Reaction mechanism development of the methane-acetylene rich-combustion for the hydrogen production efficiency enhancement based on molecular dynamics simulation

In this work, the reaction mechanisms under different equivalence ratios and acetylene blending ratios through chemical kinetics were investigated. The validity of the chemical reaction force field was verified using density functional theory calculations. The combustion process was divided as ignition delay, rapid combustion and post-combustion. Effects of equivalence ratio and blending ratio on hydrogen production efficiency were examined and underlying reaction pathways were analyzed to explain the observed phenomena. Additionally, the combined effects of high equivalence ratios and high blending ratios on hydrogen production efficiency were studied, highlighting their similarities and differences and the results were compared with macro-scale reactor simulations. The results show that increasing the blending ratio can enhance the hydrogen production efficiency from 17.5 % to 41.1 %, while increasing the equivalence efficiency can raise it from 17.5 % to 27.5 %. Both methods effectively increase the fuel-to-oxygen ratio (actual equivalence ratio) in the mixture, and the hydrogen production efficiency exhibits a positive correlation with the actual equivalence ratio. However, an excessively high equivalence ratio may lead to flame blow-off. In contrast, the addition of acetylene enables stable combustion at high actual equivalence ratio conditions. By analyzing hydrogen generation rates at different reaction temperatures, the first-order reaction activation energy for hydrogen production under various blending and equivalence ratios was calculated, which shows that acetylene blending can reduce the activation energy of hydrogen generation to 221.40 kJ/mol.