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Investigations of structure and reaction zones of unconfined methane-hydrogen laminar jet diffusion flames are presented. In a lab-scale burner, experiments have been conducted using a mixture of pure methane and pure hydrogen in different volumetric proportions. Digital photographs of the flames have been captured and the radial temperature profiles at different axial locations outside the flame zone have been measured. Numerical simulations are carried out with a C2 chemical kinetics mechanism having 25 species and 121 reaction steps and an optically thin radiation sub-model. The numerical results are validated against the experimental data. Parametric studies have been carried out for a range of methane-hydrogen mixtures with volumetric proportion of hydrogen in the mixture varying from 0% to 80%. Variation of flame height, contours of temperature, mass fractions of product species and the net reaction rates of methane and hydrogen for various cases are presented and discussed in detail. Further, analysis of net reaction rates of important reactions involving methane and hydrogen with radicals such as O, H and OH are analyzed. The maximum temperature in the domain is seen to decrease for the fuel mixtures with higher hydrogen content. The overall flame length also decreases. For a fuel mixture having 40% hydrogen by volume, the net molar consumption rates of methane and hydrogen are found to be almost equal. Examination of individual reactions of fuel species with radicals shows that hydrogen is mainly consumed by its reaction with OH, whereas methane consumption is mainly through its reactions involving H as well as OH radicals. � 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Numerical investigation of laminar counterflow premixed methane-hydrogen-air flames at a low strain rate is presented. Simulations are carried out with a numerical model incorporated with C2 chemical mechanism having 25 species and 121 reaction steps, and with an optically thin radiation submodel. The numerical model is validated using the experimental data reported in the literature in terms of temperature and species concentrations in flames from opposed flow premixed methane-air and hydrogen-air streams. Parametric studies are performed for opposed flowing methanehydrogen and air mixtures. A premixed methane-hydrogen and air with a rich mixture equivalence ratio (1.75) flows from the top duct, and one having a lean mixture equivalence ratio (0.25) flows from the bottom duct. The volumetric fraction of hydrogen in the fuel mixture has been varied from 20 to 80%. The strain rate used in the present study is kept constant at 50 s -1. Variation of velocity, temperature, species concentrations, and net reaction rates of oxygen, methane and hydrogen along the axis for various cases are presented and discussed in detail. Double flame zones are observed for all the cases. The addition of hydrogen to the rich side stream is seen to be effective in modifying the extents of both reaction zones. The reaction rate of methane is seen to be enhanced with the addition of hydrogen. � 2011 by Begell House, Inc.