Comparison of O2-enriched and N2O oxidizers on dual-flame structure and entropy generation

This study utilizes a triple concentric burner to generate a dual-flame structure and investigates the impact of dual flames on entropy generation under varying fuel-oxidizer velocity ratio (R), ultimately identifying the dominant pathways. The study also examined the substitution of nitrous oxide (N₂O) with a nitrogen-oxygen (N₂−O₂) mixture to understand the influence of N₂O decomposition on entropy generation. The research evaluated the irreversibility of chemical reactions in the presence of a dual-flame structure. It was observed that the chemical reaction term in the N₂O case (R = 3) was approximately twice as intense as in the O₂-enriched case (R = 5) due to the more vigorous reaction of N₂O, despite similar energy input. Reactions involving N₂O, such as those related to the cyanato radical (NCO) and isocyanic acid (HNCO), were slightly more pronounced in the N₂O case compared to the O₂-enriched case, even though the R ratio was lower in the N₂O case. In conclusion, increased entropy generation reduces exergy and decreases second-law efficiency (ηII) from 88.5 % to 78.8 % in O₂-enriched cases and from 74.3 % to 66.3 % in N₂O cases as R increases. This decrease is more pronounced in dual-flame structures, where η_II drops below 80 %, primarily due to heat conduction and chemical reactions.