Simplified Modeling of a Lean NOx Trap Catalyst for an Engine Control System

The lean NOx trap catalyst is a flow through device used in the aftertreatment of lean-burn engine exhaust gas. A simple model capable of simulating catalyst performance would be extremely useful in the development of a viable control system for switching back and forth between lean and rich operation in order to use a lean NOx trap catalyst. Such a model would have to be simple and yield calculated results quickly if it is to serve the ultimate objective of implementing a practical engine control unit for lean-burn engines. The model developed in this work adopts a datamap search approach featuring a simple NOx storage reaction mechanism. More specifically, the model accurately simulates NOx that is not adsorbed under lean conditions (NOx leak) and NOx that is not purified under rich conditions (NOx slip). By projecting the impact of ageing on catalyst performance, the model can also estimate diminished NOx emission capacity and fuel economy.