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The diesel combustion characteristics and the exhaust emissions of biodiesel are affected by the composition of fatty acid methyl esters (FAMEs). In this study, the combustion characteristics and the exhaust emissions from single compositions of FAMEs, such as methyl palmitate, methyl oleate and the others, are investigated by using a single cylinder DI diesel engine. Experimental five FAME fuels are neat methyl oleate and the rest are blended mixtures based on methyl oleate. From the experimental results, the ignition delays of saturated FAMEs decrease with longer straight chain of the hydrocarbon molecules while in the same carbon number FAMEs, the ignition delays increase by increasing carbon-carbon double bonds. The break thermal efficiencies of the five FAME fuels and the gas oil are almost the same.

In order to reduce NOx and smoke emissions of palm oil methyl ester (PME), the combustion characteristics and exhaust emissions for emulsified PME were investigated using a single cylinder DI diesel engine. As the results, stable emulsified PME can be obtained without adding any emulsifier like as emulsified rapeseed oil methyl ester (RME). Emulsified PME is able to reduce NOx and smoke emissions as emulsified RME. The optimum water mass fraction for emulsified PME is 15wt% with regard to the exhaust emissions. The ignition delay of emulsified PME with 15wt% water is almost the same as that of gas oil because of the higher ignitionability of PME. Due to the higher ignitionability and better combustion characteristics of PME, emulsified PME with 15wt% water has shorter ignition delay and lower NOx, HC, CO and smoke emissions compared with emulsified RME with 15wt% water.