AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Evaluation of the Classification Performance of the New Centrifugal Particle Mass Analyzer
JONATHAN SYMONDS, Cambustion
Abstract Number: 694 Working Group: Instrumentation and Methods
Abstract The CPMA (Olfert and Collings, 2005) classifies particles by their mass to charge ratio, by applying opposing electric and centrifugal forces between two rotating cylindrical electrodes between which a potential difference is applied. Unlike the Aerosol Particle Mass (APM) Analyzer (Ehara et. al, 1996), the CPMA’s inner electrode spins slightly faster than the outer electrode, which allows the centrifugal and electrical forces to balance across the entire classification region. This stable system of forces has previously been shown to give a higher transmission efficiency for otherwise equivalent geometries and setpoints.
An evaluation of the newest implementation of the CPMA classifier, in terms of mass accuracy and penetration efficiency is presented. Mass accuracy is determined by comparison with the effective mass calculated for DMA classified PSL and NaCl particles (taking into account dynamic shape factor where necessary). The two methods show consistent agreement to within <5%, across a wide range of particle sizes (20–200 nm), with no systematic loss of accuracy observed for either the smallest or largest particles. Error analysis indicates that the uncertainties in the CPMA measurement are much less than the uncertainties in the DMA equivalent mass technique. In terms of penetration, once static diffusive losses are taken into account, dynamic particle loss is generally low, though some increase in loss is seen at the very highest rotational speeds.