Inner Selective Non-Catalytic Reduction Strategy for Nitrogen Oxides Abatement: Investigation of Ammonia Aqueous Solution Direct Injection with an SI Engine Model

This study contributes to a method based on an aqueous solution of ammonia direct injection for NOx emissions control from internal combustion engines. Many previously published studies about deNOx technology are based on selective catalytic reduction (SCR), but only few deal with inner selective non-catalytic reduction (inner SNCR) technology, which is an intensive improvement of selective non-catalytic reduction (SNCR) applied in the in-cylinder purification procedure. Before numerical calculations were carried out, the computational fluid dynamic (CFD) simulation model was validated with steady-state experimental results. The main results revealed that with the increasing concentration of aqueous solution of ammonia, nitrogen oxides gradually decrease, and the largest decline of NOx is 65.1% with little loss of cylinder peak pressure. Unburned hydrocarbon (UHC) and carbon monoxide (CO) may increase using inner SNCR, and soot emissions show a decreased tendency. However, there is little change when ammonia content varies. Ulteriorly, refining the direct injection phase is of great help to inner SNCR technology to enhance the reduction of NOx and reduce NH3 oxidation and NH3 slipping.