Long-Term Durability of Passive Diesel Particulate Filters on Heavy-Duty Vehicles 2004-01-0079

A multi-year technology validation program was completed in 2001 to evaluate ultra-low sulfur diesel fuels and passive diesel particle filters (DPF) in several different diesel fleets operating in Southern California. The fuels used throughout the validation program were diesel fuels with less than 15-ppm sulfur content. Trucks and buses were retrofitted with two types of passive DPFs. Two rounds of emissions testing were performed to determine if there was any degradation in the emissions reduction. The results demonstrated robust emissions performance for each of the DPF technologies over a one-year period. Detailed descriptions of the overall program and results have been described in previous SAE publications [2, 3, 4, 5].

In 2002, a third round of emission testing was performed by NREL on a small subset of vehicles in the Ralphs Grocery Truck fleet that demonstrated continued robust emissions performance after two years of operation and over 220,000 miles. As of 2003, there are still questions about the durability of the passive DPF technology.

Will the technology maintain emissions reduction performance over a long period of operation? Will it meet the durability criteria expected by the heavy-duty diesel community? A fourth round emissions evaluation of a subset of the Ralphs Grocery Truck fleet from the original ARCO EC-Diesel™ Technology Validation Program [2] was performed and an assessment of the technology will be presented in this paper. Emissions testing was performed during the summer of 2003 to provide data covering 3-½ years of operation and 340, 000 miles. The evaluation will examine some of the key parameters that allows for the successful implementation of the passive DPF in this heavy-duty application. This will include examining the engine exhaust gas temperatures, the backpressures created by the DPF and NOx/PM ratios provided by the engine application. The results will show that with a NOx/PM ratio better than 20:1 and exhaust gas temperatures above 250°C, the technology will provide robust long-term performance with emission reductions of 99% PM, 85% HC, and 65% CO in a heavy-duty application with some significant variability associated with the CO and HC measurements.