论文标题

灭绝应变率与层流速度之间的动力学相似性

Kinetic Similarity between Extinction Strain Rate and Laminar Flame Speed

论文作者

Ji, Weiqi, Yang, Tianwei, Ren, Zhuyin, Deng, Sili

论文摘要

灭绝应变速率(ESR)和层状火焰速度(LFS)是燃料/空气混合物的基本特性,通常用作湍流燃烧中的缩放参数。尽管对大气和升高压力的LFS进行了广泛的研究,但使用逆流预混合火焰对ESR的实验测量通常会在火焰不稳定性方面非常有限,往往发生在灭绝量附近,尤其是在高压下。由于ESR测量值的稀缺性,大多数燃烧动力学模型主要对LFS进行验证和优化。但是,对于ESR和LFS而言,控制反应是否相同,因此这些模型也有效预测ESR值得怀疑。这项工作通过分析其动力学敏感性方向来量化ESR和LF之间的动力学相似性。该方向由由ESR或LFS的归一化灵敏度组成的单位矢量表示每个元素反应的速率常数。因此,两个方向之间的相似性是通过相应单位向量的内部产物来衡量的。对于各种燃料,等效比和压力,发现ESR和LF的灵敏度方向是平行的。此外,对于最高温度,火焰坐标中的各个位置的局部温度以及逆流预混合火焰中的ESR,以各种应变速率的灵敏度方向也相似。这些发现表明,LFS和ESR与在动力学模型中约束和优化速率常数的目标相似。此外,根据ESR和LFS的动力学灵敏度,对应变速率的灵敏度方向的独立性也使我们能够对具有广泛应变速率的湍流定量进行不确定性定量。

Extinction strain rate (ESR) and laminar flame speed (LFS) are fundamental properties of a fuel/air mixture that are often utilized as scaling parameters in turbulent combustion. While LFS at atmospheric and elevated pressures are extensively investigated, experimental measurements of ESR with counterflow premixed flames are very limited for flame instability often occurs near extinction, especially at high pressures. Due to the scarcity of ESR measurements, most combustion kinetic models are mainly validated and optimized against LFS. However, it is questionable whether the controlling reactions are the same for ESR and LFS such that those models are also valid for predicting ESR. This work quantifies the kinetic similarities between ESR and LFS by analyzing their kinetic sensitivity directions. The direction is represented by a unit vector composed of the normalized sensitivity of ESR or LFS to the rate constant for each elemental reaction. Consequently, the similarity between the two directions is measured by the inner product of the corresponding unit vectors. The sensitivity directions of ESR and LFS are found parallel for various fuels, equivalence ratios, and pressures. Furthermore, sensitivity directions at various strain rates are also similar for the maximum temperature, local temperature at various locations in the flame coordinate, and ESR in counterflow premixed flames. These findings suggest that LFS and ESR are similarly effective as the target for constraining and optimizing rate constants in kinetic models. In addition, the independence of the sensitivity directions on the strain rate also enables us to perform uncertainty quantification for turbulent flames with a wide range of strain rates based on the kinetic sensitivity of ESR and LFS.

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