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Experimental and numerical studies to assess the benefits of water mist system in Mont-Blanc tunnel Sylvain DESANGHERE 1 , ´ Eric CESMAT 1 , David GIULIANI 2 (1) Lombardi (France), (2) GEIE TMB (France) More information : [email protected] 1. OVERVIEW Study of the use of water mist system in the Mont-Blanc tunnel : Bibliographic review of existing fixed fire- fighting systems (FFS) Experimental performance assessment of several types of FFS at scale 0.8 Numerical simulations to evaluate the in- teraction of water mist system with existing safety equipment and procedures 2. EXPERIMENTAL CAMPAIGN 15 fire tests carried out in the TST tunnel tests facility (San Pedro, Spain) [1, 2]. 3 FFS technologies : SPK, low-pressure water mist, high-pressure water mist 2 fire load compositions: 30 MW wood, 50 MW wood and gasoil 2 activation strategies : as fire detected, at t = 7 min (firefighters arrival) Monitoring of temperature, velocity, gas composition, heat flux, etc. 22 m 3 /s 22 m 3 /s 22 m 3 /s 22 m 3 /s ~ 2 m/s ~ 1,5 m/s ~ 1 m/s ~ 0,5 m/s ~ 0 m/s F N025 N050 N075 N100 N125 N150 S175 S150 S125 S100 S075 S050 S025 N175 TST jets fans SOUTH NORTH Spraying S010 N010 High-pressure water mist system provides the best performance (gas cooling and fire suppression). 3. NUMERICAL STUDY Working approach CFD modeling using FDS (NIST, USA) [3] Spray parameters validation by simulating 6 experimental tests Extensive use of FDS to simulate realistic fire scenarios Rosin-Rammler/log-normal droplets size distribution: F (D)= 1 √ 2π Z d 0 1 σ d 0 exp - [ln(d 0 /d m )] 2 2σ 2 dd 0 (d ≤ d m ) 1 - exp -0.693 d d m γ (d > d m ) 0 10 20 30 40 50 60 70 80 90 100 f(d) x 10 3 d (µm) 0 10 20 30 40 50 60 70 80 90 100 F(d) d (µm) Comparison with experimental data 0 100 200 300 400 500 600 700 800 0 1 2 3 4 5 6 7 8 9 10 Température (°C) Temps (min) Essai R1 - Section N010 TE_N010_5 TE_N010_4 TE_N010_3 TE_N010_2 TE_N010_1 TE_N010_5 FDS TE_N010_4 FDS TE_N010_3 FDS TE_N010_2 FDS TE_N010_1 FDS 0 50 100 150 200 250 300 350 400 0 1 2 3 4 5 6 7 8 9 10 Température (°C) Temps (min) Essai BEHP1B - Section S050 TE_S050_5 TE_S050_4 TE_S050_3 TE_S050_2 TE_S050_1 TE_S050_5 FDS TE_S050_4 FDS TE_S050_3 FDS TE_S050_2 FDS TE_S050_1 FDS Good agreement ⇒ possible use of FDS to simulate fire scenarios in the tunnel. 4. RESULTS Design heat release rate curves Simplified HRR curves derived from TST tests and from scientific litterature [4] : 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Time (min) 10 20 30 40 50 60 70 80 90 100 0 15 MW 6 MW 10 MW HRR (MW) 15 MW Early activation Delayed activation No activation 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 10 20 30 40 50 60 70 80 90 100 0 30 MW 6 MW 15 MW Time (min) HRR (MW) 30 MW Early activation Delayed activation No activation 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 10 20 30 40 50 60 70 80 90 100 0 50 MW 10 MW 20 MW Time (min) HRR (MW) 50 MW Early activation Delayed activation No activation 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 10 20 30 40 50 60 70 80 90 100 0 100 MW 30 MW 50 MW HRR (MW) Time (min) 100 MW Early activation Delayed activation No activation Numerical results analysis FDS results postprocessing to analyse water mist effect and to identify evacuation con- ditions along the tunnel Intensive use of REVAC in-house numerical model for simulating evacuation and firefight- ers intervention (including traveling speed reduction and fractional effective dose for users incapacitation derived from [5]) Walking speed vs visibility distance Estimated visibility distance through water mist 5. CONCLUSION 36 realistic fire scenarios (4 fire loads, 3 natural draught conditions, 3 FFS activation) Significant degradation of visibility and temperature in the flooding area No real asset for safety of users because the smoke management system is effective Good results to protect structure and equipment when facing big fires 6. REFERENCES SETEC TPI-CSTB : Campagne de tests de sfli par le GEIE TMB, 2013. R´ ef. 003-23776/6/T/145/JMV-TU-FR-20121114-v2. IFAB : Campagne de tests des syst` emes fixes des lutte contre l’incendie pour le tunnel du Mont-Blanc, dossier de pr ´ esentation du tunnel d’essai, 2011. NIST Special Publication 1019. Fire Dynamics Simulator User’s Guide, 2017. SOLIT : Safety of life in tunnels, water mist fire suppression for road tunnels, final report, 2007. SFPE : SFPE Handbook of Fire Protection Engineering, Third edition. National Fire Protection Association, Quincy, 2002.
