Flame self-interaction during turbulent boundary layer flashback of hydrogen-rich premixed combustion
Flame self-interaction during turbulent boundary layer flashback of hydrogen-rich premixed combustion
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富氢预混燃烧湍流边界层回火过程中火焰自相互作用
DOI：
10.1103/physrevfluids.8.023202
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发表时间：
2023
影响因子：
2.7
通讯作者：
Ahmed U
中科院分区：
文献类型：
--
作者：
Ahmed U
为了研究火焰自相互作用（FSI）事件，对当量比为1.5的富氢预混火焰湍流边界层回火的三维直接数值模拟数据库进行了分析。槽道流的非反应湍流特性是基于摩擦速度的雷诺数的代表。氢-空气燃烧采用九组分二十反应的骨架化学机理。反应进程变量的三种定义，，基于的质量分数，和，已被认为是定义的进展变量。结果发现，FSI事件主要发生在靠近燃烧气体侧的所有定义在所有的壁正常距离。在基于和质量分数的定义中，没有发现壁面附近的FSI事件，而在基于近壁区的定义中，FSI事件发生。在离壁较远的区域，所有定义都表明隧道形成和隧道闭合型FSI事件仍然占主导地位，这与Griffithset等人的早期发现一致。[程序。燃烧。Inst.35，1341（2015）1540-748910.1016/j.proci.2014.08.003]，涉及剪切流条件下的氢气-空气预混火焰。在这项工作中，基于质量分数，未燃烧的气体口袋也已确定在所有壁的正常距离，是富氢的火焰性质的结果。的拓扑结构的变化与基于不同的物种和壁的正常距离的定义的变化的原因是几个因素的结果，包括在湍流边界层内的湍流水平的变化，在近壁区域的等温壁的热损失，和差分扩散引起的非统一刘易斯数。分析结果表明，湍流边界层和壁面热损失对流固耦合的拓扑结构有重要影响。不同定义之间FSI事件的定性性质和分布的差异对湍流边界层内富氢火焰基于火焰表面的建模方法的可能扩展具有重要影响。
A three-dimensional direct numerical simulation database of turbulent boundary layer flashback of a hydrogen-rich premixed flame with an equivalence ratio of 1.5 has been analyzed to investigate flame self-interaction (FSI) events. The nonreacting turbulence characteristics of the channel flow are representative of the friction-velocity-based Reynolds number,. A skeletal chemical mechanism with nine species and twenty reactions is employed for the representation of hydrogen-air combustion. Three definitions of the reaction progress variable,, based on the mass fractions of, and, have been considered to define the progress variable. It is found that the FSI events predominantly occur close to the burned gas side for all definitions ofat all the wall normal distances. No FSI events adjacent to the wall have been identified for thedefinition based onandmass fractions, whereas FSI events occur forbased onin the near-wall region. In the regions further away from the wall, alldefinitions show that tunnel formation and tunnel closure type FSI events remain predominant, which is consistent with the earlier findings by Griffithset al.[Proc. Combust. Inst. 35, 1341 (2015)1540-748910.1016/j.proci.2014.08.003] involving hydrogen-air premixed flame under shear flow conditions. In this work forbased onmass fraction, unburned gas pockets have also been identified at all wall normal distances and are a consequence of the hydrogen-rich nature of the flame. The reason for the variations in topologies with the change in the definition ofbased on different species and wall normal distance is a consequence of several factors, including the changes in the level of turbulence within the turbulent boundary layer, heat loss to the isothermal wall in the near-wall region, and the differential diffusion induced by the nonunity Lewis number. The results from the current analysis show that the turbulent boundary layer and heat loss at the wall play important roles in determining the FSI topologies. The differences in the qualitative nature and distributions of the FSI events between different definitions ofhave important implications on the possible extension of flame-surface-based modeling methodology for hydrogen-rich flames within turbulent boundary layers.
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