Diesel particulate filters are indispensable for diesel engines to meet the increasingly stringent emission regulations. A large amount of ash would accumulate in the diesel particulate filter over time, which would significantly affect the diesel particulate filter performance. In this work, the lubricant-derived ash effects on diesel particulate filter pressure drop, diesel particulate filter filtration performance, diesel particulate filter temperature field during active regeneration, and diesel particulate filter downstream emissions during active regeneration were studied on an engine test bench. The test results show that the ash accumulated in the diesel particulate filter would decrease the diesel particulate filter pressure drop due to the “membrane effect” when the diesel particulate filter ash loading is lower than about 10 g/L, beyond which the diesel particulate filter pressure drop would be increased due to the reduction of diesel particulate filter effective volume. The ash loaded in the diesel particulate filter could significantly improve the diesel particulate filter filtration efficiency because it would fill the pores of diesel particulate filter wall. The diesel particulate filter peak temperature during active regeneration is consistent with the diesel particulate filter initial actual soot loading density prior to regeneration at various diesel particulate filter ash loading levels, while the diesel particulate filter maximum temperature gradient would increase with the diesel particulate filter ash loading increase, whether the diesel particulate filter is regenerated at the same soot loading level or the same diesel particulate filter pressure drop level. The ash accumulation in the diesel particulate filter shows little effects on diesel particulate filter downstream CO, total hydrocarbons, N2O emissions, and NO2/NO x ratio during active regeneration. However, a small amount of SO2 emissions was observed when the diesel particulate filter ash loading is higher than 10 g/L. The ash accumulated in the diesel particulate filter would increase the diesel particulate filter downstream sub-23 nm particle emissions but decrease larger particle emissions during active regeneration.

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It is challenging for aqueous urea injection control to achieve high NO x conversion efficiency while restricting tailpipe ammonia (NH3) slip. Optimizing the selective catalytic reduction systems can reduce diesel engine emissions, potentially improve fuel economy and urea utilization efficiency, and finally reduce aftertreatment costs. In this article, a model-based multi-objective genetic algorithm is adopted to optimize selective catalytic reduction systems related to trade-off between NO x emission and NH3 slip. Selective catalytic reduction model is a one-state selective catalytic reduction model based on continuous stirred tank reactor theory, which significantly reduces the computational burden. The optimal NH3 coverage ratio map was obtained globally based on world harmonized transient cycle. The effect of temperature on optimal NH3 coverage ratio, Zonal control logics extracted from the optimal solution, and the control problems on different zones were analyzed. The zonal control logics were validated on multiple test cycle with different initial NH3 coverage ratios. Results show that the zonal control achieves high NO x conversion while restricting the tailpipe NH3 slip. With this method, NO x emission and NH3 slip of optimal solution can meet the requirements of the Euro VI emission regulation for heavy-duty diesel engines.

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