Abstract
Biodiesel has received great attention in recent years because of its potential to replace a portion of petroleum diesel used in compression ignition engines. Most of the biodiesels have been produced from vegetable feedstock and animal tallow and have been used in blends with petroleum diesel. But properties of biodiesel vary depending on the feedstock and chemical processes used in its manufacture. The variations in physical and chemical properties of the fuel are known to impact engine performance. Of particular interests are biodiesel produced from soy and animal tallow. The physical properties and chemical composition of these fuels are somewhat different which can impact engine efficiency and exhaust emissions.
In this investigation, a single-cylinder DI diesel engine was operated on blends of biodiesels derived from soy and animal tallow. Its performance was studied experimentally and through a simulation model. Soy blends had lower viscosity and slightly higher oxygen content than the tallow blends but the energy content of the soy blend was lower than that of the tallow blend for identical biodiesel concentration. The results show very small difference in engine efficiency between the two blends but oxides of nitrogen with soy blends were higher than those of tallow blends. On the other hand, particulate levels were higher when tallow blends were used compared to soy blends. The simulation model, which incorporated blend compositions and their properties, showed increased oxygen content in the soy blends produced higher oxides of nitrogen. The higher viscosity of tallow blends leads to higher levels of particulates in the engine exhaust.
KEYWORDS – Biodiesel, Tallow, Diesel, Combustion, Emissions