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TECHNICAL PAPERS

Thermal and Flow Fields Modeling of Fast Spark Discharges in Air

[+] Author and Article Information
O. Ekici, O. A. Ezekoye, M. J. Hall, R. D. Matthews

Department of Mechanical Engineering,  The University of Texas at Austin, Austin, TX 78712

J. Fluids Eng 129(1), 55-65 (Jun 10, 2006) (11 pages) doi:10.1115/1.2375130 History: Received February 08, 2006; Revised June 10, 2006

In this study, a two-dimensional axisymmetric computational model of spark discharge in air is presented to provide a better understanding of the dynamics of the process. Better understanding of the modeling issues in spark discharge processes is an important issue for the automotive spark plug community. In this work we investigate the evolution of the shock front, temperature, pressure, density, geometry, and flow history of a plasma kernel using various assumptions that are typically used in spark discharge simulations. A continuum, inviscid, heat conducting, single fluid description of the flow is considered with radiative losses. Assuming local thermal equilibrium, the energy input due to resistive heating is determined using a specified current profile and temperature-dependent gas electrical conductivity in the gap. The spark discharge model focuses on the early time flow physics, the relative importance of conduction and radiation losses, the influence of thermodynamic model choice and ambient pressure effects.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Specific heat ratio for air under LTE (solid curve with TDM-3, dashed curves with TDM-2)

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Figure 2

Computational domain and electrode geometry

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Figure 3

Current and cumulative energy deposition as a function of time

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Figure 4

Shock wave radius as a function of time

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Figure 5

Scaled mass density profiles in the z=0 plane at 5μs(a), and at 10μs(b); “+” experiment (20)

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Figure 6

Temperature as a function of radial coordinate at 10μs for the z=0 plane; “+” model predictions of Akram (17)

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Figure 7

Temperature as a function of radial coordinate at 20μs for the z=0 plane

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Figure 8

Pressure distribution at 2.0μs

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Figure 9

Temperature distribution at 2.0μs

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Figure 10

Pressure distribution at 5.0μs

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Figure 11

Temperature distribution at 5.0μs

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Figure 12

Velocity vector field at 5.0μs

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Figure 13

Velocity vector field at 10.0μs

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Figure 14

Temperature distribution at 10.0μs

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Figure 15

Temperature contours for the assumed ignition range at 15.0μs, for TDM-1, TDM-2, and TDM-3

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Figure 16

Conduction to the electrodes and radiated energy as a function of time

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Figure 17

Energy deposition as a function of time at different pressures

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Figure 18

Total deposited energy as a function of pressure

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Figure 19

Blast wave and plasma kernel radii as a function of time

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Figure 20

Percentage decrease in blast wave radius relative to 1atm values

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Figure 21

Percentage decrease in plasma kernel radius relative to 1atm values

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