The effect of Temperature and blending on the specific gravity and viscosity of Jatropha Methyl ester

Abstract

The specific gravity and viscosity of biodiesel fuels are key properties in determining the suitability for use of such fuels in diesel engines. Though generally higher than those of #2 diesel fuel (DF2), they have been mostly reduced by blending with DF2 and preheating to achieve comparable values as DF2. The objectives of this study were to investigate the effects of temperature and blending on specific gravity and viscosity of Jatropha methyl ester, and also investigate the effect of modifying Clements blending equation by substituting volume fraction for mass fraction. Correlation models were developed to predict the variation of specific gravity and viscosity with both temperature and % biodiesel in a blend. Blends of Jatropha methyl ester (JME) and DF2 on volume basis were prepared and investigated in the temperature range 15-60°C together with the pure fuels. Blends B20, B35, B50 and B75 were made. Specific gravity was determined using specific gravity method whereas viscosity was evaluated was determined using the Ostwald viscometer. Specific gravity of JME was found to be generally 4.83% higher than that of DF2. Blending with DF2 lowered the specific gravity significantly, and a correlation model was developed for use to approximate the specific gravity of any JME-DF2 fuel blend. Preheating the fuels lowered the specific gravity as temperature increased. Correlation models were developed to predict the specific gravity of the test fuels as function of both temperature and amount of JME in the blend. Calculating specific gravity using the Specific gravity blending equation proposed by Clements was found to give results within ± 0.5% of the measured values with mass fraction replaced by volume fraction. The viscosity of JME was found to be 42.09% higher than that of DF2. Blending with DF2 resulted in significant viscosity reduction, which varied linearly with the amount of DF2 in the blend. Correlation models were proposed to approximate the viscosity of any blend as a function temperature in the range from 15°C to 60°C, and as a function of % biodiesel. Results showed that blends with up to 50% JME conformed to both specific gravity and viscosity without the need of preheating.