| Energy Engineering |
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| Effect of rich air/fuel ratio and temperature on NOx desorption of lean NOx trap |
| Lei Liu, Zhi-jun Li, Hong-yang Zhang, Qing Chang, Bo-xi Shen |
| State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China |
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Abstract An experimental and model-based study of the effect of rich air/fuel ratios (AFRs) and temperature on the NOx slip of a lean NOx trap (LNT) was conducted in a lean-burn gasoline engine with an LNT after-treatment system. The emissions of the engine test bench and the inlet temperature of the LNT were used as the major inlet boundary conditions of the LNT. The engine periodically operated between a constant lean AFR of 23 with alterable rich AFRs of 10, 11, 12, 13, and 14. A decrease in the rich AFR of the engine strengthened the desorption atmosphere in the LNT, an effect closely related to the number of reductants, and further heightened the NOx desorption of the LNT, but with a penalty in fuel consumption. To eliminate that penalty, the inlet boundary conditions of the LNT were varied by adjusting the inlet temperature within a range between 200 °C and 400 °C. An increase in inlet temperature heightened the NOx desorption of the LNT, and a NOx breakthrough occurred after the inlet temperature exceeded 390 °C. To control NOx breakthrough, the inlet temperature can be adjusted to offset the strong desorption atmosphere in the LNT commonly created by a rich AFR.
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Received: 13 June 2013
Published: 04 November 2013
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