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Performance of Small Plate and Tube Unipolar Particle Chargers at Low Corona Current

Category: Aerosol Physics and Instrumentation

Accepted Manuscripts
DOI: 10.4209/aaqr.2018.02.0060
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Xiaotong Chen1,2, Qiaoling Liu2, Jingkun Jiang1, Da-Ren Chen 2

  • 1 State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
  • 2 Particle Laboratory, Department of Mechanical and Nuclear Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA

Highlights

The performance of small -tube and -plate unipolar particle chargers was evaluated.
Studied unipolar chargers were operated at low corona discharge current.
Tested particle chargers were designed for compact mobility-based particle sizers.
Small-plate charger attaches less charge on particles than small-tube charger.


Abstract

The performance of two small plate and tube particle chargers operated at the low DC-corona current was compared. Both studied chargers were designed for compact/miniature electrical-mobility-based particle sizers because of their compact size. Both chargers were operated at the corona current of 0.3 µA for the low energy consumption while keeping high charging efficiency. A thin wire was utilized in the plate charger for the ion generation via the DC corona discharge while a sharp-tip needle was used in the tube charger. The intrinsic and extrinsic charging efficiencies of particles in various electrical mobility sizes were measured for both chargers at the aerosol flow rates of 0.3 and 0.6 L min–1. In general, the plate charger had a lower intrinsic charging efficiency than the tube charger. For the plate charger, the extrinsic charging efficiency at the 0.3 L min–1 flow rate was slightly higher than that at the 0.6 L min–1 flow rate. The extrinsic efficiency of the plate charger reached approximately 80% for particles in sizes larger than 40 nm. For the tube charger, its extrinsic charging efficiency at the 0.6 L min–1 aerosol flow rate was higher than that at the flow rate of 0.3 L min–1 for particles in sizes greater than 60 nm. The above observation was reversed for particles with sizes less than 60 nm. The extrinsic charge distributions of particles with mobility sizes less than 300 nm were also characterized. It was found that the multiple-charge status on particles occurred at the particles with sizes larger than 20 nm for both chargers. Particles of the same size attached more charges in the tube charger than the plate charger. The birth-and-death charging model was proposed to calculate the extrinsic charge distributions of particles measured in this study. In addition, the Gaussian distribution function was also suggested to best fit the measured extrinsic charge distributions of particles.

Keywords

Compact/Miniature aerosol charger DC-corona unipolar charger Small tube charger Small plate charger Ultrafine and fine particles


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