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WARSAW UNIVERSITY OF TECHNOLOGY INSTITUTE OF HEAT
ENGINEERING DIVISION OF AEROENGINES
3-D ELECTRICAL CAPACITANCE TOMOGRAPHY FOR FLAME
VISUALIZATION
Piotr Wolanski _at_ Zbigniew Gut
University of Michigan, Aerospace Engineering, 6
- May - 2009
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Introduction
ELECTRICAL CAPACITANCE TOMOGRAPHY
2D
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Measurement system principle of operation
The basic idea of ECT is to measure the changes
in the electrical capacitances between all
possible combinations of electrodes that occur
when a dielectric material is introduced into the
measurement space. These inter-electrode
capacitance changes are caused by variations in
the permittivity of the material inside the
vessel

• - permittivity
• A area of electrode
• d distance between electrodes

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Measurement system 2D
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Uklad pomiarowy

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Analog-Digital Converter
Control reconstruction
Sensor
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Algorith of reconstruction
The complete set of relationships for all
electrode pairs can be written in matrix form as
follows
forward problem
inverse problem
The method which we shall use is called Linear
Back Projection (LBP)
C matrix containing the normalized
electrode-pair capacitancesK matrix
containing the normalized pixel permittivityS
matrix containing the set of sensitivity matrices
for each electrode-pair.
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Reconstruction iterative algorithm
set of normalized electrode-pair capacitances C1
no
end of iteration
yes
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Reconstruction combustion process
When fuel is burning, a large number of charged
particles are generated. These will modify both
the permittivity and conductivity of the reaction
zone. So, signal level depends on the
concentrations of the various kinds of charged
particles present during combustions.
Charges generated during combustion

• electrons
• positive ions
• negative ions

CHEMI-IONIZATION THERMAL IONIZATION
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Research different burners configuration
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Reconstruction
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Reconstruction simple LBP and with iterations
LBP
LBP
LBP
50 iterations
50 iterations
50 iterations
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Reconstruction of gaseous flame
Reconstructed images of single flame inside the
model cylinder can
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Reconstruction of gaseous flame
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Reconstruction of gaseous flame
ignition
Decreasing gas flow
Constant gas flow
Flame extinguish
Reconstruction of flame and the variations of
normalized flame capacitance for different flame
intensity.
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Reconstruction of gaseous flame
temperature profile (full scale)
normalized pixel permittivity profile
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Reconstruction of gaseous flame
temperature profile (range 500oC - 1200oC)
normalized pixel permittivity profile
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Reconstruction of gaseous flame in combustion
chamber
GTD-350 turboshaft engine
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Reconstruction of gaseous flame in combustion
chamber
Picture of the combustion chamber GTD-350 with
ECT visualization of flame.
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Reconstruction of gaseous flame in combustion
chamber
Reconstruction of flame in the combustion chamber
GTD-350 and variations of normalized capacitance
charge for different flame intensity.
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Reconstruction of gaseous flame in combustion
chamber
Reconstruction of flame in the combustion chamber
GTD-350 and variations of normalized capacitance
charge for different flame intensity.
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Reconstruction of gaseous flame in combustion
chamber
Reconstruction of flame in the combustion chamber
GTD-350 and variations of normalized capacitance
charge for defective combustion process.
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3-D ECT
Development of techniques to get an image of a 3D
object in an cylindrical combustion chamber.
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Reconstruction 2.5D
Simulation of the 36-electrode 3D ECT sensor. 3D measurement and image reconstruction in contrast to the 2.5D interpolation
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Reconstruction 2.5D

2.5D reconstruction of beam model using 2D
chamber.
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Reconstruction 2.5D
2.5D reconstruction of beam model using 2D
chamber.
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Measurement system 3D
1 row
2 row
3 row
4 row
View of capacitance tomography electronic unit
(six cards).
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Mesh
2D 3D

Nodes855 Elements1612
Nodes7680 Elements13338
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Sensitivity map
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3D sensitivity map between 1-11 and 1-7
electrodes
2D sensitivity map between 1-5 electrodes
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Software

• The ECT-3D program allows
• control system
• data acquisition with on-line image monitoring
• image visualization in a very wide range of
  formats and views
• data storage in different formats
• and more .....

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Reconstruction 3D objects
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Reconstruction 3D objects
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Reconstruction 3D of gaseous flame
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Reconstruction 3D of gaseous flame
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Reconstruction 3D of gaseous flame
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Development of techniques to get an image of a 3D
object in an annular combustion chamber.
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Images reconstruction in an annular chamber
View of a model annular chamber.
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Images reconstruction in an annular chamber
2D images reconstruction in an annular chamber
using measurement data from 8 electrodes sensor.
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Images reconstruction in an annular chamber
3D images reconstruction in an annular chamber
using spherical object from 24 electrodes sensor
(8x3).
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Summary 3D

• 3-D ECT system was designed and build at the
  Warsaw University of Technology
• special algorithm for image reconstruction was
  prepared and tested
• reconstruction of the 3-D images of dynamic
  flames were tested
• obtained data are very promising
• addition of NaCl significantly increase signal
  from flame
• it is still necessary to overcome some problems
  of signal processing and reconstruction of images
  to get better time and spatial resolution

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Thank you for your attention!