Laminar Flame Characteristics of Partially Premixed Prevaporized Palm Methyl Ester and Diesel Flames

Palm methyl ester (PME) is a renewable biofuel that is produced by the transesterification of palm oil and is a popular alternative fuel used in the transportation sector, particularly in Asia. The objective of this investigation was to study the combustion characteristics of flames of prevaporized number 2 diesel and PME in a laminar flame environment at initial equivalence ratios of 2, 3, and 7 and to isolate the factors attributable to chemical structure of the fuel. The equivalence ratio was changed by altering the fuel flow rate, while maintaining the air flow rate constant. The global CO emission index of the PME flames was significantly lower than that of the diesel flames; however, the global NO emission index was comparable. The radiative fraction of heat release and the soot volume fraction were lower for the PME flames compared to those in the diesel flames. The peak temperatures were comparable in both flames at an equivalence ratio of 2, but at higher equivalence ratios, the peak temperatures in the PME flames were higher. The measurements highlight the differences in the combustion properties of biofuels and petroleum fuels and the coupling effects of equivalence ratio.