Experimental and kinetic modeling studies on high-pressure oxidation of RP-3 surrogate fuel. Part Ⅱ: The effect of aromatic component

This study aims to guide the optimization of surrogate fuels and reduce development time and experimental costs by investigating the effect of three C₉H₁₂ isomers as aromatic components on the high-pressure oxidation of a surrogate fuel for RP-3 kerosene. Consistent with Part I, the surrogate fuel consists of 66.2 % n-dodecane, 18.0 % 1,3,5-trimethylcyclohexane, and 15.8 % aromatic compounds (in mole fraction). The three C₉H₁₂ isomers are n-propylbenzene (A1C₃H₇), 1,3,5-trimethylbenzene (T135MB), and 1,2,4-trimethylbenzene (T124MB). The oxidation experiments were conducted in a jet-stirred reactor at an equivalence ratio of 0.4, temperatures ranging from 500 to 1020 K, and a pressure of 12.0 atm. A comprehensive kinetic model comprising 1596 species and 8376 reactions was developed to elucidate the influence of aromatic components. As observed in Part I, the surrogate fuel exhibits a three-stage oxidation phenomenon, regardless of the aromatic component. Aromatic components minimally affect the mole fraction profiles of n-dodecane and 1,3,5-trimethylcyclohexane due to their low concentration and reactivity. Interestingly, A1C₃H₇, the most reactive aromatic component, is consumed slower than T135MB and T124MB during the oxidation of the surrogate fuel in Stages II and III. This behavior is attributed to A1C₃H₇ being more readily regenerated via reactions of fuel radicals with HȮ₂, and radicals such as HȮ₂ in the surrogate fuel oxidation depending on n-dodecane. The impact of aromatic components on products is primarily seen in aromatic products, with minimal effects on CO, CO₂, and light hydrocarbons. A1C₃H₇ predominantly produces unsaturated mono-substituted benzene, T135MB primarily forms m-xylene, and T124MB produces o-/m-/p-xylene. The fuel consumption pathways align closely with ȮH radical generation. A1C₃H₇ and T124MB exhibit pronounced low-temperature chain-branching oxidation, whereas T135MB does not. Considering the molecular structure of aromatic components is essential for more accurate prediction of aromatic consumption, product formation, and ignition behavior of real RP-3 kerosene.