基于多重蒙特卡洛方法的二次气溶胶颗粒核化过程的数值研究

A Numerical Study on the Nucleation Process of Secondary Aerosol Particle by Multi-Monte Carlo Method

气粒转化中均质成核是产生二次气溶胶颗粒物的重要途径,即由过饱和体系中分子团吸附气体分子而使得自身尺度超过临界成核尺度形成二次气溶胶颗粒物。基于此,文中在颗粒稀疏和分子混沌假设的基础上,对雾霾环境H_2SO_4-NH_3-H_2O均质异分子气粒转化的过程建立成核和生长的热力学和动力学模型。基于颗粒群平衡模拟,利用多重蒙特卡罗算法开展三元均质核化的研究。数值讨论环境温度、湿度对颗粒成核速率、临界胚胎尺度的影响,分析环境中不同气态硫酸浓度下成核颗粒物数目和粒径的演化过程。计算结果表明:环境温度低、湿度高,H_2SO_4-NH_3-H_2O三元成核速率较大,并且核化生成的颗粒粒径主要处于1nm-3nm范围内。

For the homogeneous nucleation, the conversion from gas to particle is an important way to pro- duce secondary aerosol particles, which are caused by molecules adsorbing gas molecules from the supersaturated system to make particles scale exceeding the scale of critical nucleation. Based on the particle sparse and molecular chaos assumption, the nucleation and growth thermdynamical and dynamical models are established, and homogeneous nucleation of three molecules H2SO4-NH3-H20 in fog and haze atmos- pheres are studied based on particle balance modeling and multi-Monte Carlo method. Moreover, the influ- ence of temperature and humidity on particle nucleation rate and critical scale of molecular cluster are nu- merically analyzed. The evolution processes of particle number and diameter under the different concen- trations of gaseous sulfuric acid are also discussed. The computed results show that the lower temperature and higher humidity can lead to larger nucleation rate, and scale of particles generated is mainly in the range of 1nm-3nm.