Diffusional-thermal instability of diffusion flames
Diffusional-thermal instability of diffusion flames
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DOI：
10.1017/s0022112096008543
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发表时间：
1996-11
影响因子：
3.7
通讯作者：
J. Kim;F. Williams;P. Ronney
中科院分区：
文献类型：
--
作者：
J. Kim;F. Williams;P. Ronney
扩散热不稳定性，这会导致条纹淬火模式，已观察到的扩散火焰，分析通过研究模型的一维对流扩散火焰中的扩散火焰制度的活化能渐近。注意力主要集中在刘易斯数小于1的近消光条件下，其中具有高扩散系数的反应物扩散到反应片的强段中，使得强段之间的区域变得缺乏反应物并且受到导致条纹图案的局部猝灭。该分析不同于其他火焰稳定性分析，因为分散关系的完整描述是从具有常规对流扩散缩放和具有反应区缩放的分析结果的复合扩展获得的。结果预测，条纹图案将发生，火焰足够接近准稳态灭绝，与有限的波数，在对流扩散缩放是成比例的Zel'dovich数的立方根。对流扩散响应有助于稳定的长波长的干扰通过正过剩的frackpies的火焰变得更耐不稳定性，而反应区响应提供稳定的短波长的干扰通过横向扩散，在反应内层，这放宽了对它们的未扰动状态的扰动标量场。当接近准定常灭绝时，首先在这两个尺度之间的中间范围内出现边际稳定性。通过数值求解相关的广义特征值问题，得到了该分岔点的参数结果。不同的反应物和稀释剂组的测量图案尺寸的比较显示出良好的定性协议。
The diffusional–thermal instability, which gives rise to striped quenching patterns that have been observed for diffusion flames, is analysed by studying the model of a one-dimensional convective diffusion flame in the diffusion-flame regime of activation-energy asymptotics. Attention is focused principally on near-extinction conditions with Lewis numbers less than unity, in which the reactants with high diffusivity diffuse into the strong segments of the reaction sheet, so that the regions between the strong segments become deficient in reactant and subject to the local quenching that leads to the striped patterns. This analysis differs from other flame stability analyses in that the complete description of the dispersion relation is obtained from a composite expansion of the results of an analysis with the conventional convective-diffusive scaling and one with reaction-zone scaling. The results predict that striped patterns will occur, for flames sufficiently close to quasi-steady extinction, with a finite wavenumber that in convective–diffusive scaling is proportional to the cube root of the Zel'dovich number. The convective–diffusive response contributes to the stabilization of long-wavelength disturbances by through positive excess enthalpies by which the flame becomes more resistant to instability, while the reaction-zone response provides stabilization of short-wavelength disturbances by transverse diffusion, within the reactive inner layer, which relaxes the perturbed scalar fields towards their unperturbed states. As quasi-steady extinction is approached, marginal stability arises first at an intermediate range between these two scalings. Parametric results for this bifurcation point are obtained through numerical solutions of the associated generalized eigenvalue problems. Comparisons with measured pattern dimensions for different sets of reactants and diluents reveal excellent qualitative agreement.