Simplified modeling combustion chemistry of neat and blended large hydrocarbon fuels with different functional groups

Abstract

In the present study, a simplified modeling approach based on a two-step reaction scheme (TSRS) was developed to describe the high-temperature combustion chemistry of large hydrocarbon fuels. The characteristic reaction time scale analysis indicated a distinct two-step reaction property for the conversion of large hydrocarbon molecules. Along with the quasi-steady state assumption, TSRS utilized a seven-reaction sub-model to describe the fuel decomposition to a small group of intermediate products, and a detailed foundational fuel combustion chemistry model to describe the oxidation of these decomposed products. In the first half of this paper, the TSRS model was constructed for four fuel components with different functional groups, including n-heptane, iso-octane, methylcyclohexane, and n-butylbenzene, and validated sequentially by their speciation data, and global combustion properties of ignition delay time and laminar flame speed data. Sensitivity analysis and rate of production analysis revealed the primary decomposition paths in the TSRS model. Then, in the second half of the paper, algebraically blending the TSRS models of neat fuel components enabled the construction of surrogate fuel models for real fuels, including a two-component primary reference fuel (PRF), a three-component gasoline surrogate fuel (toluene-PRF), a four-component Chinese jet fuel (RP-3) surrogate, and a four-component diesel surrogate. Predictions from the TSRS-based surrogate models for real fuels were shown to be consistent with the speciation data as well as the global combustion properties, whenever available in the literatures, indicating the robustness and broad applicability of the TSRS approach.