Abstract
Characteristics of diesel combustion with low cetane number fuels with similar distillation temperatures to ordinary diesel fuel, including fuels with cetane number 32 and 39 (LC32, LC39), and a blend of normal cetane and heptamethylnonane with cetane number 32 (CN32), were investigated. The effects of cooled EGR and pilot injection on combustion and exhaust gas emissions with these fuels were examined in a single cylinder diesel engine equipped with a common-rail type fuel injection system. Even with the low cetane number fuels, quiet combustion with low levels of exhaust gas emissions comparable to ordinary diesel fuel was established by suitable control of intake oxygen levels and pilot injections. At light and medium loads, low smoke, low NOx, and quiet combustion is possible by decreasing intake oxygen concentration with EGR. At high loads, pilot injection can suppress NOx emissions and the maximum rate of pressure rise to levels similar to ordinary diesel fuel. Smoke emissions at low intake oxygen and NOx emissions at high intake oxygen with the low H/C ratio fuel, LC32, are higher than with CN32, the high H/C ratio fuel at the same cetane number.
