甲烷/氧气层流反扩散火焰形态及滞后特性研究

Mode and hysteresis of laminar methane/oxygen inverse diffusion flame

对空气气氛中甲烷/氧气反扩散火焰的形态和推举滞后特性进行了实验研究.实验中通过改变气体流量考察了气速变化对火焰形态演变及滞后特性的影响,并利用紫外相机系统研究了气速对不同形态火焰中OH*分布的影响.研究结果表明:甲烷气速、氧气气速和火焰的历史状态是决定火焰形态的三个重要参数,并以此对实验范围内的火焰形态进行了分区;氧气气速对不同形态反扩散火焰轴线上的OH*分布有相似的影响,当氧气缺乏时,反扩散反应区较短,当氧气富余时,反扩散反应区在轴向分布较广;同轴甲烷的气速对反扩散火焰的滞后特性影响显著,随着甲烷气速的增加,反扩散火焰的推举速度和再附着速度呈线性减小,部分预混火焰向反扩散火焰转变的速度呈线性增加.

Flame modes and liftoff hysteresis of the methane/oxygen inverse diffusion flame （IDF） are experimentally studied in still air. The effects of gas velocity on flame mode and liftoff hysteresis are investigated by changing the gas flow rate, and the influences of gas velocity on OH＊ distribution in different modes of flame are investigated using an ultraviolet camera. The results show that methane velocity, oxygen velocity and history of the flame mode are the key factors in determining the flame mode. Flame mode regimes are identified according to the three factors. The OH＊ profile along the axis of the nozzle in the IDF indicates that the reaction zone is narrow in fuel rich condition and broad in fuel lean condition. The hysteresis characteristics of the IDF are significantly influenced by the coaxial methane velocity. With the increase of coaxial methane velocity, the liftoff velocity and attachment velocity of the IDF decrease linearly, while the transition velocity increases linearly from partly premixed flame to IDF.