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

Abstract

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 NO 2 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-Ø267mmX305mm (Ø10.5"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.

Characteristics and Effects of Lubricant Additive Chemistry on Ash Properties Impacting Diesel Particulate Filter Service Life

“…In addition to setting a cap on sulfated ash, the CJ-4 specification places specific chemical limits on the total amount of sulfur and phosphorous in the lubricant [8]. Engine manufacturers have also sought to address the issue through reduced engine oil consumption, and aftertreatment system manufacturers have developed unique means for increasing the ash storage capacity of DPFs [9]. Despite these measures, little is known regarding the effect of individual lubricant additives on DPF performance degradation, and diesel particulate filters still require periodic servicing for ash cleaning.…”

Diesel aerosols and gases in underground mines: guide to exposure assessment and control.

“…), which are composed of metallic elements. When these fluids are consumed during combustion, these metallic elements can form inorganic solids known as ash [Whitacre et al 2010;Jung et al 2003;Aravelli and Heibel 2007]. Normal wear of metallic engine components are another, though less substantial, s ource of ash generation.…”

“…Although the process of oil consumption is still not clearly understood, it is suggested that lubrication oil may enter the combustion chamber through reverse blowby (i.e., flow from crankcase gases past piston rings), vaporization from the cylinder walls, leaks in the valve stem seals, the turbocharger lubrication system, a nd other pathways [Froelund and Yilmaz 2004;Yilmaz 2003;Jung et al 2003]. Some products resulting from the combustion of lubricating oil are increased organic emissions of DPM, gaseous sulfuric emissions, a nd noncombustible DPM known as ash [Plumley 2005;Miller et al 1997;Aravelli and Heibel 2007;Kittelson et al 2008].…”

“…The base oil is formed from petroleum-derived mineral oils and provides the lubrication qualities of the liquid. The additive package is a combination of various chemicals and metal compounds that act as detergents, dispersants, acid neutralizers, antioxidants, corrosion and rust inhibitors, and anti-wear additives [Whitacre et al 2010;Jung et al 2003;Aravelli and Heibel 2007]. Most of these metals contribute to the formation of ash or solid, noncombustible byproducts that can accumulate within DPFs [Miller et al 2007a;Vouitsis et al 2007] .…”

A transfer matrix approach for structural–acoustic correspondence analysis of diesel particulate filter

“…Asymmetric cell design was introduced under the pursuit of providing additional filtration area and storage space for the ashes that inevitably accumulate in the DPF. 6,[30][31][32] In the asymmetric DPF design especially the asymmetric hexagonal shape configuration were more inlet channels than outlet channels to obtain larger filtration area. Table 3 shows four typical types of asymmetric and variable cell DPF layout.…”