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


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



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



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



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



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



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



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)



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



uj = 3.7 m/s, no congestion, visualization

Results

= 2 s

Backlayer



uj = 3.7 m/s, no congestion, velocity distribution uabs

Results

Time-averaged velocity distributions for different periods

Streamlines show development of backlayer



uj = 3.7 m/s, congestion in the tunnel, visualization

Results

= 2 s

Backlayer



uj = 3.7 m/s, congestion in the tunnel, velocity distribution uabs

Results



Results

uj = 5.0 m/s, congestion in the tunnel, visualization and velocity

distribution uabs



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



Results

Piston effect on smoke propagation (without ventilation)

Averaged velocity distributions uabs

traffic direction before stop

in smoke propagation opposite smoke propagation bidirectional



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……)

18 8th International Conference ‘Tunnel Safety and Ventilation’ 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

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