Diesel combustion characteristics of saturated fatty acid methyl ester

Biodiesel produced from vegetable oil is mixture of fatty acid methyl ester (FAME). The FAME composition of biodiesel can vary the combustion characteristics and the exhaust emissions. In this study, the combustion characteristics and the exhaust emissions from various pure saturated FAMEs such as methyl laurate (ML), methyl myristate (MM), methyl palmitate (MP) and methyl stearate (MS) are investigated using a single cylinder DI diesel engine. Two neat fuels, ML and methyl oleate (MO, unsaturated FAME), and four mixture fuels (50/50 mass%), ML/MO, MM/MO, MP/MO and MS/MO, are used as test fuels. From the experimental results, the ignition delay of saturated FAME decreases with longer straight chain of the hydrocarbon molecules, while the ignition delay of FAME mixture increases by increasing unsaturated FAME content. The six FAME test fuels have almost the same brake thermal efficiency compared with JIS no. 2 gas oil. In the four saturated FAME mixture test fuels, the NOx emission from MP/MO is lowest. The smoke emission decreases by increasing the oxygen content in the six FAME test fuels and the smoke emission from ML is lowest.