Experimental Investigation on the Combustion and Emissions Characteristics of n-Butanol / GTL and n-Butanol/Diesel Blends in a Single-Cylinder MD-CI Engine

摘要

In this study, the combustion and emissions characteristics of n-butanol/GTL and n-butanol/ultra-low sulfur diesel (ULSD) blends are compared in a single-cylinder experimental diesel engine. The n-butanol was blended with a Fischer-Tropsch (FT) gas-to-liquid (GTL) fuel, at 25% and 50% mass. N-butanol was also blended with ULSD at the same mass ratios. FT fuels are an attractive alternative to petroleum based fuels because they can be used as a drop-in fuel with existing infrastructure. N-butanol is renewable fuel capable of being produced from waste biomass sources. The investigations were conducted at 1500 rpm and three loads of 2.75, 4.75, and 6.75 IMEP, representative for the research engine. 15% exhaust gas recirculation was utilized along with a supercharger to increase the intake pressure to 1.2 bar absolute. Neat ULSD and GTL, respectively, were investigated as a baseline. For all loads, the combustion pressures increased as the concentration of n-butanol in the blends increased. As a result of the lower cetane number (CN) of GTL, the GTL fuel and blends exhibited lower peak combustion pressures and heat release rates, when compared to the ULSD and ULSD blends. The low CN of n-butanol led to increased ignition delays for all blends from 1.0 to 1.9 ms. Although there was an observed extended ignition delay for the blends, CA50 occurred earlier for each blend when compared to the neat fuels. The GTL/n-butanol blends reduced soot by nearly 90%. However, neat GTL showed a considerable increase in soot when compared to ULSD. The GTL/n-butanol blends also produced 20% less NO_x when compared to ULSD. At each tested engine load, the 50% n-butanol/50% GTL fuel blend (by mass) resulted in a simultaneous reduction in soot and NO_X. The GTL fuel, which lacks aromatics aided in NO_X reductions while the oxygenated n-butanol fuel further oxidized the particulate matter. The results indicate that the n-butanol blends are capable of controlling harmful emission formation while maintaining consistent engine operation. Further studies will include injection timing sweeps and increased injection pressure to control NO_X formation.