Influence of the functional group of fuels on the construction of skeletal chemical mechanisms: A case study of 1-hexane, 1-hexene, and 1-hexanol

Abstract

To investigate the oxidation and combustion performance of practical fuels, surrogate fuels including various types of fuels are usually introduced. The unique functional groups of different fuels dominate the fuel oxidation behaviors of different fuels, thus it is crucial to take account of the impact of fuel function groups for the development of the skeletal chemical mechanisms of surrogate fuels. In this work, by integrating the reaction class-based global sensitivity analysis and the decoupling methodology, a skeletal chemical mechanism of fuels is built, and the influence of the functional group was specially considered in the construction of the chemical mechanisms. First, the reaction class-based global sensitivity and path sensitivity analyses were employed to recognize the important reaction classes in the fuel-related sub-mechanism, and the reaction classes relevant to the fuel function group were identified. Second, a representative reaction was selected from each important reaction class by the rate of production analysis, and the skeletal fuel-specific sub-mechanism was obtained. Third, the initial skeletal chemical mechanism of fuels was formed by assembling the skeletal fuel-specific sub-mechanism with a detailed C0–C1 sub-mechanism and a reduced C2–C3 sub-mechanism based on the decoupling methodology. Finally, the optimization aiming at the ignition delay times and the concentrations of fuel, H2O, CO, and CO2 was conducted based on the genetic algorithm by tuning the reaction rate coefficients in the fuel-specific sub-mechanism within their uncertainties to enhance the performance of the skeletal mechanism. Using the above method, a skeletal chemical mechanism for 1-hexane, 1-hexene, and 1-hexanol was established containing 72 species and 243 reactions. The validation results indicated that decent consistency between the simulated and experimental data in premixed and opposed flames, jet-stirred reactors, and shock tubes was achieved for the three fuels over wide operating conditions. Moreover, the unique oxidation behavior of 1-hexane, 1-hexene, and 1-hexanol was captured by the present skeletal mechanism due to the identification of the functional group reactions.