Relating the cetane number of biodiesel fuels to their fatty acid composition: a critical study

The cetane number is one of the most significant properties to specify the ignition quality of a fuel for use in a diesel engine. The cetane number of biodiesel fuels is considerably influenced by their fatty acid methyl ester composition. The determination of cetane number of biodiesel is an expensive and time-consuming process. The objective of the present work is to predict the cetane numbers of different biodiesels using their fatty acid ester composition. Fifteen different biodiesel (including three blends) fuels were prepared and their cetane numbers were experimentally measured. An extensive literature review was made and the measured cetane numbers were compared with the reported values. To predict the cetane numbers of biodiesel fuels from their fatty acid methyl ester composition, a Multiple linear regression model wits developed. The cetane numbers and fatty acid compositions of 57 biodiesel fuels and 7 pure fatty acid methyl esters from the available literature were given as inputs. The experimentally measured cetane numbers and fatty acid compositions Of four biodiesel fuels were also given as inputs to develop the regression model. The regression model has yielded an R-2 value of 0.953 and a standard deviation of 2.271. The predicted cetane numbers are comparable with the experimentally measured cetane numbers. The maximum prediction error from the present model was found to be 8 per cent. Similarly, the present model was compared with the available litrature models. The maximum prediction error from the literature models was found to be 15 per cent. The present model also shows a good agreement with the measured cetane numbers.