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Physical sub-models to be included in the main model. In Physical Modelling the conservation equations (mass, momentum, energy) are solved. Observations, experiments, and modelling show that there is gas flow. ... ahead of the flame near the fuel bed. Bellemare, 2000. - PowerPoint PPT Presentation
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Fire Star conclusive symposium: Marseille March 18th 2005 1
Physical sub-models to be included in the main model
In Physical Modelling the conservation equations
(mass, momentum, energy) are solved
Observations, experiments, and modelling
show that there is gas flow ...
... ahead of the flame near the fuel bed ...
... and inside the porous fuel bed
Bellemare, 2000
Obviously, there is also flow inside shrubs and inside foliage
Fire Star conclusive symposium: Marseille March 18th 2005 2
Physical sub-models to be included in the main model
Several sub-models are used to deal with a number of phenomena
The temperatures of fuel bed, shrubs, foliage, and of the gas
that flows inside them are not necessarely the same
heat transfer between the gas and these fuel matrixes occurs
This energy exchange plays an important role in the
decrease of fuel moisture content and in the fuel pyrolysis
The flow inside the fuel matrices is subjected to aerodynamic drag
sub-models for heat transfer and aerodynamic drag are,
therefore, necessary
Fire Star conclusive symposium: Marseille March 18th 2005 3
Physical sub-models to be included in the main model
There is no data on porous beds similar to forest fire fuel matrices
Data on packed beds from chemical engineering have been used
But ...... chemical packed beds are very different from
the forest fuel matrices
Objective :
- to measure the heat transfer coefficient h and pressure drop through matrices of forest fuels
Fire Star conclusive symposium: Marseille March 18th 2005 4
Physical sub-models to be included in the main model
Existing wind tunel(used for aerodynamic studies very good performance)
Section 1 : electric resistances (5 kW) to heat the flow
Section 2 : working section packed with pine needles
1000 x 160 x 240 mm (l x h x w)
6 thermocouples and pressure taps
insulated walls
1 honeycombhoneycomb
heating elementsworking section
honeycomb pine needles
heating elements
or twigs and leavesor just twigs
o o o o o o
working section
honeycomb pine needles
thermocouple
heating elements
pressure tap
Fire Star conclusive symposium: Marseille March 18th 2005 5
Physical sub-models to be included in the main model
125m K type thermocouple
“inserted” at the fuel particle’s surface
125m K type thermocouple in the air at the
vicinity of the fuel particle
Thicker wire
(250m) to which
the thin wire is
attached
Thin thermocouples had to be “inserted” at the fuel surfaces
Fire Star conclusive symposium: Marseille March 18th 2005 6
Physical sub-models to be included in the main model
Examples of the curves obtained for h and for pressure drop
0
2
4
6
8
10
12
0 20 40 60 80 100 120 140 160
Re
Nu
This work (Pinus pinae) J Rodrigues (Pinus pinaster)
Zabrosky Bellemare (Pinus sp.)
This work (Quercus coccifera) Incropera (cylinders)
Mills (spheres & cylinders)
Quercus coccifera
0
5
10
15
20
25
30
35
40
0.0 1.0 2.0 3.0 4.0 5.0
Mean velocity inside the fuel bed (m/s)
Pre
ssu
re d
rop
pe
r u
nit
len
gth
(P
a/m
)
Upper level with leaves Upper level without leaves
Medium level with leaves Medium level without leaves
Poly. (Upper level with leaves) Poly. (Upper level without leaves)
Poly. (Medium level with leaves) Poly. (Medium level without leaves)
Pressure drop per unit lengthfor Quercus coccifera
Influence of the strata location
and existence (or not) of leaves
Nu as a function of Re forPinus pinaster and Quercus coccifera
h = Nu = Nu D 4 / SVR
k k
Fire Star conclusive symposium: Marseille March 18th 2005 7
Experimental fires in the INIA wind tunnel
Experimental fires in the wind tunnel were devoted to:
• Validate the behaviour model of wildland fire
• Analyse effects of
• Wind speed
• Shrub moisture content
• Width of a discontinuity
on the fire behaviour
in a fuel complex of Pinus pinaster litter
and Chamaespartium tridentatum shrubs
General view of
INIA wind tunnel
Fire Star conclusive symposium: Marseille March 18th 2005 8
Experimental fires in the INIA wind tunnel
Example of test :• Wind speed = 1 m/s• Shrub m.c.: 40 %• Width of discontinuity = 0 m
P. pinaster litter
C. tridentatum shrubs
Fire Star conclusive symposium: Marseille March 18th 2005 9
Example of Test on discontinuous fuel:
Wind speed = 0 m/s Shrub m.c.: 40 % Width of discontinuity = 2 m
Experimental fires in the INIA wind tunnel
Fire Star conclusive symposium: Marseille March 18th 2005 10
Variation of Rate of Spread with Wind Speed
Similar set of results are available for:
* Flame height
* Byram´s fireline intensity
Examples of results obtained at INIA wind tunnel
Experimental fires in the INIA wind tunnel
y = 0.2101e0.5977x
R2 = 0.9264
y = 0.3663e0.6013x
