Influence of Compression Ratio and Fuel Cetane Number on Ultra-high EGR Low Temperature Diesel Combustion

-Discussion of the Effect of Premixing and Lowering Temperature-

Abstract

To independently analyze the effects of lowered combustion temperature and improved fuel-air mixing with ultra high EGR on smoke reduction,fuels with five cetane numbers as well as three compression ratios were systematically examined.Smokeless combustion was realized 1)at the "premixed-combustion state" when the premixed duration defined as the period between the end of fuel injection and ignition is larger than 4°CA regardless of combustion temperature; and also 2) with sufficiently low combustion temperature at the "premixed-combustion transition state" when the premixed duration is between 0 and 4°CA. A combination of low compression ratio and low cetane number fuel is advantageous to realize smokeless combustion.