Effects of the cetane number on chemical ignition delay

This study evaluates the effects of cetane number (CN) on autoignition reactivity and chemical ignition delay. Recent interest in sustainable aviation fuels and single-fuel policies in the US necessitates the investigation of the effect of various fuels' properties on combustion. CN is a representative metric quantifying ignition quality across a range of fuels’ relevant properties. However, there is no concrete relationship between CN and chemical reactivity. To investigate the impact of CN on combustion characteristics, a set of test fuels have been formulated with varying CNs while maintaining other properties. Fuels were tested in the RCM and shock tube at various conditions. Typically, the reactivity is linearly proportional to the CN. However, the results showed that DCN could not be the sole predictor of ignition delay across the range of thermodynamic conditions relevant to propulsion systems. CN has been used as an indirect marker (or correlation) of chemical composition effects on ignition, and it is known that the DCN correlation breaks down for certain conditions and fuels. The structure of chemical components mainly affects combustion pathways by fuel breakdown, hydrogen abstraction, and isomerization. The results provide a guideline for practical experiments to evaluate the impact of CN on combustion characteristics.