利用平面激光诱导荧光技术及CH滤镜测量微喷管射流火焰OH及CH基元

Measurement of OH and CH radicals in micro-jet flames using planar laser induced fluorescence and CH filter

微射流火焰形貌观测及火焰中重要基元的准确测量,对利用微尺度火焰燃烧特性研制开发微型燃烧动力系统具有重要意义。本文建立了微喷管射流火焰实验及光学测量系统,对H_2和CH_4微射流火焰进行了实验研究,测量了两种重要基元(CH,OH)的空间分布。首先,探索了相机曝光时间对H_2微射流火焰成像的影响,得到了不同流速下H_2微射流火焰形貌的变化规律。其次,采用平面激光诱导荧光测量技术得到了不同燃料流速下H_2及CH_4微射流火焰中OH基元分布,同时还利用单反相机加CH滤镜通过长时间曝光(30s)的方法获得了CH_4微射流火焰中CH基元的分布。结果表明,火焰图像清晰度随曝光时间增加提高,曝光时间30s时可获得H_2微射流火焰的清晰照片;采用分辨率2 048×2 048的ICCD相机可获得微尺度火焰OH基元分布的清晰图像。微射流火焰形貌及重要基元的实验结果表明相关数值计算方法准确可靠。

The observation of micro-jet flame shape and measurements of important radicals in micro- jet flame are of great significance to the research and development of micro energy and power system based on combustion characteristics of micro-jet flames. In this work, an optical measurement system of mcro-jet flames was established experimentally to study micro-jet flames using H2 and CH4 as fuels and to measure the spatial distribution of two important radicals, CH and OH. Firstly, the effect of exposure time of camera on images of the H2 micro-jet flames was explored, obtaining the variation of micro-jet flame shape under different flow velocities. Then, the Laser Induced Predissociative Fluorescence （OH-PLIF） technique was applied to obtain the distribution of OH radical in H2 and CH4 micro-jet flames under different fuel flow velocities, meanwhile, a Digital Single Lens Reflector （DSLR） plus a CH filter with a long time exposure （30 s） was employed to obtain the distribution of CH radical in CH4 micro-jet flame. The results showed that, the clarity of flame image is promoted as the exposure time increased and a clear image of H2 micro-jet flame is acquired when exposure time is 30 s; a clear image of distribution of OH radical in micro-scale flames is captured via an ICCD camera with a resolution of 2 048 × 2 048. The experimental results indicate that the numerical computation of micro- jet flame shape and important radicals is accurate and reliable.