Fire Technology

, Volume 55, Issue 1, pp 149–174 | Cite as

Fully Coupled CFD Simulation of the Ignition Risk of Unburnt Gases in an Exhaust System Connected to a Mechanically Ventilated Enclosure Fire

  • H. Q. Dong
  • B. Magnognou
  • J. P. Garo
  • B. Coudour
  • H. Y. WangEmail author


Predictive simulations of liquid pool fires are based on the previous experimental study from a reduced mechanically ventilated enclosure with a length/height and width of 2 m. An external ventilation system provides an air supply rate ranging from 24 m3/h to 40 m3/h, corresponding to 3 and 5 Air Change Per Hour, respectively. A circular heptane or dodecane pan with a diameter varying from 23 cm to 40 cm is placed in the middle of the enclosure. The proposed liquid evaporation model in combustion environments is fully coupled with CFD simulation. The results show that the fuel pan above 30 cm leads to faster fire growth implying more important peak up to 200 kW in heat release rate and thus more dangerous fire. In the early stages of a fire, a stratified hotter unburnt fuels layer with a concentration beyond the Lower Flammability Limit is formed in the extraction duct connected to a mechanically ventilated enclosure fire. With a long time delay (about 21 min in the current study), the energy released per mass of oxygen consumed allows to raise the smoke temperature above 350°C. Occurrence of flame extinction in vitiated air enclosure with an oxygen concentration below 5% makes a sudden decrease of the pressure level inside enclosure due to cooling effects. This induces a sudden supply of fresh air from dilution duct, providing a sufficient oxygen concentration with a molar fraction of about 10% for triggering the ignition of a hotter fuel–air mixture near the extraction duct. Such auto-ignition, determined experimentally by visual identification of fire, is likely a random phenomenon with a probability of 50% due to the heat leakage through the walls of the experimental facility. When the compartment is more heat-tight by using an insulating material, the auto-ignition occurs for each fire tests. Globally, the phenomena with ignition near the extraction duct can be identified by a rapid decrease of unburnt fuel concentration towards a stoichiometric fuel–air mixture and a sharp increase of temperature with a peak reaching a typical flame temperature of 550°C there.


Enclosure fire Liquid fuel Ventilation rate Ignition risk Extraction duct Dilution duct 



