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Fine particle transport and separation using electrostatic travelling wave methods

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Title: Fine particle transport and separation using electrostatic travelling wave methods
Authors: Yu, Yue
Item Type: Thesis or dissertation
Abstract: An electrostatic travelling wave (ETW) field can be produced by a set of electrodes, insulated from each other and connected to AC poly-phase voltage sources. ETW techniques have been previously applied to transport particles, but the separation of particles by size has not been considered, and this is the focus of this thesis. The use of ETW to separate particles by size requires understanding of the forces acting on particles. This is done using models for the electrostatic field, single particle motion and for multiple particles. The accuracy of the calculation of the electric field distribution was improved by using advanced numerical methods and included in a more rigorous particle motion simulation model. The simulations explore how different parameter combinations affect the transition of particle motion modes, the particle moving velocity and levitation height. The experimental research verified the simulation model and clarified basic mechanisms. The recording of particle trajectory clearly identified the three typical motion modes. The analysis comparing dielectrophoresis (DEP) and Coulomb force explains the reason for the backward motion of poorly charged particles. In the multiple particle experiments, the fraction of particles transported in forward and backward directions exhibited frequency-dependence. At lower frequencies, most particles moved forward, but as the frequency increased, the fraction of particles being transported backward increased. A crossover frequency was identified and defined, at which a particle is equally likely to move forward or backward. This critical frequency decreases as the particle size increases. The crossover frequency can be used to select the appropriate frequencies to separate particles by size by making the fine particles mostly move forward and coarse particles mostly move backward. A mixture of 30 to 50 μm and 75 to 110 μm particles was tested and the results showed good separation performance.
Content Version: Open Access
Issue Date: Feb-2024
Date Awarded: Jun-2024
URI: http://hdl.handle.net/10044/1/112861
DOI: https://doi.org/10.25560/112861
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: Hadler, Kathryn
Cilliers, Johannes
Wang, Yanghua
Starr, Stanley
Department: Earth Science & Engineering
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Earth Science and Engineering PhD theses



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