Surrogate formulation for HEFA sustainable aviation fuels: a new approach based on pyrolysis experiments

Pyrolysis experiments were conducted in a flow reactor at atmospheric pressure on three distinct hydroprocessed esters and fatty acids synthetic paraffinic kerosene (HEFA-SPK) fuels, with species concentration profiles obtained via online gas chromatography (GC). The results indicated similar pyrolysis characteristics across the fuels. A surrogate for HEFA-SPK was developed by selecting n-dodecane and isododecane as the surrogate components. The ratio of these components was determined based on the concentration profiles of pyrolysis products. A detailed kinetic model for the n-dodecane and isododecane mixture was developed, encompassing 2464 species and 8939 reactions, to simulate pyrolysis across various composition ratios and identify the optimal surrogate composition. Simulations highlighted the sensitivity of C₂H₄, C₂H₆, C₃H₄-A, and C₃H₄-P concentration profiles to the n-dodecane and isododecane ratio. These profiles served as matching targets to ascertain the optimal composition, yielding a surrogate of 73 % n-dodecane and 27 % isododecane by weight. Validation against experimental data, including pyrolysis data from this study and oxidation species concentration and ignition delay time data from literature, confirmed the surrogate's ability in replicating HEFA-SPK's combustion characteristics and the method's validity. Furthermore, a skeletal mechanism for the surrogate, comprising 66 species and 186 reactions, was developed and validated against literature data, demonstrating its accuracy in predicting the oxidation behavior of pure n-dodecane, pure isododecane, and HEFA-SPK.