Interaction between self-excited oscillations and fuel-air mixing in a dual swirl combustor
Interaction between self-excited oscillations and fuel-air mixing in a dual swirl combustor
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DOI：
10.1016/j.proci.2018.08.042
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发表时间：
2019-01-01
影响因子：
3.4
通讯作者：
Meier, Wolfgang
中科院分区：
文献类型：
--
作者：
Chen, Zhi X.;Swaminathan, Nedunchezhian;Meier, Wolfgang
采用大涡模拟（LES）方法对接近工业设计的部分预混燃气涡轮机模型燃烧室进行了研究。计算了两种火焰，一种稳定火焰，另一种不稳定火焰，并伴有自激振荡。特别是，这项研究解决了以前无法解释的过渡火焰形状的实验中，从V形到平面时，火焰变得声学不稳定，这表明一个显着的变化，在热声反馈回路中的重要对流延迟。大涡模拟结果与实测的速度、温度和质量分数吻合较好。从LES的不稳定火焰获得的声功率谱密度（PSD）也同意与测得的振幅在空气增压室和燃烧室，并合理地捕捉频率略有低于预测。稳定和不稳定的情况下的比较显示不同的混合和反应行为，尽管相似的平均速度场。进一步详细的分析表明，不同的混合行为是由显着变化的空气质量分裂之间的两个空气通道在热声振荡周期。这种变化是由于通过具有不同内部几何形状的两个旋流喷射器通道传播的压力振荡所经历的不同阻抗。这导致在两个涡旋空气流之间喷射的燃料射流的径向动量的周期性变化。所产生的燃料射流的拍打产生增强的径向燃料-空气混合，这导致在不稳定情况下的扁平火焰。这为实验中观察到的火焰形状转变提供了新的物理解释。(C)2018燃烧研究所爱思唯尔公司出版All rights reserved.
A partially premixed gas turbine model combustor close to an industrial design is investigated using Large Eddy Simulation (LES). Two flames, one stable and another unstable with self-excited oscillations are computed. In particular, this study addresses the previously unexplained transition of flame shape in the experiments, from V-shaped to flat when the flame becomes acoustically unstable, suggesting a notable change of the important convective delay in the thermoacoustic feedback loop. The LES results show good agreement with the measured velocities, temperature and mass fractions. The acoustic power spectral density (PSD) obtained from the LES of the unstable flame also agrees well with the measured amplitudes in the air plenum and combustion chamber, and reasonably captures the frequency with a slight under-prediction. A comparison of the stable and unstable cases shows different mixing and reaction behaviours despite similar mean velocity fields. Further detailed analysis shows that the different mixing behaviour is driven by the significantly varying air mass split between the two air passages during a thermoacoustic oscillation cycle. This variation is due to the different impedances experienced by the pressure oscillations propagating through the two swirling injector passages with different internal geometries. This causes a periodic variation of the radial momentum of the fuel jets injected between the two swirling air flows. The resulting flapping of the fuel jets creates an enhanced radial fuel-air mixing that leads to a flattened flame in the unstable case. This provides a new physical explanation for the transitions of flame shape observed in the experiments. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.