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This study compared the NOx emissions of a nonroad compression ignition engine using pilot injection and a NH 3 -SCR system and revealed their effects on NOx reduction. Furthermore, the interaction of pilot injection and the NH 3 -SCR system on NOx reduction was also studied by simultaneously using the two technologies under broad engine operating conditions. The pilot-main interval and the rate of pilot-to-main injection used in this study are in the range of 2∼8 CA and 9.5∼58.5%, respectively. Results showed that alteration in the pilot-main injection interval and the pilot-injection fuel amount under low load conditions was prone to lead to more variation in NOx emissions in comparison with that under high-load conditions. Relative to the pilot-main injection interval, the pilot-injection fuel amount played a more important role in the NOx emission. Lower NOx emissions could be achieved when using a smaller pilot-injection amount. However, excessively advanced pilot injection and a larger pilot-injection amount would increase the NOx emissions. Under a lower engine load, the effect of pilot injection on NOx reduction enhanced, whereas the effect of the NH 3 -SCR system diminished. Over broad operating conditions, the NOx reduction percentage by pilot injection coupled with the SCR system was lower than the total reduction degree when separately using pilot injection and the SCR system.

Amorphous phase MnOx/TiO2 catalysts were prepared by two different methods, their catalytic activities for low temperature selective catalytic reduction (SCR) of NOx with NH3 in the presence of excess oxygen were investigated. The catalysts were characterized by XRD, XPS and HRTEM. The results showed that the catalyst prepared by soft template method had better catalytic active than those prepared by sol-gel method, its catalytic property could reach 98.2% at 200°C. From the microstructure characterization, it could be known that the catalyst prepared by soft template had the shape of nanorod, this shape was contributed to the dispersion of the manganese oxides and possessed higher surface lattice oxygen concentration. Furthermore, narrow slit-shaped pores associated with rod-like particles could provide efficient transport pathways to reactant molecules and products. Due to these, the catalyst performed catalytic active very well.