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Numerical and experimental study on the critical velocity and smoke maximum temperature in the connected area of branch tunnel

  • Research Article
  • Indoor/Outdoor Airflow and Air Quality
  • Published:
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Abstract

The objective of this study is to investigate critical velocity and smoke maximum temperature beneath the ceiling in the connected area of branch tunnel with varying fire locations. The fire sources were located in the divergent connected area of the branch tunnel, to imitate traffic accidents near the branch point. A 1/20 scale model branch tunnel was built including main line before branch, main line after branch, and ramp. Experimental tests and numerical simulations were performed to explore smoke movement characteristics with longitudinal ventilation. The results showed that the enlarged cross-sectional area in branch tunnel caused the shortening of the back-layering length, and a modified model of back-layering length was proposed. The higher tunnel height in this work affected the critical condition of large fire; it caused a larger transition point of dimensionless critical velocity. A revised model was proposed for the maximum temperature rise of tunnel fires in the connected area of branch tunnel. The critical velocity kept unchanged when the branch angle increased from 0° to 20° because there is little change in the longitudinal smoke temperature. As the local tunnel width of fire source was increased, the required critical velocity was increased while the local effective velocity kept nearly the same.

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Abbreviations

A :

tunnel cross-sectional area (m2)

A local :

sectional area of fire source (m2)

A inlet :

sectional area of velocity measurement (m2)

c p :

specific heat capacity of air (kJ/(kg·K))

D*:

characteristic length of fire

Fr :

Froude number

g :

gravitational acceleration (m/s2)

H :

tunnel height (m)

\(\overline H \) :

hydraulic diameter(m)

h c :

heat of combustion (kJ/kg)

L :

back-layering length (m)

l* :

dimensionless back-layering length

ṁ :

fuel mass burning rate (kg/s)

\(\dot Q\) :

total heat release rate (kW)

\({\dot Q_{\rm{c}}}\) :

convective part of the heat release rate of fire source (kW)

\({\dot Q^\ast}\) :

dimensionless heat release rate

\({\dot Q^\prime}\) :

dimensionless heat release rate in Eq. (2)

r :

radius of fire source (m)

T a :

ambient temperature (K)

T f :

average downstream gas temperature (K)

ΔT max :

maximum smoke temperature rise (K)

u :

ventilation velocity (m/s)

u* :

characteristic plume velocity (m/s)

u′ :

dimensionless ventilation velocity in Eq. (13)

u a,mean :

mean air velocity (m/s)

u a,rms :

root-mean-squared fluctuation velocity (m/s)

V c :

critical velocity (m/s)

V* :

dimensionless ventilation velocity

V c*:

dimensionless critical velocity

V local :

local effective velocity at fire source section (m/s)

V inlet :

designed inlet velocity at velocity measurement section (m/s)

W :

tunnel width (m)

α, β :

coefficients

η :

combustion efficiency

ρ a :

ambient density (kg/m3)

References

  • Fan CG, Ji J, Sun JH (2015). Influence of longitudinal fire location on smoke characteristics under the tunnel ceiling. Fire and Materials, 39: 72–84.

    Article  Google Scholar 

  • Guo F, Gao Z, Wan H, et al. (2019). Influence of ambient pressure on critical ventilation velocity and backlayering distance of thermal driven smoke in tunnels with longitudinal ventilation. International Journal of Thermal Sciences, 145: 105989.

    Article  Google Scholar 

  • Han J, Liu F, Wang F, et al. (2020). Study on the smoke movement and downstream temperature distribution in a sloping tunnel with one closed portal. International Journal of Thermal Sciences, 149: 106165.

    Article  Google Scholar 

  • Harish R, Venkatasubbaiah K (2015). Large eddy simulation of thermal plume behavior in horizontally partitioned dual enclosure. Building Simulation, 8: 137–148.

    Article  Google Scholar 

  • Hu LH, Huo R, Peng W, et al. (2006). On the maximum smoke temperature under the ceiling in tunnel fires. Tunnelling and Underground Space Technology, 21: 650–655.

    Article  Google Scholar 

  • Hu LH, Huo R, Chow WK (2008). Studies on buoyancy-driven back-layering flow in tunnel fires. Experimental Thermal and Fluid Science, 32: 1468–1483.

    Article  Google Scholar 

  • Hu L, Hu J, Liu S, et al. (2015). Evolution of heat feedback in medium pool fires with cross air flow and scaling of mass burning flux by a stagnant layer theory solution. Proceedings of the Combustion Institute, 35: 2511–2518.

    Article  Google Scholar 

  • Ingason H, Li Y (2010). Model scale tunnel fire tests with longitudinal ventilation. Fire Safety Journal, 45: 371–384.

