Comparative Analysis of Effect of Diesel and N-Butanol Blend Properties on Combustion Process and Hydrocarbon Emission at Various Oxygen-Intake Concentrations

Abstract

The effects of the cetane number (CN) and latent heat of vaporization (LHV) of diesel/n-butanol fuel on the hydrocarbon (HC) emission and combustion process at various oxygen intake concentrations (Coxy) were studied in a modified four-cylinder light-duty diesel engine. Three fuels were studied in this experiment: neat diesel (B00), diesel blending with 20% n-butanol by volume (B20), and diesel blending with 20% n-butanol and 0.7% 2-ethylhexyl nitrate by volume (B20+EHN). The conclusion reached is that the ignition delay period has a decisive influence on HC emissions and the combustion process. A comparison of the B20 and B00 fuels reveals that, as Coxy decreases, the degree of the influence of the LHV on in-cylinder combustion temperature (IT) and combustion duration (CD) gradually increases, and the degree of influence of CN gradually decreases. Additionally, the increasing in-cylinder average temperature difference is the primary factor for the increase in the difference between the HC emissions of the two fuels, whereas the influence of CD is relatively weak. A comparison of the B20+EHN with B20 fuels revealed their different in-cylinder average temperatures that resulted from the influence of their CN on the combustion phase were mainly responsible for the different HC emissions of the two fuels; this difference becomes increasingly obvious as Coxy decreases.