An efficient reduced model of NH3-SCR converters for mobile aftertreatment systems

We derive reduced models (RM) of NH3-SCR automotive converters as a strategy to provide accurate simulations with minimized computational costs, in view of applications to the rapid calibration of SCR kinetics and to on-board control of the engine after-treatment systems. In the first part of this work, a reduced model of SCR monolithic catalysts is developed. To decrease the computational effort, a combination of explicit Euler methods for ODEs integration in time and backwards finite differences for discretization of space derivatives is implemented, adopting a simplified approach to calculate the region of stability of the explicit method. In the second part, we compare the reduced model with a reference, fully detailed SCR monolith converter model in terms of accuracy and computational costs for different engine test cycles, comprising cold start transients, for both light- and heavy-duty diesel engines. The tests demonstrate a decrease in the computational time for RM with respect to the reference full model by one to two orders of magnitude, while retaining a comparable accuracy.