O_(2)对乙烯扩散火焰在轴线上碳烟生成的影响

Effect of O_(2)on soot formation in ethylene diffusion flame on axis

为探究乙烯扩散火焰在轴线上的碳烟生成特性,在一台层流同轴扩散火焰装置上,将氧气浓度(体积分数)控制为21%,24%,26%,28%和31%,使用碳烟颗粒采样装置对乙烯扩散火焰中不同轴向位置的碳烟进行采样.利用高分辨率透射电子显微镜对不同氧气浓度的碳烟颗粒样本进行观察和分析,结果表明:在相同的氧气浓度下,随火焰高度的增加,火焰轴线位置处的基本碳粒子平均粒径呈现先增大后减小的趋势,分形维数增加,团聚体从条状和链状向团状和簇状发展;在同一火焰高度,随着氧气浓度增大,基本碳粒子平均粒径减小,团聚体的分形维数变大,生成更多致密的网状团聚体,微晶的平均碳层间距和扭曲度都有所增加,碳层从平行排列变成弯曲排列.

In order to explore the soot generation characteristics of ethylene diffusion flame on the axis,the oxygen concentration was controlled to 21%,24%,26%,28%and 31%on a laminar coaxial diffusion flame device.The soot particle sampling device was used to sample the soot at different axial positions in the ethylene diffusion flame.The samples of soot particles with different oxygen concentrations were observed and analyzed by high-resolution transmission electron microscope.The results show that under the same oxygen concentration,with the increase of flame height,the average particle size of primary carbon particles at the flame axis first increases and then decreases,the fractal dimension increases,and the morphology of soot aggregates develop from strip and chain to cluster.At the same flame height,with the increase of oxygen concentration,the average particle size of primary carbon particles decreases,the fractal dimension of aggregates increases,and more dense network aggregates are formed.The average carbon layer spacing and carbon layer torsion resistance increased,and the carbon layers changed from parallel arrangement to curved arrangement.