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With Bharat Stage VI (BSVI) regulations on the horizon [3],[4]tighter particulate matter (PM) regulations will require the use of wall flow diesel particulate filters for on-road heavy duty (HD) diesel engines in India. The Indian HD vehicle market is very cost sensitive, especially with the majority of engine displacement being less than 7L [5] therefore, after treatment cost plays a significant role in design of the system. Robust wall flow diesel particulate filter solutions with the ability to deliver high filtration requirements required for particle number regulations can be designed in a cost-efficient manner. In this paper advanced design for diesel particulate filters with pressure drop, ash capacity, regeneration, and filtration performance are discussed. Corning’s asymmetric cell technology (ACT) was created to improve ash capacity and reduce pressure drop and has the potential to downsize up to 45%.

Diesel particle filters (DPF) have become a standard aftertreatment component for all current and future on-road diesel engines used in the US. In Europe the introduction of EUVI is expected to also result in the broad implementation of DPF's. The anticipated general trend in engine technology towards higher engine-out NOx/PM ratios results in a somewhat changing set of boundary conditions for the DPF predominantly enabling passive regeneration of the DPF. This enables the design of a novel filter concept optimized for low pressure drop, low thermal mass for optimized regeneration and fast heat-up of a downstream SCR system, therefore reducing CO₂ implications for the DPF operation. In this paper we will discuss results from a next-generation cordierite DPF designed to address these future needs.

A theory of diesel exhaust catalysis using an oxidation flow-through type catalyst to reduce particulate emissions is explained. The effects of converter design, catalyst support materials, and the use of noble metals for light and heavy duty applications are discussed. Experiments were performed to determine, 1) the sulfur storage and release characteristics of alumina and silica catalyst support materials and 2) the ability of platinum and palladium to oxidize SO2 to sulfate particulate. Light duty FTP and heavy duty transient results are also presented.

A simple 1-dimensional filter model, with symmetric and asymmetric channels, has been developed to investigate the fundamental behavior and performance of ceramic partial diesel particulate filters (PFs). The governing equations of mass and momentum are similar to those of a full DPF [7, 15]. A standard DPF with the plugs at its inlet face removed has been referred to as a ‘rear-plugged PF’ while, one with the plugs at the outlet face removed has been referred to as a ‘front-plugged PF’ in the present study. Removal of some of the plugs from a standard ceramic DPF reduces the (i) overall pressure drop (ΔP) across the filter, (ii) filtration efficiency (FE) of the DPF, and (iii) manufacturing cost. Partial filters stand a high chance of being deployed in diesel exhaust after-treatment systems for the emerging markets (Brazil, Russia, India, China) that follow Euro 4 emission regulations.

The effects of oil derived poisons and thermal degradation on three-way automotive catalysts is investigated. Dynamometer rapid aging test (RATsm) schedules that incorporate both thermal and oil-derived poison degradation are used to age catalysts for FTP emissions studies. This paper presents three investigations. Vehicle aged converters are analyzed to determine the axial phosphorus distribution through out the catalyst. These phosphorus profiles are compared to dynamometer RATsm aged catalyst. Also, 27 converters were RATsm aged on three different RAT schedules at three different accelerated poison levels. The amount of phosphorus on the catalyst is compared to the amount of equivalent oil consumed by the aging engine. Finally, 24 converters were aged on three different RATsm schedules to determine the effects of catalyst volume, aging temperature and oil derived poisoning on FTP emissions using both Pd and Pt/Rh catalyst technologies.

Automotive catalysts deactivate by thermal and poison mechanisms. Thermal degradation reduces catalyst efficiency by both agglomeration of precious metals and by reduction in surface area of the washcoat. Engine oil derived poisons degrade catalyst performance by coating the outer surface of the washcoat. Numerous catalyst technologies are aged using accelerated dynamometer aging schedules that simulate the thermal and poison degradation of field aged catalysts. Pd, Pd/Rh, Pt/Pd/Rh, and Pt/Rh catalyst technologies are aged and evaluated on various rapid aging test (RATsm) schedules in an effort to ascertain what catalyst technologies may be best for low temperature and high temperature applications. The performance of these catalyst technologies are evaluated on an air/fuel sweep test and a 3.8L auto-driver FTP stand. Results show that the RATsm schedule applies a phosphorus poison distribution (due to engine oil consumption) similar to vehicle aged catalysts.

