Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Effectiveness assessment of road
tunnel fire-fighting strategies by
ventilation and water mist systems
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
1
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Objectives
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
In order to assess the effectiveness of fire-fighting strategies applied
to an urban twin-bore road tunnel, a numerical analysis was done,
including three different numerical tools: a one - dimensional model
(SES), a lumped – parameters model (ECART) and a CFD model
(FDS).
The study focuses on verifying the capability of longitudinal and
transversal ventilation strategies adopted when fire occurs at a given
location, of preventing the spread of smoke along the tunnel.
These simulations have permitted to verify that some of the strategies
considered are sufficient to confine and extract smoke, in order to
determine satisfactory safety condition during the estimated egress time
for people and for the eventual intervention of fire brigades.
In particular, temperatures and combustion products concentration
along the tunnel show that successful strategies, in terms of smoke
confinement and temperature mitigation, can be achieved with the
ventilation system. The activation of a water mist system can help
fighting the fire but some critical aspects must be taken in account if
discharging while people are still in the tunnel.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
2
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Road tunnel
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
The twin-bore tunnel, assumed for this study, is equipped with jet fans at
portals plus a transversal ventilation system, to guarantee the fresh air
flow and the vehicle smoke extraction during normal operation and, with
properly sized fans, the smoke control and extraction in case of fire.
The traffic is unidirectional traffic and each bore (tube) consists of 2
traffic lines and 1 for emergency.
The tunnel consists in many areas per each bore, with different geometric
characteristics and intake and exhaust air vents.
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
3
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Road tunnel
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
The air flows are provided by a ceiling exhaust ventilation ducts running the length of the
tunnel, and by lateral ducts for fresh air intake, one per bore. During the normal exercise
of the tunnel the fresh air income is provided by lateral air vents distributed every 10 m of
length almost at tunnel bottom level. The exhaust system extract the same air flow (normal
operation), and it is consisting of air vents at ceiling disposed every 50 m. When fire
occurs, the supply of fresh air is reduced at 20% and the extraction is very increased, but
limited to a 200 – 250 m length area (consisting in four or five activated exhaust vents
identifying the “protected area”) including the fire and its surrounding. In addition, totally
invertible jet fans are provided in each tunnel portal, used normally to push the air in the
traffic direction; but, in case of fire, is possible to reverse their airflow direction to help the
confinement of smoke in the extraction – protected area, by pushing air only inside the
tunnel.
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
4
Galli E.
MM S.p.A.
Unità tecnica impianti
Manzini G.
Politecnico di Milano
Department of Energy
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire protection strategies
Objectives
Road tunnel
Fire protection
strategies
The objective of the strategies is to confine the smoke in the protected area (in order to
extract them) and mitigate the temperature outside such area, with the aim to impose
satisfactory safety conditions during the expected egress time for people and for the eventual
intervention of fire brigades. Without the local extraction, determined by the transversal
ventilation and, eventually, helped by the jet fan inversion, temperatures and smoke
concentration won't be controlled as long as necessary.
Time [s]
Fire scenarios
Event
0
Results
Conclusions
Appendix
Fire ref.
Numerical tools
Fire start
120
Fire detection
160
Fire ventilation activation
180
Fire ventilation is at regime
The hypothesized high-pressure water-mist deluge system is aimed to control, suppress and extinguish the
combustion and has the following main characteristics:
- group of 30 m long racks of nozzles disposed at ceiling, consisting of num. 4 lines of 10 nozzles each;
-injection is activated at the same time of the fire ventilation system (160 s from the fire start) with an
operative pressure of 80 bar and a K factor of 3.8 l/(min bar1/2), with a characteristic diameter supposed as
Dv90= 200 μm;
- two consecutive racks of nozzles (corresponding to 60 m of tunnel length) are used.
