AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Accurate Signal Prediction of SEMS under Fast-Scan Operation
MARK KANAPARTHI, Suresh Dhaniyala, Clarkson University
Abstract Number: 505 Working Group: Instrumentation and Methods
Abstract The Scanning Electrical Mobility Spectrometer (SEMS) has been traditionally used to make Aerosol size distribution measurements. The SEMS is generally operated by stepping up the voltage exponentially (up-scan) followed by an exponential step down (down-scan). The classification characteristics are dictated by the instrument transfer function. Dubey and Dhaniyala (2008) proposed a semi-theoretical approach to calculate the SEMS transfer function under an up-scan operation. In this study, the approach of Dubey and Dhaniyala has been extended to calculate the transfer function for a down-scan operation. Also, the calculation approach has been extended to consider the effect of concentration smearing on both and up-scan and down-scan transfer functions. The calculated transfer functions are validated experimentally for a range of scan times and DMA operating conditions. The effects of signal smearing and plumbing delays are considered in the validation. Our study determined that a scan-time-dependent offset time is required to match theoretical predictions with experimental data. Using computational fluid dynamics (CFD) simulations, the possible influence of geometry non-idealities on the observed scan-time-dependent offset time was examined. We will present the details of the theoretical calculation, experimental validation and the implication of the results for accurate inversion of fast-scan data.