Abstract
ABSTRACTThe Aerodynamic Aerosol Classifier (AAC) is a novel instrument that selects aerosol particles based on their relaxation time or aerodynamic diameter. Additional theory and characterization is required to allow the AAC to accurately measure an aerosol’s aerodynamic size distribution by stepping while connected to a particle counter (such as a Condensation Particle Counter, CPC). To achieve this goal, this study characterized the AAC transfer function (from 32 nm to 3 μm) using tandem AACs and comparing the experimental results to the theoretical tandem deconvolution. These results show that the AAC transmission efficiency is 2.6–5.1 times higher than a combined Krypton-85 radioactive neutralizer and Differential Mobility Analyzer (DMA), as the AAC classifies particles independent of their charge state. However, the AAC transfer function is 1.3–1.9 times broader than predicted by theory. Using this characterized transfer function, the theory to measure an aerosol’s aerodynamic size distribution usin...
Highlights
A new instrument, the Aerodynamic Aerosol Classifier (AAC), was recently developed by Tavakoli and Olfert (2013) and released commercially by Cambustion Ltd
The AAC transmission efficiency increases as particle size increases, and ranges from 44% and 80% across its classification limits
Since the AAC classifies particles independent of their charge state, its transmission efficiency is 2.6–5.1 times higher than a Differential Mobility Analyzer (DMA) for the same particle size
Summary
A new instrument, the Aerodynamic Aerosol Classifier (AAC), was recently developed by Tavakoli and Olfert (2013) and released commercially by Cambustion Ltd. It classifies nanoparticles based on their aerodynamic diameter ðdaÞ, an equivalent particle diameter with unit density (ro) that has the same settling velocity as the particle of interest This characteristic is the main consideration where particle inertia dominates, such as respiratory deposition (Finlay 2001), atmospheric lifetime/settling (Hinds 1999), and particle separation/collection using filters, cyclones, and impactors (Kulkarni et al 2011). The AAC selects particles of a single aerodynamic diameter (in reality, a narrow range of aerodynamic diameters distributed about its setpoint) by passing the aerosol sample between concentric cylinders spinning at the same speed. Only particles within this narrow aerodynamic diameter range follow the correct trajectory and pass through the AAC classifier (Tavakoli and Olfert 2013). Particles with aerodynamic diameters smaller than the AAC setpoint have insufficient radial trajectory and remain entrained in the sheath flow, while larger aerodynamic diameters have excessive radial trajectory and impact the outer surface of the classifier
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