Improved Lifetime Pressure Drop Management for Robust Cordierite (RC) Filters with Asymmetric Cell Technology (ACT)

The stricter emissions legislation in the US, require the implementation of Diesel Particulate Filters (DPF) for Heavy Duty Diesel engines to meet the 2007 PM emissions targets. Cordierite based wall-flow filters with high filtration efficiency, low p and good thermal durability are the product of choice for these applications. Continuous passive oxidation of the soot by NO2 is desired, however under certain operating and ambient conditions periodic active oxidation of the soot at elevated temperatures (>550oC) is required. A part of the PM emissions of the engine contains noncombustible contributions (ashes). These materials accumulate in the filter over lifetime, resulting in an increase in pressure drop as well as a reduction of the filter volume available for soot accumulation. As the pressure drop rises above manageable levels from a performance perspective, ash cleaning of the filter is required. The ash storage capacity of the filter determines the service interval for the filter. Long service intervals are desired by the end customer. To mitigate the impact of the ash accumulation in the filter, Corning Incorporated has developed filters with the proprietary asymmetric cell technology (ACT), providing high ash capacity with good strength attributes. These filters have larger inlet and smaller outlet channels and therefore a higher volume available for ash storage. The present work summarizes the results of on-engine (HD) ash testing on uncoated Robust Cordierite (RC) filters – O267mmX305mm (O10.5”x12”) in both Standard (200/19) and ACT (270/16) design configurations. The work demonstrates, for an equal size filter a 30% improved ash storage capacity and therefore longer service interval for the ACT design over the standard filter. Good durability of the filters for a long operation timeframe (up to 2700h) was demonstrated. Furthermore the paper summarizes a wide set of post testing evaluations, both non-destructive and destructive to understand the ash distribution and interactions in the filter. INTRODUCTION Due to their high efficiency, excellent power output and good durability aspects diesel engines have been selected as the most attractive propulsion system in key sectors of the economy. With the increase in fuel costs and further improvements in diesel engine technology the expansion of diesel engine technology in other application segments is anticipated. On the other hand the ever tightening emissions regulations require significant reduction in the tailpipe emissions. For example the US HDD on road emissions legislation requires 90% reduction in PM emissions by 2007(relative to 2006 PM limits) and 80% reduction in NOx by 2010 (relative to 2009 NOx limits). The lower emissions are achieved by improvements in engine technology and the use of advanced emissions technologies. Diesel Particulate filters are required for achieving the low PM emissions levels to meet the 2007 US on-road regulations. It is expected that the 2010 NOx limits will be achieved by further advancements in engine technology, improved controls and implementation of DeNOx technology in the form of Selective Catalytic Reduction (SCR) system or Lean NOx Traps (LNT) or a combination of both. Cordierite wall flow monoliths have emerged as the choice of the industry for use as diesel particulate filters (DPFs) due to their compactness and robust design. The design of diesel particulate emissions systems requires balancing of various competing constraints. On the one hand the soot capacity of the filter needs to be sufficiently high to enable the desired regeneration intervals. The soot capacity is driven by the filter volume, the regeneration conditions and control strategy. On the other hand engine back pressure needs to be managed. This includes management of clean and life-time pressure drop for optimized performance of the engine. Corning’s Robust Cordierite (RC) material was developed for medium and heavy duty OEMs and retrofit applications. It provides good soot loading capacity, low pressure drop and excellent durability and strength. 2007-01-0920 Improved Lifetime Pressure Drop Management for Robust Cordierite (RC) Filters with Asymmetric Cell Technology (ACT) Krishna Aravelli and Achim Heibel Corning Incorporated, Diesel Technologies Development