The role of unequal diffusivities in ignition and extinction fronts in strained mixing layers

被引:100
作者
Daou, J [1 ]
Liñán, A [1 ]
机构
[1] Univ Politecn Madrid, ETSI Aeronaut, Dept Motoprop & Termofluidodinam, E-28040 Madrid, Spain
关键词
D O I
10.1088/1364-7830/2/4/007
中图分类号
O414.1 [热力学];
学科分类号
摘要
We have studied dame propagation ina strained mixing layer formed between a fuel stream and an oxidizer stream, which can have different initial temperatures. Allowing the Lewis numbers to deviate from unity, the problem is first formulated within the framework of a thermo-diffusive model and a single irreversible reaction. A compact formulation is then derived in the limit of large activation energy and solved analytically for high values of the Damkohler number. Simple expressions describing the dame shape and its propagation velocity are obtained. In particular, it is found that the Lewis numbers affect the propagation of the triple flame in a way similar to that obtained in the studies of stretched premixed dames. For example, the flame curvature determined by the transverse enthalpy gradients in the frozen mixing layer leads to flame-front velocities which grow with decreasing values of the Lewis numbers. The analytical results are complemented by a numerical study which focuses on preferential-diffusion effects on triple flames. The results cover, for different values of the fuel Lewis number, a wide range of values of the Damkholer number feeding tea propagation speeds which vary from positive values down to large negative values.
引用
收藏
页码:449 / 477
页数:29
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