The development and structure of flame instabilities and cellularity at low Markstein numbers in explosions
The development and structure of flame instabilities and cellularity at low Markstein numbers in explosions
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DOI：
10.1016/s0010-2180(00)00113-9
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发表时间：
2000-07
影响因子：
4.4
通讯作者：
D. Bradley;C.G.W. Sheppart;R. Woolley;D. Greenhalgh;R. Lockett
中科院分区：
文献类型：
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作者：
D. Bradley;C.G.W. Sheppart;R. Woolley;D. Greenhalgh;R. Lockett
利用自然光和纹影高速电影摄影技术以及OH自由基的单次平面激光诱导荧光（PLIF）技术，对球形气体爆炸过程中火焰不稳定性和胞状结构的形成进行了实验研究。高压，富烃和贫氢火焰在低Markstein数。不稳定波长的范围已被确定为Markstein和Peclet数的函数。电影摄影使细胞生长和裂变的动力学进行研究和定性解释，在火焰拉伸率和热扩散。PLIF技术使不稳定的波长被测量和火焰断裂负拉伸裂纹被观察到。不稳定波长的级联终止于细胞结构。这种结构出现在第二个临界Peclet数。较小的细胞不断地不稳定和重新稳定。随着它们的尺寸增加，细胞表面的局部拉伸速率降低，细胞变得不稳定。它通过分裂成更小的细胞以更高的局部拉伸率来重新稳定。这些单元由负曲率区域中的裂纹界定。在足够小的Markstein数的裂纹断裂。Bechtold和Matalon的稳定性分析的理论框架内的结果进行解释。
Flame instabilities and the formation of cellular structures during spherical gaseous explosions have been studied experimentally using natural light and schlieren high-speed cine photography, as well as single-shot planar laser-induced fluorescence (PLIF) from the OH radical. High-pressure, rich-hydrocarbon and lean-hydrogen flames at low Markstein numbers were employed. Ranges of unstable wavelengths have been identified as a function of Markstein and Peclet numbers. The cine photography enables the dynamics of cell growth and fissioning to be studied and qualitatively interpreted, in terms of flame stretch rates and thermodiffusion. The PLIF technique enabled unstable wavelengths to be measured and flame fracture at negatively stretched cracks to be observed. A cascade of unstable wavelengths terminates in a cellular structure. This structure appears at a second critical Peclet number. The smaller cells are continually destabilizing and restabilizing. As they increase in size, the localized stretch rate on the cell surface decreases and the cell becomes unstable. It restabilizes by fissioning into smaller cells with higher localized stretch rates. The cells are bounded by cracks in regions of negative curvature. At sufficiently small Markstein numbers the cracks are fractured. The results are interpreted within the theoretical framework of the stability analysis of Bechtold and Matalon.