甲烷-空气低旋流火焰中自由基的辐射特性

Radiation Characteristics of Radicals in LowSwirl Methane-Air Flames

关键词:  化学发光  低旋流火焰  自由基  火焰结构  燃烧诊断

Key words:  Chemiluminescence  Low swirl flame  Excited-state radicals  Flame structure  Combustion diagnosis

摘要:

为了研究低旋流火焰中CH*和OH*自由基的辐射特性，设计了开放式低旋流火焰燃烧器，对旋流数为0.45~0.60，甲烷流速为0.33m/s~0.83m/s的甲烷-空气低旋流火焰进行了实验研究。利用ICCD相机和相应滤光片获取了CH*和OH*的化学发光图像，对CH*中的背景光干扰进行了消除，并研究了旋流数和气流速度对两种自由基辐射发光的影响。结果表明，CH*和OH*都主要分布在火焰锋面上，OH*更能表征化学反应的存在；旋流数对燃烧的反应程度、反应位置以及火焰的结构有明显影响，OH*的轴向峰值和旋流数的线性相关系数为0.975，要强于CH*；随气流速度增大，CH*的发光强度减小，而OH*的发光强度明显增大。

Abstract:

An open low swirl burner was designed to investigate the radiation characteristics of CH* and OH* in low swirl flames, varying the swirl number from 0.45 to 0.60, and flow velocity of CH₄ from 0.33m/s to 0.83m/s. Spatial distribution images of CH* and OH* chemiluminescence were obtained via ICCD camera coupled with narrow-band-pass filters, and a processing method was introduced to subtract contributions from background emissions in CH* chemiluminescence. The effects of swirl number and flow velocity on the radiation of the two radicals were analyzed. Results show that both CH* and OH* are mainly distributed on the flame front, and OH* is more effective in marking the reaction region in combustion. Swirl number has an obvious influence on the reaction degree, reaction region and flame structure, and the linear correlation coefficient of OH* axial peak value and swirl number is 0.975, which is stronger than that of CH*. With the increase of flow velocity, the luminescent intensity of CH* decreases and that of OH* increases.