CAJ | 학술논문

为进一步降低柴油机的颗粒排放。针对柴油机的排气颗粒，采用热重分析和同步辐射X射线小角散射的方法，分析了颗粒在氧化过程中的内部特征、孔隙结构参数以及孔隙数量和尺寸分布等随氧化温度的变化规律。结果表明，随着氧化温度的升高，颗粒中电子密度差逐渐增大，颗粒之间的统计平均距离增大，颗粒尺寸逐渐减小；颗粒孔隙分布分维数、截面平均孔径、回转半径以及轴向长度均有明显增加；颗粒孔隙的结构紧密程度下降，随着氧化温度升高，小尺寸孔隙数量逐渐减少，大尺寸孔隙逐渐增加，100℃时的颗粒孔隙尺寸主要分布在6～7 nm，200℃是的颗粒孔隙尺寸主要分布在8～9 nm，400℃的颗粒孔隙尺寸主要分布在12～13 nm，总体上孔隙的尺寸和数量呈上升趋势。利用同步辐射X射线小角散射的方法，掌握颗粒氧化过程中孔隙结构的变化规律，对于丰富颗粒的测量方法提供了借鉴，为完善颗粒的氧化机理提供了相关基础数据。
위진일보강저시유궤적과립배방。침대시유궤적배기과립，채용열중분석화동보복사X사선소각산사적방법，분석료과립재양화과정중적내부특정、공극결구삼수이급공극수량화척촌분포등수양화온도적변화규률。결과표명，수착양화온도적승고，과립중전자밀도차축점증대，과립지간적통계평균거리증대，과립척촌축점감소；과립공극분포분유수、절면평균공경、회전반경이급축향장도균유명현증가；과립공극적결구긴밀정도하강，수착양화온도승고，소척촌공극수량축점감소，대척촌공극축점증가，100℃시적과립공극척촌주요분포재6～7 nm，200℃시적과립공극척촌주요분포재8～9 nm，400℃적과립공극척촌주요분포재12～13 nm，총체상공극적척촌화수량정상승추세。이용동보복사X사선소각산사적방법，장악과립양화과정중공극결구적변화규률，대우봉부과립적측량방법제공료차감，위완선과립적양화궤리제공료상관기출수거。
Particles which contain soluble organic fraction (SOF), soot, and inorganic salt are mainly the result from an incomplete combustion or pyrolysis of fossil fuels and other organic materials. In a diesel engine, the poor mixing of fuel and air creates fuel-rich zones that support particle formation at high temperatures. Numerous studies show that they are harmful to human health when inhaled and may cause cancer. For that reason, it is important to reduce the formation or at least the emission of particles to the environment. Meanwhile, the strict regulations for particulate matter emission have been enforced in many developed countries. A diesel particulate filter (DPF) is currently the dominant diesel particulate emissions control technology to meet stringent air quality standards, however, the oxidation ability of particles is important to the regeneration of the filter bed in DPF. Temperature has a great influence on the oxidation process of particles. Many physical and chemical changes of particles happen at a high temperature, leading to porosity formation of particles during oxidation. The porosity structure of particles is important to the oxidation ability of particles. The micro-orifice uniform deposition impactor (MOUDI) is a favorable apparatus for obtaining the particle size distribution and collecting the particles in different size ranges after classification. Thermogravimetric analysis (TGA) has been widely used as an analytical method for investigating the relationship between the material weight and temperature under the condition of programming a temperature rise. The curve of the sample weight then can be obtained with the temperature. A derivative thermal gravimetry (DTG) curve, the first order differential to a TG curve, can reveal the features of mass variation with the temperature. Small-angle X-ray scattering (SAXS) is a widely used diffraction method for studying the structure of the sample. In this study, the micro-orifice uniform deposit impactor was used to collect particle samples;the thermal gravimetric analysis was used to investigate the ignition of particles as a basis for determining the oxidation temperature; and the change rules of porosity structure parameters, porosity quantities, and size distribution of particles in the oxidation process were investigated by synchrotron (SAXS). The results of the thermogravimetric analysis showed that the ignition temperature of diesel particles was 487℃, and the oxidation temperature range should be set up under 400℃for study on the porosity structure of particles during oxidation. The results of small-angle X-ray scattering showed that the electron density difference of combustion particles increased, and the size of particles reduced the fractal dimension, average radius, gyration radius, and axial length all significantly increased as the oxidation temperature increased. The tightness of the porosity structure decreased, and the number and size of porosity all increased with increasing oxidation temperature. The porosity size of particles at 100℃was mainly distributed in a range of 6-7 nm. The porosity size of particles at 200℃was mainly distributed in a range of 8-9nm. The porosity size of particles at 400℃was mainly distributed in a range of 12-13 nm.The study provided valuable information on mechanisms of particle oxidation.