Abstract The present work investigates the spark ignition and flame kernel formation processes in hydrogen–air mixtures under real engine-relevant conditions from a chemical-physical perspective. A one-dimensional numerical model based on the INSFLA solver with cylindrical geometry is used to resolve the coupled effects of detailed chemical kinetics and molecular transport during the ignition phase. The initial and boundary conditions (e. g. initial pressure, initial temperature, equivalence ratio, spark width and duration) are directly taken from a hydrogen-fueled internal combustion engine (H2-ICE) operation point. The simulations capture both failed and successful spark ignition events. Sensitivity analyses identify chain-branching and chain-termination reactions as the dominant chemical kinetic factors controlling the speed of flame kernel formation, while molecular transport effects become significant only after the onset of flame propagation. Furthermore, the evolution of NO emissions is analyzed in detail, showing that thermal NO dominates at high temperatures, whereas the NNH pathway contributes substantially during the early ignition stage, with the N₂ O route playing a minor role. Overall, the study provides mechanistic insights into the chemical and transport processes governing early flame development and NO formation in hydrogen-fueled engines, offering a scientific foundation for optimizing spark ignition strategies and reducing NOx emissions under realistic engine conditions.
Yu et al. (Thu,) studied this question.