纳米颗粒在火焰中聚结过程湍流稀释的数值模拟

Simulation of Dilution Effect Caused by Radial Eddy Dispersion in Process of Nanoparticle Coagulation in Flame

针对TiO2纳米颗粒合成过程,利用CFD商业软件FLUENT及其自定义函数功能,模拟了燃烧室中湍流扩散火焰的温度场和组分场;把二氧化钛作为一种准气体,在颗粒动力学模型中考虑了火焰中径向湍流引起的稀释作用对颗粒聚结的影响,对产物颗粒直径、聚集块中颗粒的数目等进行了预测,并对结果进行了分析;同时与未加径向湍流稀释项的模拟进行了比较,得出湍流的稀释作用对颗粒的生长过程有一定的影响,并分析了火焰温度、先驱物载体气体、燃料、氧化剂流量等对生成颗粒或者颗粒聚集块的尺寸的影响。

By the commercial CFD-code FLUENT＇s functions, the temperature freld and the component field of the turbulent diffusion flame in combustor were simulated in view of the composition process of TiO2 nanoparticles. The effect of dilution caused by radial eddy dispersion in the flame, the growth process of titania nanoparticle synthesized in a diffusion flame of propane and oxygen were investigated, The particle size and the particle number in the outcome were calculated, analysed and compared, The results showed that the dilution caused by radial eddy dispersion in the flame increased the size of primary particles slightly, but still much smaller than experimental results,and the influence which the flame structure have on the character of particle is analyzed. Some probable reasons were given.