气溶胶微滴的蒸发及界面现象

EVAPORATION AND INTERFACIAL PHENOMENA OF A SINGLE AEROSOL MICRODROPLET

用电动平衡仪和光散射技术研究气溶胶微滴蒸发及其伴随的界面现象.研究的系统有缓慢蒸发的有机物微滴、快速蒸发的水滴和含表面活性剂的水滴.实验结果表明:蒸发速率影响着微滴的温度;表面活性剂显著地降低了水滴的蒸发速率;表面电荷密度的增加会导致微滴的分裂.这些研究结论对控制工业装置中液滴的蒸发和燃烧过程有着重要意义.

The electrodynamic balance and light-scattering techniques have been used to study the kinetics of microdroplet evaporation and attendant interfacial phenomena. In the electrodynamic balance a single microdroplet was suspended and adjusted in a polarized laser beam. The scattered light from the microdroplet was detected by a 512-element linear photodiode array and a photomultiplier tube at the scattering angle of 90°. Comparing the light-scattering profile (intensity versus scattering angle) and the resonance spectra with Mie theory, the size and the change of the microdroplet were determined precisely. The techniques have been used to measure the slow evaporation of organic microdroplets, rapid evaporation of water microdroplets, and rapid evaporation of microdroplets of aqueous surfactant solutions. The experimental results show that the interiacial temperatures of rapid evaporation.microdroplets estimated from the data are significantly lower than the surrounding gas temperature; insoluble monolayer formed by surfactant at the microdroplet interface greatly reduces the evaporation rate and microdroplet fission due to interfacial charge effects can occur below the Rayleigh limit, and the charge and the mass loss before and after a fission can be determined by using suspension voltage measurements combined with light-scattering techniques.