Development of a 5-component gasoline surrogate model using recent advancements in the detailed H2/O2/CO/C1-C3 mechanism for decoupling methodology

Abstract

In the present work, a 5-component gasoline surrogate chemical kinetic mechanism has been developed and validated. The first novelty of this mechanism is that a recently advanced H2/O2/CO/C1 detailed sub-mechanism is adopted for accurately predicting the laminar flame speeds over a wide range of operating conditions and a recently advanced C2-C3 detailed sub-mechanism is used due to its potential benefits on accurate flame propagation simulation in order to overcome the drawbacks in the original decoupling methodology. The second novelty of this mechanism is that the sub-mechanisms of propyne and allene which are important for soot formation from non-aromatics have been improved significantly. For each of the five gasoline surrogate components (iso-octane, n-heptane, iso-hexane, 1-hexene, and toluene) a skeletal submechanism, which determines the simulation of ignition delay times, is constructed for species C4-Cn. The five skeletal sub-mechanisms are coupled with the new C2-C3 and H2/O2/CO/C1 detailed sub-mechanisms. Together with a reduced NOx (oxides of nitrogen) sub-mechanism, the 5-component gasoline surrogate chemical kinetic mechanism has 214 species and 1233 reactions, which are feasible currently for CFD simulation of gasoline engine combustion, emissions, and knock. The new H2/O2/CO/C1 and C2-C3 detailed sub-mechanisms were 2 validated with selected experimental data of ignition delay times, laminar flame speeds, and important species profiles in the literature. The reaction rate constants of the five skeletal sub-mechanisms were optimized in this work to match available experimental data of either pure fuels or fuel blends, including real gasoline fuels. The validation results show that the prediction accuracy of the 5-component gasoline surrogate chemical kinetic mechanism of the present work can be less than 5% for various fuel blends under a pressure range of 1.0~80.0 bar, a temperature range of 300~1260 K, and an equivalence ratio range of 0.5~2.5.

Development of Multipurpose Skeletal Core Combustion Chemical Kinetic Mechanisms

“…Unlike previously derived skeletal mechanisms for small fuels, the current skeletal mechanisms include comprehensive core fuel molecules, especially the sub-mechanisms for allene and propyne, which are critical for the prediction of soot formation from nonaromatic fuels. 10,11 The two skeletal mechanisms are validated against IDT, laminar flame speed (LFS), and species profiles from a JSR and flow reactor (FR) over a wide range of combustion conditions from an extensive literature review, with details given in the Supporting Information. 11,19,20 compared to AramcoMech3.0.…”

“…10,11 The two skeletal mechanisms are validated against IDT, laminar flame speed (LFS), and species profiles from a JSR and flow reactor (FR) over a wide range of combustion conditions from an extensive literature review, with details given in the Supporting Information. 11,19,20 compared to AramcoMech3.0. 9 Figure 1 shows the predicted IDT and LFS for propene (C 3 H 6 ), isobutene (iC 4 H 8 ), and n-butane using the generated skeletal mechanisms and the detailed NUIGMech1.1 and AramcoMech3.0 mechanisms.…”

“…The validation results indicate that the prediction accuracy of the five-component gasoline surrogate model with the skeletal mechanism can also well reproduce the modeling results compared to the detailed mechanism. 11 It is worth noting that the developed detailed mechanisms for real fuels can still be further reduced for engine simulations. Following a similar procedure to derive the core skeletal mechanism together with the computational singular perturbation method to remove unimportant reactions, the constructed reaction mechanism of the five-component gasoline surrogate model is further reduced under engine conditions to a skeletal mechanism with only 95 species and 321 reactions, and the performance for IDTs and LFSs under typical conditions against the detailed mechanism is provided as Figure 3.…”

“…Table lists the size of the generated skeletal mechanism for each fuel with the predicted error of IDT less than 10% and the maximum error and mean absolute error (MAE) of the predicted IDT via the merged C 0 –C 3 and C 0 –C 4 skeletal mechanisms, which include 170 species and 1002 reactions and 341 species and 1977 reactions, respectively. Unlike previously derived skeletal mechanisms for small fuels, the current skeletal mechanisms include comprehensive core fuel molecules, especially the sub-mechanisms for allene and propyne, which are critical for the prediction of soot formation from non-aromatic fuels. , The two skeletal mechanisms are validated against IDT, laminar flame speed (LFS), and species profiles from a JSR and flow reactor (FR) over a wide range of combustion conditions from an extensive literature review, with details given in the Supporting Information. Table summarizes these experimental conditions of various C 0 –C 4 fuels used for validation of the two skeletal mechanisms.…”

“…To develop a unified core kinetic model, the mechanism development group at the National University of Ireland (NUI) Galway have re-evaluated the kinetics and thermochemistry of C 0 –C 4 base chemistry based on recent ab initio studies and experimental diagnostics. The widely used AramcoMech mechanisms − have been updated and recently published as NUIGMech1.1, which has been comprehensively validated against a large database for combustion properties of C 0 –C 4 hydrocarbon and oxygenated hydrocarbon fuels. ,− However, its large size limits its applicability. Although a series of reduced mechanisms for small fuels were developed, − almost all of them were targeted for specific fuels or combustion conditions, limiting their applications as a core mechanism for the development of detailed mechanisms of large fuels.…”