Images of the quenching of a flame by a vortex-To quantify regimes of turbulent combustion
Images of the quenching of a flame by a vortex-To quantify regimes of turbulent combustion
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涡流熄灭火焰的图像 - 量化湍流燃烧状态
DOI：
10.1016/0010-2180(93)90019-y
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发表时间：
1993
影响因子：
4.4
通讯作者：
L. Goss
中科院分区：
文献类型：
--
作者：
W. Roberts;J. Driscoll;M. C. Drake;L. Goss
层流环形涡与层流预混火焰相互作用，以隔离和可视化湍流燃烧的一些基本物理。使用平面激光诱导荧光成像的超平衡OH分子在涡流前缘附近的逆流火焰前锋区域观察到局部淬火的火焰。测量了作为涡流大小和强度的函数的淬火极限曲线。在研究的第二部分中，测量相结合的概念提出的Poinsot，Veynante，和坎德尔，以推断薄火焰的限制，即发病的分布反应，在一个经典的预混湍流燃烧制度图。测得的薄火焰极限表明，当层流小火焰理论变得无效，因为淬火允许热的产品和反应物共存。结果与Klimov-Williams准则进行了比较。在某些情况下，涡核直径与火焰厚度一样小。主要结论是，小涡是不太有效的淬火火焰比以前认为，因此，推断的制度内薄火焰理论是有效的扩展到湍流强度，这是一个数量级以上，比以前预测的。结果还表明，微观混合模型，假设最小的涡流施加最大的应变火焰，是不现实的。测量的趋势与Poinsot等人的直接数值模拟一致，但绝对值不同。测得的涡流Karlovitz数，需要熄灭火焰是不恒定的，但减少了四倍的涡流大小增加从一个到五个火焰厚度。薄膜高温计被用来量化的辐射热损失;淬火时发生的产品冷却到约1300 K，这是在协议与拉伸层流火焰计算，包括详细的化学。丙烷-空气火焰的淬火Karlovitz数不同于甲烷-空气火焰的淬火Karlovitz数，表明详细的化学和传输特性的重要性。火焰曲率被观察到导致增强（或减少）的局部反应速率，这取决于刘易斯数，在一种方式，这是一致的拉伸火焰理论。
A laminar toroidal vortex is interacted with a laminar premixed flame in order to isolate and to visualize some of the fundamental physics of turbulent combustion. Localized quenching of the flame was observed using planar laser-induced fluorescence imaging of superequilibrium OH molecules in the counterflow flamefront region near the vortex leading edge. A quenching limit curve was measured as a function of vortex size and strength. In the second part of the study, the measurements are combined with concepts proposed by Poinsot, Veynante, and Candel in order to infer the thin flame limit, namely, the onset of distributed reactions, on a classical premixed turbulent combustion regime diagram. The measured thin flame limit indicates when laminar flamelet theories become invalid, since quenching allows hot products and reactants to coexist. Results are compared with the Klimov-Williams criterion. Vortex core diameters were as small as the flame thickness in some cases. The main conclusion is that small vortices are less effective at quenching a flame than was previously believed; therefore the inferred regime within which thin flame theories are valid extends to a turbulence intensity that is more than an order of magnitude larger than that which was previously predicted. Results also indicate that micromixing models, which assume that the smallest eddies exert the largest strain on a flame, are not realistic. Measured trends are in agreement with direct numerical simulations of Poinsot et al., but absolute values differ. The measured vortex Karlovitz number that is required to quench a flame is not constant but decreases by a factor of four as vortex size increases from one to five flame thicknesses. Thin-film pyrometry was used to quantify the radiative heat losses; quenching occurs when the products cool to approximately 1300 K, which is in agreement with stretched laminar flame calculations that include detailed chemistry. The quenching Karlovitz number for propane-air flames differs from that of methane-air flames, indicating the importance of detailed chemistry and transport properties. Flame curvature was observed to cause enhancement (or reduction) of the local reaction rate, depending on the Lewis number, in a manner that is consistent with stretched flame theory.