Three Way Catalyst and Lean NOx Trap Modeling for a Lean Burn SIDI Gasoline engines

Jian  Gong, University of wisconsin-Madison

ORAL PRESENTATION: A Three Way Catalyst (TWC) model and a Lean NOx Trap (LNT) model with global kinetics for lean burn DISI engines were developed and validated. Ammonia (NH3) kinetics and new nitrous oxide (N2O) kinetics were added into the TWC model to study NH3 and N2O formation in TWC systems. Absorption and desorption of NOx were modeled in the LNT model.
The TWC and LNT model were validated over a wide range of engine operating conditions using various types of experimental data from a lean burn automotive SIDI engine. The data was provided by Oak Ridge National Laboratory (ORNL) with General Motors Research and Development (GM R&D) support. First, well controlled time-resolved steady state data was used for calibration and initial model tests. In these steady state operations, the engine was dithered between lean and rich conditions. Then, the TWC and LNT model were further validated using a large set of time-averaged steady state data. Temperature dependency of NH3 and N2O kinetics were examined using the TWC model. NOx absorption and desorption characteristics in the LNT were studied. Finally, the developed models were tested in a highly transient FTP drive cycle with cold start conditions. Comparisons between the data and simulation results indicate that the TWC and LNT models are able to predict the experimental data fairly well. The global kinetics of the TWC and LNT models in this study are good starting points for further refinement of kinetics.

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