• Engine dual fuel combustion with NH 3 high-pressure direct injection is investigated. • Influence of fuel injection strategies on performance and emissions is discussed. • NH 3 injection pressure exceeding 600 bar pressure doesn’t improve combustion and results in higher unburned emissions. • Substitution rates of 95 % and a 70 % reduction of GHG emissions have been achieved. • NO x emissions were 33 % lower compared to conventional diesel combustion. Ammonia-fueled engines are emerging as a promising solution for decarbonizing global shipping and power generation. High-pressure liquid ammonia injection has demonstrated potential to reduce harmful emissions primarily in experimental set-ups such as rapid compression machines and constant volume combustion chambers, with limited data available for large-bore engine applications. This study investigates the impact of different ammonia injection strategies on engine performance and emissions, including nitrogen oxides (NO x ), nitrous oxide (N 2 O) and unburnt ammonia, in a large-bore, medium-speed engine. Investigations were conducted using a fuel-actuated common rail injector prototype developed by OMT in a dual-fuel configuration with a diesel pilot injector. Based on initial fuel spray characterization in an optically accessible constant volume chamber, investigations on injection strategies were performed in a single-cylinder research engine for a part load operating point with 12 bar IMEP. The combustion concept demonstrated stable operation with an ammonia fuel fraction of up to 95 %. Due to increasing N 2 O emissions at the lowest diesel fractions, the lowest CO 2 -equivalent emissions are achieved at substitution rates of 85 to 90 %, with reductions of up to 70 % compared to conventional diesel combustion. This reduction was achieved at an injection pressure of 600 bar, whereas higher injection pressures resulted in increased emissions. Additionally, a reduction in NO x emissions of up to 33 % can be achieved at similar combustion phasing. These findings deepen the understanding of the combustion process and lay the foundation for future research at higher loads and in connection with exhaust gas aftertreatment systems.
Roßmann et al. (Mon,) studied this question.