INVESTIGATIONS ON SMOKE PROPAGATION WITH …
Transcript of INVESTIGATIONS ON SMOKE PROPAGATION WITH …
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INVESTIGATIONS ON SMOKE PROPAGATION
WITH LONGITUDINAL VENTILATION
BY MEANS OF A MODEL TUNNEL
Wilhelm Jessen1; Andreas Klein 2
1Institute of Aerodynamics Aachen,
2Institute of Highway Engineering,
RWTH Aachen University, Germany
8th International Conference ‘Tunnel Safety and Ventilation’ 2016
Graz, 25th - 26th April 2016
2 2 8th International Conference ‘Tunnel Safety and Ventilation’ 2016
Graz, 25th - 26th April 2016
Motivation
Experimental Setup
- Model tunnel, jet fans and moving traffic
- Modelling of tunnel fires (helium-air mixture)
Measurement technique
- Particle-image velocimetry (PIV)
Results
- Smoke propagation with/without congestion
- Smoke propagation with piston effect by stopped traffic
Summary and outlook
Outline
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Graz, 25th - 26th April 2016
Optimization of longitudinal ventilation systems and tunnel design for normal
operation and the event of a tunnel fire
Development and construction of a model tunnel to investigate flows in a road
tunnel
Evaluation of ventilation concepts during the planning stage
Experimental and numerical investigations – considering a variety of parameters
with influence to smoke propagation, stratification
Processing period 07/2012- 04/2016
Supported by Federal Highway Research Institute (BASt)
Motivation
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Graz, 25th - 26th April 2016
Scale 1:18, length 12 m
Two-lane cross-sections for
unidirectional and bidirectional traffic
Rectangular or horseshoe profile
(RQ26,5t respectively 10,5t acc.
RABT 2006)
Transparent materials (PMMA, PA)
and medium density fiberboard
(MDF)
Experimental Setup
Construction of the model tunnel
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Graz, 25th - 26th April 2016
Construction of model jet fans
Velocity continuously adjustable
(usmax = 35 m/s)
Impeller diameter
Experimental Setup
1:1 500 mm 710 mm 900 mm
1:18 28 mm 40 mm 50 mm
Influence of traffic
Congestion (in case of fire)
Moving and stopped traffic - modified slot car
system, vcars,max ≈ 4 - 5 m/s
Piston effect on smoke propagation
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Graz, 25th - 26th April 2016
Isothermal approach using a helium-air mixture (VAUQUELIN [1]):
QM from 0.73 to 2.91 kW (1 - 4 MW in real scale)
Isothermal modelling of tunnel fires
Similarity between reality and model: Froude-number (inertia forces to
gravitational forces)
Experimental Setup
R
R
M
M
Lg
v
Lg
vFr
M
RMR
L
Lvv
2
5
M
RMR
L
LQQQ: heat release rate
L characteristic value of length
[1] Vauquelin, O.: “Experimental simulations of fire-induced smoke control in tunnels using an ‘air-helium
reduced scale model’: Principle, limitations, results and future”. Tunnelling and Underground Space
Technology 23 (2008)
vR / vM ≈ 4.24
QR / QM ≈ 1375
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Graz, 25th - 26th April 2016
Injection through a circular hole in the road surface, symmetry plane
Visualization of the smoke layer by seeding particles (size 1 - 2 μm)
Determination of the smoke propagation velocity by using Particle-Image
Velocimetry (PIV)
Experimental Setup
Helium-air injection into the model tunnel
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Graz, 25th - 26th April 2016
Non-intrusive measurement
technique
Whole-flow-field technique providing
instantaneous velocity vector
measurements
Adding tracer particles to the flow
Illumination of particles by pulsating
laser
Images recorded by synchronized
CCD camera
Post processing: cross correlation
Measurement Technique
Particle-Image Velocimetry (PIV)
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Graz, 25th - 26th April 2016
Influence of congestion in case of fire
Horseshoe profile, unidirectional traffic, 2 2 jet fans
Reference case (no traffic) vs. congestion of heavy good vehicles (right lane) and
passenger cars (left lane) in front of the fire
Jet exit velocities uj = 3.7 m/s and uj = 5 m/s
QR = 2 MW
PIV in x-y symmetry plane
Results
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Graz, 25th - 26th April 2016
uj = 3.7 m/s, no congestion, visualization
Results
= 2 s
Backlayer
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Graz, 25th - 26th April 2016
uj = 3.7 m/s, no congestion, velocity distribution uabs
Results
Time-averaged velocity distributions for different periods
Streamlines show development of backlayer
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Graz, 25th - 26th April 2016
uj = 3.7 m/s, congestion in the tunnel, visualization
Results
= 2 s
Backlayer
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Graz, 25th - 26th April 2016
uj = 3.7 m/s, congestion in the tunnel, velocity distribution uabs
Results
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Graz, 25th - 26th April 2016
Results
uj = 5.0 m/s, congestion in the tunnel, visualization and velocity
distribution uabs
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Graz, 25th - 26th April 2016
Results
Piston effect on smoke propagation (without ventilation)
Unidirectional traffic: passenger cars on left
lane, 50% HGVs and 50% passenger cars
on right lane
In smoke propagation direction and
opposite the smoke propagation direction
Bidirectional traffic: 50% HGVs and 50%
cars on both lanes
vcars = 1.5 m/s
Traffic stopped after 5 circulations, starting
the injection
PIV in x-y symmetry plane
QR = 2 MW
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Graz, 25th - 26th April 2016
Results
Piston effect on smoke propagation (without ventilation)
Averaged velocity distributions uabs
traffic direction before stop
in smoke propagation opposite smoke propagation bidirectional
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Graz, 25th - 26th April 2016
Summary and Outlook
Summary
Construction of a model tunnel (1:18) with jet fans and moving traffic
Modelling of tunnel fires by using a helium-air mixture
Measurement technique: particle-image velocimetry (PIV)
Results show development of a “backlayer” for a jet exit velocity of uj = 3.7 m/s
for both investigated cases (with/ without congestion) - more pronounced (faster
development) for the congestion case
At uj = 5.0 m/s no “backlayering” occurred for both cases
Piston effect on smoke propagation, dependency on the traffic direction
Outlook
Model tunnel: wide range of experimental investigations possible (validation of
numerical studies, investigation of local flow pattern, aerodynamics on tunnel
equipment……)
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Graz, 25th - 26th April 2016
Thank you for your attention!
Dr.-Ing. Wilhelm Jessen Dipl.-Ing. Andreas Klein
Institute of Aerodynamics Aachen Institute of Highway Engineering
Wüllnerstr. 5a Mies-van-der-Rohe-Str. 1
52062 Aachen, Germany 52074 Aachen, Germany
www.aia.rwth-aachen.de www.isac.rwth-aachen.de