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In-situ Spectroscopic Measurement of Turbulent Flame-Front Structure

湍流火焰锋结构的原位光谱测量

基本信息

批准号：
09650241
负责人：
IKEDA Yuji
金额：
$ 2.05万
依托单位：
KOBE UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650241/
关键词：
Turbulent flame Local chemiluminescence measurement In-situ sensor Cassegrain optics High temporal and spatial resolution Flame-front Local flame Spectra OH^*, CH^* and C2^* radicals 局所OH・CH・C_2ラジカルしわ状層流火炎反応帯厚さ

项目摘要

Local chemiluminescence measurements of OH*, CH* and C2* radicals were carried out in turbulent premixed methane flame to make clear the details of flame-front structures and chemical reactions in the reaction zone. For this measurement, specially designed Cassegrain Optics, which has a high spatial resolution as small as an LDV measurement volume, was developed. Furthermore, to achieve a high temporal resolution, each chemiluminescence was detected by PM tube at sampling rate of 250kHz.Simultaneous measurements of these three radicals and velocity by LDV were performed to obtain flame-front structure, flame propagating speed and flame thickness. Local Damkoler number were measured directly at the flame-front and their fine scale were demonstrated.The probability density function (PDF) of OH* emission showed bi-modal peaks across the flame-front location corresponding to wrinkled laminar flame or flamelet region. The first peak of the OH* PDF was corresponding to the high temperature region outside of the flame cone and the secondary peak was associated with chemical reaction at the primary reaction zone. Time series signals of local OH*, CH* and C2* emission intensities in wrinkled laminar flame region showed irregular peaks which, however, correspond to each other in the three chemiluminescence signals. This results indicated strong linkage between OH-C H-C2 reactions at wrinkled laminar flame-front. The flame-front thickness measured by CH and C2 emissions were 0.1-0.3mm, while that was about 1.0mm by OH* emissions. Furthermore, local reaction rate and local mixture strength at turbulent flame-front are examined from local CH* and C2* emission intensities in comparison with measured data bases of these emissions in laminar premixed flame.A new optical diagnostics to examine local flame-front structure and flame chemistry by means of local chemiluminescence measurement was proposed and its performance was proven.

在湍流预混甲烷火焰中进行了OH ~*、CH ~* 和C2 ~* 自由基的局部化学发光测量，以了解火焰前缘结构和反应区化学反应的细节。为了进行这种测量，专门设计的卡塞格伦光学器件被开发出来，它具有与LDV测量体积一样小的高空间分辨率。为了获得高的时间分辨率，采用PM管以250 kHz的采样率对每种化学发光进行检测，同时采用LDV对这3种自由基和火焰传播速度进行测量，得到火焰前缘结构、火焰传播速度和火焰厚度。在火焰前缘直接测量了局部Damklynn数，并给出了其精细尺度，OH* 发射的概率密度函数（PDF）在火焰前缘出现双峰，对应于褶皱层流火焰或小火焰区域。OH* PDF的第一个峰对应于火焰锥外的高温区，第二个峰与主反应区的化学反应有关。在褶皱层流火焰区，局部OH*、CH* 和C2* 发射强度的时间序列信号显示出不规则的峰，但这三个峰在三个化学发光信号中是相互对应的。这一结果表明，在褶皱层流火焰前锋的OH-C H-C2反应之间有很强的联系。CH和C2测量的火焰面厚度为0.1-0.3mm，OH* 测量的火焰面厚度约为1.0mm。通过与层流预混火焰中CH* 和C2* 的测量数据对比，研究了湍流火焰前缘的局部反应速率和局部混合物强度，提出了一种利用局部化学发光检测火焰前缘局部结构和火焰化学的光学诊断方法，并验证了该方法的有效性。