Abstract Number: 467 Working Group: Instrumentation and Methods
Abstract For size distribution measurements over a broad diameter range and with a high sample flow rate, a new high-flow dual channel differential mobility analyzer (HD-DMA) instrument design was recently designed. This electrical-mobility classification instrument has two sample ports and operates at relatively high flow rates (sheath flow ~100-300 lpm and sample flow ~ 20 lpm) while maintaining a low Reynolds number (~500) in the classification region. The reduced particle residence time in the classifier associated with the high sheath flow, enables fast scan operation with this instrument (Dubey and Dhaniyala, 2008). Classical performance characteristics of the HD-DMA, e.g., classification accuracy, precision, and particle penetration efficiency were previously established and the HD-DMA has been deployed for both airborne measurement campaigns and ground experiments. While the instrument’s performance matches theoretical predictions for classification diameters and the resolutions are only ~ 75% of theoretical expectation. This presentation will highlight our recent efforts to further characterize the instrument performance, particularly to understand particle penetrations as a function of aerosol to sheath flow ratios and to accurately determine residence time of particles in the HD-DMA and their relation to fast-scan smearing artifacts. Inversion errors associated with incorrect assessment of residence time will be demonstrated to highlight its importance in fast scan measurements.