A Study on Controlling NH ₃ and NO _X Emissions in an Ammonia/Diesel Dual-Fuel Engine Using Response Surface Methodology

With the intensification of global greenhouse effects and energy crises, zero-carbon and alternative fuels have become major development trends for internal combustion engines. Ammonia, as a potential clean fuel, is considered one of the most promising alternative engine fuels due to its widespread raw material availability, ease of storage and transportation, and carbon-free combustion products. However, ammonia-fueled engines produce significant NH₃ and NO_X emissions after combustion. In order to effectively reduce NH₃ and NO_X emissions from ammonia/diesel dual-fuel engines, engine combustion chamber models and DOC-coupled SCR after-treatment models were built using CONVERGE and GT-POWER. The control of NH₃ and NO_X emissions was then investigated by integrating these models with the response surface methodology. The results show that in the range of AER10% to AER40%, as the ammonia substitution rate increases, unburned NH₃ emissions rise but decrease significantly after oxidation by the DOC. NO_X emissions decrease. Advancing the main-injection timing reduces the unburned NH₃ content at the exhaust valve opening, while NO_X emissions increase. With an increase in injection pressure, unburned NH₃ emissions decrease, while NO_X emissions increase. Under the conditions of an engine speed of 1400 rpm and 50% load, with an ammonia substitution rate of 32%, main-injection timing of 2 °CA ATDC, and injection pressure of 140 MPa, along with a DOC carrier diameter of 119 mm, length of 80 mm, and cell density of 100 cpsi, the NH₃ and NO_X emissions of the ammonia/diesel dual-fuel engine can be effectively reduced.