American Association for Aerosol Research - Abstract Submission

AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA

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Aerodynamic Aerosol Classifier

Farzan Tavakoli, Jonathan Symonds, JASON S. OLFERT, University of Alberta

     Abstract Number: 119
     Working Group: Instrumentation and Methods

Abstract
A new aerosol particle classifier, the Aerodynamic Aerosol Classifier (AAC), is presented with some of its applications. The instrument uses a centrifugal force and sheath flow between two concentric rotating cylinders to produce a monodisperse aerosol classified byaerodynamic diameter. Since this instrument does not requirechargedparticles, it produces a true monodisperse aerosol without artefacts caused by multiply-charged particles like other classifiers. This work reports the theoretical and experimental results of the new instrument with some of its applications.

Two diffusion models and two non-diffusion models have been used to predict the performance of the AAC.The limiting trajectoryand particle streamline models are analytical methods and do not include particle diffusion. To demonstrate the diffusion effect, a convective diffusion model has been developed by solving the convective-diffusion equation for the AAC which has been solved using the Crank-Nicolson method. The diffusing particle streamline model is an analytical model which models particle diffusion as a Gaussian cross-stream profile about the corresponding non-diffusing particle streamline.The transfer functionswere obtained as a function of the particle relaxation timeand the particle aerodynamic diameter. The transfer function has been studied for different flow rates. PSL (polystyrene latex) particles and DOS (DioctylSebacate) along with a differential mobility analyzer (DMA) were used to verify the instrument and to obtain the experimental transfer function.

A DMA and the AAC were used in tandem to measurethe effective density, dynamic shape factor, and the mass of soot particles emitted from an inverted burner. The measured DMA-AAC mass–mobility exponent was 2.17 for a flame equivalence ratio of 0.67, which agrees well with DMA-CPMA measurements. The effective density was found to vary between 0.18–0.86 g/cm3and the dynamic shape factor was calculated to be 1.5–2.6 over the range of 90 to 630 nm in mobility diameter.