A comprehensive and hierarchical optimization of a joint hydrogen and syngas combustion mechanism has been carried out. The Kéromnès et al. (Combust Flame, 2013, 160, 995–1011) mechanism for syngas combustion was updated with our recently optimized hydrogen combustion mechanism (Varga et al., Proc Combust Inst, 2015, 35, 589–596) and optimized using a comprehensive set of direct and indirect experimental data relevant to hydrogen and syngas combustion. The collection of experimental data consisted of ignition measurements in shock tubes and rapid compression machines, burning velocity measurements, and species profiles measured using shock tubes, flow reactors, and jet‐stirred reactors. The experimental conditions covered wide ranges of temperatures (800–2500 K), pressures (0.5–50 bar), equivalence ratios (ϕ = 0.3–5.0), and C/H ratios (0–3). In total, 48 Arrhenius parameters and 5 third‐body collision efficiency parameters of 18 elementary reactions were optimized using these experimental data. A large number of directly measured rate coefficient values belonging to 15 of the reaction steps were also utilized. The optimization has resulted in a H2/CO combustion mechanism, which is applicable to a wide range of conditions. Moreover, new recommended rate parameters with their covariance matrix and temperature‐dependent uncertainty ranges of the optimized rate coefficients are provided. The optimized mechanism was compared to 19 recent hydrogen and syngas combustion mechanisms and is shown to provide the best reproduction of the experimental data.

No abstract

A large set of experimental data was accumulatedfor hydrogen combustion: ignition measurements in shock tubes (770 data points in 53 datasets) and rapid compression machines development. An analysis of sensitivity coefficients was carried out to identify reactions and ranges of conditions that require more attention in future development of hydrogen combustion models. The influence of poorly reproduced experiments on the overall performance was also investigated.3

A detailed reaction mechanism for methanol combustion that is capable of describing ignition, flame propagation and species concentration profiles with high accuracy has been developed. Starting from a modified version of the methanol combustion mechanism of Li et al. (Int. J. Chem. Kinet. 2007) and adopting the H2/CO base chemistry from the joint optimized hydrogen and syngas combustion mechanism of Varga et al. (Int. J. Chem. Kinet., 2016), an optimization of 57 Arrhenius parameters of 17 important elementary reactions was performed, using several thousand indirect measurement data points, as well as direct and theoretical determinations of reaction rate coefficients as optimization targets. The final optimized mechanism was compared to 18 reaction mechanisms published in recent years, with respect to their accuracy in reproducing the available indirect experimental data for methanol and formaldehyde combustion. The utilized indirect measurement data, in total 24,900 data points in 265 datasets, include measurements of ignition delay times, laminar burning velocities and species profiles captured using a variety of experimental techniques. In addition to new best fit values for all rate parameters, the covariance matrix of the optimized parameters, which provides a quantitative description of the temperature-dependent ranges of uncertainty for the optimized rate coefficients, was calculated. These posterior uncertainty limits are much narrower than the prior limits in the temperature range for which experimental data are available. The uncertainty of the self-reaction of HȮ2 radicals and important H-atom abstraction reactions from the methanol molecule are discussed in detail.

a b s t r a c tA large set of experimental data was accumulated for syngas combustion: ignition studies in shock tubes (732 data points in 62 datasets) and in rapid compression machines (492/47), flame velocity determinations (2116/217) and species concentration measurements from flow reactors (1104/58), shock tubes (436/21) and jet-stirred reactors (90/3). In total, 4970 data points in 408 datasets from 52 publications were collected covering wide ranges of temperature T, pressure p, equivalence ratio u, CO/H 2 ratio and diluent concentration X dil . 16 recent syngas combustion mechanisms were tested against these experimental data, and the dependence of their predictions on the types of experiment and the experimental conditions was investigated. Several clear trends were found. Ignition delay times measured in rapid compression machines (RCM) and in shock tubes (ST) at temperatures below 1000 K could not be well-predicted. Particularly for shock tubes, facility effects at temperatures below 1000 K could not be excluded. The accuracy of the reproduction of ignition delay times did not change significantly with pressure. The agreement of measured and simulated laminar flame velocities is better at low initial (i.e. cold side) temperatures, at fuel-lean conditions, for CO-rich and highly diluted mixtures. The reproduction of the experimental flame velocities is better when these were measured using the heat flux method or the counterflow twin-flame technique, compared to the flame cone method and the outwardly propagating spherical flame approach. With respect to all data used in this comparison, five mechanisms were identified that reproduce the experimental data similarly well. These are the NUIG-NGM-2010, Kéromnès-2013, Davis-2005, Li-2007 and USC-II-2007 in decreasing order of their overall performance. The influence of poorly reproduced experiments and weighting on the performance of the mechanisms was investigated. Furthermore, an analysis of local sensitivity coefficients was carried out to determine the influence of selected reactions at the given experimental conditions and to identify those reactions that require more attention in future development of syngas combustion models.

A detailed multi-purpose reaction mechanism for ethanol combustion was developed for the use in high-fidelity numerical simulations describing ignition, flame propagation and species concentration profiles with high accuracy. Justified by prior analysis, an optimization of 44 Arrhenius parameters of 14 crucial elementary reactions using several thousand direct and indirect measurement data points was performed, starting from the ethanol combustion mechanism of Saxena and Williams (2007). The final optimized mechanism was compared to 13 reaction mechanisms frequently used in ethanol combustion with respect to their accuracy in reproducing the various types of experimental data.

No abstract

A detailed review of the performances of 24 butanol combustion mechanisms, published between 2008 and 2020, is given using a comprehensive experimental data collection (89,388 data points in 266 datasets from 32 publications). The data cover wide ranges of equivalence ratio (φ = 0.38–2.67), diluent ratio (0.15–0.98), initial temperature (672–1886 K), and pressure (0.9–90 atm). The collection includes ignition delay time measurements in shock tubes and rapid compression machines, concentration determinations in shock tubes, jet-stirred reactors, flow reactors, and laminar burning velocity measurements. The experimental data were recorded in ReSpecTh Kinetics Data Format (RKD format) v.2.3 XML data files, which are available in the ReSpecTh site (). The standard deviations of the measurements were estimated using both the published experimental uncertainty and the scatter error of the datasets determined by code Minimal Spline Fit. Mechanism CRECK 2020 was found to be the best mechanism for n-butanol (biobutanol) combustion, while the mechanisms Sarathy 2014, Vasu 2013, and Yasunaga 2012 (in this order) were the best considering the experimental data for all isomers. A part of the simulations failed, and to improve the ratio of successful simulations, the code ThermCheck was created, which detects discontinuities and nonsmoothness of thermodynamic functions defined by NASA polynomials provided with the published mechanisms and corrects them by tuning their coefficients. Local sensitivity analysis applied to the experimental conditions was used to identify the most important reaction steps of the mechanism Sarathy 2014. The sensitivity analysis was extended to the adiabatic ignition of n-butanol–air mixtures by systematically changing the initial temperature and pressure. All butanol combustion mechanisms were also tested on a hydrogen combustion data collection, which indicated that some of them were inaccurate due to their inadequate hydrogen combustion reaction block. Suggestions were given for the improvement of the Sarathy 2014 mechanism.