Tomographic reconstruction of heat release rate perturbations induced by helical modes in turbulent swirl flames
Tomographic reconstruction of heat release rate perturbations induced by helical modes in turbulent swirl flames
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DOI：
10.1007/s00348-013-1498-2
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发表时间：
2013-04
影响因子：
2.4
通讯作者：
J. Moeck;Jean-François Bourgouin;D. Durox;T. Schuller;S. Candel
中科院分区：
文献类型：
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作者：
J. Moeck;Jean-François Bourgouin;D. Durox;T. Schuller;S. Candel
具有涡流击穿的涡流流广泛应用于工业燃烧系统中，以稳定火焰。众所周知，这种类型的流动可以维持旋转螺旋结构的流体动力学不稳定性，它的一个常见表现是进动漩涡核心。这种非定常流动模式在燃烧中的作用尚不清楚，其与燃烧不稳定性和火焰稳定的相互作用也尚不清楚。因此，评估由这种螺旋模式引起的火焰扰动的结构是很重要的。基于层析重建原理，提出了一种确定与螺旋模式相关的热释放率扰动的三维分布的方法。由于这种流动不稳定性是旋转的，从火焰发出的光的投影图像的相位分辨序列与燃烧室体积中光强分布的Radon变换相同，因此可以用于层析重建。这只需要一个固定的相机，与多相机设置或相机重新定位相比，大大减少了实验和硬件要求，这通常需要层析成像重建。讨论了从图像中提取振荡相干部分的不同方法。推导了两种新的层析重建算法，专门针对与螺旋模式相关的热释放率扰动的结构。首先将重建技术应用于一个人工场，以说明重建技术的准确性。在湍流旋流稳定燃烧室设置中获得的高速成像数据具有强螺旋模式振荡，然后用于重建火焰中相关扰动的三维结构。
Swirl flows with vortex breakdown are widely used in industrial combustion systems for flame stabilization. This type of flow is known to sustain a hydrodynamic instability with a rotating helical structure, one common manifestation of it being the precessing vortex core. The role of this unsteady flow mode in combustion is not well understood, and its interaction with combustion instabilities and flame stabilization remains unclear. It is therefore important to assess the structure of the perturbation in the flame that is induced by this helical mode. Based on principles of tomographic reconstruction, a method is presented to determine the 3-D distribution of the heat release rate perturbation associated with the helical mode. Since this flow instability is rotating, a phase-resolved sequence of projection images of light emitted from the flame is identical to the Radon transform of the light intensity distribution in the combustor volume and thus can be used for tomographic reconstruction. This is achieved with one stationary camera only, a vast reduction in experimental and hardware requirements compared to a multi-camera setup or camera repositioning, which is typically required for tomographic reconstruction. Different approaches to extract the coherent part of the oscillation from the images are discussed. Two novel tomographic reconstruction algorithms specifically tailored to the structure of the heat release rate perturbations related to the helical mode are derived. The reconstruction techniques are first applied to an artificial field to illustrate the accuracy. High-speed imaging data acquired in a turbulent swirl-stabilized combustor setup with strong helical mode oscillations are then used to reconstruct the 3-D structure of the associated perturbation in the flame.