Experimental study of the effect of physical and chemical properties of alcohols on the spray combustion characteristics of alcohol-diesel blended fuels

To reveal the effect of different long carbon-chain alcohols blended into diesel on combustion characteristics and soot emissions under different ambient temperatures, the spray combustion processes of diesel and four sets of blends (the volume ratio of propanol/diesel, butanol/diesel, pentanol/diesel, and hexanol/diesel being 20%/80%) were investigated in a constant volume combustion chamber (CVCC) using optical techniques. It was discovered that the physical (cooling effect, dilution effect, diesel evaporation inhibition) and chemical reaction properties of alcohols have a competitive effect on the spray combustion characteristics of alcohol-diesel blended fuels. The combustion pressures of alcohol-diesel blended fuels were lower than that of pure diesel due to lower heating values, and this difference became more obvious under higher ambient temperature. Alcohols blended into diesel fuel could improve the combustion efficiency. The ignition delay times (IDTs) of alcohol-diesel blended fuels decreased with increased carbon chain lengths of alcohols under low ambient temperature conditions. However, this trend was reversed with increasing ambient temperature, and the IDTs of alcohol/diesel blends became lower than that of pure diesel at higher ambient temperatures. Propanol or hexanol blended into diesel could significantly inhibit the generation of soot at low ambient temperatures, but other alcohols promoted it. Interestingly, all alcohol-diesel blend fuels inhibited the generation of soot under high ambient temperature conditions, and propanol was the most significant.