(In addition, some simulations have considered the application of a low pressure water mist, with the same
configuration and volumic flow, but with a nozzles pressure of 12 bar, and others cases have been inherent
a high pressure water mist system with two of the four ceiling rack lines of nozzles put on the wall horizontal injection, close to tunnel bottom).
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Galli E.
MM S.p.A.
Unità tecnica impianti
Manzini G.
Politecnico di Milano
Department of Energy
5
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenario analysis
Objectives
Road tunnel
Fire protection
strategies
The fires considered have been determined on the basis of the references available upon car and HGV
fires and are illustrated in the figures. The curve with the maximum HRR of 30 MW (relative to an HGV
fire, HRR4) has been applied as consistent with PIARC and Metropolitana Milanese indications for the
design of fire protection systems. In addition an HRR curve with a maximum of 10 MW (relative to a fire
comprising 2 or 3 cars and derived from the one with the 30 MW peak, HRR4’) was adopted for some
Cars HRR
simulations.
25
20
Results
HRR [MW] .
Fire scenarios
15
HRR1
HRR2
HRR3
HRR4'
10
5
Conclusions
0
0
500
1000
1500
t [s]
Appendix
2000
2500
3000
HGV HRR
180
160
Fire ref.
140
HRR [MW] .
120
Numerical tools
HRR4
HRR5
HRR6
100
80
60
40
20
0
0
500
1000
1500
t [s]
2000
2500
3000
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
6
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenario analysis
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
To achieve the objectives, five main tasks have been carried out and they are briefly
enumerated as follows:
• Phase 0: identification of design fire scenarios;
• Phase 1: preliminary analysis with simple correlations to assess critical velocity,
confinement velocity, smoke production and air/smoke velocity causing droplets floating;
• Phase 2: simulations of the relevant fire scenarios by the SES (used to study the ventilation
strategies adopted and the consequent airflows in tunnel sections);
• Phase 3: simulations of the relevant fire scenarios by ECART (focusing on the different
ventilation strategies and on the combinations of different ventilation strategies plus a deluge
water mist system);
• Phase 4: simulations of the most meaningful fire scenarios with only ventilation strategies
(selected on the basis of the previous results) by FDS.
Numerical simulations have been carried out to assess the effect of the different fire
protection strategies. By SES, only the ventilation strategies have been analyzed, while by
ECART the ventilation and the ventilation + fire control strategies have been analyzed;
finally, by FDS, have been analyzed only some ventilation strategies (some ventilation + fire
control strategies have been analyzed only for research purposes, on the basis of insufficient
capabilities of FDS for water mist fire scenario simulations).
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
7
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenario analysis results
Objectives
Road tunnel
SES road tunnel discretization
scheme (long segments cases).
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
Segment air/smoke temperatures curves corresponding to different time instants [°C] (HRR4, Fire
scenario 2, Fire operation ventilation strategy, 4 extraction vents, Fire segment= 5), SES tool
results.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
8
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenario analysis results
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
Segment air/smoke CO2 concentration [ppm] – red line: under volume, blue line: upper volume simulation segments 50 – 500 m (“Progressiva” segment coordinates from the west portal) (HRR4,
Fire scenario 2, Fire in 250 – 300 m segment, Fire operation ventilation strategy, 4 extraction vents),
ECART tool results.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
9
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenario analysis results
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
Segment air/smoke CO2 concentrations [ppm] / Temperatures [°C] – t= 1000 s from the fire start –
south bore (HRR4, Fire scenario 2, from the figures bottom: Fire operation ventilation strategy, Fire
operation ventilation + water mist injection strategy, Fire operation ventilation + water mist* injection
strategy, 4 extraction vents), ECART tool result.
Segment air/smoke Temperatures [°C] – t=
498 s from the fire start – south bore (HRR4,
Fire scenario 2, from the figures bottom: Fire
operation ventilation strategy num. 8
extraction vents, Fire operation ventilation
strategy num. 4 extraction vents), ECART
tool results.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
10
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenario analysis results
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
Segment air/smoke Temperatures [ °C] – t= 119, 299 s from the fire start – south bore (HRR4, Fire
scenario 2, Fire operation ventilation, 4 extraction vents), FDS tool results.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
11
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Conclusions
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
The hypothesized tunnel ventilation system (which complies with PIARC standards) provides sufficient
safety condition for people to egress the tunnel.
