EQUATIONS FOR PREDICTING THE CETANE NUMBER OF DIESEL FUELS FROM THEIRPHYSICAL-PROPERTIES

Twenty-two equations for predicting the cetane number of diesel fuels were tested for accuracy by comparing the predicted values for > 500 f uels with the measured values. All the equations and measured values w ere taken from the literature. It was found that the predictive capabi lity of certain equations was high: several could predict the cetane n umber with a standard error of < 2. It is concluded that it is unlikel y that the standard error can be reduced significantly below 1.5, beca use the measured cetane numbers are themselves subject to experimental error. The equations were unable to predict accurately the cetane num ber of untypical diesel fuels, such as vegetable oils and diesel blend s containing alcohols. This was expected, since these empirical equati ons were constructed from databases for typical diesel fuels only. The measured cetane number of diesel fuels was found to correlate very we ll with their aniline point. Six of the 22 equations were functions of only the aniline point, and two of them showed very good predictive c apability.