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Experimental Research - Large-Scale TunnelFire Tests and the use of CFD Modelling to
predict Thermal Behavior
Gabriele Vigne16 October 2009
Fire Protection and Life Safety in Buildings and Transportation Systems , Santander 16 October 2009
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Presentation
Introduction
The Tests
The Models
Results and Future Works
Fire Protection and Life Safety in Buildings and Transportation Systems , Santander 16 October 2009
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Introduction
-Arup Fire in Madrid forms part of a European constructionTechnology Platform (ECTP)
- Test series were conducted in La Ribera del Folgoso (Spain) in a
50m cross section tunnel during March 2009
- Similar tests were conducted in 2008 and the results have been
considered when realizing these tests
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The Tests
Five tests were conducted in the tunnel,
each one with the same configuration and
external conditions in order to quantify the
uncertainty of the experimentalmeasurements.
Fire Size: 5-6 MW
Duration: 8 minutes
Ventilation :
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Geometry
- Cross Section Area of 50m
- 100m Length
- Concrete surface
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The Fire
A metal containers designed to achieve a
Fire Power of 5-6MW
Dimension: 2.0m x 1.00m
The container was filled with a thin layer of
water and a layer of Heptane
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1.0000
6.5005.5000
4.00
1.5000
2.0002.5000
3.5000
2.50
2.50
1.0000
1.0000
4.00
2.0000
1.0000
2.0000
2.0000
5.0000
2.0000
2.0000
2.0000
2.0000
2.0000
2.0000
5.0000
8.0000
Instrumentation
Thermocouples were placed at ceiling height along the tunnel, every
2m from the fire and through the fire plume
Four couple of plate thermometers were placed 4m from the fire at a
height of 2.5m and 3.5m.
Two velocimeters were positioned 5m from the fire to ensure that lowvelocities were maintained at the start of each test.
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Models Setup
3 simple Models were run, each one with a different grid resolution
40
20
10
D*/x
9
5
3
Totalnumber of
meshes
0.10.05FDS 3
0.20.1FDS 2
X0.20.2FDS 1
Recommendedvalue
Resolutionof the other
meshes (m)
Resolutionof the Fire
mesh (m)
Modelname
Fire Protection and Life Safety in Buildings and Transportation Systems , Santander 16 October 2009
Assuming a 5.5MW fire => D*=2.0
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The Model
-Software used: FDS 5.3.1
- HRR: from test data
- Reaction: heptane
- Walls: concrete, thermally thick
- THCPs modelled as thermocouples
- Velocity: none
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Results
Fire Protection and Life Safety in Buildings and Transportation Systems , Santander 16 October 2009
-Temperature
Above the fire plume FDS has a tendency to heavily over predict the temperatures, once outside the
plume the temperatures are closer to the measured temperatures.
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Results
-Temperature
It is difficult to capture the correct temperature above the plume due to the continuous fluctuation of
the flame.
For this reason it is very difficult to draw valid conclusions about the temperature of the thermocouple
placed above the fire.
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Results
Heat Release Rate
HRR from mass loss measurements was close towhat expected from empirical pool-fire calculations
The fuel was burning consistently for 5 minutes
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Results
The combination of the experimental uncertainty associated with both the model input
parameters and the measured model outputs served as a benchmark for evaluation of the
models
A range of 10% was obtained as result of the experiments.
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Results
Measured vs. predicted gas temperature, 2m from the fire
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Results
Measured vs. predicted gas temperature, 4m from the fire
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Results
Measured vs. predicted gas temperature, 6m from the fire
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Results
Measured vs. predicted gas temperature, 8m from the fire
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Plate Thermometers
Due to the quantity of Heptane available during the tests and the wish
to perform as many tests as possible, the time allowed to the pool fire
to burn consistently was limited to about 5 minutes. Because of the
thermal inertia of the plate thermometers, the duration of the fire didnot permitted the plate thermometers to reach steady state conditions
during the tests as can be seen in the graph below.
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Conclusions
-FDS has shown a good performance in predicting the temperature magnitudeinside the tunnel
-The evaluation showed the importance of using a correct grid resolution to
get reliable results. This is very important it should be assured that a proper
grid resolution always is to be used.
- To be able to fully investigate and analyse the heat flux behaviour it isnecessary with longer burning times.
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Further Works
The duration of the fire was enough to reach steady state condition for the
normal thermocouples whilst it was not possible for the plate
thermometers
The FDS model was deliberately built in a simple way as it would have
been created by an average user; further adjustments to the FDS model
could lead to better results
Additional tests will be performed in order to investigate the heat flux
behaviour around the fire.
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Acknowledgement
-Fundacin Santa Barbara
- NIST, VTT
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Gabriele Vigne16 October 2008
Thanks
Fire Protection and Life Safety in Buildings and Transportation Systems , Santander 16 October 2009