Experimental and 2-D simulation studies on urea pulse strategies to investigate chemical reactions in Cu-Chabazite SCR catalysts

Abstract

To meet the stringent emission regulation of future diesel engines, it is essential to develop innovative aftertreatment systems, especially selective catalyst reduction (SCR) systems. NOx emissions are purified in the SCR systems using urea water injection to the catalyst surface. The SCR system can convert NOx efficiently under a wide temperature range. However, its conversion performance deteriorates at exhaust gas temperatures T ≤ 200°C. Therefore, urea pulse injection strategy improves SCR conversion rate under low exhaust temperatures. This work aims to develop a more precise numerical model that follows the engine test results. Therefore, firstly the radial temperature distributions are recorded to decide the model boundary conditions. The measured engine test data are then used for validation on the simulation model under exhaust gas temperature of T = 200°C (constant and pulse supply). Additionally, the reaction rate of T = 300°C was compared with validation of chemical reaction rate. The model was able to predict the NOx conversion processes reasonably, which leads to a further understanding of the production rate of major gas and solid species in the Cu-chabazite SCR system. The effect of reaction rate parameters on NO and NO₂ emissions are also reported.