Experimental study of lubricant-derived ash effects on diesel particulate filter performance

Abstract

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.