An Experimental Study on the Effect of Slope on the Critical Velocity in Tunnel Fires

Abstract

The present article deals with the experimental study to investigate the effects of tunnel slope on the critical velocity in the tunnel fires. The 1/20 reduced-scale model tunnel is adopted on the basis of Froude scaling law. The methanol, acetone, and n-heptane pool fires are used as fire sources with the heat release rate ranging from 1.11 to 1.85 kW, 3.13 to 5.21 kW, and 9.16 to 15.6 kW, respectively. The angle of tunnel slope is varied as five different degrees 0, 2, 4, 6, and 8°. A load cell is used to measure the mass loss rate of the burning fuel. The location of smoke layer is determined on the basis of temperature variation measured at the tunnel ceiling by K-type thermocouples. The present experiments observe the effects of the tunnel slope, fire size, and ventilation velocity on the back-layering distance. The results showed that critical velocity increases with tunnel slope due to the stack effect. The correlation between the critical velocity and the angle of tunnel slope was obtained for the pool fires whose heat release rate was varied with the ventilation velocity.

Keywords

tunnel fire slope tunnel scaling law critical velocity stack effect.

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References

Beard, A. and Carvel, R. ( 2004). The Handbook of Tunnel Fire Safety, pp. 10-41, Thomas Telford, London, UK.

Cha, C.H. and Kim, J.K. (1999). Smoke Control in Subway Tunnels, Korean Journal of Air-conditioning and Refrigeration Engineering, 16(2): 135-141.

Oka, Y. and Atkinson, G.T. ( 1995). Control of Smoke Flow in Tunnel Fires, Fire Safety Journal, 25(4): 305-322.

Wu, Y. and Bakar, M.Z.A. ( 2000). Control of Smoke Flow in Tunnel Fires Using Longitudinal Ventilation Systems - A Study of the Critical Velocity, Fire Safety Journal, 35(4): 363-390.

Lee, S.R. and Ryou, H.S. (2004). An Experimental Study of the Effect of the Aspect Ratio on the Critical Velocity in Longitudinal ventilation tunnel fires, Journal of Fire Sciences, 23: 119-138.

Carvel, R.O. , Beard, A.N. and Jowitt, P.W. ( 2001). The influence of Longitudinal Ventilation Systems of Fires in Tunnels, Tunnelling and Underground Space Technology , 16: 3-21.

Carvel, R.O. , Beard, A.N. , Jowitt, P.W. and Drysdale, D.D. (2001). Variation of Heat Release Rate with Forced Longitudinal Ventilation for Vehicle Fires in Tunnels, Fire Safety Journal, 36: 569-596.

Yang, S.S. , Kim, S.C. and Ryou, H.S. ( 2005). An Experimental Study on the Effect of Longitudinal Ventilation on the Variation of Burning Rate in Tunnel fires, Tunnel & Underground Space (in Korean), 15(1): 55-60.

Yang, S.S. and Ryou, H.S. ( 2005). An Experimental Study on the Ventilation velocity of the Variation of Burning rate in Tunnel Fires-heptane pool fire case, Tunnelling Technology (in Korean), 7(2): 109-117.

10.

Roh, J.S. , Yang, S.S. and Ryou, H.S. (2007). Tunnel Fires: Experiments on Critical Velocity and Burning Rate in Pool Fire During Longitudinal Ventilation , Journal of Fire Sciences , 25(2): 161-176.

11.

Atkinson, G.T. and Wu, Y. (1996). Smoke Control in Sloping Tunnels, Fire Safety Journal, 27(4): 335-341.

12.

McCaffrey, B.J. and Quintiere , J.G. (1977). Buoyancy Driven Countercurrent Flows Generated by Fire Source, In: Spalding, D.B. and Afgan, N. (eds), Heat Transfer and Turbulent Buoyant Convection , Hemisphere Publishing Co., Washington , USA, pp. 457-472.

13.

Quintiere, J.G. (1989). Scaling Applications in Fire Research, Fire Safety Journal, 15: 3-29.