Investigation on the reduction in unburned ammonia and nitrogen oxide emissions from ammonia direct injection SI engine by using SCR after-treatment system

Currently generated nitrogen oxides (NO(x)) and unburned ammonia (NH(3)) can be converted into nitrogen and moisture that are harmless to the human body and environment using selective catalytic reduction (SCR). The concentrations of NO(x) and unburned NH(3) emitted from the ammonia combustion engines are significantly higher than those emitted by engines using existing hydrocarbon fuels. In this study, ammonia, a representative carbon-free fuel, was used in spark ignition engines for existing passenger vehicles to identify the trends in exhaust gases emitted from engines and conduct experiments on after-treatment strategies to reduce NO(x) and unburned NH(3). The addition of oxygen significantly maximized the conversion efficiency of the SCR after-treatment system by changing the concentration of both NO(x) and NH(3) in the exhaust gas.