Particulate Traps: Some Progress; Some Problems
Two ceramic monolith wall flow diesel particulate traps, incorporating a new split flow design with a base metal catalytic coating were tested on line haul highway trucks to investigate their performance characteristics. The trucks were equipped with a 300 HP turbocharged and after-cooled engine. After-cooler by-pass was used to effect the regeneration of the trap and an elapsed-time scheme was employed to control the regeneration process. Tests were terminated after one trap completed 147,500 miles of operation on the truck for in-depth examination of the trap to determine the cause of substantial increase in back pressure. Tests with the second trap of identical design was also terminated due to filtering efficiency loss, the cause of which was traced to a flaw in the canning arrangement. This arrangement permitted exhaust flow to by-pass the element and led to melt down of the trap, due to reduced flow during regeneration.