Dynamics Analysis of a Jet-Fuel Surrogate and Development of a Skeletal Mechanism for Computational Fluid Dynamic Applications

Abstract

The autoignition dynamics of a three-component surrogate jet fuel (66.2% n-dodecane, 15.8% n-proplylbenzene, 18.0% 1,3,5-trimethylcyclohexane) suitable for usage as Jet A-1 and RP-3 aviation fuels are analyzed, using the detailed mechanism of Liu et al. (2019). The conditions considered are relevant to the operation of gas turbines and the analysis is performed using mathematical tools of the computational singular perturbation (CSP) method. The key chemical pathways and species are identified in the analysis of a homogeneous adiabatic and constant pressure ignition system for a wide range of initial conditions. In particular, the key role of hydrogen and CO-related chemistry is highlighted, with an increasing importance as the initial temperature increases. The C2H4→C2H3→CH2CHO pathway is also identified as playing a secondary but nonnegligible role with an importance increasing with initial temperature, favoring the system’s explosive dynamics and, thus, promoting ignition. Finally, C2H4 is identified as being a species with a key (secondary) role to the system’s explosive dynamics, but its role is replaced by C3H6 and, eventually, by O2 as the initial temperature increases. In the second part of the current work, a 58-species skeletal mechanism is generated using a previously developed algorithmic process based on CSP. The developed skeletal mechanism was tested in a wide range of initial conditions, including both ignition delay time and laminar flame speed calculations. For the conditions that were of interest in the current work, the skeletal mechanism approximated the detailed mechanism with very small error. The 58-species skeletal mechanism is shown to be ideal for use in computational fluid dynamics applications not only because of its small size but also because of its sufficiently slow associated fast timescale.