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Methane is the major component of natural gas, which is one of the most widely used fuels. A large number of shock tube (ST) and rapid compression machine (RCM) ignition delay measurements are available in the literature for validating its detailed combustion mechanisms. A large set of experimental data was collected for methane combustion: ignition studies in STs (4939 data points in 574 datasets) and in RCMs (582/69). In total, 5521 data points in 643 datasets from 76 publications were collected, covering wide ranges of temperature T, pressure p, equivalence ratio φ, and diluent concentration. For a quantitative assessment of methane combustion models, a least-squares function is used to show the agreement between measurements and simulations. Thirteen recent methane combustion mechanisms were tested against these experimental data, and the dependence of their predictions on the types of experiments and the various experimental conditions was investigated. The mechanism comparison results show that most mechanisms could well reproduce the experimental ignition delay times (IDTs) measured in STs. IDTs measured in RCMs and STs at low temperatures (below 1000 K) could also be well predicted by several mechanisms. SanDiego-2014, Caltech-2015, Aramco-II-2016, and Glarborg-2018 were found to be the most accurate mechanisms for the simulation of methane combustion under ST experimental conditions, while Aramco-II-2016 had the smallest prediction error under RCM conditions. Local sensitivity analysis was carried out to determine the effect of reactions on the simulation results obtained under given experimental conditions and to identify the critical reaction steps for improving the methane combustion models.

Tranter et al. conducted a series of experiments of ethane oxidation and pyrolysis covering a wide range of temperature (800 K -1500 K) and pressure (5 bar -1000 bar) in a high pressure shock tube. The oxidation and pyrolysis of ethane were carried out behind reflected shock waves, and the concentrations of the reaction products were measured by gas chromatography. The results of these experiments were re-evaluated by optimizing selected rate parameters of the NUIG C5 combustion mechanism. The rate coefficients of 14 reactions were selected based on sensitivity analysis and preliminary uncertainty estimations for optimization. Arrhenius parameters (A, n, E) of the selected reaction steps were optimized using not only the experimental data of Tranter et al., but also the results of direct measurements related to these reactions. The obtained mechanism with the optimized rate parameters described the experiments of Tranter et al. much better than the original mechanism. New rate coefficient recommendations were obtained for all reactions with temperature dependent uncertainties including well studied reactions such as C2H6+OH = C2H5+H2O and less-known reactions like C2H3+O2 = CH2CHO+O.

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