A thick reaction zone model for premixed flames in two-dimensional channels
A thick reaction zone model for premixed flames in two-dimensional channels
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二维通道中预混火焰的厚反应区模型
DOI：
10.1080/13647830.2023.2174046
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发表时间：
2023
影响因子：
1.3
通讯作者：
Rajamanickam P
中科院分区：
文献类型：
--
作者：
Rajamanickam P
当反应区厚度与流动长度尺度相当或大于流动长度尺度时，预混火焰中流场与化学反应之间会发生直接相互作用。为了研究这样的相互作用，层流模型被认为是有直接的轴承稳定传播的爆燃在Hele-Shaw通道与背景平面Poilluille流。该研究采用渐近分析，有关大的活化能和润滑理论，并考虑了一个显着的限制，其中通道宽度是可比的反应区厚度，考虑到热膨胀和热损失的影响。反应区结构和燃烧速率取决于三个参数，即Peclet数、刘易斯数和通道半宽与反应区厚度之比。特别是当参数较小时，反应区较厚时，输运过程受Taylor弥散机制控制，并得到了有效燃烧速度的显式表达式。该公式表明，对于，这有趣地符合最近的实验预测的湍流火焰速度在一个高度湍流射流火焰。结果表明，在层流和湍流情况下，微分扩散效应所起的作用是显着的。至少在我们的层流模型中，这种特殊依赖性的原因可以归因于泰勒分散。据推测，这种依赖性可能是由于一个类似的，但更一般的机制，在湍流分布的反应区制度，而不是扩散热曲率效应。然而，后者的影响起着重要的作用，在确定有效的传播速度较薄的反应区，特别是，当在我们的模型是大的。据发现，在熄火时的热损失的大小，这直接影响到混合物的可燃性极限，乘以一个factorin相比，相应的无流动的情况下，在狭窄的通道。
Direct interactions between the flow field and the chemical reaction in premixed flames occur when the reaction zone thickness is comparable to, or greater than flow length scales. To study such interactions, a laminar model is considered that has direct bearings to steadily propagating deflagrations in a Hele-Shaw channel with a background plane Poiseuille flow. The study employs asymptotic analyses, pertaining to large activation energy and lubrication theories and considers a distinguished limit where the channel width is comparable to the reaction zone thickness, with account being taken of thermal-expansion and heat-loss effects. The reaction zone structure and burning rates depend on three parameters, namely, the Peclet number,, the Lewis number,and the ratio of channel half-width to reaction zone thickness,. In particular, when the parameteris small wherein the reaction zone is thick, transport processes are found to be controlled by Taylor's dispersion mechanism and an explicit formula for the effective burning speedis obtained. The formula indicates thatfor, which interestingly coincides with a recent experimental prediction of the turbulent flame speed in a highly turbulent jet flame. The results suggest that the role played by differential diffusion effects is significant both in the laminar and turbulent cases. The reason for the peculiardependence can be attributed, at least in our laminar model, to Taylor dispersion. Presumably, this dependence may be attributed to a similar but more general mechanism in the turbulent distributed reaction zone regime, rather than to diffusive-thermal curvature effects. The latter effects play however an important role in determining the effective propagation speed for thinner reaction zones, in particular, whenis large in our model. It is found that the magnitude of heat losses at extinction, which directly affects the mixture flammability limits, is multiplied by a factorin comparison with those corresponding to the no-flow case in narrow channels.
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