Analysis of turbulent jet ignition phenomena in a large-scale ammonia–hydrogen marine engine

The maritime sector faces increasing pressure to reduce its environmental impact, making carbon-free fuels such as ammonia and hydrogen a viable pathway for decarbonization. In this scenario, this study analyzes the combustion development in a large-scale marine engine fuelled with ammonia–hydrogen blends, employing turbulent jet ignition to overcome ammonia combustion limitations and enhance flame propagation. Using a previously validated numerical model, turbulent jet behavior, in-cylinder turbulence, and combustion development are investigated under realistic operating conditions. Results show that jet ignition promotes high turbulence levels, enabling fast and stable flame propagation at an equivalence ratio of 0.8 with slight hydrogen enrichment. Advancing ignition reduces combustion duration and enhances performance but may lead to autoignition issues. Under knock-limited conditions, increasing hydrogen content leads to higher burning speeds and shorter combustion durations, while peak pressure, thermal efficiency, and indicated work remain nearly unchanged, and emissions remain low and manageable via post-treatment systems.