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Electrohydrodynamic flow in a barbed plate electrostatic precipitator




McKinney, Peter J., author
Davidson, Jane H., advisor
Wilbur, Paul J., committee member
Sandborn, Virgil A., committee member
Meroney, Robert N., committee member

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The large scale secondary flows and turbulence induced by the inhomogeneous negative corona discharge in the conventional wire-plate precipitator are known to reduce collection efficiencies, particularly in applications with high mass loadings of fine particulates. Electrohydrodynamic theory suggests that a modification in electrode geometry is necessary to control the electrically induced flow. A plate-plate precipitator using a barbed plate discharge electrode is designed to provide a more uniform current density distribution. Electrical and fluid dynamic characteristics of four model barbed plate electrodes, with varying plate-to-plate and barb spacing, are evaluated and compared to characteristics of a laboratory wire-plate precipitator in a specially designed wind tunnel facility. Current voltage characteristics of each electrode are presented and the visual appearance of the corona discharge discussed. Hot-film anemometer measurements of the turbulent flow field downstream of the active precipitator include mean and turbulence intensity profiles, as well as spectral analysis of the flow. Gas eddy diffusivities are estimated from integral length scale calculations. A laser light sheet is used to visualize the flow in the inter-electrode space. Results show that the electrical characteristics of the planar electrodes are well within the range needed for industrial precipitation and that the scale of the current in homogeneities within the precipitator are reduced. Fluid dynamic measurements confirm that electrode geometry has a significant effect on the electrohydrodynamic turbulence production. Turbulence intensity data indicate that the point discharges in the planar geometry cause higher turbulence levels than the wire discharges. Turbulent diffusivites are correspondingly higher in the planar geometry. These results indicate that mixing may actually be enhanced in the suggested design. Flow field measurements made downstream of the precipitator may not however be representative of the electrically induced flow within the precipitator. Plate end effects observed in the visualization procedure may have a significant effect on the downstream flow and bias the measurements. Additional study is necessary to determine if the planar geometry is a viable design. The most important test of any new precipitation design is measurement of its particle collection efficiency.


Covers not scanned.
Print version deaccessioned 2020.

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Fluid mechanics


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