Synergetic DOC-DPF System Optimization Using Advanced Models

Modern ‘DOC-cDPF’ systems for diesel exhaust are employing Pt-, Pd- as well as Pt/Pd alloy- based coatings to ensure high conversion efficiency of CO, HC even at low temperatures. Depending on the target application, these coatings should be also optimized towards NO₂ generation which is involved in low temperature soot oxidation as well as in SCR-based deNOx. Zeolite materials are also frequently used to control cold-start HC emissions. Considering the wide variety of vehicles, engines and emission targets, there is no single optimum coating technology. The main target is therefore to maximize synergies rather than to optimize single components. At the same time, the system designer has nowadays a wide range of technologies to choose from, including PGM alloyed combinations (Pt/Pd), multiple layers and zones applicable to both DOCs and DPFs. This paper attempts to deal with the specific problem of optimizing such complex synergies, using advanced modeling techniques and exploiting a large number of ‘virtual’, rather than ‘real’ experiments. A systematic study of simple (single-PGM, single-layered) coating technologies is the starting point to generate a reaction model database, which is then used to simulate more complex, multi-component, multi-zoned and multi-layered systems.