Effects of hydrogen enrichment on adiabatic burning velocity and NO formation in methane + air flames

Experimental measurements of the adiabatic burning velocity and NO formation in methane + hydrogen + air flames are presented. The hydrogen content in the fuel was varied from 0% to 35%. 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 ±0.8 cm/s in the whole range of enrichment by hydrogen. A procedure for estimation of errors in equivalence ratio was extended to binary fuel mixtures. The relative accuracy of the equivalence ratio was found to be below 1.47%. Adiabatic burning velocities of methane + hydrogen + air mixtures were found in satisfactory agreement with the literature results and with the Konnov model predictions. A new correlation for the adiabatic laminar burning velocity of methane + hydrogen + air mixtures burning at standard conditions was derived. The NO concentrations as a function of equivalence ratio were measured using probe sampling at a fixed distance from the burner. In lean flames enrichment by hydrogen has little effect on [NO], while in rich flames the concentration of nitric oxide decreases significantly. The numerical predictions are in good agreement with the experiment.

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