AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
The Effect of Polydispersity of Ultrafine Aerosol Particles on Electrical Charge Measurements in Low-cost Sensors
ROBERT NISHIDA, Nene Yamasaki, Adam M Boies, Simone Hochgreb, University of Cambridge
Abstract Number: 739 Working Group: Aerosol Physics
Abstract Electrical charging of particles and subsequent electrical current measurement is commonly used in low-cost ultrafine particle sensors. The devices are experimentally calibrated with controlled aerosol sources to provide metrics such as mean particle size and total concentration from one or more electrical current measurements. However, a polydisperse aerosol with a large standard deviation will provide a significantly different signal from a monodisperse aerosol with the same mean particle size. Therefore, further understanding of effect of polydispersity on integrated electrical current signal is required to improve the accuracy of low-cost sensors. In this work, we solve the conservation equations for particle/ion charging and transport (convection, diffusion and electrical transport) for a laminar, steady-state, incompressible flow along a cylindrical geometry. The particle charging method is direct ultraviolet photoionization, currently used in the development of a low-cost environmental sensor. The polydisperse particle size distributions are represented by multiple size bins, each with multiple charge levels. Results are presented for integrated electrical current from lognormal distributions of varying mean particle size, concentration, standard deviation and electric field strength. The results show that there are significant differences in signal between monodisperse and lognormal particle distributions, and that these differences increase with standard deviation.