Development of a 1D Urea-SCR system model coupling with wall film decomposition mechanism based on engine bench test data

Abstract

Selective Catalytic Reduction (SCR) is a most promising technique for reduction of nitrogen oxides (NOx) for diesel engines. Urea Water Solution (UWS) is injected into hot exhaust gas stream to generate gaseous ammonia. The thermal decomposition of urea has a crucial effect on the performance of the SCR system. A 1-D multi-step global kinetic SCR model was developed using real engine exhaust data. The model was calibrated with the carefully chosen steady state experimental data and was validated by engine test data covering a wide range of temperature and space velocity (SV). In order to reduce the mean errors at low temperature and low SV, a 1-D wall film model was coupled with the current SCR kinetic model. The results show that the predictions at 210℃ can be significantly improved by the application of the wall film model. Moreover, the main trend of the fluctuation effect of transient profile at 310℃ can be also seized by the model.