The Impact of Diesel Injection Strategy and In-Cylinder Temperature on the Combustion and Emissions of Ammonia/Diesel Dual-Fuel Marine Engine

Abstract

This study investigates the impact of different combustion control strategies on marine engine combustion and emission characteristics at a high ammonia energy ratio. Compared to the strategy of maintaining a constant fuel injection duration, the strategy of keeping the fuel injection pressure constant allows the kinetic energy of diesel to remain at a higher level. This results in an increase in combustion efficiency and indicated the thermal efficiency of the engine, while also reducing CO2 and soot emissions. However, when the ammonia energy ratio increases to more than 50%, the indicated thermal efficiency starts to decrease along with the increase in the emissions of N2O and unburned ammonia. To address these issues, one of the potential means is to improve the in-cylinder combustion environment by increasing the in-cylinder gas temperature. This can enhance combustion efficiency and ultimately optimize the performance and emission characteristics of dual-fuel engines, which results in an increase in the combustion efficiency to 98% and indicated thermal efficiency to 54.47% at a relatively high ammonia energy ratio of 60%. Emission results indicate that N2O emissions decrease from 1099 ppm to 25 ppm, while unburned ammonia emissions drop from 16016 ppm to 100 ppm. Eventually, the greenhouse gas emissions were reduced by about 85.3% in comparison with the baseline case.