AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
An Inversion Routine to Determine a Two Dimensional Mass-Size Distribution Function from DMA-APM Measurements of Non-Spherical Particles and Externally Mixed Aerosols
VIVEK RAWAT, David Buckley, Shigeru Kimoto, Nobuhiko Fukushima, Christopher Hogan Jr., University of Minnesota
Abstract Number: 85 Working Group: Instrumentation and Methods
Abstract Two dimensional mass and mobility measurement techniques are essential for analysis of highly aggregated soot particles, to identify structurally or chemically dissimilar particle populations in an aerosol with multiple modes and to study particle formation/synthesis in realtime. A differential mobility analyzer (DMA) coupled with an aerosol particle mass analyzer (APM) and a condensation particle counter (CPC) can be employed to classify these complex nanoparticles based on their electrical mobility and mass to charge ratio, with an advantage that classification in the APM is typically independent of the particle shape. However, to accurately infer useful quantitative information from these measurements, it is necessary to have an appropriate inversion routine. In this work, we develop and test an inversion routine to deconvolute the measurement data from DMA and APM transfer functions while correcting for appropriate charge distribution, CPC detection efficiency and transport losses in the system. Specifically, we recover a two dimensional distribution in particle mobility diameter and mass from the experimental data which can be later used to establish a relationship between mobility diameter and mass for non-spherical particles or distinctively identify the particles of different modes in a mixed population. The inversion technique used here is similar to the Twomey-Markowski approach used for DMA-CPC inversion. We test this inversion routine with experimental measurements of diffusion flame generated soot particles and oleic acid particles generated using a nebulizer. These two populations are allowed to mix together in a coagulation chamber and the evolution of the two dimensional distribution is observed as a function of residence time in the chamber.