Abstract 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. 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. The best mechanism for the reproduction of ignition delay times and flame velocities is Keromnes-2013, while jet-stirred reactor (JSR) experiments and flow reactor profiles are reproduced best by GRI3.0-1999 and Starik-2009, respectively. According to the reproduction of all experimental data, the Keromnes-2013 mechanism is currently the best, but the mechanisms NUIG-NGM-2010, OConaire-2004, Konnov-2008 and Li-2007 have similarly good overall performances. Several clear trends were found when the performance of the best mechanisms was investigated in various categories of experimental data. Low-temperature ignition delay times measured in shock tubes (below 1000 K) and in RCMs (below 960 K) could not be well-predicted. The accuracy of the reproduction of an ignition delay time did not change significantly with pressure and equivalence ratio. Measured H2 and O2 concentrations in JSRs could be better reproduced than the corresponding H2O profiles. Large differences were found between the mechanisms in their capability to predict flow reactor data. The reproduction of the measured laminar flame velocities improved with increasing pressure and total diluent concentration, and with decreasing equivalence ratio. 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. Flame cone method data were especially poorly reproduced. The investigation of the correlation of the simulation results revealed similarities of mechanisms that were published by the same research groups. 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. 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.

Comparison of the performance of several recent hydrogen combustion mechanisms (proceedings)

Selection Criteria and Screening of Potential Biomass-Derived Streams as Fuel Blendstocks for Advanced Spark-Ignition Engines

As a kind of renewable biofuel for use in internal combustion engines, biogas has been widely paid attention to recently. In this review, the researches on basic combustion characteristics and chemical kinetics of biogas are summarized, and its applications in internal combustion engines are also discussed. These studies show that the main challenge of the large-scale application of biogas is the instability of its components, which is due to differences in the production process and the raw material species. Detailed chemical kinetics and simplified chemical kinetic models for multiple components of biogas need to be validated. In engine applications, a certain proportion of H2 added to biogas can improve the combustion properties. The application of biogas in dual fuel mode is an attractive way to promote the efficient utilization of biogas. However, further studies on the efficiency and emissions of engines under variable conditions need to be analyzed in detail.

Review of the state-of-the-art of biogas combustion mechanisms and applications in internal combustion engines

Understanding the antagonistic effect of methanol as a component in surrogate fuel models: A case study of methanol/n-heptane mixtures

Here we present a publicly available database of opacities for molecules of astrophysical interest named ExoMolOP that has been compiled for over 80 species, and is based on the latest line list data from the ExoMol, HITEMP, and MoLLIST databases. These data are generally suitable for characterising high-temperature exoplanet or cool stellar and substellar atmospheres, and have been computed at a variety of pressures and temperatures, with a few molecules included at room temperature only from the HITRAN database. The data are formatted in different ways for four different exoplanet atmosphere retrieval codes; ARCiS, TauREx, NEMESIS, and petitRADTRANS, and include both cross sections (at ) and k -tables (at ) for the 0.3–50 μ m wavelength region. Opacity files can be downloaded and used directly for these codes. Atomic data for alkali metals Na and K are also included, using data from the NIST database and the latest line shapes for the resonance lines. Broadening parameters have been taken from the literature where available, or have been estimated from the parameters of a known molecule with similar molecular properties where no broadening data are available.

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The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres

Hydrogen sulfide combustion has been of interest in recent years due to its presence in coal-derived syngas and in sour gas. However, there are limited data available for the calibration of chemical kinetics models of high-temperature H2S oxidation. Ignition delay times and laser-absorption water time histories were therefore measured in two different shock tubes around atmospheric pressure over a range of temperatures from 1445 to 2210 K for H2S-O2 mixtures diluted in 98% Ar. While modern H2S models from the literature predicted the ignition delay times with fair accuracy, the water profiles were initially very poorly predicted with the same kinetic mechanisms. A model analysis showed that the reaction R62, SH + HO2 ⇆ H2S + O2 (in reverse), was chiefly responsible for these poor predictions. It was possible to obtain better water predictions when the rate for R62 was divided by 10. A tentative model is proposed herein, based on this assumption for R62, and good predictions were obtained for both the ignition delay times and water profiles, as well as for former high-pressure shock-tube data with H2-H2S mixtures. The present study shows that more accurate rates for the reactions R62 (SH + HO2 ⇆ H2S + O2), R75 (SH + O2 ⇆ HSO + O), and R46 (SH + SH (+M) ⇆ HSSH (+M)) would be needed to better predict H2S combustion chemistry.

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Clayton R. Mulvihill

Papers

Shock-tube water time-histories and ignition delay time measurements for H2S near atmospheric pressure

Experimental study of ethanol oxidation behind reflected shock waves: Ignition delay time and H2O laser-absorption measurements

Assessment of modern detailed kinetics mechanisms to predict CO formation from methane combustion using shock-tube laser-absorption measurements

Speciation measurements in shock tubes for validation of complex chemical kinetics mechanisms: Application to 2-Methyl-2-Butene oxidation

Ignition delay time and H2O measurements during methanol oxidation behind reflected shock waves