WARSAW UNIVERSITY OF TECHNOLOGY

INSTITUTE OF HEAT ENGINEERINGDIVISION OF AEROENGINES

3-D ELECTRICAL CAPACITANCE TOMOGRAPHY

FOR FLAME VISUALIZATION

Piotr Wolanski @ Zbigniew Gut

University of Michigan, Aerospace Engineering, 6 - May - 2009

Institute of Heat Engineering – Warsaw University of Technology

Introduction

2D

ELECTRICAL CAPACITANCE TOMOGRAPHY

Institute of Heat Engineering – Warsaw University of Technology

Measurement system – principle of operation

d

ACij

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:

C23

2

3 1

4

C12

C14 C34

C13

C24

- permittivityA – area of electroded – distance between electrodes

Institute of Heat Engineering – Warsaw University of Technology

Measurement system – 2D

Instytut Techniki Cieplnej – Politechnika Warszawska

Układ pomiarowy

SensorAnalog-Digital

ConverterControl &

reconstruction

1212

3

4

5

6 7 89

10

11

Institute of Heat Engineering – Warsaw University of Technology

Algorith of reconstruction

The complete set of relationships for all electrode pairs can be written in matrix form as follows:

KSC

C – matrix containing the normalized electrode-pair capacitances;K – matrix containing the normalized pixel permittivity;S – matrix containing the set of sensitivity matrices for each electrode-pair.

CSK T inverse problem

forward problem

The method which we shall use is called: Linear Back Projection (LBP)

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction – iterative algorithm

model LBP ILBP

yes

no

set of normalized electrode-pair capacitances C1

end of

iteration

Institute of Heat Engineering – Warsaw University of Technology

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

Instytut Techniki Cieplnej – Politechnika Warszawska

Research – different burners configuration

Instytut Techniki Cieplnej – Politechnika Warszawska

Reconstruction

Instytut Techniki Cieplnej – Politechnika Warszawska

Reconstruction – simple LBP and with iterations

50 iterations

LBP LBPLBP

50 iterations 50 iterations

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of gaseous flame

Reconstructed images of single flame inside the model cylinder can

Institute of Heat Engineering – Warsaw University of Technology

Gas supply

Flame front

Combustion mixture

Gas

Flame front

Combustion mixture

Combustion products and air

Combustion products and

air

Reconstruction of gaseous flame

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of gaseous flame

0 50 100 150 200 250 300 350 400 450 500 550 600nr klatki

0

0.2

0.4

0.6

0.8

1

Cn

Q - const

Reconstruction of flame and the variations of normalized flame capacitance for different flame intensity.

ignition

Constant gas flow

Decreasing gas flowFlame

extinguish

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of gaseous flametemperature profile (full scale)

normalized pixel permittivity profile

0 5 10 15 20 25 30 35 40 45

d [m m]

0

200

400

600

800

1000

1200

T [

o C]

0

0.2

0.4

0.6

0.8

1

norm

aliz

ed p

ixel

per

mitt

ivity

center

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of gaseous flame

0 5 10 15 20 25 30 35 40 45d [m m ]

500

700

900

1100

1300

T [o C

]

0

0.2

0.4

0.6

0.8

1

norm

aliz

ed p

ixel

per

mitt

ivity

center

normalized pixel permittivity profile

temperature profile (range 500oC - 1200oC)

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of gaseous flame in combustion chamber

GTD-350 turboshaft engine

Institute of Heat Engineering – Warsaw University of Technology

Picture of the combustion chamber GTD-350 with ECT visualization of flame.

Reconstruction of gaseous flame in combustion chamber

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of flame in the combustion chamber GTD-350 and variations of normalized capacitance charge

for different flame intensity.

Reconstruction of gaseous flame in combustion chamber

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of flame in the combustion chamber GTD-350 and variations of normalized capacitance charge

for different flame intensity.

Reconstruction of gaseous flame in combustion chamber

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction of flame in the combustion chamber GTD-350 and variations of normalized capacitance charge

for defective combustion process.

Reconstruction of gaseous flame in combustion chamber

Institute of Heat Engineering – Warsaw University of Technology

3-D ECT

Development of techniques to get an image of a 3D object in an cylindrical

combustion chamber.

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction – 2.5Dmodel 2.5 D iterpolation

sensor 1

sensor 2

sensor 3

3D measurement and reconstruction

Simulation of the 36-electrode 3D ECT sensor. 3D measurement and image reconstruction in contrast to the 2.5D interpolation

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction – 2.5D

2.5D reconstruction of beam model using 2D chamber.

+

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction – 2.5D

2.5D reconstruction of beam model using 2D chamber.

Institute of Heat Engineering – Warsaw University of Technology

Vi

Ve

R2

R1

R1

Cf

Cf

Rf

Rf

A3

A2

A1

Si(4)

Si(3)

Si(2)

Si(1)

R1

A ltera E P M 7 06 4A E T C 44

signal card

AD

G12

04

AD

G20

2

s igna l con tro l 1

Measurement system – 3D

1 row

2 row

3 row

4 row

View of capacitance tomography electronic unit (six cards).

Institute of Heat Engineering – Warsaw University of Technology

Mesh

2D 3D

Nodes=855Elements=1612

Nodes=7680Elements=13338

Institute of Heat Engineering – Warsaw University of Technology

Sensitivity map

3D sensitivity map between 1-11 and 1-7 electrodes

1

11

7

2D sensitivity map between 1-5 electrodes

Institute of Heat Engineering – Warsaw University of Technology

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 .....

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction 3D objects sensor 18 electrodes sensor 12 electrodes

model LBP ILBP (100 iteration)

LBP ILBP (100 iteration)

a)

b)

c)

d)

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction 3D objects

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction 3D of gaseous flame

Institute of Heat Engineering – Warsaw University of Technology

Reconstruction 3D of gaseous flame

Institute of Heat Engineering – Warsaw University of Technology

0 100 200 300 400 500 600 700 800

num ber of fram e

0

0.2

0.4

0.6

0.8

1

Cn

gas gas + water + NaCl

Reconstruction 3D of gaseous flame

Institute of Heat Engineering – Warsaw University of Technology

Development of techniques to get an image of a 3D object in an annular

combustion chamber.

Institute of Heat Engineering – Warsaw University of Technology

View of a model annular chamber.

Images reconstruction in an annular chamber

Institute of Heat Engineering – Warsaw University of Technology

LBP ILBP – 100 iterations

2D images reconstruction in an annular chamber using measurement data from 8 electrodes sensor.

Images reconstruction in an annular chamber

Institute of Heat Engineering – Warsaw University of Technology

Images reconstruction in an annular chamber

3D images reconstruction in an annular chamber using spherical object from 24 electrodes sensor

(8x3).

Institute of Heat Engineering – Warsaw University of Technology

• 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

Summary – 3D

Institute of Heat Engineering – Warsaw University of Technology

Thank you for your attention!