Diffusion charging of nanometer-sized liquid aerosol particles

Abstract

Aerosol particles play an important role in atmospheric physical or chemical reactions. Charging of aerosol particles is also widely used in various engineering applications, such as electrical low-pressure impactors and differential mobility analyzers. In this paper, the charging process of nanometer-sized liquid aerosol particles in an atmospheric environment is studied theoretically and experimentally. The traditional charging equation is modified taking the variation of carried charges and the number density of liquid aerosol particles into consideration, due to the coalescence of liquid aerosol particles that brings 100% charge conversion efficiency. By fitting the experimental data under a low discharge voltage, an appropriate combination (r, η) is selected, where r is a specific droplet radius and η is the corresponding equivalent conversion factor of charges. The results from the fitting combination (r, η) are in good agreement with the experimental data and it further demonstrates that the charging evolution of droplets with various radiuses under various voltages can be derived from the existing experimental data under a low voltage. In addition, the concept of a charging time constant τ 0.1 is introduced to describe the charging rate. This paper may provide a reference to reveal and optimize the charging process of liquid aerosol particles and broaden the engineering applications for the charging of aerosol particles.