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This paper describes the development of a 0-D-sulfur poisoning model for a NOx storage catalyst (NSC). The model was developed and calibrated using findings and data obtained from a passenger car diesel engine used on testbed. Based on an empirical approach, the developed model is able to predict not only the lower sulfur adsorption with increasing temperature and therefore the higher SOx (SO2 and SO3) slip after NSC, but also the sulfur saturation with increasing sulfur loading, resulting in a decrease of the sulfur adsorption rate with ongoing sulfation. Furthermore, the 0-D sulfur poisoning model was integrated into an existing 1-D NOx storage catalyst kinetic model. The combination of the two models results in an “EAS Model” (exhaust aftertreatment system) able to predict the deterioration of NOx-storage in a NSC with increasing sulfation level, exhibiting higher NOx-emissions after the NSC once it is poisoned.

The introduction of more stringent standards for engine emissions requires continuous improvement of exhaust gas aftertreatment systems. Modern systems require a combined design and application of different aftertreatment devices. Computer simulation helps to investigate the complexity of different system layouts. This study presents an overall aftertreatment modeling framework comprising dedicated models for pipes, oxidation catalysts, wall flow particulate filters and selective catalytic converters. The model equations of all components are discussed. The individual behavior of all components is compared to experimental data. With these well calibrated models a simulation study on a DOC-DPF-SCR exhaust system is performed. The impact of pipe wall insulation on the overall NOx conversion performance is investigated during four different engine operating conditions taken from a heavy-duty drive cycle.

Optimizing non-road applications is an ongoing challenge with the increasingly stringent emissions legislations. TIER 4 final will be introduced in the US starting in 2013 and Stage IV in the EU one year later. India, China and Japan are moving towards implementing similar emissions levels. Rapid deployment of advanced technologies will be needed to achieve the emissions regulations with minimized fuel consumption as well as low system and development costs. The enormous diversification of engines within the different power classes requires specific solutions to meet the legislation limits. New technologies will be introduced such as electronic fuel injection, cooled EGR and exhaust aftertreatment systems like a PM filter and/or SCR. Off-road operation has specific requirements regarding duty cycles, exhaust temperatures, robustness and durability, therefore on-road emissions solutions are only transferable to a limited extent.