Model-based optimization methods of combined DPF+SCR Systems

The design of integrated exhaust lines that combine particulate and NO_x emission control is a multidimensional optimization problem. The present paper demonstrates the use of an exhaust system simulation platform which is composed of well-established multidimensional mathematical models for the transient thermal and chemical phenomena in DOC, DPF and SCR systems as well as connecting pipe heat transfer effects. The analysis is focused on the European Driving Cycle conditions. Illustrative examples on complete driving cycle simulations with and without forced regeneration events are presented for alternative design approaches. The results illustrate the importance of DOC and DPF heat capacity effects and connecting pipe heat losses on the SCR performance. The possibility of combining DPF and SCR functionality on a single wall-flow substrate is studied. The analysis proceeds by simulations of forced regeneration studies in order to assess the effect of different design approaches on DPF regeneration rate, which is linked on the one hand to fuel consumption penalties and on the other hand to thermal stability.