Unipolar field charging of particles by electrical discharge: effect of particle shape

Unger, Lomig; Boulaud, D.; Borra, Jean‐Pascal

doi:10.1016/j.jaerosci.2004.01.006

Cited by 52 publications

(49 citation statements)

References 7 publications

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“…The authors reported that neglecting the space charge effect can lead to significant errors when the ion concentration in the charger is greater than 5 × 10 13 ions/m 3 . Another type of unipolar corona-wire charger designed for use without sheath air has also been recently proposed by Unger et al (2000Unger et al ( , 2004 and later studied by Intra and Tippayawong (2005). It consisted of a coaxial corona-wire electrode placed along the axis of a metallic cylinder.…”

Section: Corona Discharge Chargersmentioning

confidence: 99%

An Overview of Unipolar Charger Developments for Nanoparticle Charging

Intra

Tippayawong

2011

Aerosol Air Qual. Res.

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Charging of nanoparticles is an important process in aerosol sizing. A unipolar charger is one of the most important upstream components in aerosol particle sizing and measurement systems by electrical mobility analysis. The aim of particle charging for an electrical mobility analyzer is to impose a known net charge distribution on the aerosol particles for each size. Charger performance depends on the extrinsic charging efficiency and stable operation. A well-designed unipolar charger should provide high extrinsic charging efficiency and stability that can be accurately determined for any given operating conditions. Depending on the mechanisms used to generate the ionized gas, the chargers can be classified into: (i) a corona discharge chargers, (ii) a radioactive chargers, and (iii) a photoelectric chargers. In this article, a brief overview on the development of existing unipolar aerosol chargers for nanoparticles is presented. Descriptions of the operating principles as well as detailed physical characteristics of these chargers, including the corona discharge, ionizing radiation, and photoelectron emission, are given.

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Section: Corona Discharge Chargersmentioning

confidence: 99%

An Overview of Unipolar Charger Developments for Nanoparticle Charging

Intra

Tippayawong

2011

Aerosol Air Qual. Res.

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“…Electrostatic charging by corona dischargers is commonly used in electrical mobility classificaCorrespondence to: H. E. Manninen (hanna.manninen@helsinki.fi) tion. Different corona charger designs have been developed and tested in various conditions to optimise particle charging efficiency and to minimise losses of ions and particles inside the chargers (Hernandez-Sierra et al, 2003;Unger et al, 2004;Biskos et al, 2005;Qi et al, 2007; review by Intra and Tippayawong, 2009). The charging efficiency, average charge of particles and their penetration through the charger depend on corona voltage, particle diameter and residence time (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Experiments with corona dischargers have focused on particles in the diameter range from 4 nm to ∼1 µm (e.g. Pui et al, 1988;Unger et al 2004;Tan and Wexler, 2007).…”

Section: Introductionmentioning

confidence: 99%

Characterisation of corona-generated ions used in a Neutral cluster and Air Ion Spectrometer (NAIS)

et al. 2011

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Abstract. We characterized size and chemical composition of ions generated by a corona-needle charger of a Neutral cluster and Air Ion Spectrometer (NAIS) by using a high resolution differential mobility analyzer and a time-of-flight mass spectrometer. Our study is crucial to verify the role of corona-generated ions in the particle size spectra measured with the NAIS, in which a corona charger is used to charge aerosol particles down to the size range overlapping with the size of generated ions. The size and concentration of ions produced by the corona discharging process depend both on corona voltage and on properties and composition of carrier gas. Negative ions were <1.6 nm (0.8 cm 2 V −1 s −1 in mobility) in all tested gas mixtures (nitrogen, air with variable mixing ratios of water vapour), whereas positive ions were <1.7 nm (0.7 cm 2 V −1 s −1 ). Electrical filtering of the corona generated ions and not removing all charged particles plays an important role in determining the lowest detection limit. Based on our experiments, the lowest detection limit for the NAIS in the particle mode is between 2 and 3 nm.

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“…Numerous corona-based unipolar chargers were designed to achieve high charging efficiency using either a wire or a needle as the discharge electrode (Whitby 1961;Medved et al 2000;Kruis and Fissan 2001;Hernandez-Sierra et al 2003;Unger et al 2004;Biskos et al 2005a;Alonso et al 2006;Qi et al 2007Qi et al , 2008Kimoto et al 2010;Park et al 2010;Li and Chen 2011). However, the loss of charged nanoparticles is usually severe in the unipolar charger, resulting in only a small fraction of charged nanoparticles exiting the charger.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger

Chien

Tsai

Chen

et al. 2011

Aerosol Science and Technology

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A single-wire corona unipolar aerosol charger with a sheath air to avoid particle loss was designed and experimental charging efficiencies were obtained at a fixed aerosol flow rate of 1 L/min using monodisperse silver nanoparticles of 2.5 to 20 nm in diameter. The charger has a cylindrical casing of 30 mm in inner diameter in which a gold wire of 50 µm in diameter and 2 mm in length is used as the discharge electrode. A two-dimensional (2-D) numerical model was developed to predict nanoparticle charging efficiency in the unipolar charger. Laminar flow field was solved by using the Semi-Implicit Method for Pressure Linked Equations (SIMPLER method), while electric potential and ion concentration fields were solved on the basis of Poisson and convection-diffusion equations, respectively. The charged particle concentration fields and charging efficiencies were then calculated on the basis of the convection-diffusion equation in which ion-particle combination coefficient was calculated by Fuchs diffusion charging theory (Fuchs, N. A. (1963). On the Stationary Charge Distribution on Aerosol Particles in a Bipolar Ionic Atmosphere. Geophys. Pura. Appl., 56:185-193). Good agreement between predicted and experimental extrinsic charging efficiencies was obtained. Numerical results showed the advantage of using sheath air to minimize charged particle loss and indicated the location where major charged particle loss occurred. It is expected that the present model can be used to facilitate the design of more efficient corona-wire unipolar charger in the future.

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Unipolar field charging of particles by electrical discharge: effect of particle shape

Cited by 52 publications

References 7 publications

An Overview of Unipolar Charger Developments for Nanoparticle Charging

An Overview of Unipolar Charger Developments for Nanoparticle Charging

Characterisation of corona-generated ions used in a Neutral cluster and Air Ion Spectrometer (NAIS)

Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger

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