Study of the properties of vegetable oil as an alternative to diesel fuel

Abstract

In view of the energy crisis and emission problems, alternative fuels are promising substitute to the conventional petroleum fuels. Among them, vegetable oils seem attractive substitute to diesel fuels. They have the advantage of being geographically widely produced, in a variety of products and are renewable in nature and thereby not contributing to the net atmospheric concentrations of the green house gas, CO2• However, higher viscosity and lower volatility are identified as the main reasons for the unsuitability of vegetable oils as straight diesel fuel substitute. So, in this study attempts have been made to study the possibiiity of using vegetable oils as diesel fuel substitute by modifying their properties. Hence, kerosene is blended with 4 different vegetable oils ( Rapeseed, Soyabean, Sesame and Lin •. seed) in equal volumes to serve the purpose. Testing of the properties of the vegatable oils, pure and blended, are then performed. It is found that the desities and viscosities of pure vegetable oils are significantly higher than those of diesel (about 10% higher in case of densities & about 12 times higher in case of viscosities). However, when blended with kerosene, these properties are found reduced to a comparable figure (about 0.50% higher in case of densities & about 2.5 times higher in case of viscosities). It is also found that the energy densities of the blended vegetable oils are very close to that of diesel. Carbon residue of vegetable oils are found lower and the ash percentages are found higher than the diesel values. Volatility curves obtained for the blends also indicate the lower boiling temperatures at the early stage of evporations, while boiling temperatures similar to that of diesel values are observed at the end portions of the distillate. From these blends, Sesame and Soyabean blends are then tested to study the engine performance. From the experimental results, it is seen that vegetable oil blends result in slightly reduced performance, showing higher bsfc (about 10% higher) and slightly lower brake thermal efficiencies (about 2% lower). It is also found that these two blends result in the performances very close to each other. So, it is concluded that vegetable oils can be substituted for diesel fuel with little sacrifice in power and efficiency. Hence, conclusion is also drawn that with vegetable oil blends, modification in viscosity and volatility would result in comparable performance with diesel fuels.