    Article  Google Scholar 

  • Ingason H, Li YZ, Lönnermark A (2015). Tunnel Fire Dynamics. New York: Springer.

    Book  Google Scholar 

  • Karlsson B, Quintiere JG (2000). Enclosure Fire Dynamics. Boca Raton, FL, USA: CRC Press.

    Google Scholar 

  • Kennedy WD (1996). Critical Velocity: Past, Present and Future. In: Seminar of Smoke and Critical Velocity in Tunnels. London: JFL Lowndes.

    Google Scholar 

  • Król M, Król A, Koper P, et al. (2017). Full scale measurements of the operation of fire ventilation in a road tunnel. Tunnelling and Underground Space Technology, 70: 204–213.

    Article  Google Scholar 

  • Król M, Król A, Koper P, et al. (2019). The influence of natural draught on the air flow in a tunnel with longitudinal ventilation. Tunnelling and Underground Space Technology, 85: 140–148.

    Article  Google Scholar 

  • Kong J, Xu Z, You W, et al. (2021). Study of smoke back-layering length with different longitudinal fire locations in inclined tunnels under natural ventilation. Tunnelling and Underground Space Technology, 107: 103663.

    Article  Google Scholar 

  • Kurioka H, Oka Y, Satoh H, et al. (2003). Fire properties in near field of square fire source with longitudinal ventilation in tunnels. Fire Safety Journal, 38: 319–340.

    Article  Google Scholar 

  • Lee YP, Tsai KC (2012). Effect of vehicular blockage on critical ventilation velocity and tunnel fire behavior in longitudinally ventilated tunnels. Fire Safety Journal, 53: 35–42.

    Article  Google Scholar 

  • Li Y, Lei B, Ingason H (2010). Study of critical velocity and backlayering length in longitudinally ventilated tunnel fires. Fire Safety Journal, 45: 361–370.

    Article  Google Scholar 

  • Li Y, Lei B, Ingason H (2011). The maximum temperature of buoyancy-driven smoke flow beneath the ceiling in tunnel fires. Fire Safety Journal, 46: 204–210.

    Article  Google Scholar 

  • Li J, Li YF, Cheng CH, et al. (2019). A study on the effects of the slope on the critical velocity for longitudinal ventilation in tilted tunnels. Tunnelling and Underground Space Technology, 89: 262–267.

    Article  Google Scholar 

  • Long Z, Yang Y, Liu C, Zhong M (2021). Study on the optimal operation mode of ventilation system during metro double-island platform fire. Building Simulation, 14: 779–792.

    Article  Google Scholar 

  • van Maele K, Merci B (2008). Application of RANS and LES field simulations to predict the critical ventilation velocity in longitudinally ventilated horizontal tunnels. Fire Safety Journal, 43: 598–609.

    Article  Google Scholar 

  • McGrattan K, Hostikka S, McDermott R, et al. (2013). Fire Dynamics Simulator (Version 6)—User’s Guide. Gaithersburg, MD, USA: National Institute of Standards and Technology.

    Google Scholar 

  • Mei F, Tang F, Ling X, et al. (2017). Evolution characteristics of fire smoke layer thickness in a mechanical ventilation tunnel with multiple point extraction. Applied Thermal Engineering, 111: 248–256.

    Article  Google Scholar 

  • Meng N, Yang W, Xin L, et al. (2018). Experimental study on backlayering length of thermal smoke flow in a longitudinally ventilated tunnel with blockage at upstream of fire source. Tunnelling and Underground Space Technology, 82: 315–324.

    Article  Google Scholar 

  • NFPA 502 (2020). Standard for Road Tunnels, Bridges, and Other Limited Access Highways. National Fire Protection Association.

  • Oka Y, Atkinson GT (1995). Control of smoke flow in tunnel fires. Fire Safety Journal, 25: 305–322.

    Article  Google Scholar 

  • Oka Y, Kurioka H, Satoh H, et al. (2001). Fire properties with longitudinal ventilation in a tunnel. Bulletin of Japan Association for Fire Science & Engineering, 5: 156–170.

    Google Scholar 

  • Orloff L, de Ris J (1982). Froude modeling of pool fires. Symposium (International) on Combustion, 19: 885–895.

    Article  Google Scholar 

  • Peng M, Zhang S, Yang H, et al. (2020). Experimental study on confinement velocity in tunnel fires with longitudinal ventilation. Journal of Wind Engineering and Industrial Aerodynamics, 201: 104157.

    Article  Google Scholar 

  • Potter MC, Wiggert DC, Ramadan BH (2011). Mechanics of Fluid, 4th edn. Boston, MA, USA: Cengage Learning.

    Google Scholar 

  • Quintiere JG (1989). Scaling applications in fire research. Fire Safety Journal, 15: 3–29.

