The effects of enrichment by carbon monoxide on adiabatic burning velocity and nitric oxide formation in methane flames

The present paper discusses the fundamentals of specific fuel mixtures as they may be used in lean premix flames in power installations. Experimental measurements of the adiabatic burning velocity and NO formation in (CH4 + CO) + (O2 + N2) flames are presented. The carbon monoxide content in the fuel was varied from 0 to 15%. The oxygen content in the air was varied from 20.9% to 18%. These ranges are typical for addition of reformer gas to methane burners. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The Heat Flux method was used to determine burning velocities under conditions when the net heat loss of the flame is zero. An overall accuracy of the burning velocities was estimated to be better than ±1 cm/s in the whole range of enrichment by carbon monoxide. The relative accuracy of the equivalence ratio was found to be below 1.6%. Adiabatic burning velocities of methane + carbon monoxide + nitrogen + oxygen mixtures were found in satisfactory agreement with the modeling. The concentrations of O2, CO, CO2 and NO in these flames were measured in the burnt gases at a fixed distance from the burner using probe sampling. Enrichment by carbon monoxide leads to the increase of NO formation in lean and stoichiometric mixtures. Dilution by nitrogen decreases [NO] at any equivalence ratio. Numerical predictions and trends were found in good agreement with the experiments. The results of enrichment by CO on adiabatic burning velocity and nitric oxide formation in methane flames are discussed and compared with similar flames enriched by hydrogen. Experimental peculiarities due to contamination of the fuel mixtures with metal carbonyls are described

Structure of H2/O2/N2 flames at atmospheric pressure studied by molecular beam mass spectrometry and modeling

Structure of laminar premixed flat H2/O2/N2 flames with different equivalence ratios at atmospheric pressure isinvestigated experimentally and by numerical modeling. Concentration profiles of stable species (H2, O2, H2O) as well as of H atoms and OH radicals in the flames were measured using molecular beam mass-spectrometry with soft ionization by electron impact. A good agreement between the obtained experimental data and the results of numerical simulation using three different detailed kinetic mechanisms indicates the robustness of these models in predicting the structure of hydrogen-oxygen flames at atmospheric pressure

Structure of H2/O2/N2 flames at atmospheric pressure studied by molecular beam mass spectrometry and modeling

Structure of laminar premixed flat H2/O2/N2 flames with different equivalence ratios at atmospheric pressure isinvestigated experimentally and by numerical modeling. Concentration profiles of stable species (H2, O2, H2O) as well as of H atoms and OH radicals in the flames were measured using molecular beam mass-spectrometry with soft ionization by electron impact. A good agreement between the obtained experimental data and the results of numerical simulation using three different detailed kinetic mechanisms indicates the robustness of these models in predicting the structure of hydrogen-oxygen flames at atmospheric pressure

Kinetics and mechanism of chemical reactions in H2/O2/N2 flames at atmospheric pressure

The kinetics and mechanism of chemical reactions in the H2/O2/N2 flame were studied experimentally and by simulating the structure of premixed laminar flat atmospheric H2/O2/N2 flames of different initial compositions. The concentration profiles for stable compounds (H2, O2, and H2O), H atoms, and OH• radicals in flames were measured by molecular-beam sampling mass spectrometry using soft electron-impact ionization. The experimental data thus obtained are in good agreement with the results of simulations in terms of three familiar kinetic mechanisms, suggesting that these mechanisms are applicable to the description of the flame structure in hydrogen-oxygen mixtures at atmospheric pressure