Combustion characterization of GTL diesel fuel

In-cylinder imaging in a Cummins 5-9L, turbocharged, six-cylinder, four-stroke direct injection diesel engine using an engine videoscope system was presented. The imaging studies provided a comparison of the fuel injection timing, ignition timing, spray formation, and flame luminosity between different fuels. In the Cummins ISB engine, the BP15 fuel was injected at 0.2 crank angle degrees earlier than the ConocoPhillips Fischer-Tropsch (COP F-T) diesel, thus comparisons were made relative to start of injection. The higher cetane number of the COP F-T diesel caused the F-T diesel blend to perform well despite retarded injection timing. At the late injection timing, CO emissions increased and fuel consumption increased for the ultra low sulfur diesel fuel relative to the COP F-T diesel. NO_x emissions had more complex trend with fuel type. NO_x decreased with retardation of injection timing. However, at light load, NO_x emissions were slightly lower for the ultra low sulfur diesel fuel than for the F-T diesel. While in-cylinder imaging comparisons of ultra low sulfur diesel fuel and synthetic diesel fuel showed no significant differences in spray or flame structure, injection timing and heat release analysis showed that the high cetane number and low bulk modulus of compressibility of the F-T diesel fuel lead to significant differences in heat release and pollutant formation.