Study on split diesel injection ammonia/hydrogen mixture fuel combustion on engine combustion and emission performance

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Ammonia has gained increasing attention as a carbon-free alternative fuel for freight applications, particularly in the shipping industry. However, the challenges associated with nitrous oxide (N₂O) emissions, which have a global warming potential nearly 300 times that of carbon dioxide (CO₂) and ammonia slip remain significant obstacles for ammonia utilization in compression ignition diesel engines. To address these limitations, this study investigates hydrogen enriched ammonia/diesel dual-fuel combustion and evaluates the effects of split diesel injection in an ammonia/hydrogen/diesel ternary fuel (ADHTF) engine under medium load conditions. Unlike previous studies that focused mainly on binary ammonia/diesel or ammonia/hydrogen systems, this work provides the first combined assessment of hydrogen enrichment and split injection in a ternary ADHTF configuration, highlighting its novel contribution.The results indicate that introducing hydrogen into a single-injection diesel strategy significantly improves combustion characteristics. Compared to ammonia/diesel dual-fuel combustion, the ternary fuel configuration reduces CO emissions by over 63 % and unburned ammonia emissions by up to 34 %, albeit with a slight increase in CO₂ emissions. Hydrogen enrichment also enhances mixture reactivity and stabilizes combustion.Furthermore, the implementation of split diesel injections，increases peak cylinder pressure by up to 3.3 MPa and raises the temperature field by approximately 200 K. In terms of emissions, NOₓ emissions increase by approximately 30 %, while CO emissions are significantly reduced, soot emissions decrease by 50 %, and N₂O emissions drop by over 63 %. These changes result from improved ignition timing control and enhanced fuel–air mixing enabled by the split-injection strategy. Overall, this study demonstrates an effective pathway to overcome key barriers associated with ammonia fueled compression ignition engines and provides new insights for optimizing in-cylinder combustion and reducing greenhouse gas emissions.

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