Highly efficient wall-flow diesel particulate filters (DPF) are the primary means of PM emissions control in light-duty diesel vehicles. The successful commercialization of DPF technology has allowed combining attractive characteristics (good fuel economy, high low-end torque characteristics) of a diesel engine with significant PM emissions reductions to meet the stringent legislation. The design for advanced filter systems is driven by the lifetime pressure drop requirements with the accumulation of non-combustible materials (ashes) over time in the filter. More compact filter designs can be achieved by using filters with the proprietary Asymmetric Cell Technology (ACT) providing a larger inlet channel volume and therefore a higher ash storage capacity in the same space envelope without compromising the filter bulk heat capacity and mechanical integrity.

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 Δp 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 (>550°C) is required. A part of the PM emissions of the engine contains non-combustible 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 objective of this effort was to develop an understanding of how different converter substrate cell structures impact tailpipe emissions and pressure drop from a total systems perspective. The cell structures studied were the following: The catalyst technologies utilized were a new technology palladium only catalyst in combination with a palladium/rhodium catalyst. A 4.0-liter, 1997 Jeep Cherokee with a modified calibration was chosen as the test platform for performing the FTP test. The experimental design focused on quantifying emissions performance as a function of converter volume for the different cell structures. The results from this study demonstrate that the 93 square cell/cm2 structure has superior performance versus the 62 square cell/cm2 structure and the 46 triangle cell/cm2 structure when the converter volumes were relatively small. However, as converter volume increases the emissions differences diminish.

An investigation into the design, development and evaluation of a “new” washcoat technology family that enables significant reductions in rhodium usage levels has been concluded. These findings were demonstrated on three vehicle applications utilizing different calibration A/F control strategies. Additional testing investigated optimal Rh placement on a two brick catalyst system and the impact on FTP and US-06 test cycles. This study concludes with an evaluation of full useful life aged catalysts tested on 6 and 8 cylinder applications that are shown to have met Bin 4 FFV and ULEVII emission standards.

Engine laboratory tests were conducted to assess the impact of B20 biodiesel on the performance of cordierite diesel particulate filters (DPFs). Test fuels included 20% soy based methyl ester blended into ultra low sulfur diesel fuel, and two ULSD on-road market fuels. B20 has a higher cetane number, boiling point and oxygen content than typical on-road diesel fuels. A comparative study was performed using a model year 2007 medium duty diesel truck engine. The aftertreatment system included a diesel oxidation catalyst (DOC) followed by a cordierite wall flow DPF. A laboratory-grade supplemental fuel doser was used in the exhaust stream for precise regeneration of the DPF. Tests revealed that the fuel dosing rate was higher and DOC fuel conversion efficiency was poorer for the B20 fuel during low exhaust temperature regenerations. The slip of B20 fuel past the DOC was shown to produce significantly higher exotherms in the DPF during regeneration.

The relationship between engine oil formulations and catalyst performance was investigated by comparatively testing five engine oils. In addition to one baseline production oil with a calcium plus magnesium detergent system, the remaining four oils were specifically formulated with different additive combinations including: one worst case with no detergent and production level zinc dialkyldithiophosphate (ZDTP), one with calcium-only detergent and two best cases with zero phosphorus. Emissions performance, phosphorus loss from the engine oil, phosphorus-capture on the catalyst and engine wear were evaluated after accumulating 100,000 miles of taxi service in twenty vehicles. The intent of this comparative study was to identify relative trends.

The regulative environment is poised for ultra-low emissions in the 2024+ time frame with ultra-low NOx proposals from CARB and PN PEMS testing requirements from EU. GHG emissions limits are getting tighter in the next few years along with extended full useful life (FUL) requirements. Diesel Particulate Filters (DPF) will be an integral part of all diesel exhaust aftertreatment systems for the next several years and will need advanced technology solutions to meet the challenges above, without compromising on high performance requirements, namely, low lifetime pressure drop, high filtration efficiency, high durability (extended FUL), increased service intervals or lifetime filter solutions (high ash storage capacity). This paper discusses the primary challenges associated with meeting these future demands and possible technological solutions to address them.

With the introduction of the current EU5 standards the diesel particulate filter has become a key element in the aftertreatment of diesel passenger cars. The upcoming future emission standards target primarily a further reduction in NOx emission as well as reduced fleet average CO₂ emissions. Although the particulate filter has no direct influence on the reduction of these species, the needs of future aftertreatment systems impose additional requirements on advanced filter technologies. In this paper we are introducing two new filter products based on a new low porosity aluminum titanate family that complement the current DuraTrap® AT filter products. The new products offer the potential for an increased soot mass limit or a significant reduction in pressure drop. The enhanced performance of the new filter products is discussed and demonstrated in a large number of experimental data obtained in engine bench tests.

