Experimental and kinetic modeling study on propane enhancing the laminar flame speeds of ammonia

The laminar flame speeds of ammonia/propane in air were investigated in a constant volume combustion bomb at 1–5 atm, over 298–453 K, at the equivalence ratios of 0.7–1.6, with the propane in fuel varying from 0 to 90 vol%. The measured data were provided for the validity of the proposed M-NUIG model. The comparison showed that M-NUIG model could successfully predict the measured data of propane, ammonia and mixtures under wide conditions. The results showed that the addition of 20% propane can enhance the LBV of ammonia by a factor of 3 at 1 atm, 298 K. Based on kinetic analysis, NH₂ is mainly consumed by the oxidation of N-contained species in NH₃/air flame, and it is completely consumed through reacting with O, OH, H and HO₂ in NH₃/C₃H₈/air flame. As for the NH₃/C₃H₈ interactions, NH can react with CH₃, forming CH₂NH which completely converts to HCN. HNO also reacts with CH₃ to generate NO. Thus, the C–N interactions are crucial to the formation of harmful emissions. Moreover, with 50% propane addition, the peak concentrations of OH and H radicals are much higher than in NH₃/air flame which is the main reason for the higher LBV.