The effects of different baffled configurations of acoustic dampers placed downstream of the dump plane of a combustor on the mean flowfield, coherent structures, acoustics, stability and dynamics of partially premixed methane flames were experimentally investigated. Particle image velocimetry (PIV) was used to capture the instantaneous flowfield downstream of the dump plane or the baffles and proper orthogonal decomposition (POD) was used to analyze coherent structures. High-speed imaging was used to capture flame dynamics, and a Bruel and Kjaer microphone was used to perform acoustics measurements. Two interchangeable baffle configurations were tested; one consists of eight-blade radial baffles attached to a circumferential baffle and placed underneath of a circumferentially-slotted cup (AD#1), and another consists of eight-blade radial baffles attached to a circumferential baffle (AD#2). The results revealed significant improvement in flame stability when using baffles. This is attributed to several factors. First, the burner baffled configurations caused a significant reduction in the amplitude of coherent structures and acoustics. Second, the presence of baffles promoted either a very narrow CRZ (in case of AD#2) or no ORZ with a weak CRZ (in case of AD#1). This positive axial velocity convected vortical structures farther downstream of AD#1. Third, both flame–flame interaction in AD#1 configuration (resulting from the axial flow off the circumferential slots and that from the swirling flow in the core flow region) and flame-baffles interaction in AD#2 configuration (resulting from the interplay between baffles’ tips and the swirling flame in the core region) helped reducing the azimuthal mean velocity and its rms component in the flow core region. This consequently resulted in a significant change in the azimuthal acoustic waves’ behavior within the combustor/confinement. The results revealed that the baffled burner configurations enhanced mixing as witnessed by the more flame bluish color and consequently its stability.

中文翻译：

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消声器对封闭涡流部分预混甲烷火焰特性的影响

实验研究了放置在燃烧器倾卸平面下游的不同挡板配置的消音器对部分预混甲烷火焰的平均流场、相干结构、声学、稳定性和动力学的影响。粒子图像测速 (PIV) 用于捕获倾卸平面或挡板下游的瞬时流场，并使用适当的正交分解 (POD) 来分析相干结构。高速成像用于捕捉火焰动力学，Bruel 和 Kjaer 麦克风用于执行声学测量。测试了两种可互换的挡板配置；一个由连接到圆周挡板并放置在圆周槽杯 (AD#1) 下方的八叶片径向挡板组成，另一个由连接到圆周挡板 (AD#2) 的八叶片径向挡板组成。结果表明，使用挡板时火焰稳定性有显着改善。这归因于几个因素。首先，燃烧器挡板配置导致相干结构和声学振幅的显着降低。其次，挡板的存在促进了非常窄的 CRZ（在 AD#2 的情况下）或没有具有弱 CRZ 的 ORZ（在 AD#1 的情况下）。这种正轴向速度使 AD#1 下游更远的涡旋结构对流。第三，AD#1 配置中的火焰 - 火焰相互作用（由圆周槽的轴向流动和核心流动区域的旋流产生）和 AD#2 配置中的火焰 - 挡板相互作用（由挡板之间的相互作用产生）尖端和核心区域的旋流火焰）有助于降低流动核心区域的方位平均速度及其均方根分量。因此，这导致燃烧室/限制内的方位角声波行为发生显着变化。结果表明，挡板燃烧器的配置增强了混合，这可以通过更多的火焰蓝色及其稳定性来证明。因此，这导致燃烧室/限制内的方位角声波行为发生显着变化。结果表明，挡板燃烧器的配置增强了混合，这可以通过更多的火焰蓝色及其稳定性来证明。因此，这导致燃烧室/限制内的方位角声波行为发生显着变化。结果表明，挡板燃烧器的配置增强了混合，这可以通过更多的火焰蓝色及其稳定性来证明。