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A series of tests run on the fully transient engine test benches, in Redwitz, Germany, clearly demonstrate that SCR technology is effective in both NOx and particulate emissions reduction. With different particulate measuring technologies, influences of parameters like the sulfur content of the fuel and the influence of the reducing agent are examined. A reduction of the particulate within the health-relevant range (around 100 nm) is proven. Apart from an effective reduction in the organic fraction of the PM, the system is also able to reduce the carbon fraction. Over the ESC / OICA cycle a decrease of elementary carbon of approximately 25% is obtained. Using an SCR system, a clear decrease of the nano-particulate mass emissions is found under all dosing conditions up to approximately 70%.

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.