Analysis of the combustion characteristics of ammonia/air ignited by turbulent jet ignition with assisted hydrogen injection in pre-chamber

Turbulent jet ignition (TJI) is an advanced ignition strategy that can improve the ignition and combustion characteristics of low-reactivity mixtures. The utilization of TJI system may be reliable to achieve the application of ammonia (NH₃) internal combustion engines. Hydrogen (H₂) is a potential auxiliary fuel for the pre-chamber, and the injection of a small amount of H₂ in the pre-chamber is beneficial for promoting the ignition and combustion of NH₃/air in the main chamber. In this study, the ignition and combustion characteristics of NH₃/air adopting the active TJI with assisted H₂ injection in pre-chamber were investigated, and the relevant experiments were conducted in the constant volume combustion bomb system. The results show that the H₂ pre-chamber can improve the flammability of NH₃/air, and properly increasing H₂ injection is conducive to the rapid ignition of NH₃/air in the main chamber. The turbulence introduced into the main chamber by the hot jet enhances the combustion process, and the generation of turbulence weakens the sensitivity of the combustion rate to the reactivity of the unburned mixture. The turbulence intensity can be increased by decreasing the pre-chamber orifice diameter, which increases the ignition delay but significantly shortens the combustion duration.