The Effects of Diesel Fuel Properties on Performance, Smoke, and Emissions

Diesel fuels were blended from selected components to provide aromatics contents from 10 to 57 percent and viscosities from 2.21 to 6.95 cSt (mm²/s) at 100°F (38°C) in a 14 fuel set which included a commercial diesel fuel as a reference fuel. Tests of the fuels were conducted under full load at several speeds and in the Federal 13-mode and smoke-cycle procedures, using a 2-stroke naturally aspirated engine and a 4-stroke turbocharged engine. Fuel properties such as viscosity, aromaticity, cetane number, gravity, distillation points, and heat of combustion, some of which were partially correlated, were examined individually and in combinations as predictors of the engine performance data. The two test engines responded similarly to fuel variables, but with some differences in sensitivity. Power output (bhp) and fuel economy (bhp-h/lb) were correlated with the heats of combustion on volume and weight bases, respectively. Smoke increased with the amount of fuel boiling above 640°F (338°C) and was not apparently affected by fuel aromatic content. Emissions of nitrogen oxides and of nitrogen oxides plus hydrocarbons increased with increasing fuel aromatics by itself or with increasing fuel specific gravity and decreasing fuel 50 percent-distillation temperature. Hydrocarbon emissions decreased with increasing viscosity or cetane number. Carbon monoxide emissions increased with increasing 90 percent-distillation temperature and with decreases in cetane number.