Assessment of crossed-plane tomography for flamelet surface normal measurements
Assessment of crossed-plane tomography for flamelet surface normal measurements
复制标题
火焰表面法线测量的交叉平面断层扫描评估
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
D. C. Bingham
中科院分区：
文献类型：
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作者：
D. Knaus;F. Gouldin;D. C. Bingham
最近推出的方法测量三维火焰面法向矢量，N，在湍流，预混火焰的描述和评价。交叉平面层析成像允许从两个同时采集的激光层析成像图像确定N。该方法进行评估，通过比较与单平面测量的涡街扰动V型火焰的数据，并通过误差分析。使用交叉平面层析成像测量的N s与垂直于火焰稳定杆对准的垂直图像平面之间的角度的标准偏差为3.7°，与扰动火焰的瞬时二维结构一致。PDF的N到这个垂直平面上的投影的方向进行比较，PDF的N S使用单平面断层扫描测量的方向，这两个被发现是，在大多数情况下，在统计不确定性的一个。由于电子噪声和标记散粒噪声的随机误差的分析结果与实验结果一致，因此可以通过解析表达式估计不确定度。讨论了由交叉平面层析成像测量生成的PDF的统计加权，以及根据N与任意定向线η之间的角度的平均反余弦来评估火焰面密度。它表明，这个PDF是加权的概率，火焰穿过两个照明平面之间的交叉线，交叉加权PDF，平均反余弦项也是交叉加权平均，其中η是交叉线。火焰面密度表示为平均反余弦项与单位长度上火焰面平均交叉数η的乘积，即火焰面交叉密度。有人认为，η的优选取向是垂直于nfc的常数表面，并从以前的工作（Bingham，Gouldin，和Knaus，1998年）的N s的PDF拟合被用来评估平均反余弦项。结果表明，该方向的最大η值略大于2，表明大燃速火焰必须具有大的小火焰面交叉密度值。
A recently introduced method for measuring three-dimensional flamelet surface normal vectors, N , in turbulent, premixed flames is described and evaluated. Crossed-plane tomography allows the determination of N from two simultaneously acquired laser-tomographic images. The method is evaluated through comparisons with data from single-plane measurements made on a vortex-street perturbed v-flame, and through an error analysis. The standard deviation of the angle between N s measured using crossed-plane tomography and a vertical image-plane aligned perpendicular to the flame stabilizing rod is 3.7°, consistent with the instantaneous, two-dimensional structure of the perturbed flame. PDFs of the orientation of the projection of N onto this vertical plane are compared to PDFs of the orientation of N s measured using single-plane tomography, and the two are found to be, for the most part, within statistical uncertainty of one another. The results of an analysis of random error due to electronic noise and marker shot noise are consistent with experimental results, and thus uncertainty can be estimated through analytic expressions. The statistical weighting of PDFs generated by crossed-plane tomography measurements is discussed, as is the evaluation of the flamelet surface density in terms of the mean inverse cosine of the angle between N and an arbitrarily oriented line η. It is shown that this PDF is weighted by the probability that the flamelet crosses the line of intersection between the two illumination planes, a crossing-weighted PDF, and that the mean inverse cosine term is also a crossing-weighted average, where η is the line crossed. The flamelet surface density is written as the product of the mean inverse cosine term and the average number of flamelet crossings of η per unit length, the flamelet crossing density. It is argued that the preferred orientation of η is perpendicular to ⟨ c ⟩ constant surfaces, and a PDF fit for the N s from previous work (Bingham, Gouldin, and Knaus, 1998) is used to evaluate the mean inverse cosine term. It is found that the maximum value for this orientation of η is slightly more than two, indicating that large burning rate flames must have large corresponding values of the flamelet crossing density.