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Author
Date
2021Type
- Doctoral Thesis
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Abstract
This thesis is concerned with three aspects of numerical simulations of
electric arcs:
Part 1 extends a previous numerical scheme in 1D to 3D and
non-constant timestepping for a plasma
defined in an Euler-Maxwell framework.
The main feature of the scheme is that it
allows for the scaled Debye length as a modeling parameter to
continuously blend between the full Maxwell system and the
eddy current model; this feature is known as asymptotic preserving.
The generalization to higher dimensions is involved because it requires
a dual mesh strategy and interpolation of the electromagnetic field.
The submodels of the newly designed scheme are validated with testcases;
however, setting the scaled Debye length to zero unveiled that assuming a
linear relation in Ohm's law prevents the new 3D scheme from being
asymptotic preserving.
Part 2 focuses on radiation modeling.
It reviews the relevant modeling assumptions that reduce the radiative
transfer equation to a computationally tractable model as it is found in
applied numerical simulations. However, the main issue lies in the complex structure
of the absorption coefficient. We consider the Elenbaas-Heller equation as
the simplest model for a wall-stabilized arc and derive the linearized
equation. A sensitivity analysis permits to analyze effects of uncertainties in
the spectral absorption coefficient on the arc voltage and temperature
profile.
We also consider the line limited Planck mean and show that an
appropriately chosen renormalization length permits to retrieve the
correct temperature profile at minimal computational costs.
Part 3 presents applied numerical simulations
of electric arcs in circuit breakers.
It is hard to find simulation suites that permit for a robust coupling
of the numerous modeling aspects as required for applied thermal plasma
simulations, which encompass gas dynamics, electromagnetism, and radiative heat
transfer, rigid body motion, mesh morphing, and other modeling aspects.
Our software choice enabled us to consider a
low voltage circuit breaker and evaluate the contact arm motion with respect
to mechanics, plasma pressure, and electromagnetic force. A second case
analyzes a recent design of a high voltage direct current circuit breaker
and shows results of the electric field and gas flow field complementing previous
measurement. Combining a caloric estimate with the simulation results of
radiative heat flux to the nozzle wall, we provide an argument for the
experimental observation that wall ablation is measured only for
sufficiently large currents. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000489867Publication status
publishedExternal links
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Publisher
ETH ZurichSubject
ELECTRIC ARCS (ELECTRICAL ENGINEERING); Numerical modeling; radiative transfer; asymptotic preservingOrganisational unit
03632 - Hiptmair, Ralf / Hiptmair, Ralf
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ETH Bibliography
yes
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