乙烯预混火焰中碳烟微观形貌、纳观结构及氧化特性研究

发布时间：2018-02-02 05:19

  本文关键词： 碳烟颗粒 乙烯/氧气/氩气预混火焰 燃空当量比 火焰高度 纳观结构 氧化特性　出处：《天津大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来,化石燃料排放的碳烟颗粒对大气环境和人体健康造成了严重的危害,导致政府和公众对燃烧源颗粒物的关注程度不断提高。燃烧过程中碳烟颗粒的生成机理及演化历程已成为国内外的研究热点。本文基于乙烯/氧气/氩气预混燃烧系统,采用了热泳探针取样和毛细管取样系统,并结合场发射透射电子显微镜(TEM)、拉曼光谱仪(RS)、热重分析仪(TGA)等多种先进的分析技术,系统而深入地研究了燃烧工况对碳烟颗粒微观形貌、纳观结构、石墨化程度等物理特性及氧化活性的影响规律。主要研究内容和结论如下:微观形貌研究发现,碳烟颗粒的演化历程包括:初期的成核,中期的表面生长,凝并和团聚,末期的氧化。随着火焰高度的增加,碳烟颗粒从初生态碳烟逐渐演化为成熟的团聚态碳烟。团聚态碳烟的分型维数介于1.36~2.03之间,且随着火焰高度和燃空当量比的增加而逐渐增大;基本碳粒子的平均粒径介于14.706~21.397nm之间,随燃空当量比和火焰高度的增大,基本碳粒子平均粒径逐渐增大。基本碳粒子粒径分布范围大致介于8~29nm之间,呈单峰分布,峰值集中在14~25nm的范围内;粒径峰值分布随着燃空当量比和火焰高度的增大也逐渐增加。预混火焰所生成碳烟颗粒基本碳粒子的平均微晶尺寸、微晶曲率和层间距分别介于0.741~1.250nm、1.385~1.491和0.348~0.390nm之间;随着燃空当量比和火焰高度的增加,微晶尺寸逐渐增大,微晶曲率和层间距逐渐变小。预混火焰碳烟颗粒的AD1/AG介于1.82-2.76之间,D2和D4峰面积比重分别介于14.78%~20.62%与3.76%~7.51%之间。随燃空当量比和火焰高度的增加,AD1/AG逐渐增加,而D2和D4峰面积比重逐渐降低。表明,随燃空当量比和火焰高度的增加,碳烟颗粒的石墨化程度不断增加,无序化程度逐渐降低。碳烟颗粒样品的起始氧化温度(Ti)、最大燃烧速率温度(Tmax)和燃尽温度(Th)分别介于480.43~552.75℃、566.57~656.33℃和632.37~725.83℃之间,表观活化能在136.71~165.69KJ·mol~(-1)之间变化。随燃空当量比和火焰高度的增加,以上四个氧化特征参数均呈逐渐增大的趋势,表明碳烟颗粒的氧化活性降低。本文的研究结果对碳烟颗粒生成机理、演化过程的认知以及柴油机微粒的控制有着一定的理论参考价值。
[Abstract]:In recent years, soot particles emitted from fossil fuels have caused serious harm to atmospheric environment and human health. As a result, the government and the public pay more and more attention to the particulate matter of combustion source. The mechanism and evolution of soot particles in the combustion process have become a hot topic at home and abroad. This paper based on ethylene / oxygen / argon premixed combustion. Burning system. The thermal probe sampling system and capillary sampling system were used, and various advanced analytical techniques, such as field emission transmission electron microscope (TEM), Raman spectrometer (RS) and thermogravimetric analyzer (TGA), were used. The effects of combustion conditions on the morphology, nano structure, graphitization degree and oxidation activity of soot particles were studied systematically and deeply. The main contents and conclusions were as follows: the microscopic morphology was found. The evolution process of soot particles includes initial nucleation, surface growth, condensation and agglomeration, and final oxidation with the increase of flame height. Soot particles gradually evolved from ecological soot to mature agglomerated soot. The parting dimension of agglomerated soot was between 1.36 and 2.03, and increased with the increase of flame height and ratio of combustion-to-air ratio. The average particle size of the basic carbon particles is between 14.706 and 21.397nm, which increases with the increase of the ratio of combustion to air volume and the flame height. The average particle size of the basic carbon particle increases gradually. The distribution range of the basic carbon particle size is about 829 nm, with a single peak distribution, the peak value being in the range of 14 ~ 25 nm. The peak particle size distribution increases with the increase of the ratio of combustion to air ratio and the flame height. The average microcrystalline size of the basic carbon particles produced by the premixed flame is also increased. The curvature and interlayer spacing of the microcrystals are between 0.741Nm 1.250nm 1.385Nm 1.491 and 0.348Nm 0.390 nm, respectively. With the increase of the ratio of fuel to air and the flame height, the size of microcrystal increases, the curvature of microcrystal and the interlayer spacing become smaller. The AD1/AG of the pre-mixed flame soot particles is between 1.82-2.76. The peak area ratios of D2 and D4 were between 14.78% and 3.76%, respectively, and AD1 / AG gradually increased with the increase of the ratio of fuel to air volume and the height of flame. However, the peak area specific gravity of D2 and D4 decreases gradually, which indicates that the graphitization degree of soot particles increases with the increase of the ratio of combustion / air ratio and flame height. The initial oxidation temperature (Tmax) and the maximum combustion rate (Tmax) of soot particle samples are between 480.43 and 552.75 鈩，

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