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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.

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.

To meet tightening emissions standards, alternate pollution abatement technologies are necessary, such as an In-Line Adsorber (ILA) system. The ILA has a first catalyst, an adsorber, and a second catalyst. A diverter directs exhaust gas through the adsorber to capture unconverted hydrocarbons until the first catalyst reaches light-off temperature. The ILA system was designed so that the second catalyst becomes active concurrent with the adsorber hydrocarbon desorption. The system was evaluated using the FTP test with two different secondary air strategies on 3.8 liter V6 and 4.0 liter V8 vehicles. The ILA system performance consistently reduced ∼50-60% of cold start hydrocarbon emissions. This study examined a simplified ILA system designed to operate with a commercial secondary air pump powered by the engine.

Extruded metal honeycombs are used as electrically heated catalysts (EHCs). The durability requirements of this application make demands on high surface area, thin cross-section metal honeycombs. Significant durability improvements over previous extruded metal honeycomb EHCs have been achieved by material and package design changes. The product redesign was supported by finite element models and extensive testing. The redesigned EHC has passed severe laboratory and field testing. The tests include electrical cycling to 1000°C/1600 cycles, hot vibration to 60g/900°C and demanding on-vehicle exposure. Excellent durability of the extruded metal honeycomb has been demonstrated.

Low mass, extruded electrically heated catalysts (EHC) followed directly by a light-off and main converter reduced cold start non-methane hydrocarbons (NMHC) by greater than 80 percent. These reductions were demonstrated on several vehicle applications operating over the Light Duty Federal Test Procedure (FTP). To achieve this level of reduction, the design of the EHC cascade system, power level and heating time must be appropriately established. This paper discusses the impact of these design parameters on cold-start emissions reduction. From the test results, a generic empirical model was developed to predict EHC system conversion efficiency as a function of EHC power, heating time, and inlet exhaust temperature to the EHC.

Ceramic preconverters have become a viable strategy to meet the California LEV and ULEV standards. To minimize cold start emissions the preconverter must light-off quickly and be catalytically efficient. In addition, it must also survive the more severe thermomechanical requirements posed by its close proximity to the engine. The viability of the ceramic preconverter system to meet both emissions and durability requirements has also been reported recently(1,2). This paper further investigates the impact preconverter design parameters such as cell density, composition, volume, and catalyst technology have on emissions and pressure drop. In addition, different preconverter/main converter configurations in conjunction with electrically heated catalyst systems are evaluated. The results demonstrate that ceramic preconverters substantially reduce cold start emissions. Their effectiveness depends on preconverter design and volume, catalyst technology, and the system configuration.

Low mass extruded electrically heated catalysts (EHC) followed directly by light-off and main converters resulted in non-methane hydrocarbon emissions (NMHC) between .020 and .023 g/mi at power levels as low as 1 kw and energy levels as low as 4 whr. These results were achieved on a 1993, 2.2 liter vehicle. The success of this system is due to rapid heat up of the catalyzed surface areas of both the heater and light-off converter. The energy added to the exhaust from both the heater and the light-off is then efficiently transferred to the main converter. In addition, the impact of power and energy on NMHC levels was determined. The Ultra-Low Emissions Vehicle (ULEV) standard was also achieved with uncatalyzed heaters and on a 1990, 3.8 L vehicle. The new California Low Emission Vehicle (LEV) and Ultra Low Emission Vehicle (ULEV) standards require a significant reduction in tail pipe emissions compared to current standards.

This paper details the development of the EX-80 composition, a new cordierite material for use as a diesel particulate filter (DPF), that was developed based on the following objectives; (1) improved thermal durability, (2) high filtration efficiency and (3) low pressure drop. The achievement of these goals was demonstrated through engine testing, stress modeling, and other evaluations. EX-80 has a low coefficient of thermal expansion (CTE) averaging less than 4x10-7°C-1 (25°C-800°C), the Modulus of Rupture (MOR) averages greater than 350 psi and the Modulus of Elasticity (MOE) averages less than 0.8 x 106 psi. The improvement of these three properties has resulted in improved thermal durability for EX-80 as compared to the current Corning DPF compositions (EX-47, EX-54 and EX-66). The new cordierite composition has been designed to achieve a low pressure drop as a function of soot loading (0.30 inHg/gm of soot collected), coupled with high efficiency, averaging greater than 90%.

Improved designs of extruded metal electrically heated catalysts (EHC) in combination with a traditional converter achieved the California ultra-low emission vehicle (ULEV) standard utilizing 50% less electrical energy than previous prototypes. This energy reduction is largely achieved by reducing the mass of the EHC. In addition to energy reduction, the battery voltage is reduced from 24 volts to 12 volts, and the power is reduced from 12 kilowatts to 3 kilowatts. Also discussed is the impact EHC mass, EHC catalytic activity, and no EHC preheating has on non-methane hydrocarbon emissions, energy requirements, and power requirements.

Previous papers have considered the role of the substrate in the catalyst system. It has been shown that the total catalyzed surface area of the substrate (defined as the substrate geometric surface area multiplied by the substrate volume) can act as a surrogate for the catalyst performance. The substrate affects the back pressure of the exhaust system and therefore, the available power. Relationships have been developed between the substrate physical characteristics, and both the pressure drop and total surface area of the substrate. The substrate pressure drop has also been related to power loss. What has been lacking is a means of quantitatively relating the substrate properties to the conversion efficiency. This paper proposes a simple relationship between the substrate total surface area and the emissions of the vehicle as measured on the FTP cycle.

The primary objective of this work is to demonstrate that an extruded metal electrically heated catalyst (EHC) in combination with a traditional converter can achieve the Low and Ultra-Low California standards. With various aged EHC/converter systems and various heating strategies, typical FTP non-methane hydrocarbon (NMHC) emissions range from .015 to .030 g/mi. However, NMHC emissions as low as .008 g/mi are achieved. In addition to reducing emissions, experiments were conducted to investigate the impact various heating strategies and system design parameters have on electrical energy usage. The conclusions are that electrical energy requirements can be significantly reduced by: Locating the EHC close to the main converter. Locating the EHC and main converter close to the engine. Reducing the mass of the EHC. Heating the EHC prior to engine start-up.

The current automotive catalytic converter is highly dependable and provides excellent emissions reduction while at the same time it offers little resistance to the flow of gasses through the exhaust system. As automobile performance requirements increase, and as the allowable tailpipe emissions are tightened, there is a need on the one hand to reduce the back pressure even further, and on the other, to increase the already excellent catalytic performance. This paper will analyze the substrate factors which influence the pressure drop and conversion efficiency of the catalyst system. The converter frontal area has the most significant influence on both pressure drop and conversion efficiency, followed in order by part length, cell density, and wall thickness.

Ceramic monolithic catalyst supports have been an integral part of automotive emissions control systems since the early 70's. This investigation examines the impact of physical (cell density, frontal area, volume) and material (porosity, thermal mass) design parameters on vehicle emissions and pressure drop. This study indicates that CO and HC emissions can be reduced by larger volume and/or higher cell density substrates. Materials changes have little or no impact on catalyst performance. Pressure drop is increased by using a longer substrate, and dramatically reduced with a larger frontal area part.