权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Study on the improvement mechanism of the premixed turbulent combustion by preferential diffusion effect

优先扩散效应改善预混湍流燃烧机理研究

基本信息

批准号：
11450087
负责人：
KIDO Hiroyuki
金额：
$ 7.23万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

This study has been carried out the verification and determination qualitatively of the preferential diffusion effect, which becomes important particularly for the lean mixtures, on the premixed turbulent combustion. And, an attempt has been made to be proposed a new technique to improve the premixed turbulent combustion by application of the molecular preferential diffusion effect. In order to examine it, fuel/oxygen/inert-gas mixtures with nearly identical laminar burning velocities were used. The main conclusions are as follows.From the instantaneous tomograms of turbulent flame, the turbulent flame areas at the same turbulence intensity are nearly equal, depending slightly on the kind of fuel and inert gas. This indicates that the local burning velocity is an important factor as governing the turbulent burning velocity.From the continuous tomograms, the local flame displacement velocities of propagating turbulent flame S_F as local burning velocity are not a constant equal to the laminar burning velocity and distributed over a wide range. This fact seems to contradict the concept of the conventional models. And, S_F of hydrogen mixture tends to distribute more extended than one of hydrocarbon mixtures.For leaner methane and hydrogen mixtures and richer propane mixtures, S_F on the convex part toward the unburned mixture tends to be larger than that toward the burned gas. This phenomenon can be explained qualitatively by the concept of the preferential diffusion. This indicates that the quantitative value of preferential diffusion effect can be determined by using S_F.Judging from the results, a new technique to improve the turbulent combustion can be proposed : The turbulent combustion characteristics of fuel/oxygen/inert-gas mixtures can be improved by using the smaller molecule with higher diffusion coefficient than oxygen as fuel and the heavier molecule with lower diffusion coefficient than oxygen as inert gas.

本研究定性地验证和确定了对于稀薄混合气尤为重要的优先扩散效应对预混湍流燃烧的影响。并且，已经尝试提出了一种新的技术，以改善预混湍流燃烧的分子的优先扩散效应的应用。为了检验它，使用了具有几乎相同的层流燃烧速度的燃料/氧气/惰性气体混合物。主要结论如下：从湍流火焰的瞬时层析图像来看，在相同湍流强度下，湍流火焰的面积几乎相等，对燃料和惰性气体的种类影响不大。这表明局部燃烧速度是控制湍流燃烧速度的重要因素，从连续的层析图像上可以看出，湍流传播火焰的局部火焰位移速度S_F作为局部燃烧速度，并不是一个与层流燃烧速度相等的常数，而是分布在很宽的范围内。这一事实似乎与传统模型的概念相矛盾。对于贫甲烷和贫氢气混合物以及富丙烷混合物，凸部处朝向未燃混合物的S_F大于朝向已燃气体的S_F。这种现象可以用择优扩散的概念来定性地解释。这表明，利用S_F可以定量地确定优先扩散效应的大小，并据此提出了改善湍流燃烧的新技术：研究了燃料/氧气/惰性气体的湍流燃烧特性，通过使用扩散系数比氧气高的较小分子作为燃料和扩散系数比氧气低的较重分子作为惰性气体，可以改善气体混合物。