Research Projects

Arthur D. Little, Cummins Engine Company, and Rhodia Rare Earth's performed a project to demonstrate a fuel-borne catalyst system and low NOx control technology for reducing particulate and NOx emissions from on-road diesel engines. The system developed was a combination of cooled, exhaust gas recirculation (EGR) coupled with a diesel particulate filter. Cerium catalyst was added to the diesel fuel to assist in filter regeneration. The system was applied to the Cummins B Series (5.9L ISB) diesel engine.

Considerable development work was required before a working system could be demonstrated. The filter system initially focused on a compact, low volume silicon carbide design. This system was emission tested and then installed in a UPS package car for demonstration in Southern California. The system was able to achieve NOx levels of 2.5 g /bhp-hr and particulate of 0.03 g/bhp-hr over the transient heavy duty test cycle. Checkout testing prior to entering UPS service indicated filter face plugging. Cummins and Rhodia investigated the reasons for this plugging and tested several alternative filter options. This testing indicated that filter face plugging occurred as a result of unburned fuel during engine restarts and using a high cell density filter (300 cells per square inch). Tests showed reducing the filter density eliminated face plugging. A HJS metallic filter with wide frontal area openings was found to be acceptable, albeit not optimized for the application.

The UPS package car operated with the EGR engine alone for 8 months accumulating over 16,000 trouble free miles. The HJS equipped system operated in UPS service for an additional 2 months and accumulated 6,000 miles. Based on the experience obtained in this project, it appears that a combination system of cooled EGR, cerium catalyst in diesel fuel, and particulate filter is feasible for reducing NOx and PM emissions in heavy duty diesel vehicles. However, considerably more work is necessary to commercialize such as system and to make sure that filter regeneration occurs reliability over all vehicle operating modes.