Shock-Induced Ignition of Methane, Ethane, and Methane/Ethane Mixtures Sensitized by NO2

Ignition delay times of stoichiometric CH4/NO2/O2/Ar, C2H6/NO2/O2/Ar, and CH4/C2H6/NO2/O2/Ar mixtures are measured with a shock tube to investigate the role of NO2 in ignition of methane, ethane, and natural gas (CH4/C2H6 = 9:1). All measurements are carried out at 1016–1981 K and 5–16 atm. Different NO2 concentrations (0, 25, 50, and 75% of fuel molar concentrations) are explored. The addition of NO2 promotes considerably the ignition of methane and natural gas but moderately for ethane. In addition, the promoting effect is temperature-dependent. Four assembled models are examined against the present measurements, and an updated kinetic model is proposed and validated in comparison to the experimental data. The current model is chosen for sensitivity and reaction pathway analyses, which reveal the role of NO2 in ignition of methane, ethane, and natural gas.本研究采用激波管（shock tube）对化学计量比CH₄/NO₂/O₂/Ar、C₂H₆/NO₂/O₂/Ar以及CH₄/C₂H₆/NO₂/O₂/Ar混合气体的着火延迟时间进行了测量，旨在探究NO₂在甲烷、乙烷以及摩尔比为9:1的CH₄/C₂H₆天然气混合气着火过程中的作用。所有测量实验均在1016~1981 K、5~16 atm的工况下开展。研究中设置了不同的NO₂添加浓度，分别为燃料摩尔浓度的0、25%、50%与75%。NO₂的添加可显著促进甲烷与该天然气混合气的着火过程，但对乙烷的促进效果相对温和。此外，该促进效应具有温度依赖性。本研究将4套已组装的动力学模型与本次实验测量数据进行了比对校验，并提出了一套更新后的动力学模型，通过与实验数据的对比完成了模型验证。选取本次提出的更新动力学模型开展敏感性分析与反应路径分析，揭示了NO₂在甲烷、乙烷及该天然气混合气着火过程中的作用机制。