Research Projects

A ceramic particulate filter (trap) was designed as a muffler replacement for application to a GMC RTS II 04 city bus powered by a Z-stroke DDAD 6V-92TAC heavy-duty diesel engine. Preliminary testing indicated that the design was of adequate capacity and filtering efficiency to reduce total particulate by more than 70 percent and eliminate visible smoke emissions. Three different catalyst formulations were applied to three trap units to enhance on-board trap regeneration. Although some balancing of accumulated particulate with regenerated particulate was obtained below 500°C, notable regeneration was not obtained until the catalyzed substrates reached a temperature range of 510 to 550°C. The trap units were located before the turbocharger, where high exhaust temperatures, promoted by creating periodic engine upset, could best be utilized for regeneration. Even though low-temperature regeneration was not observed with any of the three catalyzed traps, all three were able to eliminate visible smoke and reduce total particulate by 80 percent; however, on-board regeneration could only be accomplished through periodic high-load operation of the bus. The durability of these catalyzed traps has yet to be established in field a demonstration because they lack suitable low-temperature regeneration characteristics to permit general use of the bus.