Lower and upper flammability limits (LFL and UFL) are widely and effectively used as simple safety boundaries for preventing gas-mixture ignition, and predicting them for new compounds would be valuable, especially the LFLs for low-flammability non-C/H/O species. Prediction with mechanistic flame models uses the idea that as these limits are reached, the flame speed and temperature drop below a threshold of flame feasibility because of radiant heat loss. Using methane as a reference study because its mechanisms and flammability are well characterized, non-adiabatic laminar flame speeds and profiles of temperature, flame structure, and chemiluminescent OH* and CH* are calculated using a modification of the hydrocarbon kinetics model of Hashemi et al. (2016), executed in CHEMKIN and Cantera. LFL prediction is emphasized here; large-hydrocarbon and soot radiant losses have been proven to be necessary for accurate UFL values (Bertolino et al., 2019) but were not included in this work. Property dependences on concentration are compared to published flammability limits of 5–15% methane concentration for methane/air mixtures at $T_0=$ 298 K and 1, 5, and 10 atm. At 1 atm, the LFL occurs at a laminar flame speed of 2.7 cm/s, and at the UFL, flame speeds between 4.5 and 6 cm/s correspond to the limit. Similarly, adiabatic temperature of 1450 K in a fuel-lean environment and 1560–1670 K in a fuel-rich environment correlate with the flammability limits. The ASTM standard test for flammability uses visual detection of a flame; ultraviolet chemiluminescence of OH* radical at limits of less than mole fraction of 10⁻³ is shown to reflect the methane LFL, and the equivalence-ratio dependence of OH* should resemble that of the visible C₂* emission. Effects of pressure and challenges for modeling are discussed.

易燃性上限和下限（LFL和UFL）被广泛有效地用作防止混合气着火的简单安全界限，并且预测它们对新化合物的作用将是有价值的，尤其是对于低易燃性非C / H / O的LFL种类。机械火焰模型的预测使用这样的思想，即达到这些限制时，由于辐射热损失，火焰速度和温度下降到火焰可行性阈值以下。由于甲烷的机理和可燃性已得到很好的表征，因此将其用作参考研究，使用对Hashemi等人的碳氢化合物动力学模型的修改，可以计算出非绝热层流的火焰速度和温度，火焰结构以及化学发光的OH *和CH *的分布。 。（2016），在CHEMKIN和Cantera执行。此处强调LFL预测；大量的碳氢化合物和烟尘的辐射损失已被证明对于准确的UFL值是必不可少的（Bertolino等，2019），但未包括在这项工作中。将特性对浓度的依赖性与已发布的甲烷/空气混合物中甲烷浓度为5-15％的可燃性限值进行比较${Ť}_0=$298 K和1、5和10 atm。在1个大气压下，LFL以2.7 cm / s的层流火焰速度发生，而在UFL，4.5至6 cm / s的火焰速度对应于极限。同样，在稀燃环境中的绝热温度为1450 K，在富含燃料的环境中的绝热温度为1560–1670 K，这与可燃性限值相关。ASTM可燃性标准测试使用火焰的视觉检测；在小于10 ^-3的摩尔分数的极限下，OH *自由基的紫外化学发光显示出可反映甲烷LFL，并且OH *的当量比依存关系应类似于可见的C ₂ *发射。讨论了压力的影响和建模挑战。