Generation and transport of equivalence ratio fluctuations in an acoustically forced swirl burner
Generation and transport of equivalence ratio fluctuations in an acoustically forced swirl burner
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DOI：
10.1016/j.combustflame.2019.07.007
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发表时间：
2019-11-01
影响因子：
4.4
通讯作者：
Oberleithner, Kilian
中科院分区：
文献类型：
--
作者：
Bluemner, Richard;Paschereit, Christian O.;Oberleithner, Kilian
在热声不稳定性的背景下，有关当量比波动的产生和传输的知识对于正确模拟其对火焰传递函数的影响非常重要。在这项工作中，研究了现代燃气轮机燃烧器典型的声学强制、部分预混旋流燃烧器的混合部分中的空间分辨当量比扰动。使用波长调制方法的可调谐二极管激光吸收光谱用于评估径向方向上的空间不均匀当量比场。粒子图像测速用于测量轴向速度场。基于这些结果，利用断层扫描重建来推断两个轴向位置处的局部燃料分布。计算综合的全局当量比波动并与简单的视线测量进行比较。研究了强迫频率和振幅的影响，并发现不同测量方法之间具有良好的一致性。观察到由旋流器中的空气速度波动以及燃料喷射器中的压力波动驱动的与频率相关的当量比扰动产生机制。将模拟扩散和色散的两种不同的混合传递函数与结果进行比较，并揭示了显着的差异，表明传输速度的相干波动对混合的显着影响，而这两个模型都没有考虑到。 (C) 2019 年燃烧研究所。由爱思唯尔公司出版。保留所有权利。
In the context of thermoacoustic instabilities, knowledge about the generation and transport of equivalence ratio fluctuations is highly important to correctly model their impact on the flame transfer function. In this work, spatially resolved equivalence ratio perturbations in the mixing section of an acoustically forced, partially premixed swirl burner typical of modern gas turbine combustors are investigated. Tunable diode laser absorption spectroscopy using a wavelength-modulation approach is applied to assess the spatially inhomogeneous equivalence ratio field in the radial direction. Particle image velocimetry is applied to measure the axial velocity field. Based on these results, a tomographic reconstruction is utilized to deduce the local fuel distribution at two axial locations. Integrated, global equivalence ratio fluctuations are calculated and compared to simple line-of-sight measurements. The influence of the forcing frequency and amplitude is investigated and good agreement was found between the different measurement approaches. Frequency dependent equivalence ratio perturbation generation mechanisms driven by air velocity fluctuations in the swirler, as well as pressure fluctuations at the fuel injector, are observed. Two different mixing transfer functions modeling diffusion and dispersion are compared to the results and reveal substantial differences, indicating a significant impact of coherent fluctuations of the transport velocity on the mixing that are not accounted for by either of the models. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.