燃烧温度对柴油固体颗粒物形貌及氧化特性影响的试验研究

依据柴油机缸内的燃烧环境状态,采用TF-1200X管式炉,采集了柴油在不同温度条件下燃烧产生的颗粒物.应用扫描电镜SEM、X射线衍射仪和热重分析仪,对不同燃烧温度下颗粒的平均粒径、计盒维数、元素质量分数、颗粒表面氧化活性等变化规律进行了研究.结果表明:燃烧温度介于523～623 K之间时,柴油燃烧形成的固体颗粒物主要由颗粒状焦组成,呈片状和珠串状,颗粒中的C元素质量分数随燃烧温度的增加而增加,颗粒着火温度、活化能随燃烧温度的增加而降低;燃烧温度大于723 K时,颗粒呈球状和团簇状,平均粒径随温度的增加而减小,颗粒的C元素质量分数、计盒维数及活化能随燃烧温度的增加而增加,颗粒着火温度随燃烧温度的增加呈上升趋势;柴油在523～923 K之间燃烧形成的颗粒物,随着热重氛围气中氧体积分数的增加,颗粒氧化放热速率增加,活化能变化不大.

Experimental study on effects of combustion temperature on morphology and oxidation characteristics of diesel particles

According to the state of combustion environment in the diesel engine, The particulate matter(PM)from the processes of diesel combustion at different temperatures was collected by TF-1200x tubular furnace. The particle size, box dimension, element mass fraction and surface oxidation activity of the PM were measured by SEM, X-Ray diffractometer and thermogravimetric equipment. The results show that the PM is mainly composed of amorphous carbon and it is in the state of flake and bead, when the combustion temperature is in the range of 523 K and 623 K. With an increase of temperature, the mass fraction of element C in the PM increases, while the ignition temperature and activation energy of the PM decrease. When the combustion temperature is greater than 723 K, the outside shape of the PM is shown in the spherical and clustered, and the average particle size decreases with the increasing of temperature. The mass fraction of element C, counting box dimension and activation energy of the PM increase with the increasing of temperature, and the ignition temperature of the PM rises as temperature increases. The oxidation heat release rate of the PM formed in the range of temperature of 523 K and 923 K increases along with the increasing of the oxygen volume fraction in the thermogravimetric atmosphere gas, while the activation energy of the PM is changed little.