Abstract Measurements of flame propagation velocities and extinction states in counterflow provide a valuable source of flame data that contain information about fundamental combustion physics. The approach to properly account for stretch effects in counterflow flame measurements through non-intrusive laser-based local velocity characterization was advanced in the mid-80s by Law and coworkers at atmospheric conditions with simple fuels. Subsequently, several research groups have extended the measurements to elevated pressures and complex fuels. However, counterflow flame data at subatmospheric pressures are limited. In the present study, a method is introduced for measuring laminar flame speeds and extinction strain rates in subatmospheric counterflow flames. A numerical study was performed to assess the dynamics of tracer particles used to facilitate measurements. It was found that the particle phase dynamics used in particle velocimetry measurements are not always representative of the underlying gas phase motion due to thermophoresis and insufficient drag, especially at low pressures. A numerical scheme was implemented whereby the computed particle phases were used for proper comparison with measurements and, based on the computed results, to infer the corresponding values of the gas phase. The method was applied to premixed methane/air and non-premixed methane–nitrogen/oxygen flames at pressures as low as 0.1 atm. Complimentary flame structure simulations were carried out which show that the kinetics of formyl radical prompt dissociation strongly impact the computed subatmospheric flames and may influence the validation of unimolecular and bimolecular reactions rate constants when tested against laminar flame data.

中文翻译：

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亚大气压逆流甲烷火焰的传播与熄灭

摘要 逆流中火焰传播速度和熄灭状态的测量提供了宝贵的火焰数据来源，其中包含有关基本燃烧物理的信息。在 80 年代中期，Law 及其同事在大气条件下使用简单燃料提出了通过基于非侵入式激光的局部速度表征来正确解释逆流火焰测量中拉伸效应的方法。随后，几个研究小组将测量范围扩展到高压和复杂燃料。然而，负压下的逆流火焰数据是有限的。在本研究中，介绍了一种用于测量亚大气压逆流火焰中层流火焰速度和消光应变率的方法。进行了一项数值研究，以评估用于促进测量的示踪粒子的动力学。发现由于热泳和阻力不足，尤其是在低压下，粒子测速测量中使用的粒子相动力学并不总是代表潜在的气相运动。实施了一种数值方案，其中计算出的粒子相用于与测量值进行适当比较，并根据计算结果推断气相的相应值。该方法适用于压力低至 0.1 atm 的预混甲烷/空气和非预混甲烷-氮/氧火焰。