AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Aerosol Mobility Imaging for Rapid Size Distribution Measurements
Steven Spielman, Susanne Hering, Chongai Kuang, Jian Wang, TAMARA PINTERICH, Aerosol Dynamics Inc.
Abstract Number: 562 Working Group: Instrumentation and Methods
Abstract The Aerosol Mobility Imaging (AMI) system aims to provide an aircraft-deployable electrical mobility particle sizing system that spans the 10nm – 500 nm size in a single snapshot. The AMI builds on two established technologies: the Fast Integrated Mobility Size Spectrometer developed by Kulkarni and Wang, and laminar flow water-based condensation methodology of Hering and co-workers. As with conventional scanning mobility particle spectrometers, the AMI system has a drift tube to separate particles of differing electrical mobility. The mobility-separated particles are enlarged through water condensation along their flow trajectories, and their positions and concentration within the channel are captured via a digital image. The growth region is designed using a “moderator” stage (Hering et al, 2014) to remove excess water vapor so as to provide the necessary condensational enlargement without risking condensation on the downstream optical components. Rather than sampling one size fraction at a time, as done with traditional mobility sizing systems, all particles are captured at once, with data acquisition rates of 10Hz.
Initial experiments were done using a single electrode, with a constant voltage across the plates of the mobility drift tube. This has now been adapted to the wide-range mobility separation concept outlined by Wang. The wide range mobility sizing uses a complex electrode, with multiple separation voltages at different positions along the width of the electrode. This provides a two-dimensional size separation. Mono-mobility particles are separated in an arc across the channel, with the higher mobility particles distinguished at one end of the channel, and the lower mobility particles separated at the other end. This approach provides simultaneous size separation of particles from 10 to 500 nm.