Experimental study on the effect of combustion and emission performance of biodiesel–ammonia dual-fuel engine.

This article investigates the combustion and emission characteristics of biodiesel–ammonia dual-fuel engines to support the International Maritime Organization’s (IMO) 2050 net-zero greenhouse gas emission target. Experiments conducted at fixed speed and load with varying ammonia mass ratios (AMRs) up to 82.72% demonstrate that increasing AMR reduces in-cylinder pressure and brake thermal efficiency, with the heat release rate peaking at 57.13% AMR. Compared to pure biodiesel operation, the dual-fuel engine significantly lowers emissions of nitrogen oxides (NOx), carbon dioxide (CO2), and soot, while emissions of nitrous oxide (N2O) and unburned ammonia increase linearly with AMR; however, the rise in N2O does not offset the overall reduction in CO2 equivalent emissions (CO2e). These findings highlight the potential of biodiesel–ammonia dual-fuel engines as a low-carbon alternative for marine propulsion, while also identifying challenges related to unburned ammonia emissions.