The activation of a water mist system (wheather high or law pressure) can be useful in order to fight the fire
and confine the smoke but provides some difficulties in order to manage it when people are still in the
tunnel due to the destratification that happen after the activation of the system.
The results concerning the cases applying solely the fire ventilation strategy, determined by a reduction of
the fresh air income and an increment of the extraction, localized nearby the fire location (resulting therefore
in a semi-transversal ventilation) are good in terms of limiting and slowing down the spread of smoke along
the tunnel.
The results concerning fire operation ventilation strategies with low pressure water mist system or some
high pressure water mist nozzles on the wall are similar to previous ones. But, the positioning of some
nozzles close to tunnel bottom and with an horizontal discharge can improve the safety condition in the area
occupied by people and vehicles.
In general, the solution with fire operation ventilation strategies with 5 exhaust vents instead of 4 (operating
at the same total volume flow rate) gives better results. Besides, if the reduction of fresh air income is not
realized, but the normal intake flow rate is continued when the fire ventilation strategy is activated, results
show a modest improvement of safety condition in the area of the fire without a sensible decrease beyond
the protected area. The smoke destratification is relevant in every cases, in particular beyond the extraction
zone, but the water mist discharge has determined a more and quicker destratification of the combustion
products. It has to be underlined that the uncertainty associated to the results about water mist strategies is
very high, because of the lack of data available (about dimensional and velocities distribution of the
droplets, and the complex phenomena related to spray behavior). Therefore, there are strong limitations in
the modeling approach adopted by the codes that have been used. Although CO and HCN concentrations are
relevant in determining the safety condition for people during the egress, because of the inherent criticality
of the combustion models, this work has not focused on the quantification of their production and
consequent distribution along the tunnel.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
12
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Appendix
Conclusions
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
13
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenarios
Objectives
Road tunnel
FIT
Fire protection
strategies
Fire scenarios
Results
W= 57 – 240 GJ
Conclusions
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
14
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenarios
Objectives
• Indicazioni internazionali
FIT
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
15
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenarios
Objectives
Road tunnel
Fire protection
strategies
FIT
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
16
Manzini G.
Politecnico di Milano
Department of Energy
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenarios
Objectives
Road tunnel
Galli E.
MM S.p.A.
Unità tecnica impianti
FIT
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
17
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Fire scenarios
Objectives
Road tunnel
SFPE
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
NFPA
200 MW
Numerical tools
Memorial tunnel: HRR= 50 ÷ 100 MW
UPTUN: HRR= 25 MW
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
18
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
Numerical tools
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
•
•
Results
Conclusions
Appendix
•
•
proSES (vs. 1.0.6, developed by Politecnico di Milano Department of Energy - and owned by Metropolitana Milanese
S.p.A.);
SES (Subway Environment Simulation vs. 4.1, one-dimensional
tool developed by the Department of Transportation of United
States of America);
ECART (vs. 4W0F, lumped parameter tool, a property of ERSE);
FDS (Fire Dynamics Simulator vs. 5.2, CFD tool developed at
Building and Fire Research Laboratory of NIST).
