Broken C-shaped extinction curve and near-limit flame behaviors of low Lewis number counterflow flames under microgravity
Broken C-shaped extinction curve and near-limit flame behaviors of low Lewis number counterflow flames under microgravity
复制标题
DOI：
10.1016/j.combustflame.2018.05.014
复制
发表时间：
2018-08
影响因子：
4.4
通讯作者：
T. Okuno;Takaki Akiba;H. Nakamura;R. Fursenko;S. Minaev;T. Tezuka;S. Hasegawa;M. Kikuchi;K. Maruta;K. Maruta
中科院分区：
文献类型：
--
作者：
T. Okuno;Takaki Akiba;H. Nakamura;R. Fursenko;S. Minaev;T. Tezuka;S. Hasegawa;M. Kikuchi;K. Maruta;K. Maruta
为了研究路易斯数对消光边界、火焰状态和零星火焰形成的影响，对 CH4/O2/Kr (Le≈0.7–0.8) 和 CH4/O2/Xe (Le≈0.5) 混合物的逆流火焰进行微重力实验，以及三种类型的计算，这是使用详细化学的基于 PREMIX 的代码的一维计算，以及三和 使用整体一步反应的热扩散模型进行一维计算。在微重力实验中，识别了平面火焰、具有传播边缘的平面火焰、具有后退边缘的平面火焰、星形火焰、蜂窝状火焰和零星火焰，并获得了它们在当量比-拉伸率平面中的存在区域。在实验中，Xe 混合物会形成零星火焰，但 Kr 混合物不会形成零星火焰。类似地，在热扩散模型的三维计算中，Le=0.50 时会形成零星火焰，而Le=0.75 时不会形成零星火焰。此外，零星火焰的火焰状态远远超出了实验和三维计算中一维计算中获得的消光边界。此外，在三维计算中对零星火焰和火焰球的比较表明，零星火焰是从火焰球到传播火焰的中间燃烧模式。
To examine the effect of Lewis number on the extinction boundary, flame regimes, and the formation of sporadic flames, microgravity experiments on counterflow flames for CH4/O2/Kr (Le≈ 0.7–0.8) and CH4/O2/Xe (Le≈ 0.5) mixtures, and three types of computations, which are one-dimensional computations with a PREMIX-based code using detailed chemistry, and three- and one-dimensional computations with the thermal-diffusion model using an overall one-step reaction were conducted. In the microgravity experiments, planar flames, planar flames with propagating edges, planar flames with receding edges, star-shaped flames, cellular flames, and sporadic flames were identified, and their regions of existence in the equivalence ratio-stretch rate plane were obtained. Sporadic flames were formed for Xe mixtures but not for Kr mixtures in the experiments. Similarly, sporadic flames were formed atLe= 0.50 but not atLe= 0.75 in the three-dimensional computations with the thermal-diffusion model. Also, the flame regime of sporadic flames extended far beyond the extinction boundaries obtained in the one-dimensional computations in both experiments and the three-dimensional computations. Furthermore, a comparison of the sporadic flames and flame balls in the three-dimensional computations showed that sporadic flames are intermediate combustion modes that segue flame balls to propagating flames.