Development and validation of surrogates for RP-3 jet fuel based on chemical deconstruction methodology

Abstract

In this work, surrogates for RP-3 jet fuel have been developed based on chemical deconstruction methodology. In surrogate formulation, eight constraints have been taken into consideration, of which four factors are related to molecular structure, such as carbon number, hydrogen number, hydrogen/carbon ratio and degree of unsaturation and four others related to chemical composition, including concentrations of n-alkane, iso-alkane, cyclo-alkane and aromatics. In consideration of different weight coefficients, two kinds of surrogates S1 and S2 have been proposed. S1 surrogate is developed in particular consideration of the molecular structures while S2 focuses more on chemical compositions. Therefore, S1 surrogate is comprised of five components including n-dodecane, 2,2,4,4,6,8,8-heptamethylnonane, 2-methylheptane, decalin and o-xylene (0.058/0.342/0.019/0.418/0.163 by mole fraction) while S2 has the same components but in different proportions (0.171/0.184/0.038/0.497/0.11). In order to validate the S1 and S2 surrogates, comprehensive verification tests, including those on physical and chemical properties, have been conducted. Results showed that both surrogates had good performance in predicting the physical properties such as density, viscosity and surface tension. In terms of chemical characteristics, point-to-point validations of oxidation properties of surrogate and target fuels were conducted in a laminar flow reactor. Besides, autoignition properties of surrogates have been compared with experimental data of RP-3 jet fuel in a heated shock tube and rapid compression machine. It can be concluded that both of the S1 and S2 surrogates can well reproduce the oxidation properties of the target fuel, whereas S2 surrogate had better performance in predicting autoignition properties, especially in NTC region. Finally, surrogate models have been constructed and validated, including 2851 species and 12,242 reactions. These high-fidelity surrogate models have potentials in predicting combustion characteristics of RP-3 jet fuel.