Comparative visualization of jet-wall interaction in zero-carbon ammonia-hydrogen pre-chamber turbulent jet ignition: Effects of pre-chamber parameters and hydrogen enrichment

Ammonia-hydrogen mixed fuel offers the potential for zero carbon emissions for internal combustion engines. Pre-chamber turbulent jet ignition (TJI) technology can significantly improve combustion performance. However, in the confined space of an engine, jet-wall impingement is inevitable. This study investigates the jet-wall interaction effect in an ammonia-hydrogen pre-chamber TJI system using a visualized constant volume combustion chamber. The results indicate that a higher hydrogen volume ratio (VH) in the main chamber markedly shortens both ignition delay and combustion duration. When VH rises from 0 to 0.1, the ignition delay and combustion duration of the wall-impinging jet are reduced by 91.7 % and 32.0 %, respectively. A transition to direct ignition behavior occurs at Φpre,ℎ ≥ 1.5, significantly accelerating combustion. Additionally, a strong coupling effect between pre-chamber orifice diameter (Dpre) and hydrogen equivalence ratio (Φpre,ℎ) is observed, where larger Dpre (≥3.5 mm) and higher Φpre,ℎ (≥1.7) shorten ignition delay by enhancing jet penetration and reactivity. The shortest combustion duration occurs at Dpre = 3.0–3.5 mm and Φpre,ℎ = 1.6–1.8, optimizing hot jet penetration and turbulence generation.