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An Experimental Approach to Vortex-Flame Interaction in Practical Turbulent Fields

实际湍流场中涡旋火焰相互作用的实验方法

基本信息

批准号：
12650201
负责人：
OHIWA Norio
金额：
$ 2.3万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650201/
关键词：
Turbulent Premixed Flame Turbulent Burning Velocity Vortex-Flame Interaction Plane Shear Flow Coherent Structure Karman Vortex Street Wake behind Cylindrical Rod Array Unsteady Propagating Flame 乱流予混合火炎円柱格子乱流火炎と渦の相互干渉火炎伸長トモグラフィ

项目摘要

In this investigation the processes of vortex-flame interaction of a spark-ignited flame with either coherent structure in the plane premixed shear flow or Karman vortex street in the wake behind a fine cylindrical rod array are experimentally examined, in order to clarify effects of adjacent eddies on the vortex bursting. Propane-air mixture is used in this investigation with an equivalence ratio varied. The results obtained are summarized as follows.(1) In case of the spark ignition at the center of a large scale organized eddy, a flame propagates faster in the axial direction than in the radial one, indicating that the vortex motion enhances the propagation velocity. After completing combustion within an eddy, a pair of flames protrude to adjacent boundary regions on upstream and downstream sides and propagate in the flow direction. The propagation velocity is promoted by the rolling-up motion inherent in the shear flow. In case of the spark ignition at the boundary between adjacent eddies, a flame extends along the contact surface between two mixture streams and becomes S-shaped. It is found that the flame velocity in the flow direction is almost equal to that in the axial direction. When the tips of S-shaped flame reach adjacent eddies, the vortex bursting again enhances the axial flame propagation. It is concluded that there exist two kinds of vortex-flame interactions; one is the vortex bursting, the other is the vortex boosting, and that combination of these two enhancement mechanisms constitutes one of the key factors to the turbulent combustion.(2) A spark-ignited young flame generated in the mixture wake behind a fine cylindrical rod array suffers from the intense cooling and stretching by multiple attacks of Karman vortex. The vortex-flame interaction, therefore, can not always augment flame propagation, but lead to flame extinction in the weak mixture.

本文对平面预混剪切流中的拟序结构和细圆柱阵列尾流中的卡门涡街火花点火火焰的涡-火焰相互作用过程进行了实验研究，以阐明相邻涡对涡破裂的影响。在本研究中使用的丙烷-空气混合物的当量比变化。所得结果总结如下。(1)在大尺度有组织涡流中心点火时，火焰轴向传播速度比径向传播速度快，表明涡流运动提高了火焰传播速度。在涡流内完成燃烧之后，一对火焰突出到上游侧和下游侧上的相邻边界区域，并且在流动方向上传播。剪切流中固有的卷起运动促进了传播速度。在相邻涡流之间的边界处的火花点火的情况下，火焰沿着两个混合物流之间的接触表面延伸并且变成S形。研究发现，火焰在流动方向上的速度几乎等于轴向的速度。当S形火焰的尖端到达相邻的旋涡时，旋涡的爆发又一次增强了火焰的轴向传播。结果表明，在湍流燃烧过程中存在两种涡-火焰相互作用，一种是涡的爆发，另一种是涡的助推，这两种强化机制的结合是湍流燃烧的关键因素之一。(2)细棒阵列后的火花点燃的混合物尾迹中的年轻火焰受到卡门涡的多次攻击的强烈冷却和拉伸。因此，在弱混合气中，涡与火焰的相互作用并不总是促进火焰的传播，而是导致火焰的熄灭。