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
19
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
SES + proSES
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
SES
The SES code is based on a one-dimensional, incompressible, turbulent, slug-flow model developed with a
designer-oriented approach by the U.S. Department of Transportation and provide estimates of air flows,
temperatures, and humidity, as well as air conditioning requirements, for multiple-track subway systems. It
provides a dynamic simulation of different arrangement of tunnels, ventilation shafts, fan shafts, and jet fans,
plus non-steady-state heat sources used to model the fire with a prescribed heat release rate. It has been
validated in model tests and in actual practice and it is applicable to a variety of subway operating and design
configurations and has been demonstrated to be a cost-effective tool for evaluating the performance of most
types of environmental control strategies. The SES code was applied with the complementary tool proSES.
proSES
The proSES is a complementary tool to the SES code
developed by the authors of the present work and owned by
Metropolitana Milanese S.p.A., that help the user to easy
setup, modify and run multiple cases and to generate plots
and animations to rapidly compare and show results of SES
simulations. An interactive graph allows a visual
representation of the network elements (tunnels, stations,
vent shafts, ...) and their relative connections through
junctions. Nodes and segments are then described using
prototypes, so their properties values can be easily modified
in any time, simplifying the generation of different inputs
for parametric studies. The tool uses Python as a glue
programming language and for post-processing the VTK
library (http://www.vtk.org/) was chosen, so the postprocessor Paraview (http://www.paraview.org/) could be
used to visualize the dataset storing the results to perform
an easily comparation of a great number of cases.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
20
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
ECART
Objectives
Road tunnel
Fire protection
strategies
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
The computer tool ECART is dedicated to predict the consequences of an accident in a risk installation. It was
originally created to calculate the concentration of airborne radio toxic substances inside nuclear power plants in
the case of a severe accident. As it is not related to a specific design, nuclear or not, it can simulate the airborne
transport of dangerous substances throughout a generic system of rooms, pipes or plant components, together
with the removal and the re-entrainment mechanisms which may occur in the presence of structures, liquid
sumps or water sprays.
The problem of integral analysis of complex systems or industrial installations is still quite difficult using CFD
codes that are suitable for the detection of fluid motion field, but are too heavy to run detailed simulations of fire
propagation through several rooms, corridors or tunnels, accounting the flame and smoke propagation, or the
chemistry of combustion together with the thermodynamic response of atmosphere and structures. ECART is a
lump parameter model for aerosol transport with the capability of modeling water mist injectors and fire
sources. It adopts the classic well-mixed hypothesis to describe the transport within each control volume
interconnected with others via explicit junction (prescribing the mass flow rate) and implicit junction
(prescribing equivalent hydraulic diameter and head losses).
This computer tool is currently developed by ERSE, Milan, Italy ([email protected]) and has been also
supported by Italian Government, national agency ENEA, University of Pisa, Politecnico di Milano and Torino,
French EDF and the European Union. Significant efforts were spent to extend its modeling to fire
phenomenology in the recent years in cooperation with the Department of Energy of Politecnico di Milano (ref:
[email protected]; [email protected]), paying particular attention to pool fires modeling
and water mist phenomenology.
This work has been financed by the Research Fund for the Italian Electrical System under the Contract
Agreement between CESI RICERCA and the Ministry of Economic Development--General Directorate for
Energy and Mining Resources stipulated on June 21, 2007 in compliance with the Decree n.73 of June 18, 2007.
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
Manzini G.
Politecnico di Milano
Department of Energy
Galli E.
MM S.p.A.
Unità tecnica impianti
21
Effectiveness assessment of road tunnel fire-fighting
strategies by ventilation and water mist systems
FDS
Objectives
Road tunnel
Fire protection
strategies
FDS (developed by BFRL - NIST) is a Computational Fluid Dynamics (CFD) model of fire-driven fluid flow. The
model solves numerically a form of the Navier-Stokes equations appropriate for low-speed, thermally-driven
flow with an emphasis on smoke and heat transport from fires. The code is well known and has been validated
in tunnel fire scenarios, especially with the Memorial Tunnel Fir Tests simulating mechanical ventilation effect
on smoke movement.
…
Fire scenarios
Results
Conclusions
Appendix
Fire ref.
Numerical tools
XII Convegno nazionale AIIA "I Sistemi di Gestione della Sicurezza Antincendio nella Fire Safety Engineering”
Milano, 29 ottobre 2009
22