Control Oriented Models for Exhaust Gas Aftertreatment; A Review and Prospects

Modeling is of increasing significance to the automotive applications of catalyst systems. For exhaust gas after-treatment, prediction of exhaust emissions plays an important role in the design process for new vehicles. However both control and diagnosis requirements on the vehicle have created the need for control-oriented models. A control-oriented model is both compact and accurate and may be embedded in a computer system as a component of a real-time algorithm.

Modeling of catalysts can take place at a molecular level where computational techniques are only just emerging. Detailed kinetics modeling done alongside thermal and fluid modeling of the catalyst yields important details about the dynamic behavior of the catalyst system.

Approaches to developing control-oriented model have tended to use the simplest statements of kinetics. In general, the development of such models requires the inclusion of some chemical kinetics. The future demands on after-treatment systems and particularly the long term accuracy requirements for on-board diagnosis (OBD) means that control oriented models will need to become more accurate. Accuracy in turn will require that kinetics be taken into account.