A Development of SCR (Selective Catalytic Reduction) Model and Its Applications

A physics-based model for SCR (Selective Catalytic Reduction) was developed based on five independent SGB (Synthetic Gas Bench) tests. There are NH3 adsorption & desorption test, NO oxidation test, NH3 oxidation test, SCR reaction (NOx & NH3) test and SV (Space Velocity) test. To validate the accuracy of SCR model’s prediction, transient reactor tests were conducted at four different input conditions. A newly developed SCR model showed more than 90% prediction accuracy in transient test conditions in view of cumulative NOx. Validation of SCR model was conducted on 1.6L light duty diesel vehicle in the WLTC (Worldwide Harmonized Light vehicles Test Cycle). Based upon this SCR model, vehicle level SCR calibrations used for urea dosing control were made and validated in the emission test cycles like WLTC. NOx and NH3 slip from calibration data (map data for dosing control of urea solution) DCU calculated by SCR model were comparable with those from calibration data measured on engine bench and vehicle. Calibration data from SCR model replace calibration data from conventional engine and vehicle tests with negligible changes for NOx removal performance. SCR model with high prediction accuracy for NOx can reduce development time and expense by replacing calibration data from conventional tests with those from SCR model. SCR system can be developed earlier by SCR model and new SCR catalyst can be easily screened by SCR model and calibration data can be calculated by SCR model. Target NH3 storage levels at various SCR temperatures can be optimized based on SCR model with the help of minimal engine and vehicle tests. Calibration data for DCU (Dosing Control Unit) and optimal target NH3 storage levels before main development can be obtained by SCR model.