Simulation of the evaporation of drops from palm and castor oil biodiesels based on physical properties

Abstract

A reduction of oil reserves and an augmented production of greenhouse gases from fossil fuels have increased the use of biodiesel in internal combustion engines. Although physical and chemical properties of biodiesel and diesel are similar enough that allow the use of pure biodiesel in a traditional engine without considerable adjustments, differences in chemical structure of diesel and biodiesel change vaporization and combustion rates and can affect engine performance. In this study a model that can predict the evaporation rate of palm and castor oil biodiesel droplets at atmospheric pressure was developed. The model was validated with experimental data from the literature for the evaporation of n-heptane-droplets. The model estimates thermo-physical properties of biofuels using contribution group theory and was used to determine that castor oil biodiesel presents a lower evaporation rate than palm oil biodiesel due to differences in their physical properties (mainly density and vaporization enthalpy) which can be explained by a longer molecule and the presence of a hydroxyl groups in methyl ricinoleate, its main component.