Abstract This study was conducted with methane as fuel and CO2 as diluent gas. The equivalent effect of initial temperatures (323–423 K) and pressures (0.1–0.3 MPa) coupling on methane-air premixed combustion flame propagation speed (i.e. increasing or decreasing initial temperature and pressure simultaneously to have same flame propagation speeds when equivalence ratio and fraction of CO2 are unchanged) was investigated under a series of fractions of CO2 (0%–16%) and equivalence ratios (0.9, 1.0, and 1.1). Laminar burning velocities of different test conditions with similar flame propagation speeds were investigated and flame instability was also analyzed. The results show that similar flame speeds can be obtained when elevating initial temperature and pressure synchronously under constant equivalence ratio and the fraction of CO2. Similar flame propagation speeds can lead to close laminar burning velocities and similar flame structures. Flame speed under higher initial temperature and pressure is more sensitive to temperature and pressure, but dilution can suppress this sensitivity. Flame instability is stronger under higher initial temperature and pressure. Hydrodynamic instability dominates and it is mainly influenced by flame thickness. Differences are also shown in pressure and temperature during non-laminar stage. Dilution can enhance the difference in combustion duration.

中文翻译：

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初始温压耦合对甲烷稀释预混燃烧火焰速度的等效影响

摘要 本研究以甲烷为燃料，CO2 为稀释气体。初始温度（323-423 K）和压力（0.1-0.3 MPa）耦合对甲烷-空气预混燃烧火焰传播速度的等效影响（即当当量比和CO2 的分数不变）在一系列 CO2 分数（0%–16%）和当量比（0.9、1.0 和 1.1）下进行了研究。研究了具有相似火焰传播速度的不同测试条件下的层流燃烧速度，并分析了火焰的不稳定性。结果表明，在恒定当量比和CO2比例下，同步升高初始温度和压力可以获得相似的火焰速度。相似的火焰传播速度可导致接近的层流燃烧速度和相似的火焰结构。较高的初始温度和压力下的火焰速度对温度和压力更敏感，但稀释可以抑制这种敏感性。在较高的初始温度和压力下，火焰不稳定性更强。流体动力不稳定性占主导地位，主要受火焰厚度的影响。在非层流阶段，压力和温度也存在差异。稀释可以增强燃烧持续时间的差异。在较高的初始温度和压力下，火焰不稳定性更强。流体动力不稳定性占主导地位，主要受火焰厚度的影响。在非层流阶段，压力和温度也存在差异。稀释可以增强燃烧持续时间的差异。在较高的初始温度和压力下，火焰不稳定性更强。流体动力不稳定性占主导地位，主要受火焰厚度的影响。在非层流阶段，压力和温度也存在差异。稀释可以增强燃烧持续时间的差异。