The Shock Tube Autoignition of Biodiesels and Biodiesel Components

The autoignition of fatty-acid methyl ester biodiesels and methyl ester biodiesel components was studied in gas-phase shock tube experiments. Ignition delay times for two reference methyl ester biodiesel fuels, derived from methanol-based transesterification of soybean oil and animal fats, and four primary constituents of all methyl ester biodiesels, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate, were measured behind reflected shock waves for fuel/air mixtures at temperatures ranging from 900 to 1350 K and at pressures around 10 and 20 atm. Ignition delay times were determined by monitoring pressure and chemiluminescence from electronically-excited OH radicals around 310 nm. The results show similarity in ignition delay times for all methyl ester fuels considered, irrespective of the variations in organic structure, at the high-temperature conditions studied and also similarity in high-temperature ignition delay times for methyl esters and n-alkanes.