The effect of hydrogen addition on methane-air flame in a stratified swirl burner

This numerical study has focused on assessing the influence of adding 20% and 40% hydrogen (on the volume of fuel basis) in different slots of a turbulent methane-air flame. The injection configurations are as follows: in the (i) inner slot, (ii) outer slot, (iii) and both slots. RANS numerical results has been obtained using OpenFOAM code. The impact of enrichment configuration and level on various flow fields have been investigated in the stratified and premixed cases. The results showed that adding hydrogen in the outer slot does not change the flow characteristics significantly, and adding H-2 in both slots showed a slight difference compared to adding hydrogen in the inner slot. Hydrogen addition in the inner slot and both slots increased the combustion intensity near the burner exit and resulted in a robust flame attachment which is mainly the result of the enhancement of reaction rates of OH + H-2 = H + H2O and OH + CH4 = CH3 + H2O in the premixed case. In the stratified case, in addition to the pathways mentioned above, the reaction rate of H + O-2 = O + OH also enhanced, which resulted in better flame attachment. Regarding pollutant emissions, H-2 addition, decreased CO and increased NOx emission in all configurations of the premixed and stratified cases.