CFD Simulation of a Low Flow Rate Omni-Directional Aerosol Inlet with Fractionator

BING GUO (1), Andrew R. McFarland (1), Daniel Wise (2)

(1) Texas A&M University, College Station, (2) Edgewood Chemical Biological Center, Aberdeen

     Abstract Number: 741
     Last modified: May 14, 2010

Abstract
An omni-directional inlet is essential to most ambient aerosol sampling systems, but characterizing inlet performance is challenging due to complexity of the flow. The effects of various parameters, such as flow rate, are yet to be better understood. In this study, particle transmission of a 10 L/min omni-directional aerosol inlet, with a fractionator for removing coarse particles, was investigated by CFD simulation using a commercial program, in conjunction with wind tunnel experiments. Three wind speed levels, 2, 8 and 24 km/h, were used in the CFD simulation and experiments; particle aerodynamic diameter ranged from 1 micrometer to over 15 micrometers. The cutoff size, mainly associated with the fractionator, appeared to be very robust, varying from approximately 10.5 micrometers to 11.5 micrometers in the range of wind speed investigated. The CFD-simulated inlet performance agreed well with the experimental results, but the CFD simulation only took a fraction of the time that was necessary to run the experiments. This study reveals some interesting characteristics of low flow rate omni-directional inlets, and it once again demonstrates the value of CFD in understanding complex aerosol flows.