Formation of nanoparticles in flames; measurement by particle mass spectrometry and numerical simulation
Formation of nanoparticles in flames; measurement by particle mass spectrometry and numerical simulation
复制标题
火焰中纳米颗粒的形成；
作者：
H. Paur;W. Baumann;H. Mätzing;H. Seifert
火焰中的纳米粒子的尺寸分布测量使用一种新型的粒子质谱仪（PMS），这是为0.3和50 nm之间的尺寸范围和109和1013之间的数量浓度。使用这种仪器，粒子采样没有事先稀释从火焰到分子束。然后，带电的纳米颗粒被电场偏转，以根据飞行时间原理确定质量。PMS安装在30 mbar下运行的低压燃烧室中。本文对乙炔/氧气层流预混火焰中的一次碳烟颗粒和氧化铁颗粒进行了测量。烟灰颗粒的尺寸随着燃烧器上方的高度和C/O比从2增加到10 nm而增加。3-5 nm的氧化铁颗粒被检测为燃烧器高度的函数。烟灰颗粒比氧化铁颗粒形成得更快。根据以前发表的反应机理，建立了氢/氧火焰中二氧化硅和氧化铁形成的模型计算。在加入单分散颗粒凝聚方案的基础上，计算了颗粒数浓度和颗粒尺寸的时间历程。与实验数据一致，计算表明，氧化铁颗粒的形成速度比二氧化硅颗粒慢。
The size distributions of nanoparticles in flames are measured using a novel particle mass spectrometer (PMS), which is developed for the size range between 0.3 and 50 nm and for number concentrations between 109 and 1013. Using this instrument the particles are sampled without prior dilution from the flame into a molecular beam. The charged nanoparticles are then deflected by an electric field, to determine the mass according to the time-of-flight principle. The PMS is installed in a low pressure combustion chamber operated at 30 mbar. Measurements are made on primary soot particles and iron oxide particles in a laminar, premixed acetylene/oxygen flame. The soot particles increase in size as a function of the height above the burner and the C/O ratio from 2 up to 10 nm. Iron oxide particles of 3–5 nm are detected as a function of burner height. The soot particles form more rapidly than the iron oxide particles. A model calculation for the formation of silica and iron oxide in hydrogen/oxygen flames is developed, based on previously published reaction mechanisms. On adding a mono-disperse particle coagulation scheme, the time history of the particle number concentration and the particle size is calculated. In agreement with experimental data, the calculations show that iron oxide particles are formed more slowly than silica particles.