In an effort to reduce hydrocarbon emissions for the upcoming vehicle emission regulations, FTP emissions were measured after the warm-up and underfloor converters using a four cylinder 2.3L 1991 engine on an auto-driver dynamometer stand. The warm-up and underfloor converter were located approximately 13 and 69 cm. respectively from the exhaust manifold. The warm-up and underfloor converter volumes varied from 0 - 2.67 liters. A total catalyst volume of 2.67 liters was distributed in 0.67 liter increments between the warm-up and underfloor converters. All of the converters were dynamometer aged appropriately with respect to their intended position in the exhaust system. Platinum/rhodium catalysts were evaluated in the underfloor location with platinum/rhodium or palladium containing catalysts in the warm-up location.

Parametric studies were performed to determine the effects and interactions between aged warm-up and underfloor converters with respect to 1) catalyst volume, 2) precious metal loading and 3) catalyst technology. All the converters were dynamometer aged appropriately with respect to their intended position in the exhaust system prior to emission testing. FTP emissions were measured using a 2.3L engine on an auto-driver dynamometer stand. Catalyst volumes of the warm-up and underfloor converters varied from 0.00 to 1.03 and 1.34 to 2.67 liters, respectively. Precious metal loading of the warm-up converters varied from 50 to 300 g/ft3 of palladium (Pd). The underfloor converters used both platinum/rhodium (Pt/Rh) and Pd precious metal combinations. Pt/Rh loadings varied from 25 to 50 g/ft3 at a 14/1 ratio. Pd loadings varied from 50 to 100 g/ft3. The underfloor catalyst technologies varied in base metal content and/or high temperature stabilizers.

A 100,000-mile fleet test in nine gasoline-powered passenger cars was carried out. The impact of motor oil phosphorus levels on engine durability, oil degradation, and exhaust emissions has been previously described. The results of additional emissions control systems studies, and measurements of the engine oil additive elements which are present on the catalysts, are now presented. These studies include conversion efficiencies for the aged catalyst at the end of the test by a combination of light-off experiments, air/fuel sweep tests, and an auto-driver FTP. The performance of the lambda sensors is also presented. The relationships between engine oil additive levels and composition and emissions systems durability is presented.

A parametric study was performed to investigate the interactions between Pd warm-up and underfloor converters on FTP emissions. Three different Pd warm-up converters were evaluated with six different underfloor converters on two different engines. The Pd warm-up converters primarily differed in the amount of ceria in the catalyst washcoat. These warm-up converters had a catalyst of 0.52 liters and a Pd loading of 100 g/ft3. The underfloor converters had a catalyst volume of 2.67 liters. Two Pt/Rh and one Pd catalyst technology were used in the underfloor converters. Each underfloor catalyst technology was investigated at two different loadings. The Pt/Rh underfloor converters were evaluated at 25 and 50 g/ft3 at a Pt/Rh ratio of 14/1. The Pd containing underfloor converters were evaluated at 50 and 100 g/ft3. All of the converters used in this study were dynamometer aged appropriately with respect to their intended position in the exhaust system.

Close coupled catalysts and new ceramic catalyst substrates have significantly improved the light-off performance of automotive converters required to meet stringent emission requirements. The hotter environment of these catalytic converters and the lower structural strength of the ceramic substrates require the rethinking of converter designs. The development of new package requirements to accommodate the change in environment and new substrates are discussed. A historical perspective on converter durability is presented as reference. Development of durability test protocols is essential to verifying product durability performance to these new environments. Data collection and documentation of testing templates are shown to demonstrate the effectiveness of tests that represent real world environments. Design improvements to address failure modes are discussed along with durability improvement results.

The emission and flow restriction characteristics of three different ceramic substrates with varying wall thickness and cell density (400 cpsi/6.5 mil, 600/4.3, and 600/3.5) are compared. These 106mm diameter substrates were catalyzed with similar amounts of washcoat and fabricated into catalytic converters having a total volume of 2.0 liters. A Pd/Rh catalyst technology was applied at a concentration of 6.65 g/l and a ratio of 20/1. Three sets of converters (two of each type) were aged for 100 hours on an engine dynamometer stand. After aging, the FTP performance of these converters were evaluated on an auto-driver FTP stand using a 2.4L, four-cylinder prototype engine and on a 2.4L, four-cylinder prototype vehicle. A third set of unaged converters was used for cold flow restriction measurements and vehicle acceleration tests.