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

Wenqiao Yuan, Alan C Hansen, Qin Zhang

Abstract


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.

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