Experimental and Numerical Study on Combustion Enhancement and Emission Reduction via Ammonia Preheating in Ammonia and Gasoline Dual-Fuel Engines

Ammonia (NH3) is considered an ideal alternative fuel for engines. However, with its combustion characteristics, using NH3 in engines might lead to unstable combustion and the production of significant amounts of nitrogen oxide (NOx) and unburned NH3. In this study, the fuel preheating method was applied to an NH3 and gasoline engine for the first time. The emissions and combustion characteristics of the engine were investigated through experiments and simulations at different NH3 preheating temperatures. The chemical reaction pathway of NH3 combustion was determined, and the mechanism by which preheating NH3 affects combustion and emissions in an engine was elucidated. The results indicate that the engine can achieve stable combustion when the NH3 blending ratio is 10%. As the NH3 preheating temperature increases from 373 K to 873 K, NO emissions decrease by 97.09%, and unburned NH3 emissions are close to zero. Analysis of the reaction path reveals that increasing the NH3 preheating temperature enhances both NH3 and gasoline dehydrogenation reactions. Additionally, it shifts the reaction pathway from N2 and H2O producing NO to NH2 consuming NO.