The influence of the main process parameters on the oscillatory behavior of methane oxidation was analyzed in conditions relevant for low-temperature combustion processes. The investigation was performed by means of direct comparisons between experimental measurements realized in two jet-stirred flow reactors used at atmospheric pressure. With the operating conditions of the two systems coupled, wide ranges of the inlet temperature (790–1225 K), equivalence ratio (0.5 < Φ < 1.5), methane mole fraction (X_CH4 from 0.01 to 0.05), bath gases (i.e., He, N₂, CO₂, or H₂O) and different overall mixture dilution levels were exploited in relation to the identification of oscillatory regimes. Although the reference systems mainly differ in thermal conditions (i.e., heat exchange to the surroundings), temperature measurements suggested that the oscillatory phenomena occurred when the system working temperature accessed a well-identifiable temperature range. Experimental results were simulated by means of a detailed kinetic scheme and commercial codes developed for complex chemistry processes. Simulations were also extended considering systems with different heat losses to the surroundings, thus passing from adiabatic to isothermal systems. Results highlighted the kinetic nature of the dynamic behavior. Because predictions were consistent with experimental tests, further numerical analyses were realized to identify the kinetics responsible for the establishment of oscillatory phenomena. Temperature oscillations were predicted for a significant reactor working temperature range, where oxidation and recombination kinetic routes, involving carbon C_1–2 species as well as reactions of the H₂/O₂ sub-scheme, become competitive, thus boosting limit cycle behaviors. Oscillatory phenomena cease when the system working temperatures exceed characteristic threshold values with the promotion of faster oxidation routes that diminish the inhibiting effects of recombination reactions.

中文翻译：

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甲烷燃烧中的振荡行为：运行参数的影响

在与低温燃烧过程有关的条件下，分析了主要工艺参数对甲烷氧化振荡行为的影响。该研究是通过直接比较在两个常压下使用的两个射流搅拌流动反应器中实现的实验测量结果进行的。结合两个系统的运行条件，宽范围的入口温度（790–1225 K），当量比（0.5 <Φ<1.5），甲烷摩尔分数（X _{CH 4}从0.01到0.05），浴液（即，He，N ₂，CO ₂或H ₂O）和不同的整体混合物稀释水平被用来确定振荡状态。尽管参考系统的主要热条件（即与周围环境的热交换）主要不同，但温度测量结果表明，当系统工作温度进入可明确识别的温度范围时，就会发生振荡现象。通过详细的动力学方案和针对复杂化学过程开发的商业法规模拟了实验结果。考虑到具有不同热量损失的系统，模拟也得到了扩展，从而从绝热系统转变为等温系统。结果突出了动力学行为的动力学性质。由于预测与实验测试一致，进行了进一步的数值分析，以确定引起振荡现象建立的动力学。预测了一个重要的反应器工作温度范围内的温度振荡，在该温度范围内，氧化和重组动力学路线涉及碳C_1–2种以及H ₂ / O ₂子方案的反应变得具有竞争性，从而增强了极限循环行为。当系统工作温度超过特征阈值时，随着促进更快的氧化途径而减弱了重组反应的抑制作用，振荡现象就停止了。