    Article  Google Scholar 

  • Tanaka F, Takezawa K, Hashimoto Y, et al. (2018). Critical velocity and backlayering distance in tunnel fires with longitudinal ventilation taking thermal properties of wall materials into consideration. Tunnelling and Underground Space Technology, 75: 36–42.

    Article  Google Scholar 

  • Tang F, Li LJ, Mei FZ, et al. (2016). Thermal smoke back-layering flow length with ceiling extraction at upstream side of fire source in a longitudinal ventilated tunnel. Applied Thermal Engineering, 106: 125–130.

    Article  Google Scholar 

  • Tang F, Cao Z, Palacios A, et al. (2018a). A study on the maximum temperature of ceiling jet induced by rectangular-source fires in a tunnel using ceiling smoke extraction. International Journal of Thermal Sciences, 127: 329–334.

    Article  Google Scholar 

  • Tang F, He Q, Mei F, et al. (2018b). Effect of ceiling centralized mechanical smoke exhaust on the critical velocity that inhibits the reverse flow of thermal plume in a longitudinal ventilated tunnel. Tunnelling and Underground Space Technology, 82: 191–198.

    Article  Google Scholar 

  • Thomas PH (1958). The Movement of Buoyant Fluid Against a Stream and Venting of Underground Fires. Watford, UK: Fire Research Station.

    Google Scholar 

  • Thomas P (1968). The movement of smoke in horizontal passages against an air flow. Watford, UK: Fire Research Station.

    Google Scholar 

  • Wan H, Gao Z, Han J, et al. (2019). A numerical study on smoke back-layering length and inlet air velocity of fires in an inclined tunnel under natural ventilation with a vertical shaft. International Journal of Thermal Sciences, 138: 293–303.

    Article  Google Scholar 

  • Weng M, Lu X, Liu F, Shi X, Yu L (2015). Prediction of backlayering length and critical velocity in metro tunnel fires. Tunnelling and Underground Space Technology, 47: 64–72.

    Article  Google Scholar 

  • Wu Y, Bakar M (2000). Control of smoke flow in tunnel fires using longitudinal ventilation systems—A study of the critical velocity. Fire Safety Journal, 35: 363–390.

    Article  Google Scholar 

  • Yao Y, Li Y, Ingason H, et al. (2019). Numerical study on overall smoke control using naturally ventilated shafts during fires in a road tunnel. International Journal of Thermal Sciences, 140: 491–504.

    Article  Google Scholar 

  • Yan G, Wang M, Yu L, et al. (2020). Effects of ambient pressure on smoke movement patterns in vertical shafts in tunnel fires with natural ventilation systems. Building Simulation, 13: 931–941.

    Article  Google Scholar 

  • Yu L, Wan H, Ji J (2021). Asymmetric flow effect in a horizontal natural ventilated tunnel with different aspect ratios under the influence of longitudinal fire locations. Building Simulation, 14: 1311–1323.

    Article  Google Scholar 

  • Zhang S, Yang H, Yao Y, et al. (2017). Numerical investigation of back-layering length and critical velocity in curved subway tunnels with different turning radius. Fire Technology, 53: 1765–1793.

    Article  Google Scholar 

  • Zhang X, Zhang T, Huang Z, et al. (2018). Local loss and flow characteristic of dividing flow in bifurcated tunnel. Journal of Zhejiang University (Engineering Science), 52: 440–445.

    Google Scholar 

  • Zhao S, Li Y, Ingason H, Liu F (2019). A theoretical and experimental study on the buoyancy-driven smoke flow in a tunnel with vertical shafts. International Journal of Thermal Sciences, 141: 33–46.

    Article  Google Scholar 

  • Zhong W, Duanmu W, Wang T, Liang T (2017). A study of the critical velocity of smoke bifurcation flow in tunnel with longitudinal ventilation. Fire Technology, 53: 873–891.

    Article  Google Scholar 

Download references

Acknowledgements

This research was supported by the National Nature Science Foundation of China (No. 52076066), Key Research and Development Project of Zhejiang Province (No. 2018C03029), and Zhejiang Provincial Natural Science Foundation of China (No. LQ19E040005), and Fellowship of China Postdoctoral Science Foundation (No. 2021M693042).

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Authors and Affiliations

  1. Safety Engineering Institute, College of Quality and Safety Engineering, China Jiliang University, Hangzhou, China

    Haihang Li

  2. State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, 230026, China

    Fei Tang

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  1. Haihang Li
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  2. Fei Tang
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Correspondence to Fei Tang.

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Li, H., Tang, F. Numerical and experimental study on the critical velocity and smoke maximum temperature in the connected area of branch tunnel. Build. Simul. 15, 525–536 (2022). https://doi.org/10.1007/s12273-021-0792-9

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  • DOI: https://doi.org/10.1007/s12273-021-0792-9

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