10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Calibration of Centrifugal Particle Mass Analyzers (CPMAs) Using a DMA-Tandem-CPMA Technique
ZHEN LI, Jingkun Jiang, Da-Ren Chen, Virginia Commonwealth University
Abstract Number: 597 Working Group: Instrumentation
Abstract Instead of using the DMA-CPMA technique (i.e., a DMA is connected in series with a CPMA) often applied previous studies for the CPMA calibration, one DMA and two CPMAs were connected in series in this work to evaluate the performance of a CPMA (i.e., the particle penetration efficiency and the transfer function of a CPMA). This method is based on the operational principle of a CPMA, in which the centrifugal force acting on particles is balanced with the applied electrical force. The calibration of a CPMA should be directly based on the particle mass, not on the particle size classified by a DMA. In this DMA-tandem-CPMA experiment, particles of tested sizes were first selected by a TSI DMA. The mass-based size distribution of DMA-classified particles was then measured using the 1st CPMA. With the measured mass-based size distribution of DMA-classified particles, test particles of selected mass were classified by the 1st CMPA operated at fixed voltage and rotational speed. The test particle steam was then directed into the 2nd CPMA operated at the same rotational speed as that of the 1st CPMA while varying its voltage in an entire applicable voltage range. A condensation particle counter (CPC) was utilized to measure the concentration of particles exiting the 2nd CPMA. Polydispere solid particles of various materials were generated by spraying solutions of test materials via a custom-made Collison atomizer and drying generated droplets in a diffusional dryer.
We found that in the cases of particles with the mobility diameter larger than 100 nm, the particle mass measured by the 2nd CPMA was in general less than 10% of that classified by the 1st CPMA when test particles were selected from the right-hand side of mass-based particle size distributions. The particles mass measured by the 2nd CPMA agreed well with that classified by the 1st CPMA when they were selected from the left-hand side of the mass-based size distribution. In the cases of particles in the mobility diameters less than 100 nm, the particle mass measured by the 2nd CPMA were in general larger than 15% of that classified by the 1st CPMA when selected from the left-hand side of mass-based DMA-classified particle size distributions. Reasonable agreement between the classified and measured particle mass was observed when selected from the right-hand side of the mass-based particle size distributions.
Based on the measured particle penetration efficiency in the experiment, the transfer function of a CPMA were evaluated via a piece-wise linear inversion scheme with the assumption of the same CPMA transfer functions of both used CPMAs. The details of this work will be presented in the conference.