Modeling the Spray Behaviors of Fatty Acid Methyl Esters in Biodiesel Fuels under Engine-Relevant Conditions

Spray behaviors of pure biodiesel and its blend with conventional diesel have been substantially studied in the last decade. However, the studies on the spray behaviors of pure fatty acid methyl esters (FAMEs) are scarce. The primary components of most biodiesel fuels are methyl palmitate (C16:0), methyl stearate (C18:0), methyl oleate (C18:1), methyl linoleate (C18:2) and methyl linolenate (C18:3), and methyl laurate (C12:0) is also the dominant component of some biodiesels. In this study, the spray behaviors of the aforementioned six FAMEs in biodiesel fuels under engine-relevant conditions were numerically studied using the KIVA-3V code. The physical properties needed for spray modeling were predicted with most recently developed property prediction models and added into the fuel library of KIVA-3V. The transient behaviors of liquid penetrations and vaporization characteristics of these FAMEs were numerically studied under various engine-relevant conditions. Results showed that the esters of 18-carbon-atom acids have much longer liquid lengths than those of C16:0 and C12:0 with relatively shorter carbon chain length. The lower volatilities of the FAMEs with longer carbon chain lengths also contributed to the longer penetrations, especially under lower ambient density and temperature conditions. The degree of unsaturation (an indicator of the number of carbon-carbon double bonds in the fatty acid chain) did not have as significant effect as that of carbon chain length on the spray behaviors of different FAMEs.