平行双射流场纳米颗粒的形成与凝聚的研究

Research on the Nucleation and Coagulation of Nanoparticles in the Parallel Twin Jets

对平行双射流中H2SO4蒸气扩散进行了大涡模拟,给出了硫酸/水系统成核生成纳米颗粒及颗粒的凝聚过程中颗粒的分布特性,分析了燃料中硫的浓度、环境相对湿度以及射流Reynolds数对于颗粒浓度和粒径分布的影响.结果表明,硫酸/水系统会成核生成大量的纳米颗粒,在双管射流的中间和射流场周围,颗粒具有较高的浓度;颗粒的凝聚过程使颗粒的数量减少、直径变大;随着硫的浓度的增加,流场中的颗粒浓度有明显增加,而成核后形成的颗粒直径减小;环境湿度和Reynolds数的增大,有利于成核过程,因而导致形成更多的颗粒.

The large eddy simulation method has been used to simulate the diffusion of H2SO4 vapor in the parallel twin jets. The distributions of number concentration and size of nanoparticles produced by nucleation and coagulation in sulfuric acid/water system were given. The functions of the sulfur content, relative humidity and jet Reynolds number were evaluated according to the distributions of number concentration and size of nanoparticles. The results show that the nucleation in sulfuric acid/water system produces large number of nanoparticles, and gas-to-nanoparticle conversion mostly takes place in the middle and interface of the twin jets. The coagulation process of particles reduces the number concentration but increases the mean particle size. For the case with higher sulfur content, more number and smaller size nanoparticles are produced by nucleation and coagulation. There is also a larger number of nanoparticles for the cases with higher relative humidity and jet Reynolds number.