As a clean gaseous fuel, methane (the main constituent of natural gas) has been widely used in the lives of residents and industrial processes. The oxy-fuel combustion technology for methane/carbon dioxide is an effective way to reduce the pollutant emissions of NO_x, which is also beneficial to the capture of carbon dioxide. Herein, the stretch extinction characteristics of non-premixed flames induced by methane/carbon dioxide mixtures versus oxygen/carbon dioxide mixtures counterflow combustion with various fuel concentrations were studied in high-pressure environments. The computed flame extinction strain rates of oxygen-enriched and air combustions in low fuel concentration range at pressures of 0.1, 0.5 and 0.7 MPa have a good consistency with the experiment results obtained from previous literature. The results show that the increase of flame extinction limit represented by the stretch rate for the oxygen-enriched combustion with increasing pressure is more significant than that for the air combustion. The analyses of reaction pathways, integral of reaction rates and sensitivity coefficients suggest that the OH formation rates of near extinction flames limits can be used to estimate the ratio of the flame extinction strain rate for oxygen-enriched combustion to that for air combustion under high pressures. The reasons for the enhancement of the OH formation rate aroused by increasing pressures were clarified.

作为一种清洁的气体燃料，甲烷（天然气的主要成分）已广泛用于居民生活和工业生产过程中。甲烷/二氧​​化碳的含氧燃料燃烧技术是减少NO _x污染物排放的有效方法，这也有利于二氧化碳的捕集。在此，研究了在高压环境下甲烷/二氧​​化碳混合物与氧气/二氧化碳混合物逆流燃烧在不同燃料浓度下引起的非预混火焰的拉伸消光特性。在0.1、0.5和0.7 MPa的压力下，低燃料浓度范围内的富氧燃烧和空气燃烧的火焰熄灭应变速率与先前文献的实验结果具有良好的一致性。结果表明，随着压力的升高，富氧燃烧的拉伸速率所代表的熄火极限的增加比空气燃烧的增加更大。反应途径的分析，反应速率和敏感系数的积分表明，接近熄灭火焰极限的OH生成速率可用于估算高压下富氧燃烧与空气燃烧的火焰熄灭应变率之比。阐明了因压力增加而引起的OH生成速率提高的原因。