Predicting the physical properties of biodiesel for combustion modeling

As the use of biodiesel becomes more widespread, researchers have shown a strong interest in modeling the combustion processes in the engine in order to understand the fundamental characteristics of biodiesel combustion. In the early phase of the simulation, accurate prediction of the physical properties of biodiesel is critical in the representation of spray, atomization, and combustion events in the combustion chamber. The objective of this article is to present methods for predicting key physical properties including critical properties, vapor pressure, latent heat of vaporization, density, surface tension, and liquid viscosity for biodiesel that can be used for combustion modeling. Predicted results were compared with published data where available, and for some properties, errors were less than 1%. While no published data were available at temperatures above 373 K to check the accuracy of the predictions from the models at the higher temperatures, the trends in the fuel properties were regarded as representative of what would be expected in the combustion chamber. These models could be used in a detailed combustion model such as KIVA to make relative comparisons between fuels.