【作者】 李娜；

【导师】 宋崇林；

【作者基本信息】 天津大学 ， 动力机械及工程， 2018， 硕士

【摘要】 目前随着各国汽车保有量的不断增多及化石燃料燃烧,颗粒物排放问题已经引起了全世界人民的重视,近年来国内外学者对于碳烟颗粒的研究已经取得了重大进步。对于柴油机来说,含碳质颗粒物的气固两相燃烧是常见的燃烧现象,但目前针对气固两相燃烧对碳烟颗粒影响的研究仍未见报道。另外柴油机燃烧工况复杂不利于研究单一变量对碳烟颗粒的影响,因此本文建立了实验室正庚烷反置扩散燃烧系统及毛细管取样系统,结合拉曼光谱仪、红外光谱仪和热重分析仪研究了在碳烟颗粒的生长过程中其有序化程度、表面官能团和氧化活性的演变规律,并采用气溶胶发生器,将碳质颗粒物均匀的离散到火焰中,作为对柴油机气固两相燃烧的近似简化,研究了添加碳质颗粒物对碳烟颗粒的上述理化特性的影响。主要研究结果如下:拉曼光谱中A_D1/A_G的值随火焰高度的增大而增大,说明随着火焰高度增大,碳烟颗粒的微观结构更有序。相同火焰高度下添加碳质颗粒物的正庚烷扩散火焰中碳烟颗粒A_D1/A_G的值比纯正庚烷扩散火焰中的值略大,说明添加碳质颗粒物使火焰中碳烟颗粒微观结构更有序。随着火焰高度增大,二阶拉曼峰变窄,即碳烟颗粒的微观结构变得更有序,与一阶拉曼光谱得到的结果一致。脂肪族碳氢表面官能团和芳香族碳氢表面官能团的相对含量A_C-H/A_C=C均随火焰高度的增大而减少,羰基表面官能团的相对含量A_C=O/A_C=C也随火焰高度的增大而减少。相同火焰高度下添加碳质颗粒物的正庚烷扩散火焰中碳烟颗粒的羰基表面官能团的相对含量比纯正庚烷扩散火焰中的更小。随着火焰高度的增大,对应的热重曲线有向右移动的趋势,说明随火焰高度增大,碳烟颗粒更难于发生氧化反应。起始氧化温度T_i、最大氧化速率温度T_max、燃尽温度T_h、表观活化能的值E_a基本随火焰高度的增大而增大。相同的火焰高度,添加碳质颗粒物的正庚烷扩散火焰中碳烟颗粒的氧化特征温度和表观活化能偏大,说明添加碳质颗粒物使火焰中碳烟颗粒的氧化活性变差。更多还原

【Abstract】 As the continuous increase of the car ownership and the combustion of fossil fuel,the particle emission has drawn great attention in the world,so it is imperative to research on the particles.In recent years,the scholars at home and abroad have made significant progress in the research on the particles.For diesel engines,gas-solid combustion is very common,however,there is still no research involving the influence of gas-solid combustion on the particles.Additionally,the combustion process is so complex for diesel engines that it is tough to determine the influence of a single variable on the soot particles.Therefore,an n-heptane inverse diffusion flame was established combined with capillary sampling system.The evolution of order degree,surface functional groups and oxidation reactivity of soot particles was studied by characterizations including Raman spectrometer(RS),Fourier transform infrared spectrometer(FT-IR)and thermo gravimetric analyzer(TGA).And an aerosol generator RBG-1000 was employed to scatter the carbon into the flame to approximate and simplify the gas-solid combustion of diesel engines.The effect of carbon addition on the above-mentioned physicochemical properties of soot particles was studied.The major work and results of this dissertation are listed as follows:The values of AD1/AG increase along the flame,indicating the microstructure of soot particles becomes more ordered as the heights above the burner(HAB)increase.The values of AD1/AG of soot particles from the carbon-addition n-heptane diffusion flame are somewhat bigger than that of soot particles from the n-heptane diffusion flame,reflecting the carbon addition contributes to the more ordered soot particles.From the second-order Raman spectroscopy,it can be seen that the peaks become narrower as the HAB increases,that is to say,the microstructure of soot particles become more ordered,which is consistent with the first-order Raman spectroscopy.The relative contents of aliphatic C–H groups and aromatic C-H functional groups which were indicated by the normalized peak area ratio(AC-H/AC=C)decrease with the increase of HAB.The relative contents of carbonyl groups AC=O/AC=C also decrease with the rise of HAB.Furthermore,the relative contents of carbonyl groups AC=O/AC=C of soot particles from the carbon-addition n-heptane diffusion flame look smaller.The oxidation reactivity of soot particles in different conditions was studied by TGA.The results show that the corresponding thermo gravimetric curves move right as the increase of HAB,indicating that it is difficult for soot particles from the bigger HAB to oxidize.The values of onset temperature(Ti),maximum rate temperature(Tmax),burnout temperature(Th)and apparent activation energies(Ea)show the trend of rise as the increase of HAB.Additionally,the oxidation reactivity characteristic temperature and apparent activation energies of soot particles from the carbon-addition n-heptane diffusion flame are larger,showing that the carbon addition could contribute to the decrease of oxidation reactivity of soot particles.更多还原