in ammonia and Ammonia–Hydrogen blends

Ammonia and hydrogen are widely regarded as promising zero-carbon alternatives to conventional fossil fuels. However, ammonia combustion presents several critical challenges, including poor ignitability, low flame propagation rates, and significant NOx emissions. Plasma-assisted combustion (PAC) has emerged as a potential strategy to address these limitations, attracting growing research interest in recent years. This study presents a numerical investigation of nanosecond pulsed plasma discharges applied to ammonia and ammonia–hydrogen combustion in air. Simulations are performed using the open-source plasma solver ChemPlasKin, both as a standalone tool and in coupled frameworks with Cantera and OpenFOAM, across a range of operating conditions. A systematic analysis is conducted on the impacts of non‑thermal plasma on ignition delay time (IDT), laminar burning velocity (LBV), and NOx emissions. In addition, the study separates plasma‑driven thermal and kinetic effects and introduces two‑dimensional simulations for plasma‑assisted ammonia–hydrogen flames. The results reveal concurrent reductions in IDT, NOx emissions, and flame thickness, alongside increases in LBV and heat release rate. Plasma enhancement is highly sensitive to both the operating regime and H 2 blend fraction. Across equivalence ratios, the strongest plasma impact occurs near stoichiometric (slightly lean to slightly rich), whereas increasing pressure substantially diminishes its effectiveness. Under atmospheric pressure and lean conditions, reductions of over 99 % in IDT and 36 % in NO emissions, along with a 39 % increase in LBV, are noticed. Both plasma-driven thermal and kinetic pathways are critical for shortening IDT; in contrast, gains in LBV are dominated by thermal effects. Two-dimensional simulations indicate that plasma provides a modest stabilizing effect on flame wrinkling, yet both conventional and plasma-assisted laminar premixed NH 3 -H 2 flames remain intrinsically unstable.