  1. 1.
    Peatross MJ, Beyler CL (1997) Ventilation effects on compartment fire characterization. In: Fire safety science—proceedings of the fifth international symposium, vol 5, pp 403–414Google Scholar
  2. 2.
    Utiskul Y (2006) Theoretical and experimental study on full-developed compartment fires. Fire Engineering, University of Maryland, USAGoogle Scholar
  3. 3.
    Tewarson A, Lee JL, Pion RF (1981) The influence of oxygen concentration on fuel parameters for fire modelling. Symp Int Combust 18:563–570CrossRefGoogle Scholar
  4. 4.
    Orloff L, de Ris J (1982) Froude modelling of pool fires. In: 19th international symposium on combustion. The Combustion Institute, pp 885–895Google Scholar
  5. 5.
    Hamins A, Yang JC, Kashiwagi T (1999) A global model for predicting the burning rates of liquid pool fires. Technical report NISTIR-6381, NISTGoogle Scholar
  6. 6.
    Beaulieu P, Dembsey N (2007) Effect of oxygen on flame heat flux in horizontal and vertical orientations. Fire Saf J 43:410–428CrossRefGoogle Scholar
  7. 7.
    Merci B, Van Maele K (2008) Numerical simulations of full-scale enclosure fires in a small compartment with natural roof ventilation. Fire Saf J 43:495–511CrossRefGoogle Scholar
  8. 8.
    Wahlqvist J, Hees PV (2013) Validation of FDS for large-scale well-confined mechanically ventilated fire scenarios with emphasis on predicting ventilation system behavior. Fire Saf Sci 62(Part B):102–114CrossRefGoogle Scholar
  9. 9.
    Beji T, Bonte F, Merci B (2014) Numerical simulations of a mechanically-ventilated multi- compartment fire. In: IAFSS symposiumsGoogle Scholar
  10. 10.
    Gay L, Sapa B, Nmira F (2013) MAGIC and Code_Saturne developments and simulations for mechanically ventilated compartment fires. Fire Saf Sci 62(Part B):161–173CrossRefGoogle Scholar
  11. 11.
    Tang F, Hu LH, Delichatsios M, Lu KH, Zhu W (2012) Experimental study on flame height and temperature profile of buoyant window spill plume from an under-ventilated compartment fire. Int J Heat Mass Transf 55:93–101CrossRefGoogle Scholar
  12. 12.
    Prétrel H, Le Saux W, Audouin L (2012) Pressure variations induced by a pool fire in well-confined and force-ventilated compartment. Fire Saf J 52:11–24CrossRefGoogle Scholar
  13. 13.
    Vilfayeau S, Ren N, Wang Y, Trouvé A (2015) Numerical simulation of under-ventilated liquid-fueled compartment fires with flame extinction and thermally-driven fuel evaporation. Proc Combust Inst 35:2563–2571CrossRefGoogle Scholar
  14. 14.
    Novozhilov V (2001) Computational fluid dynamics modelling of compartment fires. Prog Energy Combust Sci 27:611–666CrossRefGoogle Scholar
  15. 15.
    Nasr A, Suard S, El-Rabii H, Gay L, Garo JP (2011) Fuel mass loss rate determination in a confined and mechanically ventilated compartment fire using a global approach. Combust Sci Technol 183:1342–1359CrossRefGoogle Scholar
  16. 16.
    Lassus J, Studer E, Garo JP, Vantelon JP et al (2010) Influence of ventilation on ignition risk of unburnt gases in the extraction duct of underventilated compartment fire. Combust Sci Technol 182:517–528CrossRefGoogle Scholar
  17. 17.
    Lassus J, Courty L, Studer E, Garo JP, Jourda P, Aine P (2016) Estimation of species concentration during a fire in a reduced scale room. J Fire Sci 34(1):30–50CrossRefGoogle Scholar
  18. 18.
    Melguizo Gavilanes J, Shepherd JE (2015) Hot surface ignition and flow separation. In: 25th ICDERS, Leeds, UK, 2–7 Aug 2015Google Scholar
  19. 19.
    Zukoski EE (1984) Fluid dynamics aspects of room fires. In: First international symposium on fire safety science, pp 1–30Google Scholar
  20. 20.
    McGrattan K, Hostikka S, Floyd J, Baum H, Rehm R (2014) Fire dynamics simulator—technical reference guide, No. 1018. National Institute of Standards and Technology, WashingtonGoogle Scholar
  21. 21.
    Murty Kanury A (1984) Introduction to combustion phenomena. Gordon, New York. ISBN 0-677-02690-0Google Scholar
  22. 22.
    Djilali N, Gartshore I, Salcudean M (1989) Calculation of convective heat transfer in recirculating turbulent flow using various near-wall turbulence models. Numer Heat Transf 16:189–212CrossRefGoogle Scholar
  23. 23.
    Leung KM, Lindstedt RP, Jones WP (1991) A simplified reaction mechanism for soot formation in nonpremixed flames. Combust Flame 87:289–305CrossRefGoogle Scholar
  24. 24.
    Moss JB, Stewart CD, Young KJ (1995) Modelling soot formation and burnout in a high temperature laminar diffusion flame burning under oxygen-enriched conditions. Combust Flame 101:491–500CrossRefGoogle Scholar
  25. 25.
    Beji T, Zhang J, Delichatsios MA (2008) Determination of soot formation rate from laminar smoke point measurements. Combust Sci Technol 180(5):927–940CrossRefGoogle Scholar
  26. 26.
    Magnussen BF, Ertesvag IS (2000) The eddy dissipation turbulence energy cascade model. Combust Sci Technol 159(1):213–235CrossRefGoogle Scholar
  27. 27.
    Babrauskas V (2003) Ignition handbook. Fire Science Publishers, Issaquah, p 1116 Google Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • H. Q. Dong
    • 1
  • B. Magnognou
    • 1
  • J. P. Garo
    • 1
  • B. Coudour
    • 1
  • H. Y. Wang
    • 1
    Email author
  1. 1.Fluides-Thermique-CombustionInstitut P′, CNRS, ENSMA, Université de PoitiersFuturoscope Chasseneuil CedexFrance

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