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.
Bench scale fuel-engine compatibility testing showed the GTL fuel had cold flow properties suitable for year-round use in southern California and was additized to meet current lubricity standards. Bench scale elastomer compatibility testing returned results similar to those of CARB specification diesel fuel. The GTL fuel met or exceeded ASTM D975 fuel properties.
Researchers used a chassis dynamometer to test emissions over the City Suburban Heavy Vehicle Route (CSHVR) and New York City Bus (NYCB) cycles. The GTL- fueled vehicles were tested with and without the CDPFs to isolate fuel and aftertreatment effects.
All emission changes are compared to the CARB specification diesel baseline. Over the CSHVR cycle, GTL fuel (no filter) reduced all regulated emissions, with oxides of nitrogen (NOx) reductions of 8% and particulate matter (PM) reductions of 33%. Over the NYCB cycle, GTL fuel (no filter) reduced NOx and PM by 16% and 23%, respectively. Combining GTL and CDPF further reduced all regulated emissions, with NOx and PM reductions of 14% and 99%, respectively, on the CSHVR cycle. Vehicles tested over the NYCB cycle on GTL fuel and CDPF produced NOx and PM reductions of 20% and 97%, respectively.