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Studies of the Micro-Structure of Turbulent Flame in Premixed Mixtures

预混混合物湍流火焰微观结构的研究

基本信息

批准号：
61550165
负责人：
KIDO Hiroyuki
金额：
$ 1.41万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

Studies of the Micro-Structure of Turbulent Flame in Premixed MixturesThe micro-structure of turbulent flame has got a large attention in connection with the combustion rate and the flame propagation limit in internal combustion engines. It is important also to control the combustion in internal combustion engines and to make its simulation model by making clear the turbulent flame structure.To gain insight into the micro-structure of turbulent flame, an analysis of the schlieren-images of propagating flame has been made by a turbulent combustion regime model. The regime has been classified into three stages. They are the wrinkled laminar flame stage where the turbulence intensity is weak, the distributed-islands flame stage where the turbulence intensity is strong enough to make many distributed islands of unburned gas surrounded by a flame sheet and the transition stage.Combustion experiments were made in a constant volume bomb, where the characteristics of the mixture ( laminar flam … More e thickness, laminar burning velocity and oxygen concentration) and the turbulence intensity were varied independently with each other. The obtained schlieren-images showed that the wrinkling of the flame front increased and the scale of the smooth area decreased as the turbulence intensity increased.The increased wrinkling has been explained by a superimposition of the schlieren-images of turbulent flamelets existing along the combustion zone thickness. In the analytical discussion, the turbulent combustion zone has been considered to be mixed with the wrinkled laminar flame zone and the distributed-islands flame zone, where each reaction rate has been determined by a Damkohler number and each characteristic reaction time. The Damkohler number is the ratio of the characteristic time of turbulent mixing to that of chemical reaction. This combustion regime model has been shown to be able to explain the turbulent flame structure ranging from the wrinkled laminar flame stage to highly distributed flame stage, depending on both the Damkohler and the turbulent Reynolds numbers. Less

预混料中湍流火焰的微观结构研究湍流火焰的微观结构与内燃机的燃烧速率和火焰传播极限有关，受到了广泛的关注。弄清紊流火焰结构对控制内燃机燃烧和建立内燃机燃烧仿真模型也具有重要意义。为了深入了解湍流火焰的微观结构，利用湍流燃烧状态模型对火焰传播的纹影图像进行了分析。该制度被分为三个阶段。它们分别是湍流强度较弱的褶皱层流火焰阶段、湍流强度足以使许多未燃烧气体的分布岛屿被火焰片包围的分布岛屿火焰阶段和过渡阶段。在定容弹中进行了燃烧实验，在定容弹中，混合气的层流火焰、层流燃烧速度和氧浓度等特性与湍流强度相互独立变化。得到的纹影图像表明，随着湍流强度的增加，火焰锋面起皱增大，光滑区域的规模减小。褶皱的增加可以用沿燃烧区厚度存在的湍流小火焰纹影图像的叠加来解释。在分析讨论中，湍流燃烧区被认为是与褶皱层流火焰区和分布岛状火焰区混合在一起的，其中每种反应速率由Damkohler数和每种特征反应时间确定。Damkohler数是湍流混合的特征时间与化学反应的特征时间之比。根据Damkohler和湍流雷诺数，该燃烧状态模型能够解释从褶皱层流火焰阶段到高度分布火焰阶段的湍流火焰结构。少