Effects of Injection-Ignition Matching Strategies on Combustion Characteristics of Ammonia-Hydrogen Engines

Aiming at a mmonia’s high ignition energy and low combustion rate, an active pre-chamber-type ammonia-hydrogen engine combustion system was designed and developed. The influence of injection/ignition matching strategies on engine combustion characteristics under jet ignition mode was numerically investigated. The results indicate that the "inject-before-ignite" strategy with a shorter injection-ignition interval delivers optimal combustion performance (combustion duration of 26.5 ℃A, indicated thermal efficiency of 43.7%). This is attributed to the pronounced concentration stratification formed in the pre-chamber, which facilitates the formation and development of flame kernels, enhances the combustion-promoting efficacy of jet ignition, and thereby improves the indicated thermal efficiency. However, higher combustion temperatures in the cylinder lead to the increased NO_x emissions in high-temperature oxygen-rich zones, while N₂O formation due to low-temperature accumulation remains relatively low.