Numerical Investigation into the Combustion and Emission Characteristics of Ammonia Direct Injection Mechanism

The effects of diesel and the ammonia ratio on the emissions and combustion characteristics of ammonia utilized in AMMONIA direct injection (AMMONIA-Di) engines were investigated through experimental and numerical investigations. A rapid compression expansion machine (RCEM) modified to facilitate the dual direct injection fuel (diesel-ammonia) - compression ignition (CI) method was used to conduct the experiment. A compression ratio (CR) of 19 and an ammonia energy percentage ranging from 10% to 90% were used in the experiment. Changes were made to the start of injection (SOI) from 0o to 40^o before top dead center (BTDC) in order to find the best auto-ignition properties of ammonia. In order to facilitate auto-ignition, the diesel’s SOI was maintained at 10^o BTDC. Computational fluid dynamics (CFD) modeling was used to establish the detailed emission propagation during the combustion process. During the expansion step, ammonia goes through a second stage of combustion, demonstrating that the fuel cannot burn entirely during the initial auto-ignition process. Emissions of CO2, HC, and NOx rise when direct injection CI engines use up to 50% ammonia. When SOI is applied to ammonia at 0 and 40 BTDC with an ammonia energy percentage higher than 50%, the emissions vary significantly, indicating poor combustion quality that encourages the production of emissions.