Due to the emission benefits of the oxygen in the fuel molecule, the interest for the use of ethanol as fuel blend components in compression ignition engines has been increased. However the use of fuel blends with high percentage of ethanol can lead to poor fuel blend quality (e.g. fuel miscibility, cetane number, viscosity and lubricity). An approach which can be used to improve these properties is the addition of biodiesel forming ternary blends (ethanol-biodiesel-diesel). The addition of castor oil-derived biodiesel (COME) containing a high proportion of methyl ricinoleate (C18:1 OH) is an attractive approach in order to i) reduce the use of first generation biodiesel derived from edible sources, ii) balance the reduction in viscosity and lubricity of ethanol-diesel blends due to the high viscosity and excellent lubricity of methyl ricinoleate.
The fuel blend properties, gaseous and soot emissions, and particulate size distribution of ethanol-diesel blends with the addition of hydroxylated biodiesel derived from castor oil were investigated. Tests were compared with baseline experiments using rapeseed oil methyl ester (RME) which consists mainly of methyl oleate (C18:1) with the same number of carbon and unsaturation degree compared to methyl ricinoleate so that the hydroxyl group presenting in castor oil methyl ester can be evaluated. The results showed that the addition of castor oil methyl ester to ethanol-diesel blends is more effective to restore the lubricity of the fuel blend. A significant benefit in soot emissions was obtained from the combination of ethanol and hydroxylated biodiesel, while there was no penalty in regulated gaseous carbonaceous emissions. An improvement in NOX-soot trade-off was obtained by the COME blend compared to the RME blend.