Diesel Vehicle Application of an Aerodynamically Regenerated Trap and EGR System

The simultaneous control of diesel engine particulate and NO_x emissions was targeted in this study. Particulate control was achieved with a trap that incorporated a high-filtration efficiency ceramic honeycomb monolith. Aerodynamic regeneration was used to periodically backflush the monolith filter. Soot was collected in a metallic chamber and was either incinerated by an electric burner or removed by a vacuum cleaner. NO_x emissions were reduced by recirculation of filtered exhaust gases (EGR), which was made possible by the high collection efficiency of the employed monoliths. Tests were conducted on the road, driving a diesel vehicle under various loads and speeds. The levels of NO, CO and O₂ at the exhaust were continuously monitored using a portable instrument. The particulate filtration efficiency was in the vicinity of 99% using CeraMem and 97-98% using Panasonic traps, respectively, hence the EGR line was effectively particulate-free. At a level of 20% EGR, the NO concentration in the exhaust was reduced by as high as 50% at steady-state freeway speeds (90-100 km/hr) and intermediate loads. At the same time, the measured exhaust O₂ concentration dropped by 20 to 25%, while the CO concentration increased by up to 20%. Fuel consumption increased by 5-6% due to the combined effects of EGR and the particulate trap. Only mild effects on the drivability and performance of the vehicle were noticed when a particulate trap and EGR were used, as long as the pressure drop was kept below 250 mbars.