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Research Papers: Fundamental Issues and Canonical Flows

Patterns of Airflow in Circular Tubes Caused by a Corona Jet With Concentric and Eccentric Wire Electrodes

[+] Author and Article Information
Reza Baghaei Lakeh

Department of Mechanical Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1805rbaghae@siue.edu

Majid Molki

Department of Mechanical Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1805

J. Fluids Eng 132(8), 081201 (Aug 16, 2010) (10 pages) doi:10.1115/1.4002008 History: Received December 22, 2009; Revised June 16, 2010; Published August 16, 2010; Online August 16, 2010

A computational investigation is conducted to study the patterns of airflow induced by corona discharge in the cross section of a circular tube. The secondary flow induced by corona wind in various flow passages has been the subject of numerous investigations. The flow patterns are often identified by multiple recirculation bubbles. Such flow patterns have also been anticipated for circular cross sections where the corona discharge is activated by an electrode situated at the center of the cross section. In this investigation, it is shown that, contrary to public perception, a symmetric corona discharge does not generate a secondary flow in circular cross sections. This investigation then proceeds to demonstrate that the flow responsible for thermal enhancements in circular tubes often reported in the published literature is induced only when there is a slight asymmetry in the position of the electrode. The present computations are performed in two parts. In part one, the electric field equations are solved using the method of characteristics. In part two, the flow equations are solved using a finite-volume method. It is shown that the method of characteristics effectively eliminates the dispersion errors observed in other numerical solutions. The present computations show that the flow in the eccentric configuration is characterized by a corona jet that is oriented along the eccentricity direction and two recirculation zones situated on either sides of the jet. In addition to the computational approach, a number of analytical solutions are presented and compared with the computational results.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Geometry of the problem and characteristic lines

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Figure 2

The influence of grid refinement on the computational results of electric field for Vo=7.5 kV, ReEHD=2085, and ε=0% (concentric configuration)

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Figure 3

Potential distribution along the characteristic lines, shown for Vo=7.5 kV, ReEHD=2085, and comparison with analytical solution (concentric configuration)

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Figure 4

Electric field and charge density distributions for Vo=7.5 kV, ReEHD=2085, and ε=0 (concentric configuration)—the inset shows the smooth distribution of charge density in the vicinity of the corona electrode

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Figure 5

Grid refinement results of corona jet centerline velocity −Vo=7.5 kV, ReEHD=2085, and ε=1%

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Figure 6

Static pressure gradient and electric body force for Vo=7.5 kV, ReEHD=2085, and ε=0% (concentric configuration)

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Figure 7

Contour plots of velocity magnitude, kinetic energy and streamfunction in eccentric configuration for different applied potentials and ε=1%. The time-averaged corona currents and ReEHD are (0.66 mA, 2085), (2.4 mA, 5305), and (5.31 mA, 8145), respectively.

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Figure 8

The centerline velocity of the corona jet in different potentials and eccentricities

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Figure 9

The analytical and numerical results of velocity in rapid acceleration zone for Vo=7.5 kV, ReEHD=2085, and ε=1%

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Figure 10

Comparison between von Karman, computational and analytical results of corona jet velocity in impingement zone for Vo=7.5 kV, ReEHD=2085, and ε=1%

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Figure 11

Pressure distribution along the corona jet and tube perimeter for Vo=7.5 kV, ReEHD=2085, and ε=1%

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Figure 12

Contour plots of vorticity and pressure for different applied potentials and ε=1%. The time-averaged corona currents and ReEHD are (0.66 mA, 2085), (2.4 mA, 5305), and (5.31 mA, 8145), respectively.

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