Local statistics of laminar expanding flames subjected to Darrieus–Landau instability
Local statistics of laminar expanding flames subjected to Darrieus–Landau instability
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DOI：
10.1016/j.proci.2020.06.118
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发表时间：
2020-08
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影响因子：
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通讯作者：
Zirui Liu;Vishnu R Unni;Swetaprovo Chaudhuri;C. Law;A. Saha
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作者：
Zirui Liu;Vishnu R Unni;Swetaprovo Chaudhuri;C. Law;A. Saha
本文报道了一项实验研究，探讨了局部火焰面动力学对胞状不稳定预混膨胀层流火焰传播和加速的作用。同时使用Mie散射成像和粒子图像测速仪，我们测量了火焰边缘的位置及其附近的流场，随后进行处理，以量化的概率密度函数（PDF）的流速，曲率，法向应变率和切向应变率的演变。我们表明，适当的归一化的测量量可以统一的数据从不同的压力时，确定相应的Peclet数，定义为火焰半径的火焰厚度的比率。由于火焰阵面在较低的Peclet数下是稳定和光滑的，火焰诱导流场和拉伸率在火焰阵面上几乎是均匀的，从而导致窄的PDF。然而，在更高的Peclet数，火焰变得越来越皱，因此在当地的数量的变化增加，导致更宽的pdfs。此外，虽然平均曲率被发现是成反比的平均火焰半径和不敏感的细胞结构，平均法向应变率的细胞结构的强烈影响。
We, herein, report an experimental study to investigate the role of local flamefront dynamics on the propagation and acceleration of cellularly unstable premixed expanding laminar flames. Using simultaneous Mie-scattering imaging and Particle Image Velocimetry, we measured the flame edge location and its adjacent flow field, which were subsequently processed to quantify the evolution of the probability density functions (pdfs) of flow velocities, curvature, normal strain rate and tangential strain rate. We showed that appropriate normalizaton of the measured quantities can unify the data from different pressures when identified with the corresponding Peclet number, defined as the ratio of the flame radius to the flame thickness. Since the flamefront is stable and smooth at lower Peclet numbers, the flame-induced flow field and stretch rates are almost uniform over the flamefront, resulting in narrowpdfs. At higher Peclet numbers, however, the flame becomes progressively more wrinkled and hence the variations in the local quantities increase leading to widerpdfs. Furthermore, while the mean curvature was found to be inversely proportional to the mean flame radius and insensitive to the cellular structure, the mean normal strain rate was strongly influenced by the cellular structure.