甲烷-空气低旋流火焰中自由基的辐射特性

Radiation Characteristics of Radicals in Low Swirl Methane-Air Flames

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。

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 0.33 m/s to0.83 m/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.