细颗粒长大特性的直接测量

Direct measurement of fine particles growth characteristics

为了研究燃烧源产生细颗粒在过饱和条件下的长大特性,设计了基于冷气流与热水接触形成过饱和环境的生长管来促进细颗粒的长大.利用热风保温的方式防止测量窗口水汽的凝结,从而实现了直接测量细颗粒长大后的液滴粒径分布.利用实验系统研究了热水温度、初始颗粒浓度、气体流量对细颗粒长大特性的影响.实验结果表明:热水温度的上升对细颗粒的长大影响非常明显;而细颗粒的初始浓度增加则不利于细颗粒的长大;气体流量的增大在一定范围内对细颗粒的长大影响较小,而流量大于4 L/min时,则影响较大.在最优的实验条件下,平均粒径为0.197μm的细颗粒长大为5.411μm.

To study the growth characteristics of combustion emission fine particles under supersaturation condition,a growth tube in which the supersaturation was formed by cooled gas flowmeeting with hot water was designed to facilitate fine particle enlargement. The droplet size distribution after particle enlargement was measured directly by preventing vapor from condensing on measurement windowwith a hot airflow. The influences of hot water temperature,initial number concentration and gas flowon fine particle growth characteristics were studied by the experimental apparatus. The results showthat the increase of water temperature highly improves the performance of fine particle enlargement,and the higher concentration of initial particles disfavors the fine particle enlargement.The increase of gas flowslightly affects the fine particle enlargement within a certain range. However,when the gas flowincreases to 4 L / min,it has a significant influence on particle growth. Under the optimal experiment condition,the mean diameter of the fine particle with an initial mean size of0. 197 μm can be enlarged to 5. 411 μm.