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Specialization
Keywords:
electrical engineering,
electrical apparatuses, high voltage switchgear, circuit
breaker,
fluid mechanics, CFD,
numerical simulations,
FEM, FEV, ANSYS, electromagnetic
fields, fluid flows, multiphase flows, interactions - coupled tasks
Switchgear:
My research work was
during my Ph.D. study focused on study,
analyse and theoretical modelling of interrupting
process of high
voltage
circuit breakers, especially advanced "self-blast"
circuit breakers with gas SF6. The interrupting process was modelled
"per partes" as partial physical processes (mathematical models), which
were focused on elimination of critical
points of successful
interruption.
In the last years also an overall CFD model with electric arc model was
developed and tested.
The
used models can be basically divided into several groups:
- models based on gas
flow simulation - steady and unsteady gas flow computations with
consideration of energy transfer (conduction, convection,
radiation), chemical reactions (gas dissociation, PTFE evaporation) and
energy source (electric arc).
- models based on
electric field computation - computations of electrostatic field with
or without space and surface charges.
- models based on gas
pressure field and electric field interaction - models based on equations
for dielectric stress
(theoretical physics
level). The dielectric
stress of gases can be derived as rate of E/p or E/r, where E is
intensity of electric field and p is gas pressure, resp. r is gas
density. The temperature field has to be respected.
- "one -
dimensional" integral model of interrupting process.
- overall CFD model with
electric arc model
The theoretical models and methods can be also
used to optimize
other
plasma applications, e.g. plasma torch.
CFD (one- and
multiphase flows and their interaction with other physical fields):
The FLUENT
knowledge (FLUENT was used for electric arc model developmnet) is used
also for simulation of other problems in different
applications. One and more phases flows, often with heat transfer and
under different conditions are solved.
As examples can be mentioned: simulation of condensation chamber for
high-pressure system of a truck; analyse of distribution transformer
cooling in a concrete distribution station; simulation of inner arcing
short-circuit in a switching board or simulation of two phase flow in a
fabric filter.
Frequent problem is solution of complex processes with interaction of
gas or liquid flow with other physical fields. As an example can be
mentioned electrostatic precipitator, where is computed electric field
of corona discharge with its space charge distribution first and then
twophase flow with charging and separation of discrete
particles from flowing gas. Further example can be magnetic flow meter
with interaction of electromagnetic filed with flowing liquid.
Electromagnetic
field:
Regarding necessity of solution of partial tasks related to
electromagnetic field, e.g. solution of electric field distribution in
quenching chamber of a circuit breaker or magnetic field distribution
in a magnetic flow meter, also some other problems based on
electromagnetic field are solved. Theoretical simulation in this area
led for example to a new rail brake design or improved
electromagnetic drives.
Problems from this area are also submitted in Diploma and Bachelor
thesis.
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