Effect of Oxygen Mass Fraction and Reynolds Number on Methane-Hydrogen Flame in MILD Regime using LES Method

Effects of the fuel inlet Reynolds number and the oxygen mass fraction in the oxidizer stream on the flame structure were studied. In this regard، the simulation was performed for two Reynolds numbers of 5000 and 10،000 and three oxygen mass fractions of 3، 6 and 9%. Numerical results were compared with experimental measurements of Dally. The turbulence-chemistry interaction in numerically unresolved scales was modeled using the PaSR model and the full mechanism GRI-2. 11 was used to precisely represent the methanehydrogen reactions. Accuracy of the LES simulation results was evaluated by a set of criteria indicating acceptable predictions. The results show that increasing the oxygen mass fraction in the oxidizer stream decreases the flame thickness، limits the species fluctuations to a smaller zone near the nozzle’s exit plane، decreases local extinctions in the flame structure and limits the partially premixed to a zone near the shear layer line and in summary improves the flame stability especially near the nozzle exit zone. Since decreasing the Reynolds number increases the residence time of fuel and oxidizer elements، it has a favorable effect on flame stability and decreasing its susceptibility to combustion instability.