R2 = 0.9407
0
0.5
1
1.5
2
2.5
0 1 2 3 4
Wind speed
Ro
S
High Level FMC Low level FMC
a
b
a
a
b
a
y = 0,0008x3 - 0,19x2 + 6,85x + 645,53R2 = 0,975
y = 0,0008x3 - 0,19x2 + 7,71x + 739,68R2 = 0,9889
0
200
400
600
800
1000
0 50 100 150 200
TPK Height (cm)
Tem
p m
ax (
ºC)
Hih level FMC Low level FMC
a
b
ba
ba
a
b
Variation of Maximum
Temperatures with Height
Width of discontinuity = 0 m
Fire Star conclusive symposium: Marseille March 18th 2005 11
LIR-UC3M Fire parameters obtained by IR Spectral Imaging 1. Equipment set up and Images Acquisition• Tunnel and lab meas.: 2 cameras one for each band (MIR &TIR). • Field measurements: 1 camera: up to 4 MIR sub-bands
Infrared images are simultaneous, co-registered and calibrated (brightness temperatures)
Multi-spectral
TIR MIR
Visible
Bi-spectral images (MIR & TIR bands)
Multispectral images (4 MIR bands)
TIR (8-12 m)MIR (3-5 m)
Fire Star conclusive symposium: Marseille March 18th 2005 12
IR image: Physical parameters measured
T (K)
T (K)
Classmap
MIR
TIR
Bi-spectral image
(For multispectral images is
analogous)
• Brigthness temperatures• Scene classification• Rate of spread• IR flame height• Instantaneous Radiated power• Estimation of:
Total released power (roughly, 17% of the power released is radiated)Fire front intensityHeat released per unit area
LIR-UC3M Fire parameters obtained by IR Spectral Imaging2. Pixel Classification and image processing
In collaboration with INIA and CIF-Lourizan
Fire Star conclusive symposium: Marseille March 18th 2005 13
spectral absorbance
Objective: to gain knowledge on the pyrolysis chemistry FTIR spectrometry: a) identification of gases by the spectral location of absorbance bandsb) determination of gas concentration from the band depthc) acquires simultaneously information on the whole spectral range (2-16 m) Gases under study: CO2 , CO , CH4 , NH3
2500 2400 2300 2200 2100 2000
0.0
4.0x10-3
8.0x10-3
1.2x10-2
1.6x10-2
2.0x10-2
2.4x10-2
2.8x10-2
ulex europaeusCO
2
CO
Sp
ec
tra
l a
bs
orb
an
ce
Wavenumber (cm-1
)
CO2 CO
3100 3050 3000 2950 2900 2850 2800 2750
0.000
0.002
0.004
0.006
0.008
0.010
0.012
erica umbellata
sp
ec
tra
l a
bs
orb
an
ce
wavenumber (cm-1
)
CH4
LIR-UC3M Fuel Pyrolysis Studies based on FTIRS- Fourier Transform IR Spectrometry: 1. Schematics and aims
255 cm 1 cm-1
32 scans1 s/scan
300 W / 330° C
90 W / 140° C
8.5 cm
4 g
FTIRIR emitter
Fuel sampleHeater
gases
In collaboration with INIA
Fire Star conclusive symposium: Marseille March 18th 2005 14
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
Y = A + B * X
Value Error
--------------------------------------
A 0.40769 1.35236
B 0.63572 0.03323
--------------------------------------
[CO
] (
pp
m m
)
[CO2] + [CO] (ppm m)
combustion efficiency
36.0
COCOCO
CE2
2
0 10 20 30 40 500
1
2
3
4
5
Y = A + B1*X
Value Error-----------------------------------------A 0.06708 0.14521B1 0.06345 0.00546-----------------------------------------
[NH
3] (
ppm
m)
[CO] (ppm m)
- clear correlation of NH3 with CO emissions
23 105.03.6CONH
0 10 20 30 40 50 60 70 80 900
2
4
6
8
10
12
14
16
[CH
4] (p
pm m
)
[CO2]+[CO] (ppm m)
-data dispersion - low rate of CH4
emission
aver
4
COCH
02.008.0
LIR-UC3M Fuel Pyrolysis Studies based on FTIRS2. Some remarkable results
In collaboration with INIA
Fire Star conclusive symposium: Marseille March 18th 2005 15
Sketch of the experiment
5.0 5.5 4.5 3.5 4.0 6.0 3.0 2.5
X
Y
X
5 thermocouples onto a vertical
DESIRE plate
median axis of DESIRE
infrared camera
UP VIEW
SIDE VIEW
camera field of view
INRADESIRE bench
Fire Star conclusive symposium: Marseille March 18th 2005 16
Comparison of infrared signal and thermocouple temperature near fire front
thermocouple at 5 cm high gas temperature
thermocouple à 5 cm de haut température du gaz
1 pixel of the infrared image
solid fuel temperature
comparison of time signals
position of the cotton thread
position du fil de coton
INRADESIRE bench
Fire Star conclusive symposium: Marseille March 18th 2005 17
0
100
200
300
400
500
600
700
800
250 260 270 280 290 300 310 320
Time (s)
Te
mp
era
ture
(°C
)
Brightnesstemperature
Thermocoupletemperature
Moving average on thermocouple data
Time evolutions of solid fuel and gas temperature – Slope 0°
Breaking of the cotton thread
Coupure du fil de coton
the thermocouple ‘enters’ the flame
le thermocouple ‘entre’ dans la flamme
Pre-heating of the litter
Préchauffage de la litière
solid fuel temperature gas temperature
INRADESIRE bench
Slope 0° Pente 0° Moyenne mobiledes données de température
Fire Star conclusive symposium: Marseille March 18th 2005 18
0
200
400
600
800
1000
1200
90 95 100 105 110 115 120
time (s)
tem
pe
ratu
re (
°C)
Brightness temperature
Thermocouple temperature
Breaking of the cotton thread
Coupure du fil de coton
the thermocouple ‘enters’ the flame
le thermocouple ‘entre’ dans la flamme
Pre-heating of the litter
Préchauffage de la litière
solid fuel temperature gas temperature
INRADESIRE bench
Time evolutions of solid fuel and gas temperature – Slope 30°
Slope 30° Pente 30°