Modeling of Integrated Aftertreatment Systems: A Highly Configurable System Level Approach

In order to meet the increasingly stringent emissions standard it is imperative that a two pronged approach is pursued for reduction of tailpipe emissions. In this regard emissions, and often the exhaust compositions, are needed to be controlled both at its source and then subsequently cleaned up at the exhaust system. In addition, an aftertreatment system often consists of an array of catalysts and its performance depends on the transient characteristics of the exhaust gas composition. To complicate the matter furthermore, relevant technologies are still evolving at a rapid pace. Consequently, an aftertreatment modeling approach should not only be system based but also offer a high level of configurability. Thus a system level approach that includes a model of an engine and vehicle may provide an efficient means to analyze system performance and examine relative effects of competing phenomena and technologies. Additionally, it could also be an effective tool for interpretation of experimental data. Another aspect of aftertreatment modeling is that appropriate kinetics is a highly sensitive function of formulation and physical description of the catalysts. Often a set of global kinetics is used to model a particular catalyst and these are not likely to be valid for others. Furthermore, these mechanisms are closely guarded by the manufacturers and may not be readily available or shared.

In order to address these issues, a Kinetics template Library has been created in the self-contained environment of GT-POWER for modeling of aftertreatment chemistry. This library can be applied to model various aftertreatment devices incorporated as coupled subsystems of an overall engine/vehicle model. An arbitrary set of chemical mechanisms can be incorporated into the catalyst models which are then integrated by the built-in solver. Furthermore, these mechanisms can be optimized using experimental data and built-in optimizer. In this work examples of aftertreatment systems and associated control systems will be modeled and analyzed.