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Abstract: The paper presents numerical simulations of a core methane jet diffusion flame with a fuel lean mixture (consisting of methane and hydrogen, in different proportions) in the co-flow. A comprehensive numerical model, which employs a detailed chemical kinetic mechanism with 25 species and 121 reaction steps, variable thermo-physical properties, multi-component diffusion and an optically thin radiation sub-model, has been used. The results of the numerical model are validated against the experimental data from literature. The validated model is used to study the characteristics of core methane jet diffusion flames with methane and hydrogen in the co-flow. A detailed study of various quantities such as temperature, sensible enthalpies of combustion and nitric oxide emissions is carried out, for different compositions of the fuel in the co-flow oxidizer stream. The co-flow composition which results in minimum nitric oxide emissions is examined. [Copyright &y& Elsevier]

Numerical and experimental investigations of unconfined methane-oxygen laminar premixed flames are presented. In a lab-scale burner, premixed flame experiments have been conducted using pure methane and pure oxygen mixtures having different equivalence ratios. Digital photographs of the flames have been captured and the radial temperature profiles at different axial locations have been measured using a thermocouple. Numerical simulations have been carried out with a C2 chemical mechanism having 25 species and 121 reactions and with an optically thin radiation sub-model. The numerical results are validated against the experimental and numerical results for methane-air premixed flames reported in literature. Further, the numerical results are validated against the results from the present methane-oxygen flame experiments. Visible regions in digital flame photographs have been compared with OH isopleths predicted by the numerical model. Parametric studies have been carried out for a range of equivalence ratios, varying from 0.24 to 1.55. The contours of OH, temperature and mass fractions of product species such as CO, CO2 and H2O, are presented and discussed for various cases. By using the net methane consumption rate, an estimate of the laminar flame speed has been obtained as a function of equivalence ratio. [ABSTRACT FROM PUBLISHER]

Abstract: 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. [Copyright &y& Elsevier]