A New Analytic pdf for Simulations of Premixed Turbulent Combustion
A New Analytic pdf for Simulations of Premixed Turbulent Combustion
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DOI：
10.1007/s10494-020-00137-x
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发表时间：
2020-04
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影响因子：
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通讯作者：
M. Pfitzner
中科院分区：
文献类型：
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作者：
M. Pfitzner
提出了一种新的反应速率源项，用于使用单个进度变量对预混燃烧进行建模。它密切模仿大范围活化能和密度比的阿伦尼乌斯源项，同时允许对许多感兴趣的量进行分析评估。解析火焰剖面非常接近数值积分阿累尼乌斯火焰剖面。的一个重要特征是它在解析上可逆成a。推导了层流火焰特征值和层流火焰速度相关性的解析估计，这比基于渐近分析的经典结果更准确。推导了宽度 LES 单元中平坦层流火焰锋的小火焰 PDF。将反应速率的精确平均值与 beta pdf 结果进行比较，结果表明，对于过滤器宽度与火焰厚度的较大比率，特别是对于高活化能火焰，该结果是不准确的。对于多维火焰起皱，我们推导出 3D pdfp(c)、一维平面火焰 pdf、内部火焰结构变化的修正因子 I(c) 和几何起皱因子之间的精确关系。我们表明，这些数量的依赖性不能被忽视。正弦褶皱火焰锋的简单模型定性地证明了火焰褶皱对 p(c) 的影响。我们表明，对于大的情况，反应区的褶皱几乎不断地通过褶皱因子（针对最大放热等值面的表面定义）增加反应区中的 p(c)，同时将其减小到接近 p(c) 归一化所需的程度。使用减小的滤波器宽度评估的 1Dp(c) 可能是用于评估此类情况的皱纹火焰 pdf 的良好近似值。
A new reaction rate source termfor modelling of premixed combustion with a single progress variablecis proposed.mimics closely the Arrhenius source termfor a large range of activation energies and density ratios while admitting analytic evaluation of many quantities of interest. The analytic flame profilevery closely approximates the numerically integrated Arrhenius flame profiles. An important feature ofis that it is analytically invertible into a. Analytic estimates of the laminar flame Eigenvalueand of theLedependence of the laminar flame speedare derived, which are more accurate than classic results based on asymptotic analyses. The flamelet pdffor a flat laminar flame front in a LES cell of widthis derived. The exact mean of the reaction rateis compared to a beta pdf result, which is shown to be inaccurate for large ratios of filter width to flame thicknessand particularly for high activation energy flames. For multidimensional flame wrinkling we derive the exact relationshipbetween the 3D pdfp(c), the 1D flat flame pdf, a correction factorI(c) for change of inner flame structure and a geometrical wrinkling factor. We show that thecdependence of these quantities cannot be neglected for small. A simple model of a sinusoidally wrinkled flame front qualitatively demonstrates the effect of flame wrinkling onp(c). We show that for large, a wrinkling of the reaction zone almost constantly increasesp(c) in the reaction zone by a wrinkling factor(defined for the surface of the isosurface of maximum heat release) while reducing it nearas required for normalisation ofp(c). The 1Dp(c) evaluated using a reduced filter widthmay be a good approximation of the wrinkled flame pdf for evaluation offor such cases.