Investigating the oxidation characteristic of a hydro-processed bio-jet fuel: Experimental and modeling study

A rapid transition from conventional jet fuels to sustainable aviation fuels (SAFs) is imperative in order to reduce carbon emissions. Hydro-processed esters and fatty acids synthetic paraffinic kerosene (HEFA-SPK), as a type of SAF, exhibits broad applications. In this study, a new HEFA-SPK named ZH-HEFA was investigated. The fuel comprises 14% n-alkanes, 85% iso-alkanes and only 1% cycloalkanes by weight, with the majority of alkanes ranging from C₉ to C₁₇. Oxidation experiments of the fuel were conducted using an atmospheric pressure flow reactor at temperatures ranging from 550 K to 1075 K under three equivalence ratios (0.5, 1.0 and 1.5). Species mole fraction profiles were measured by an on-line gas chromatographic (GC). For comparison purposes, an experiment was also performed on RP-3, a conventional jet fuel commonly used in China, under the equivalence of 0.5. Compared to RP-3, ZH-HEFA exhibited significantly stronger low temperature reactivity and higher combustion conversion rates while demonstrating considerably lower yields of aromatics at high temperatures. The kinetic simulation of ZH-HEFA was achieved by proposing two surrogates and their corresponding kinetic models. Surrogate S-1 consisted solely of n-dodecane, while S-2 comprised 35% n-dodecane and 65% 2,6,10-trimethyl dodecane by weight. Both surrogate models were validated by the experimental data. S-1 exhibited a closer resemblance to the global oxidation characteristics of ZH-HEFA, whereas S-2 demonstrated improved accuracy in predicting the formation of small hydrocarbon intermediates during the fuel oxidation. Rate of production analysis revealed that the branched alkane component in S-2 possessed more pathways and greater capability than S-1 in generating C₃ intermediates, which are important for the generation of aromatics. Furthermore, both models displayed good predictive performance for the auto-ignition properties of HEFA-SPK fuels.-