Temporally resolved planar measurements of transient phenomena in a partially pre-mixed swirl flame in a gas turbine model combustor
Temporally resolved planar measurements of transient phenomena in a partially pre-mixed swirl flame in a gas turbine model combustor
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DOI：
10.1016/j.combustflame.2009.12.015
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发表时间：
2010-08
影响因子：
4.4
通讯作者：
I. Boxx;M. Stöhr;C. Carter;W. Meier
中科院分区：
文献类型：
--
作者：
I. Boxx;M. Stöhr;C. Carter;W. Meier
本文介绍了对10kW部分预混合、旋涡稳定的甲烷-空气火焰表现出自激热声振荡的时间依赖性行为的观察和分析。该分析基于一系列测量，其中粒子图像速度测定（PIV）和OH自由基的平面激光诱导荧光（PLIF）以5kHz重复率同时进行，持续时间为0.8s。OH*自由基的化学发光成像是单独进行的，也是在5kHz下，0.8s采集运行。这些测量具有足够的采样频率和持续时间，可以提取有关中到大尺度流场和火焰热释放特性的可用时空频率信息。该分析用于更充分地表征自激热声振荡与该火焰的主要流场结构之间的相互作用，该火焰是存在于内部再循环区域的涡核（PVC）。对单个测量序列的解释产生了对各种物理现象和驱动火焰动力学的潜在机制的见解。观察到该火焰反应区的位置跟踪轴向速度的大尺度波动，也符合大尺度涡旋结构在流场中的通道。在主压应变持续高的区域，反应区局部消失。然而，这种灭绝被认为是自我修复的，因此不会导致井喷。在出口附近未燃烧气体区域也观察到自燃迹象。可能的自燃事件经常与大型旋涡结构的中心重合，这表明这种现象与PVC核心流体在火焰中移动时增强的混合和更长的停留时间有关。
This paper presents observations and analysis of the time-dependent behavior of a 10kW partially pre-mixed, swirl-stabilized methane–air flame exhibiting self-excited thermo-acoustic oscillations. This analysis is based on a series of measurements wherein particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) of the OH radical were performed simultaneously at 5kHz repetition rate over durations of 0.8s. Chemiluminescence imaging of the OH*radical was performed separately, also at 5kHz over 0.8s acquisition runs. These measurements were of sufficient sampling frequency and duration to extract usable spatial and temporal frequency information on the medium to large-scale flow-field and heat-release characteristics of the flame. This analysis is used to more fully characterize the interaction between the self-excited thermo-acoustic oscillations and the dominant flow-field structure of this flame, a precessing vortex core (PVC) present in the inner recirculation zone. Interpretation of individual measurement sequences yielded insight into various physical phenomena and the underlying mechanisms driving flame dynamics. It is observed for this flame that location of the reaction zone tracks large-scale fluctuations in axial velocity and also conforms to the passage of large-scale vortical structures through the flow-field. Local extinction of the reaction zone in regions of persistently high principal compressive strain is observed. Such extinctions, however, are seen to be self healing and thus do not induce blowout. Indications of auto-ignition in regions of unburned gas near the exit are also observed. Probable auto-ignition events are frequently observed coincident with the centers of large-scale vortical structures, suggesting the phenomenon is linked to the enhanced mixing and longer residence times associated with fluid at the core of the PVC as it moves through the flame.