While fuel combustion in oxygen-enriched environments provides a number of significant advantages, such as reduced nitrogen oxide emissions and high carbon dioxide purity for carbon sequestration, it is characterized by different physico-chemical oxidation behavior than combustion in air. Compared to nitrogen, carbon dioxide has different specific heat and effective Lewis number, and is chemically more active. Therefore, chemical mechanisms developed for the oxidation of fuel/air mixtures can fail to predict targets of interest for oxy-combustion accurately. In this study, a chemical mechanism of methane, which has been previously validated with data from experiments using air, is evaluated in terms of its prediction accuracy at oxy-conditions by comparing against available literature data. The validation takes various combustion properties into account, including ignition delay times, laminar burning velocities, and extinction strain rates, and covers a wide range of experimental conditions with respect to temperature, pressure, equivalence ratio, and carbon dioxide concentration. As additional targets, extinction strain rates of non-premixed oxy-methane flames are determined in a counterflow burner at conditions, where literature data have not yet been reported. The extensive validation demonstrates that the mechanism is able to describe oxy-methane combustion with reasonable prediction accuracy. For further insights into the underlying kinetics of diffusion flames of methane in oxy-atmosphere compared to its oxidation in air, reaction path and sensitivity analyses are performed using the validated mechanism. Notable differences between both combustion regimes are observed in the branching ratios of H-abstraction reactions by OH and H radicals and in the consumption channels of singlet methylene, which is a key species in the formation of polycyclic aromatic hydrocarbons.

中文翻译：

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氧气燃料燃烧的甲烷机制：消光实验、模型验证和动力学分析

虽然燃料在富氧环境中燃烧提供了许多显着优势，例如减少氮氧化物排放和用于碳封存的高二氧化碳纯度，但它的特点是物理化学氧化行为与在空气中燃烧不同。与氮相比，二氧化碳具有不同的比热和有效路易斯数，并且在化学上更活跃。因此，为氧化燃料/空气混合物开发的化学机制可能无法准确预测氧燃烧的目标。在这项研究中，通过与现有文献数据进行比较，评估了甲烷的化学机制，该机制之前已通过使用空气的实验数据进行了验证，并根据其在含氧条件下的预测准确性进行了评估。验证考虑了各种燃烧特性，包括点火延迟时间、层流燃烧速度和消光应变率，并涵盖了温度、压力、当量比和二氧化碳浓度等广泛的实验条件。作为额外的目标，非预混氧 - 甲烷火焰的消光应变率在逆流燃烧器中确定，在文献数据尚未报告的条件下。广泛的验证表明，该机制能够以合理的预测精度描述氧甲烷燃烧。为了进一步了解甲烷在氧气氛中的扩散火焰与其在空气中的氧化相比的潜在动力学，使用经过验证的机制进行反应路径和敏感性分析。