Characteristics of Low Temperature Diesel Combustion with Paraffinic Hydrocarbon Fuels

Abstract

The low-temperature diesel combustion with paraffinic hydrocarbons as surrogate Fischer-Tropsch synthetic (FT) fuels was investigated in an experimental diesel engine. At first a normal paraffine and iso-paraffine blend of cetane number 57 and an ordinary diesel fuel were examined, widely varying the intake oxygen concentrations with cooled EGR. The indicated thermal efficiency shows a maximum when the intake oxygen concentrations were set around 12% due to smaller cooling losses, maintaining high combustion efficiency for both fuels. The smoke emissions with the paraffinic hydrocarbon fuel are much lower than with the ordinary diesel fuel under the low-temperature diesel combustion at medium and high IMEP conditions as well as smokeless operation is possible at low IMEP. Next, three paraffinic hydrocarbon fuels with cetane numbers of 38, 57, and 78 were examined. The smoke emissions around 12% intake oxygen concentration were suppressed with the cetane number of 38, with maintaining the premixing durations with longer ignition delays. To summarize the results, the paraffinic hydrocarbon fuels have high potential to establish clean and efficient low temperature diesel combustion due to lower soot formation.