Cynthia C. Webb

Achieving Tier 2 Bin 5 Emission Levels with a Medium Duty Diesel Pick-Up and a NOX Adsorber, Diesel Particulate Filter Emissions System-Exhaust Gas Temperature Management

Increasing fuel costs and the desire for reduced dependence on foreign oil has brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. The main obstacle to the increased use of diesel engines in this platform is the upcoming extremely stringent, Tier 2 emission standard. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies such as common rail fuel injection systems, low sulfur diesel fuel, NO x adsorber catalysts (NAC), and diesel particle filters (DPFs) allow the development of powertrain systems that have the potential to comply with these future requirements. In meeting the Tier 2 emissions standards, the heavy light-duty trucks (HLDTs) and medium-duty passenger vehicles (MDPVs) will face the greatest technological challenges. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity. The primary technology being addressed by these projects is the sulfur tolerance of the NAC/DPF system and the durability implications of varying fuel sulfur levels. The test bed for one project in this activity is a 2500 series Chevrolet Silverado equipped with a 6.6L Duramax diesel engine certified to 2002 model year (MY) Federal heavy-duty and 2002 MY California medium-duty emission standards While NAC systems have demonstrated extremely high levels of NO x reduction in steady-state laboratory evaluations, the application of a NAC system to an actual transient engine application requires the development of an integrated engine/emissions management system [1,2,3,4,5,6,7,8,9,10]. This paper discusses the integrated engine/emissions system management and regeneration control strategies that were developed. The final control strategies achieved over 98% reductions in tailpipe NO x mass emissions over the hot-start portion of the light-duty Federal Test Procedure (FTP-75). This paper discusses thermal management of exhaust gas temperature to maintain the high efficiency window for NAC operation through the use of a diesel-fueled burner. The discussion will cover cold-start strategies and low exhaust gas temperature operation.

Development of a Methodology to Separate Thermal from Oil Aging of a Catalyst Using a Gasoline-Fueled Burner System

Typically, an engine/dynamometer thermal aging cycle contains combinations of elevated catalyst inlet temperatures, chemical reaction-induced thermal excursions (simulating misfire events), and average air/fuel ratios (AFRs) to create a condition that accelerates the aging of the test part. In theory, thermal aging is predominantly a function of the time at an exposure temperature. Therefore, if a burner system can be used to simulate the exhaust AFR and catalyst inlet and bed temperature profile generated by an engine running an accelerated aging cycle, then a catalyst should thermally age the same when exposed to either exhaust stream. This paper describes the results of a study that examined the aging difference between six like catalysts aged using the Rapid Aging Test (RAT) cycle (an accelerated thermal aging cycle). Three catalysts were aged using a gasoline-fueled engine aging stand; the other three were aged using a computer controlled burner system. Both systems were programmed to run aging cycles that provided the same inlet temperature and AFR profiles, and space velocity conditions. Each catalyst was evaluated using a vehicle over the FTP emissions test cycle and an AFR sweep test suing an engine test stand before and after aging. Finally, the catalysts were cored and analyzed to provide a composition and surface area comparison. BACKGROUND

Achieving Tier 2 Bin 5 Emission Levels with a Medium Duty Diesel Pick-Up and a NOX Adsorber, Diesel Particulate Filter Emissions System - NOX Adsorber Management

