A modelling study of acetylene oxidation and pyrolysis

Abstract

This study initiates the gradual upgrade of the DLR reaction database. The upgrade plan has two main steps: an optimisation of the C 1-C 4 oxidation chemistry and a revision of the polyaromatic hydrocarbon (PAH) formation sub-mechanism based thereupon. The present paper reports the main principles applied to model improvements and results obtained for the acetylene (C 2 H 2) oxidation sub-mechanisms. The principle acetylene oxidation reactions have been revised as well as the detailed chemistry of important intermediates, i.e. methylene, ethynyl, vinylperoxy radical and also diacetylene, vinylacetylene and higher diacetylenes, important for PAH formation. The uncertainty intervals of the studied reactions were statistically evaluated, providing general bounds for the performed modifications to reaction rate coefficients. The first stage of the presented update was performed through revision of the thermochemical data and model optimisation on ignition delay data and laminar flame speed data, since they exhibit lower uncertainty in comparison to species profile data. The final model optimization was obtained through simulations of concentration profiles measured in shock tubes and laminar flames for improvement of the reaction paths and rate coefficients related to acetylene pyrolysis and PAH precursor formation. Approximately 500 data points were analysed. The updated reaction mechanism predicts all simulated experimental data, also not included in the optimisation loop data prom plug flow and jet-stirred reactors, either with good or satisfactory agreement. It was found that the vinylperoxy radical formation and consumption dictate the reaction progress at low temperatures. The performed study clearly determined that acetylene combustion proceeds through the strongly coupled reaction paths of fuel oxidation and PAH precursor formation; the same species are involved in these parallel processes. Therefore, the self-consistent reaction model for acetylene combustion could be obtained only by an optimisation performed on the experimental dataset encompassing both processes.

Predicting polycyclic aromatic hydrocarbon formation with an automatically generated mechanism for acetylene pyrolysis

“…The RMG model predictions are shown in Figures 1–3 , in comparison with the experimental measurements of Norinaga et al 49 . and predictions from published mechanisms by Norinaga et al., 36 Slavinskaya et al., 37 and Tao et al 38 . It is important to note that while the RMG and Norinaga mechanisms include acetone and related reactions, neither the Slavinskaya mechanism nor the Tao mechanism include acetone.…”

“…The RMG model predictions are shown in Figures 1-3 , in comparison with the experimental measurements of Norinaga et al 49 and predictions from published mechanisms by Norinaga et al, 36 Slavinskaya et al, 37 and Tao et al 38 It is important to note that while the RMG and Norinaga mechanisms include acetone and related reactions, neither the Slavinskaya mechanism nor the Tao mechanism include acetone. As a result, the initial composition described by Norinaga et al 36 including methane and acetone was used for simulations with the RMG and Norinaga mechanisms, while pure acetylene was used as the initial composition for simulations with the Slavinskaya and Tao mechanisms.…”

“…There have been a number of previously published mechanisms specifically for acetylene pyrolysis including PAH formation, including early work by Frenklach et al, 6 and more recent ones by Norinaga et al, 36 Slavinskaya et al, 37 and Tao et al 38 Norinaga et al compiled elementary reactions reported in the literature to obtain a mechanism predicting up to the formation of coronene. They included acetone in their model to be consistent with their experiments, which used acetylene feed containing acetone and methane impurities.…”

“…There have been a number of previously published mechanisms specifically for acetylene pyrolysis including PAH formation, including early work by Frenklach et al., 6 and more recent ones by Norinaga et al., 36 Slavinskaya et al., 37 and Tao et al 38 . Norinaga et al.…”

Kinetic Modeling of Cyclohexane and n-Propylcyclohexane Oxidation with the PAH Precursor Formation

“…The current kinetic mechanism implies C0-C2 chemistry from the recent researches of Slavinskaya et al, [28,29] the further improvements of the cyclohexane oxidation model developed by Abbasi et al [26] and the n-propylcyclohexane reactions scheme established in Slavinskaya et al [25].…”