Coherent flame oscillations generated by large-scale flow instabilities have been shown to significantly influence combustor performance and thermoacoustic instability. This study examines the influence of turbulence intensity on the large-scale dynamics of rod-stabilized flames. Instability in the flow field of a bluff-body stabilized flame, which is a function of mean shear in the flow field, turbulence intensity of the incoming flow, and the location of the flame with respect to the shear layer, manifests as coherent vortex shedding. However, this vortex shedding is not self-excited if the flow is globally stable, as is often the case in reacting flows. In this experiment, time-resolved, three-component velocity measurements from high-speed stereoscopic particle image velocimetry are taken at three turbulent inlet flow conditions and at three bulk flow velocities. To identify whether these instabilities occur, the velocities fields are filtered using a wavelet transform around select spectral bands and then decomposed using proper orthogonal decomposition to extract the most energetic motion in the flow; this filtering method retains any time-dependent, intermittent behavior. The results show that vortex shedding is intermittent and the degree of intermittency is dependent on the in-flow turbulence level. Although all the cases tested were determined to be globally stable, variations in the flow velocity change the structure of the flame and flow, which alters the receptivity of the flow to turbulent perturbations. As a result, the strength and regularity of vortex shedding increase with increasing turbulence level and increased receptivity, indicating that the system is a noise-forced globally-stable oscillator.

大规模流动不稳定性产生的相干火焰振荡已显示出对燃烧器性能和热声不稳定性的显着影响。这项研究检查了湍流强度对棒稳定火焰的大规模动力学的影响。钝体稳定火焰在流场中的不稳定性是流场中平均剪切，传入流的湍流强度以及火焰相对于剪切层的位置的函数，表现为相干涡旋脱落。但是，如果流动是全局稳定的，则这种涡旋脱落不会自激，这在反应流动中通常是这样。在这个实验中，高速立体粒子图像测速仪在三个湍流入口流动条件和三个整体流速下进行了三分量速度测量。为了识别是否发生这些不稳定性，使用围绕所选光谱带的小波变换对速度场进行滤波，然后使用适当的正交分解进行分解，以提取流中最活跃的运动。这种过滤方法保留了任何与时间相关的间歇行为。结果表明，涡旋脱落是间歇性的，间歇性取决于流入湍流的水平。尽管确定所有测试情况都是全局稳定的，但流速的变化会改变火焰和气流的结构，从而改变气流对湍流扰动的接受度。结果是，