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NH3 Dual-Fuel Combustion Emissions in a 4-stroke Marine Diesel Engine

Abstract

The presentation evaluates ammonia as a dual‑fuel for 4‑stroke marine diesel engines, highlighting its potential for deep greenhouse‑gas reductions through high ammonia substitution but also the significant challenges posed by its poor autoignition properties, slow flame speed, material compatibility issues, and toxic handling requirements. Experiments on a single‑cylinder Cummins ISB platform demonstrate that while high loads can achieve over 90% ammonia energy substitution with diesel‑like efficiency and large reductions in CO₂‑equivalent emissions, low‑load operation produces substantial N₂O, a potent greenhouse gas, alongside elevated engine‑out NOₓ and NH₃ that necessitate optimized aftertreatment. Results show that selective catalytic reduction (SCR) systems can reduce NOₓ and ammonia slip under certain conditions, though further tuning is needed to balance competing reactions and minimize N₂O formation. Additional findings include nonlinear soot reduction using bio‑pilot fuels, significant unburned fuel slip likely involving partial ammonia‑to‑hydrogen reforming, and notably reduced heat‑transfer losses, underscoring both the promise and technical hurdles of deploying ammonia dual‑fuel combustion in marine applications.