Decoding cetane number law of key aviation fuel components: From structure–property relationships to reaction pathway analysis

Aviation fuels require reliable and efficient self-ignition performance under extreme conditions to ensure engine stability and flight safety. The cetane number (CN) is commonly used to characterize this property by indicating the tendency of a fuel to auto-ignite under compression, effectively reflecting the ignition delay time. In this study, a systematic investigation is carried out on the key hydrocarbon constituents of aviation fuels, including n-alkanes, iso-alkanes, cycloalkanes, and aromatics. Each constituent is individually examined for its CN using a standardized CFR-A5 diesel cetane number tester as specified by ASTM D613. To elucidate the underlying structure–property relationships, a comprehensive analysis encompassing molecular structure, bond dissociation energy, reaction pathway, physicochemical properties, and quantum chemistry is performed. The results indicate that within homologous compounds, an increase in molecular carbon number leads to more breakable sites and smoother radical chain transfer, which favor improvements in CN performance. However, excessively long carbon chains slow molecular motion, reduce collision frequency and reactivity, and increase steric hindrance and system entropy, thereby inhibiting CN enhancement. Moreover, the presence of cyclic structures and branched-chain accumulation can weaken or even offset the upward trend driven by “carbon addition.” This research not only establish a benchmark CN database for these critical aviation fuel components but also provides valuable guidance for both refining conventional aviation fuels and developing alternative fuels, facilitating targeted CN optimization to enhance combustion performance and operational reliability in modern aero-engines.