The Specific Gravity Of Biodiesel Fuels And Their Blends With Diesel Fuel

The specific gravity of fuels is used as a precursor for a number of other fuel properties, such as heating value, viscosity and cetane number. Biodiesel fuel has significantly different properties than petroleum-derived diesel fuel. The objectives of this study were to investigate the relationship between the specific gravity and temperature of biodiesel fuels and their blends with No.2 diesel fuel, and to determine whether the ASTM D1250 Petroleum Measurement Tables were applicable to these fuels. Also specific gravity data were provided as a reference for different biodiesel fuels and their blends with No.2 diesel fuel. The specific gravity of three biodiesel fuels, two soybean oil based methyl esters and a yellow grease methyl ester, and their 75, 50 and 25% blends with No.2 diesel fuel were measured in the temperature range from about -5°C or from the onset of crystallization, to 100 °C. The measurements indicated that all the biodiesel fuels and their blends with No.2 diesel fuel had a linear specific gravity-temperature relationship similar to No.2 diesel fuel as expected. The specific gravities of the blends of biodiesel and No.2 diesel were found to be proportional to the mass fraction of the components. This proportionality was used to estimate the specific gravities of the blends of biodiesel and diesel within 0.15% of measured data for all tested fuels from 0°C to 80°C. The estimated results for specific gravity from the ASTM D1250 Petroleum Measurement Tables were compared to measured values and were found to be slightly overestimated at high temperatures while the prediction errors were less than 0.43% for all tested fuels from 0°C to 80°C.