Estimation of Opacity Tendency of Ethanol- and Biodiesel-Diesel Blends by Means of the Smoke Point Technique

Oxygenated fuels in diesel engines represent an alternative to conventional petroleum-derived fuel to achieve current European emissions standards (EURO 5), especially with regard to particulate matter (PM), where the reduction of the limit in mass concentration is 80% compared to that for the previous EURO 4 standard. Among these oxygenated fuels, biodiesel- and ethanol-diesel blends have great potential in reducing smoke opacity and, therefore, the particulate matter emitted. The smoke point is a technique used for determining the sooting tendency of kerosene and aviation fuels and it can be used as an indicator of smoke opacity. The smoke point technique can also be used with an extensive variety of fuels including automotive diesel fuels. This work proposes a new methodology for estimating the decrease in diesel engine exhaust opacity when different ethanol- and biodiesel-diesel blends are used instead of conventional diesel fuels. Different binary biodiesel- diesel and ethanol-diesel blends were tested in a smoke point lamp together with ternary ethanol-biodiesel-diesel blends. The results of binary blends were compared to the opacity obtained in a light duty diesel engine operating in a steady state mode confirming that the molecular weight to smoke point ratio accurately reproduces the decreasing trend in opacity, when normalized to a conventional diesel fuel, as a function of the percentage of biodiesel or ethanol in the blend. Moreover, the new proposed methodology showed how not only the oxygen content but also its functional group plays an important role in this decreasing opacity trend. In this way, tests of ternary ethanol-biodiesel-diesel blends on a smoke point lamp could predict the trend in smoke opacity when a diesel engine is fuelled with them.