Three Way Catalyst Modeling with Ammonia and Nitrous Oxide Kinetics for a Lean Burn Spark Ignition Direct Injection (SIDI) Gasoline Engine

A Three-Way Catalyst (TWC) model with global TWC kinetics for lean burn DISI engines were developed and validated. The model incorporates kinetics of hydrocarbons and carbon monoxide oxidations, NO_x reduction, water-gas and steam reforming and oxygen storage. Ammonia (NH₃) and new nitrous oxide (N₂O) kinetics were added into the model to study NH₃ and N₂O formation in TWC systems.

The model was validated over a wide range of engine operating conditions using various types of experimental data from a lean burn automotive SIDI engine. First, well-controlled time-resolved steady state data were used for calibration and initial model tests. In these steady state operations, the engine was switched between lean and rich conditions for NO_x emission control. Then, the model was further validated using a large set of time-averaged steady state data. Temperature dependencies of NH₃ and N₂O kinetics in the TWC model were examined and well captured by the model. Finally, the model was tested in a highly transient FTP drive cycle with cold start conditions. Comparisons between the data and simulation results indicate that the model is able to predict the experimental data fairly well. The global TWC kinetics in this study are a good starting point for further refinement.