Evaluation of chemical effects of added CO2 according flame location

A numerical study has been conducted to clearly grasp the impact of chemical effects caused by added CO 2 and of flame location on flame structure and NO emission behaviour. Flame location affects the major source reaction of CO formation. CO 2 + H → CO + OH and the H-removal reaction, CH 4 + H → CH 3 + H 2 . It is, as a result, seen that the reduction of maximum flame temperature due to chemical effects for fuel-side dilution is mainly caused by the competition of the principal chain branching reaction with the reaction, CH 4 + H → CH 3 + H 2 . while that for fuel-side dilution is attributed to the competition of the principal chain branching reaction with the reaction, CO 2 + H → CO + OH. The importance of the NNH mechanism for NO production, where the reaction pathway is NNH -> NH → HNO, is recognized. In C-related reactions most of NO is the direct outcome of (R171) and the contribution of (R171) becomes more and more important with increasing amount of added CO 2 as much as the reaction step (R171) competes with the key reaction of thermal mechanism, (R237), for N atom. This indicates a possibility that NO emission in hydrogen flames diluted with CO 2 shows less dependent behaviour upon flame temperature.