Combustion and emission characteristics of reformulated biodiesel fuel in a single-cylinder compression ignition engine

Biodiesel is a mixture of fatty acids methyl esters derived from the triglyceride of vegetable oil. Vegetable oils consist of different types of fatty acids which influence the biodiesel fuel properties, combustion, and emissions, especially oxides of nitrogen emission. Nitric oxides emissions are one of the major threats posed by biodiesel fuel due to the presence of unsaturated fatty acids (C=C double bonds). An attempt has been made to control these nitric oxides emission through reformulated biodiesel fuel approach. In this study, reformulated biodiesel fuel was prepared by blending individual biodiesels, based on their fatty acid composition percentage (v/v %). Two samples, RBF-I and RBF-II, were prepared and tested in a single-cylinder compression ignition engine. Reformulated biodiesel fuel results in increased saturated fatty acids, long-chain saturation factor, and cetane number and a decrease in the degree of unsaturation, viscosity, density, higher heating value, and iodine value compared to individual biodiesel. RBF fuel sample showed higher cylinder pressure and the advanced start of combustion compared to diesel fuel. RBF samples shows a 20% lower nitric oxides emission and 30% higher smoke emissions than diesel fuel. Carbon monoxide emission of RBF increased as compared to diesel fuel, whereas carbon dioxide emissions were lowered by 35% approximately. Hydrocarbon emissions were found to be lower for RBF-I, but it was higher for RBF-II throughout the engine test load conditions. It is inferred that reformulated biodiesel is a potential fuel formulation technique in solving challenges associated with biodiesel as fuel in diesel engines.