Development and Application of a Lean NOX Trap Model

A model was developed for a lean NOx trap (LNT) used in a diesel application. The accuracy of the LNT model was validated using data from flow reactor experiments and vehicle testing. It is demonstrated that the model agrees with the experiments reasonably well on both reactor and vehicle test data.

The LNT model was then applied to simulate the NOx emissions at the trap outlet over the FTP cycle, and quantitatively evaluate the effect of inlet CO concentration, inlet H₂ concentration, inlet gas temperature, and trap size on NOx conversion performance of the LNT.

The LNT model was also integrated with an exhaust pipe model to investigate the impact of engine exhaust configuration on NOx conversion. The integration of the LNT model with the engine exhaust model is valuable in the assessment of engine exhaust configuration and NOx trap performance. The integrated analysis tool could be used to significantly reduce the design cycle and development costs of the engine and aftertreatment system. While the comparisons in this paper were made with a diesel engine, the model is equally applicable to lean operation of SI engines.