Diesel oxidation catalyst and particulate filter technologies are well established and their applications are well known. However, there are certain limitations with both technologies due to their inherent technical characteristics. Both technologies get 75-90% reduction of HC and CO. A typical oxidation catalyst can be applied to almost any heavy duty diesel application and achieve 20 to 30% reduction in PM mass but no significant reduction in the number of PM particles. On the other hand, diesel particulate filters are very effective at removing >90% of the particles by mass and >99% by number. Unfortunately, passive DPF technology cannot be applied to all applications since the filter regeneration is limited by engine out NOx to PM ratio as well as exhaust temperature. For this reason, particulate filters can not universally be applied to older “dirtier” engines with high PM emissions. This creates a technology gap for a passive device that can be successfully applied to old, high PM emission engines to achieve significant reduction in both PM mass and PM number. This paper will discuss the development of a passive PM control device referred to as a partial filter technology or PFT. This device combines an oxidation catalyst with a unique filter technology that can reduce PM by up to 77%. The new filter material combines the attributes of a flow through substrate with those of a wall flow filter to collect some but not necessarily all the engine out soot and thus provide PM reduction without leading to filter plugging. Due to the flow through characteristics, excess soot beyond filter capacity is not collected in the PFT and thus the exhaust is able to continue to flow without a significant increase in back pressure. The PFT system also utilizes the NO2:C reaction used by passive diesel particulate filter systems to oxidize a portion of the soot and passively regenerate the filter. In addition, the filter does not accumulate significant amounts of lube oil ash and this may minimize the need for a periodic ash cleaning maintenance. Engine bench emission testing with this system has shown PM reductions ranging from 77% for fresh (degreened) system to 63% for an aged system along with >90% HC and CO reductions. On-road operational data collected on various model year applications over a two year period has shown stable back pressure since installation. In addition, no adverse operational or maintenance issues were noted which can be attributed to the installation of the PFT system. This paper describes the development and testing of this passively regenerating partial filter technology.

Six 2001 International Class 6 trucks participated in a project to determine the impact of gas-to-liquid (GTL) fuel and catalyzed diesel particle filters (DPFs) on emissions and operations from December 2003 through August 2004. The vehicles operated in Southern California and were nominally identical. Three vehicles operated "as-is" on California Air Resources Board (CARB) specification diesel fuel and no emission control devices. Three vehicles were retrofit with Johnson Matthey CCRT® (Catalyzed Continuously Regenerating Technology) filters and fueled with Shell GTL Fuel. Two rounds of emissions tests were conducted on a chassis dynamometer over the City Suburban Heavy Vehicle Route (CSHVR) and the New York City Bus (NYCB) cycle. The CARB-fueled vehicles served as the baseline, while the GTL-fueled vehicles were tested with and without the CCRT filters. Results from the first round of testing have been reported previously (see 2004-01-2959). The second round results were compared to the CARB specification diesel fuel baseline. Over the CSHVR cycle, the GTL Fuel (no filter) reduced oxides of nitrogen (NOx), hydrocarbon (HC), and particulate matter (PM) emissions by 13%, 46%, and 21%, respectively, and increased carbon monoxide (CO) by 11%. The GTL Fuel and the CCRT filter virtually eliminated the HC, CO, and PM emissions and reduced NOx emissions by 22%, a statistically significant reduction. Testing over the NYCB cycle also revealed emission reductions are possible with GTL Fuel. Compared to the CARB specification diesel fuel, the GTL Fuel provided statistically significant reductions in NOx, HC, and PM emissions by 11%, 58%, and 16%, respectively. A 10% increase in CO emissions was also noted, although not statistically significant. With the CCRT filter, the HC, CO, and PM emissions were reduced by over 95%. A statistically significant NOx reduction of 20% was observed. Reductions from round 2 were notably larger than those in round 1. To determine if the changes observed between rounds were "real", a statistical analysis was performed. The analysis found that CO emissions were higher without the filter in round 2, while no changes were observed for HC or PM emissions. The NOx emissions were significantly higher in round 1 for the NYCB cycle only. The fleet was followed for operability for 6 months and accumulated ∼20,000 miles. Driver feedback for the vehicles operating on the GTL Fuel and CCRT filters was very positive. An analysis determined that the fuel economy with the combination of GTL Fuel and CCRT filters decreased by 8%. Evaluation of the maintenance records did not reveal any impact of the GTL fuel or CCRT filters on operability.

A fleet of six 2001 International Class 6 trucks operating in southern California was selected for an operability and emissions study using gas-to-liquid (GTL) fuel and catalyzed diesel particle filters (CDPF). Three vehicles were fueled with CARB specification diesel fuel and no emission control devices (current technology), and three vehicles were fueled with GTL fuel and retrofit with Johnson Matthey's CCRT diesel particulate filter. No engine modifications were made.