Optimized reaction mechanism rate rules for ignition of normal alkanes

Abstract

The increasing demand for cleaner combustion and reduced greenhouse gas emissions motivates research on the combustion of hydrocarbon fuels and their surrogates. Accurate detailed chemical kinetic models are an important prerequisite for high fidelity reacting flow simulations capable of improving combustor design and operation. The development of such models for many

A model of tetrahydrofuran low-temperature oxidation based on theoretically calculated rate constants

“…While all the calculated rate constants will be given in the next part, Table 1 presents the kinetic parameters calculated theoretically in the present work for the reactions shown in Figure 1, in the case where a comparison between these parameters and those derived from the recent rate rules proposed for normal alkanes by Cai et al [20] can also be displayed. Table 1 shows that the presence of the oxygenated ring induces notable differences in rate constants at 600 K compared to the values obtained with the most recent rate rules proposed for acyclic alkanes.…”

“…This table also shows significant differences in the rate constants of concurrent isomerizations: the isomerizations are significantly favored, by several orders of magnitude for some relevant rate constants, when the shifted H-atom is bonded to a carbon in an alpha position relative to O atom. [20] in the case of the isomerizations, formation of dihydrofurans and HO2 radicals, and formations of bicyclic ethers shown in Figure 1. The structure of the species can be found in Table S2 of Supplementary material.…”

“…Cyclic species nomenclature is used from Table 4, Table 5, Table 6 & Table 7. 38 6700/ a Estimated from the rate rule "Addition of O2 to alkyl radicals (R) (secondary carbon sites)" [20]. b Calculated in the present work.…”

“…Because these reactions play a role at temperatures higher than 1200 K, the rate parameters for the unimolecular decompositions of THF, leading to the formation of products through H-shift and ring opening, were recalculated in the present work (reactions 1-5 in Table 2). The reaction rate parameters for bimolecular initiation between THF and molecular oxygen (reactions 6 and 7) were taken as those optimized by Cai et al [20] in the case of linear alkanes. In order to take into account the difference in C-H bond dissociation energy due to the presence of an O-atom in an alpha location, the activation energy of reaction 6 was decreased by 4 kcal/mol.…”

Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and Production

“…[140] Examples for typical reaction classes are hydrogen abstraction from the fuel molecule by different radicals or O 2 addition to the different fuel radicals,and each reaction class typically leads to an umber of elementary reactions.T hese reaction classes are applied consistently to species of different size,a nd Arrhenius parameters for the reaction rate coefficients are then assigned by so-called rate rules that depend on the reaction class and the specific sites at which the reaction occurs.Useful and accurate sets of reaction classes and associated rate rules have been published in the Angewandte Chemie Reviews recent literature. [153][154][155][156] Ab initio calculations to determine reliable bond dissociation energies,r eaction rate parameters for the most decisive reactions such as the initial hydrogen abstraction from the fuel, transition states,a nd branching ratios towards specific products are valuable complements to such efforts.…”