Evaluating Ignitability Index of Marine Fuel with Two-component Model Fuel

Abstract

  The calculation formula for the CCAI (Calculated Carbon Aromaticity Index) was derived from engine experiments using distillate and residual oils. The author prepared two-component test fuels that are a mixture of an alkane and an aromatic hydrocarbon, both of which have different boiling points. The test fuels were produced with various components and mixing ratios. This study evaluated the effect of evaporation characteristics on the CCAI and the cetane number. In addition, a method for modifying the CCAI was examined based on the liquid properties and the mixing ratios of the two components. It was confirmed that a correlation exists between the CCAI and the cetane number when test fuels with different mixing ratios of the two components are used. In contrast, test fuels containing a mixture of two different components did not have the same cetane number even if they had the same CCAI. These characteristics of the simplified two-component fuels were similar to those of marine fuels confirmed by previous studies. The evaporation rate behavior of the test fuels could be either unimodal or bimodal depending on the types of two fuels. The cetane number of a test fuel with a bimodal evaporation rate was not always small. The enhanced CCAI, which was the volume average of the CCAI formula adjusted for each alkane and aromatic component, had a higher correlation with the cetane number than the current CCAI does.