Increasing fuel costs and the desire for reduced dependence on foreign oil has brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. The main obstacle to the increased use of diesel engines in this platform is the upcoming extremely stringent, Tier 2 emission standard. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies such as common rail fuel injection systems, low sulfur diesel fuel, NO x adsorber catalysts (NAC), and diesel particle filters (DPFs) allow the development of powertrain systems that have the potential to comply with these future requirements. In meeting the Tier 2 emissions standards, the heavy light-duty trucks (HLDTs) and medium-duty passenger vehicles (MDPVs) will face the greatest technological challenges. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity. The primary technology being addressed by these projects is the sulfur tolerance of the NAC/DPF system and the durability implications of varying fuel sulfur levels. The test bed for one project in this activity is a 2500 series Chevrolet Silverado equipped with a 6.6L Duramax diesel engine certified to 2002 model year (MY) Federal heavy-duty and 2002 MY California medium-duty emission standards. While NAC systems have demonstrated extremely high levels of NO x reduction in steady-state laboratory evaluations, the application of a NAC system to an actual transient engine application requires the development of an integrated engine/emissions management system [1,2,3,4,5,6,7,8,9,10]. This paper discusses the integrated engine/emissions system management and regeneration control strategies that were developed. The final control strategies achieved over 98% reductions in tailpipe NO x mass emissions over the hot-start portion of the light-duty Federal Test Procedure (FTP-75). The discussion will cover NO x mass storage modeling and NAC regeneration management strategies for transient operation over the FTP-75, Highway Fuel Economy Test (HFET), and US06 test (an aggressive driving procedure from the supplemental FTP test) cycles.

FTP and US06 performance of advanced high cell density metallic substrates as a function of varying air/fuel modulation

The influence of catalyst volume, cell density and precious metal loading on the catalyst efficiency were investigated to design a low cost catalyst system. In a first experiment the specific loading was kept constant for a 500cpsi and a 900cpsi substrate. In a second experiment the palladium loading was reduced on the 900cpsi substrate and the same PM loading was applied to a 1200cpsi substrate with lower volume. Finally the loading was further reduced for the 1200cpsi substrate. The following parameters were studied after aging: Catalyst performance of standard cell density compared to high cell density technology Light-off performance and catalyst efficiency as a function of Palladium loading and substrate cell density Catalyst efficiency as a function of AFR biasing The performance of the aged catalysts was investigated in a lambda sweep test and in light-off tests at an engine bench. After pre-testing the catalyst were installed in a MY 2002 - V 6 vehicle to compare the performance of the aged catalysts during the FTP and US06 test cycle before and after AFR adjustments. The test results show advantages of high cell density substrates during FTP cold start and during hot transient condition. The volume of high cell density catalyst can be reduced as compared to standard cell density substrates due to the higher specific efficiency. The palladium loading of high cell density technology can be reduced as a result of faster heat up and faster light-off during FTP cold start compared to 500cpsi catalysts. The results also demonstrate the sensitivity of emission reduction to air-fuel ratio for high cell density converters.

Study of Modern Application Strategies for Catalytic Aftertreatment Demonstrated on a Production V6 Engine

A study was performed to develop optimum design strategies for a production V6 engine to maximize catalyst performance at minimum pressure loss and at minimum cost. Test results for an advanced system, designed to meet future emission limits on a production V6 vehicle, are presented based on FTP testing. The online pressure loss and temperature data serves to explain the functioning of the catalyst.

Advanced Performance of Metallic Converter Systems Demonstrated on a Production V8 Engine

It has been shown within the catalyst industry that the emission performance with higher cell density technology and therefore with higher specific geometric area is improved. The focus of this study was to compare the overall performance of high cell density catalysts, up to 1600cpsi, using a MY 2001 production vehicle with a 4.7ltr.V8 engine. The substrates were configured to be on the edge of the design capability. The goal was to develop cost optimized systems with similar emission and back pressure performance, which meet physical and production requirements. This paper will present the results of a preliminary computer simulation study and the final emission testing of a production vehicle. For the pre-evaluation a numerical simulation model was used to compare the light-off performance of different substrate designs in the cold start portion of the FTP test cycle.

Fuel Sulfur Effects on a Medium-Duty Diesel Pick-Up with a NOx Adsorber, Diesel Particle Filter Emissions Control System: 2000-Hour Aging Results

Discusses the emission results of a nitrogen oxide adsorber catalyst and a diesel particle filter in a medium-duty, diesel pick-up truck.