Abstract A high-pressure shock tube was used to study ignition delay times (IDT) of CH4/O2/Ar and natural gas/O2/Ar mixtures behind reflected shock waves. Reaction progress was monitored using sidewall pressure and direct laser absorption diagnostics of CH4 near 3.175 µm and ethylene near 10.532 µm. Stoichiometric, fuel-rich and fuel-lean mixtures of CH4/O2, highly dilute in argon, were studied over a temperature range from 1450 to 1850 K and pressures between 10 and 55 atm. Of note are the experiments conducted with fuel-rich mixtures, as there is a lack of literature data in this regime. In the current study, the methane absorption diagnostic provided a unique tool enabling both speciation of methane and a clear definition of ignition delay time. In addition to methane oxidation, we have measured ignition delay times of commercial natural gas blends over a temperature range of 1408–1541 K, at pressures near 12 atm, and at an equivalence ratio of 1. To understand the effects of minor constituents (such as ethane and propane) in commercial natural gas blends, ethylene concentration during pyrolysis experiments was monitored using a two-wavelength scheme (10.532 µm and 10.674 µm) using a CO2 gas laser. The deficiency of existing kinetic models towards predicting the high-temperature kinetics of natural gas blends was highlighted through our measurements. Therefore, this study also provides data critical for refining these models. Extensive sensitivity analysis emphasizes the importance of the reaction CH3+C2H6→CH4+C2H5 during natural gas pyrolysis, and the accuracy of the chemical kinetic models is significantly improved by using a revised reaction rate constant (Shao et al. 2019) for this reaction. These measurements extend the test conditions of earlier studies of methane and commercial natural gas.

中文翻译：

---

高压甲烷和天然气混合物的冲击点火和热解

摘要 利用高压激波管研究了CH4/O2/Ar和天然气/O2/Ar混合物在反射激波后的点火延迟时间(IDT)。使用侧壁压力和 3.175 µm 附近 CH4 和 10.532 µm 附近的乙烯的直接激光吸收诊断监测反应进程。在 1450 至 1850 K 的温度范围和 10 至 55 个大气压之间的压力下，研究了在氩气中高度稀释的化学计量、富燃料和贫燃料的 CH4/O2 混合物。值得注意的是用富含燃料的混合物进行的实验，因为在这种情况下缺乏文献数据。在当前的研究中，甲烷吸收诊断提供了一种独特的工具，可以实现甲烷的形态形成和点火延迟时间的明确定义。除了甲烷氧化，我们测量了商业天然气混合物在 1408-1541 K 温度范围内、压力接近 12 个大气压、当量比为 1 时的点火延迟时间。在商业天然气混合物中，使用 CO2 气体激光器，使用双波长方案（10.532 µm 和 10.674 µm）监测热解实验过程中的乙烯浓度。通过我们的测量，突出了现有动力学模型在预测天然气混合物高温动力学方面的不足。因此，本研究还提供了对完善这些模型至关重要的数据。广泛的敏感性分析强调了天然气热解过程中 CH3+C2H6→CH4+C2H5 反应的重要性，通过对该反应使用修正的反应速率常数 (Shao et al. 2019)，化学动力学模型的准确性得到显着提高。这些测量扩展了早期甲烷和商业天然气研究的测试条件。