An Advanced Diesel Fuels Test Program 2001-01-0150
This paper reports on DaimlerChrysler's participation in the Ad Hoc Diesel Fuels Test Program. This program was initiated by the U.S. Department of Energy and included major U.S. auto makers, major U.S. oil companies, and the Department of Energy. The purpose of this program was to identify diesel fuels and fuel properties that could facilitate the successful use of compression ignition engines in passenger cars and light-duty trucks in the United States at Tier 2 and LEV II tailpipe emissions standards. This portion of the program focused on minimizing engine-out particulates and NOx by using selected fuels, (not a matrix of fuel properties,) in steady state dynamometer tests on a modern, direct injection, common rail diesel engine.
Four fuels were chosen for this program: a specially blended fuel that reflected the typical diesel fuel available in California was used as a reference, a low sulfur hydrocracked fuel, a blend of 15% dimethoxy methane and 85% low sulfur hydrocracked fuel and a neat Fischer-Tropsch fuel. These three advanced fuels had low sulfur and low aromatics.
Tests were performed on a prototype Chrysler 1.9L, 4-valve, direct injected, turbocharged and after-cooled common rail diesel engine at four steady state speed - load points chosen to represent the urban driving cycle: 1500 RPM - 42 Nm, 2000 RPM - 32 Nm, 2300 RPM - 67 Nm, and 2500 RPM - 140 Nm. Injection timing and rail pressure were optimized for minimum fuel consumption and smoke. In addition, a second series of tests were performed with injection timing retarded to produce a 2% fuel consumption penalty.
As EGR was varied, the trade-off between total particulates and NOx emissions was obtained and the trade-off between solid particulates and NOx emissions was estimated. At high EGR rates, only the F-T fuel showed a significant reduction in total particulates. However, both the 15% DMM fuel and the F-T fuel showed significant reduction in estimated solid particulates. Furthermore, there were indications that both the 15% DMM fuel and the F-T fuel may offer a significant smoke reduction at heavy-load, off-cycle conditions.