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Modelling And Diagnositcs Of NOx After-Treatment Systems
Published October 22, 2006 by Society of Automotive Engineers of Japan in Japan
To attain a reduction in NOx emissions, various after-treatment technologies are being developed. In addition to the emission control, these systems require fault diagnostic schemes to detect failure and to diagnose faults. A by-pass Lean NOx Trap (LNT) system was used for the purpose of control and diagnosis of NOx reduction in a light-duty diesel engine was studied. In the by-pass LNT system, the exhaust was diverted from the catalyst to allow injection of the necessary reductants for regeneration. To maintain LNT operation with high NOx conversion efficiency, the regeneration control and fault diagnosis damage of the LNT are necessary. Therefore, the LNT model, which consists of the storage model and the regeneration model, was developed and verified by experimental data. The fault modes of the LNT, sulfur poisoning and thermal damage, were investigated through the analysis of the experimental data from the LNT system. The regeneration control and fault diagnosis based on the LNT model and the measurement of both LNT inlet and outlet NOx mass flow rate is proposed in this paper.