The reburning chemistry in oxy-fuel and oxy-steam combustion of methane was investigated both experimentally and numerically. Comparison experiments in O₂/N₂, O₂/CO₂, and O₂/H₂O atmospheres were performed in a flow reactor at atmospheric pressure with equivalence ratio ranging from fuel-rich to fuel-lean and temperature from 973 to 1773 K. Experimental results showed that compared with N₂ and CO₂ atmospheres NO reduction observed in H₂O atmosphere is the lowest under fuel-rich and stoichiometric conditions, while it is the highest under fuel-lean conditions. The NO reduction intensity in CO₂ atmosphere lies between N₂ and H₂O atmosphere under fuel-rich and fuel-lean conditions; however, it is the highest under stoichiometric conditions. A chemical kinetic mechanism, which was hierarchically structured and updated in our previous work, captured the main characteristics and quantity of CO and NO formation satisfactorily even under fuel-lean conditions. According to the analysis from a chemical kinetic point of view, CO₂ and H₂O exert significant impacts on altering the radical pool structure to OH dominant, subsequently varying the availability of hydrocarbon radical as a reducing agent, which is the primary reason for the different degrees of NO reduction under fuel-rich, stoichiometric, and fuel-lean conditions. In addition, CO₂ and H₂O also impact the NO reduction by nitrogen-containing radicals. For CO₂ atmosphere, NCO radical always occupies an overwhelmingly dominant position in NO reduction due to HCN → CH₃CN → CH₂CN → CN → NCO, and HNCO → NCO channel is amplified substantially. For H₂O atmosphere, under fuel-rich and stoichiometric conditions, NH₂ and NH radical are dominant due to the enhancement of NCO → HNCO → NH₂ → NH channel. Under fuel-lean conditions, NCO radical is dominant due to the strength of HNCO → NCO channel.

中文翻译：

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O ₂ / N ₂，O ₂ / CO ₂和O ₂ / H ₂ O大气中重燃化学的比较

对甲烷的氧-燃料和氧-蒸汽燃烧中的再燃烧化学进行了实验和数值研究。在大气压下在流动反应器中于O ₂ / N ₂，O ₂ / CO ₂和O ₂ / H ₂ O气氛中进行对比实验，当量比从富燃料到贫燃料，温度范围为973-1773 K.实验结果表明，与N ₂和CO ₂气氛相比，在H ₂ O气氛中观察到的NO减少在富燃料和化学计量条件下最低，而在贫燃料条件下最高。CO _2中的NO还原强度在富燃料和稀燃料条件下，大气层位于N ₂和H ₂ O气氛之间；然而，在化学计量条件下它是最高的。一个化学动力学机制，在我们以前的工作中进行了层次结构化和更新，即使在稀燃条件下也能令人满意地捕获到CO和NO生成的主要特征和数量。从化学动力学的角度分析，CO ₂和H ₂O对将自由基库结构改变为OH占主导地位产生重大影响，随后改变了烃自由基作为还原剂的可用性，这是在富油，化学计量和贫油条件下NO还原程度不同的主要原因。此外，CO ₂和H ₂ O还影响含氮自由基对NO的还原。对于CO ₂气氛，由于HCN→CH ₃ CN→CH ₂ CN→CN→NCO ，NCO自由基总是在NO还原中占据压倒性的主导地位，并且HNCO→NCO通道被大幅放大。对于H ₂ O气氛，在富燃料和化学计量条件下，NH ₂由于NCO→HNCO→NH ₂ →NH通道的增强，NH和NH自由基占主导地位。在稀燃条件下，由于HNCO→NCO通道的强度，NCO自由基占主导地位。