Flame macrostructures and thermoacoustic instabilities in stratified swirling flames
Flame macrostructures and thermoacoustic instabilities in stratified swirling flames
复制标题
分层旋流火焰中的火焰宏观结构和热声不稳定性
DOI：
10.1016/j.proci.2018.06.147
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发表时间：
2019-01-01
影响因子：
3.4
通讯作者：
Lin, Y. Z.
中科院分区：
文献类型：
--
作者：
Han, X.;Laera, D.;Lin, Y. Z.
本文研究了分层旋流火焰中火焰宏观结构与热声燃烧不稳定性之间的关系。在实验室纵向燃烧试验台上，采用北航轴向旋流独立分层（BASIS）燃烧器进行了实验研究。BASIS燃烧器是在工业贫油预混预蒸发（LPP）燃烧器基础上发展起来的一种新型双旋流燃烧系统。首先，研究和讨论了不同总当量比（phi（总））和分层比（SR）的火焰宏观结构。根据操作条件，三种不同的火焰类型在燃烧器中稳定：两种附着火焰，包括分层火焰和V形火焰（V形火焰），以及提升火焰。热声不稳定性进行了研究。振荡的幅度被发现是更敏感的SR比phi（总）。大幅度的极限环被发现为低和高值的SR，其中V型火焰和提升火焰中观察到的燃烧室，分别。火焰动力学也使用当地的瑞利指数图进行了研究。研究发现，无论是提升火焰还是V型火焰，其主要驱动力都来自于火焰与壁面的碰撞区域。沿着V形火焰的火焰刷，沿着发现了与火焰褶皱相关的相干结构。相反，分层火焰被发现是更热声稳定。最后，不可压缩的大涡模拟是用来获得在300赫兹，这是非常接近的频率，在极限环振荡发生强迫火焰响应。结果表明，分层火焰的热释放速率响应相对于其他两种火焰的热释放速率响应有明显的相位偏移，这是热声稳定的主要原因。(C)2018燃烧研究所爱思唯尔公司出版All rights reserved.
The present article investigates the correlation between flame macrostructures and thermoacoustic combustion instabilities in stratified swirling flames. Experiments are carried out in a laboratory scale longitudinal test rig equipped with the Beihang Axial Swirler Independently-Stratified (BASIS) burner, a novel double-swirled combustion system developed by adapting an industrial lean premixed prevaporized (LPP) combustor. At first, the flame macrostructures are investigated and discussed for various total equivalence ratios (phi(total)) and stratification ratios (SRs). Depending on operating conditions, three different flame types are stabilized in the combustor: two attached flames comprising a stratified flame and a V-shaped flame (V-flame), as well as a lifted flame. Thermoacoustic instabilities are then investigated. The amplitude of the oscillations is found to be more sensitive to SR than the phi(total). Large amplitude limit cycles are found for low and high values of SR, for which the V-flame and the lifted flame are observed in the combustor, respectively. The flame dynamics are also investigated using local Rayleigh index maps. It is found that for both the lifted flame and V-flame, the major driving force comes from the flame-to-wall impingement region. Coherent structures associated with flame wrinkling are found along the flame brushes of the V-flame. On the contrary, the stratified flame is found to be more thermo-acoustically stable. Finally, incompressible Large Eddy Simulations is used to obtain the flame responses to forcing at 300 Hz, which is very close to the frequencies at which limit cycle oscillations occur. The results show that the global heat release rate response of the stratified flame exhibits a significant phase shift compared to the responses of the other two flame types, and this is the most likely cause of thermoacoustic stabilization. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.