Toward High-Efficiency and Low-Emissions Hydrogen Direct Injection Internal Combustion Engine: Pre-Chamber Turbulent Jet Ignition

Hydrogen internal combustion engine (HICE) holds significant promise for transitioning to clean fuels within the transportation field. This research investigates the adaptability of pre-chamber turbulent jet ignition (TJI) in direct injection (DI) HICE, focusing on addressing challenges such as reduced flame speed under lean-burn strategy and high NOx emissions during high-efficiency operation. Using a 3D CFD model of a DI HICE, we explore the impact of different ignition modes on mixing, combustion, and NOx emissions. Our findings reveal that the passive pre-chamber mode leads to a modest improvement in thermal efficiency and a reduction in NOx emissions compared to the spark ignition (SI) mode. In contrast, the active pre-chamber mode, characterized by a faster flame velocity, enhances indicated thermal efficiency (ITE) by about 2% compared to other ignition modes. We identify an optimal injection strategy for the pre-chamber, involving the injection of 0.3 mg of hydrogen. Deviations from this hydrogen quantity adversely reduce the thermal efficiency. Moreover, advancing injection timing promotes fuller mixing at higher turbulent kinetic energy, resulting in faster flame propagation albeit with a marginal rise in NOx emissions. Adjusting the equivalence ratio leads to an extension of the lean burn limit to the equivalence ratio of 0.25, while still achieving efficient combustion with ITE exceeding 49% at equivalence ratios of 0.3 or higher. Ultimately, we demonstrate the attainment of high-efficiency and low-emission combustion, with ITE surpassing 50% and NOx emissions falling below 80 ppm.