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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.

In order to reduce the cost of exhaust aftertreatment development, OEMs are increasingly relying on simulation of catalysts, traps and associated control systems. In this regards, for example, considerable progresses have been made on modeling diesel particulate filters. The work described in this paper was sought to provide a valid diesel particulate filter (DPF) model for coupling with engine/vehicle models under the same toolbox. A comprehensive two-level modeling approach, including a lumped parameter model and a detailed 1-D 3-layer-kinetics model, has been proposed for modeling wall-flow diesel particulate filters. Both are capable of modeling virtually all aspects of filter performance in terms of deep-bed filtration, particulate matter loading and filter regeneration.

This article describes a system level 1D simulation tool that has been constructed on the Quasi-steady (QS) method. By assuming that spatial changes are much greater than the temporal ones, rigorous 1D governing equations can be considerably simplified thus becoming less computationally demanding to solve and therefore suitable for control oriented modeling purposes. With the proposed tool exhaust pipe wall temperature profiles, including multiple-wall-layer configurations, are solved through a finite difference scheme. Momentum equation is included for predicting pressure losses due to frictions and geometric irregularity. Exhaust fluid properties (transport and thermodynamic) are evaluated according to NASA or JANAF polynomial thermal data basis. The proposed tool allows the consideration of an arbitrary number of chemical species and reactions in the entire system. A novel semi-automatic approach was developed to handle catalytic reaction kinetics intuitively.

It has recently been suggested in an experimental study that an aged DOC could be net consumer of engine out NO2 (Katare et al, 2007) thus inhibiting the fast reaction (2NH3 + NO + NO2 => 2N2+3H2O) in an SCR that might follow. Both engine test and flow reactor results indicated that at low temperatures CO and HC reduces NO2 to NO and that CO is much better reductant than HC. The present study investigates the mechanistic story behind this experimentally observed phenomenon by means of a global reaction mechanism. It also investigates the role of CO inhibition of NO oxidation at higher temperature which also plays key role in the overall oxidation efficiency of a DOC. Once a suitable mechanism is defined by comparing against measurements, the current study will use it to examine conditions under which DOC can destroy NO2 and to propose possible strategies to avoid NO2 consumption in order to obtain high SCR efficiency.

Engines and vehicle systems are becoming increasing complex partly due to the incorporation of emission abatement components as well as control strategies that are technologically evolving and innovative to keep up with emissions requirements. This makes the testing and verification with actual prototypes prohibitively expensive and time-consuming. Consequently, there is an increasing reliance on Software-In-the-Loop (SIL) and Hardware-In-the-Loop (HIL) simulations for design evaluation of system concepts. This paper introduces a methodology in which detailed chemical kinetic models of catalytic converters are transformed into fast running models for control design, calibration or real time ECU validation. The proposed methodology is based on the use of a hybrid, structured, semi-automatic scheme for reducing high-fidelity models into fast running models.