![]() ![]() We also collected large amount of directly measured and theoretically calculated rate coefficients for these reactions and compared them with the rate coefficients used in the 12 mechanisms. Using local sensitivity analysis on the most accurate mechanisms, we identified 29 important elementary reactions, which, however, were not present in all the 12 mechanisms. Mechanisms Aramco-II-2016, Konnov-2009, Caltech-2015 and Glarborg-2018 have the lowest average errors for the reproduction of all available methane LBV data. Focusing on the operating conditions of natural gas engines, we recommend the application of mechanisms FFCM-I-2016, SanDiego-2014, and NUIG1.1-2021 for engine simulations. The performances of several mechanisms were relatively poor at other conditions. Most mechanisms could predict well the LBVs for stoichiometric and fuel-lean mixtures and for diluent ratios higher than 60%. Performances of 12 methane combustion mechanisms on reproducing these LBV measurements were analyzed according to experiment types and conditions. The data files are available on the ReSpecTh site (). The diluents included N2, H2O, CO2, Ar and He. Large amount of experimental data for laminar burning velocity (LBV) measurements of methane (+ H2/CO) − oxygen − diluent mixtures (5500 data points in 646 datasets) covering wide ranges of equivalence ratio, diluent ratio, cold side temperature and pressure were collected from 111 publications. ![]() The influence of poorly reproduced experiments on the overall performance was also investigated. 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. Also, simulation results calculated by the best-performing mechanisms are more strongly correlated with each other than those of the weakly performing ones, indicating a convergence of mechanism development. The investigation of the correlation of the simulation results revealed similarities of mechanisms that were published by the same research groups. Flame cone method data were especially poorly reproduced. Reproduction of the flame velocities measured using the flame cone method, the outwardly propagating spherical flame method, the counterflow twin-flame technique, and the heat flux burner method improved in this order. The reproduction of the measured laminar flame velocities improved with increasing pressure and total diluent concentration, and with decreasing equivalence ratio. Large differences were found between the mechanisms in their capability to predict flow reactor data. Measured H2 and O2 concentrations in JSRs could be better reproduced than the corresponding H2O profiles. The accuracy of the reproduction of an ignition delay time did not change significantly with pressure and equivalence ratio. Low-temperature ignition delay times measured in shock tubes (below 1000 K) and in RCMs (below 960 K) could not be well-predicted. Several clear trends were found when the performance of the best mechanisms was investigated in various categories of experimental data. According to the reproduction of all experimental data, the Kéromnès-2013 mechanism is currently the best, but the mechanisms NUIG-NGM-2010, ÓConaire-2004, Konnov-2008 and Li-2007 have similarly good overall performances. The best mechanism for the reproduction of ignition delay times and flame velocities is Kéromnès-2013, while jet-stirred reactor (JSR) experiments and flow reactor profiles are reproduced best by GRI3.0-1999 and Starik-2009, respectively. ![]() The performance of 19 recently published hydrogen combustion mechanisms was tested against these experimental data, and the dependence of accuracy on the types of experiment and the experimental conditions was investigated. A large set of experimental data was accumulated for hydrogen combustion: ignition measurements in shock tubes (770 data points in 53 datasets) and rapid compression machines (229/20), concentration–time profiles in flow reactors (389/17), outlet concentrations in jet-stirred reactors (152/9) and flame velocity measurements (631/73) covering wide ranges of temperature, pressure and equivalence ratio. ![]()
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