Uncertainty in stretch extrapolation of laminar flame speed from expanding spherical flames
Uncertainty in stretch extrapolation of laminar flame speed from expanding spherical flames
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DOI：
10.1016/j.proci.2014.05.065
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Fujia Wu;W. Liang;Zheng Chen;Y. Ju;C. Law
中科院分区：
文献类型：
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作者：
Fujia Wu;W. Liang;Zheng Chen;Y. Ju;C. Law
本文研究了在球形膨胀火焰的火焰速度测量中，将拉伸火焰外推到零拉伸的不确定性。直接数值模拟的时间演化的扩展球形火焰从一个小的点火内核到一个具有足够大的半径的传播前提供拉伸火焰速度和拉伸率之间的关系，可以用来评估外推模型的不确定性。结果表明，火焰外推的不确定性主要取决于混合物的刘易斯数。虽然化学计量的H2/空气和正庚烷/空气火焰的不确定性最小化，但对于贫H2/空气混合物，不确定性可高达60%，对于贫和富正庚烷/空气混合物，不确定性可高达10%。目前的研究结果表明，弱拉伸火焰的假设是失败的贫氢混合物，并给出了一个很好的解释之间的差异实验和模型预测的H2/空气，以及测量之间的差异正庚烷/空气使用球形和逆流火焰。给出了外推不确定度与Markstein数和Karlovitz数乘积之间的关系，该关系可用于未来和现有测量的不确定度量化。
The present work investigated the uncertainties associated with the extrapolation of stretched flames to zero stretch in flame speed measurements using expanding spherical flames. Direct numerical simulations of time evolution of expanding spherical flames from a small ignition kernel to a propagating front with sufficiently large radius provide the relations between stretched flame speed and stretch rate that can be used to assess the uncertainty of extrapolation models. It is found that the uncertainties of flame extrapolation largely depend on the mixture Lewis numbers. While the uncertainty is minimized for stoichiometric H2/air andn-heptane/air flames, the uncertainty can be as high as 60% for lean H2/air mixtures, and 10% for lean and richn-heptane/air mixtures. The present findings show that the weakly stretched flame assumption fails for lean hydrogen mixtures, and give a good explanation to the discrepancies between experiments and model predictions for H2/air as well as the discrepancies between measurements ofn-heptane/air using spherical and counterflow flames. A relation between extrapolation uncertainties and the product of Markstein number and Karlovitz number is provided, which can be useful for uncertainty quantification of future and existing measurements.