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Diesel engine emission regulations throughout the world have progressed over the last 20 years. In the U.S. the most stringent medium/heavy duty standard will be implemented for on highway vehicles starting in 2010. Although changes to engine design will improve engine out emissions, in order to meet both PM and NOx regulations, combination systems including PM and NOx aftertreatment, are planned to be utilized. In order to achieve the required regulations, a new substrate technology has been developed using advanced “turbulent” flow characteristics, and it has been combined with a novel approach to reduce system complexity: the “SCRi™” or “SCR integrated” system. Such a system uses a continuously operating PM-Metalit with advanced “turbulent” SCR-catalysts in a unique configuration. The reduction of both PM and NOx also has to be seen in context with its effect on CO2 emissions.

Diesel engine emissions regulations throughout the world have changed dramatically over the last 20 years, with the most stringent phase for medium/heavy duty being implemented starting 2007 - 2010. The general perception is, that combination systems including PM reduction devices and NOx aftertreatment, likely SCR will be applied, hence significant additional emissions equipment will need to be added to a diesel engine. The consequences of this will be increased space for packaging and increased cost, to meet the demanding regulations. Traditional substrate technology, while developing extensively for gasoline engines by use of higher cell densities has limitations when applied to CI diesel engines. New developments in substrate and coating technology now enable considerable improvement in the efficiency and packaging space needed to meet certain limit values.

Prototype selective catalytic reduction (SCR) systems using urea have been demonstrated on diesel trucks in Europe in recent years. In view of upcoming stringent emissions control standards for US HD diesel engines, urea-SCR is being evaluated by US engine and truck manufacturers. The authors and their companies have worked jointly on a project to develop, test, and demonstrate urea-SCR on a US HD diesel engine and Class-8 truck. A prototype urea-SCR system was applied to a 12-liter HD diesel engine. The engine model selected is rated at 350 bhp and is common for highway trucks. The only engine modifications were changes to the injection timing control map in order to better suit the application of the urea-SCR system. This paper details two demonstration phases of the project as follows. The first phase includes recent emissions cell tests using a new compact SCR catalyst and an engine calibration optimized for lower NOX.

NOx emission reduction for current diesel trucks was demonstrated in on-road programs. Urea-SCR systems were installed in heavy-duty trucks (Mercedes Actros, MAN F2000) powered by 6-cylinder turbocharged and intercooled engines with 12 liter displacement (OM501LA, D2866 LF). The trucks were operated by trucking companies in typical duty. Some trucks have been operated for more than 30 in the programs to date. Current European standard grade diesel fuel with a sulfur content of max. 500 PPM was used. The reducing agent for the catalytic conversion was 32.5 wt-% urea solution. Supply logistics for urea were established for the demonstration program. The program included bench testing, chassis dynamometer test, and vehicle road test with on-board measuring as well as in-use catalyst spot check investigation. Emissions were measured upstream and downstream the exhaust gas aftertreatment system, proofing the performance of SCR technology.