Key parameters governing the precessing vortex core in reacting flows: An experimental and analytical study
Key parameters governing the precessing vortex core in reacting flows: An experimental and analytical study
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DOI：
10.1016/j.proci.2014.07.035
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
S. Terhaar;K. Oberleithner;C. Paschereit
中科院分区：
文献类型：
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作者：
S. Terhaar;K. Oberleithner;C. Paschereit
本报告涉及旋流燃烧室流中自激流体动力学不稳定性发生的实验和分析研究。使用立体粒子图像测速仪测量不同燃烧器运行条件下的不同流场类型。流场的特性与遇到的火焰形状有关。结果表明，以进动涡核为特征的螺旋流不稳定性的出现强烈依赖于火焰形状。如果火焰具有足够的长度，则附着在燃烧器出口处的火焰可以抑制进动涡流核心，而对于非常短的附着火焰和所有分离的火焰则观察不到抑制。对时间平均流量进行了线性水动力稳定性分析，对不稳定频率和造波器位置进行了出色的预测，并证明自激振荡是由水动力不稳定性驱动的。进行了参数模型研究，研究了回流速度、旋流强度和密度分布的作用，揭示了射流轴上的回流和剪切层中的密度梯度本质上是决定不稳定性的抑制或激发的参数。
This report deals with an experimental and analytical study of the occurrence of self-excited hydrodynamic instabilities in swirling combustor flows. Different flow field types are measured for varying combustor operating conditions using stereoscopic particle image velocimetry. The properties of the flow field are connected to the flame shapes encountered. It is shown that the appearance of a helical flow instability, featuring a precessing vortex core, is strongly dependent on the flame shape. Flames attached to the burner exit may suppress the precessing vortex core if the flame features a sufficient length, while suppression is not observed for very short attached and all detached flames. Linear hydrodynamic stability analysis is carried out on the time-averaged flow, yielding an excellent prediction of the instability frequency and the wavemaker location and proving that the self-excited oscillations are driven by a hydrodynamic instability. A parametric model study investigating the role of the backflow velocity, the swirl intensity, and the density distribution is carried out, revealing that the backflow on the jet axis and the density gradient in the shear layer are essentially the parameters that determine the suppression or excitation of the instability.