Abstract
In this study, a series of sidewall fire experiments were carried out in an arched tunnel, and the effect brought by the fire source height, the shape and the orientation of oil pool on flame length and transverse temperature were investigated. The results show that when the long side of oil pool is parallel to sidewall, the height change of oil pool has less influence on flame under the arched ceiling, while it has a large influence under the horizontal ceiling in previous studies; when the long side of oil pool is perpendicular to sidewall, the flame bifurcates with a large aspect ratio and entrains more fresh air, and the mass loss rate increases dramatically. The height change of oil pool has less influence on the flame when the long side of oil pool is parallel to sidewall, while it has great influence when the long side of oil pool is perpendicular to sidewall. Besides, the dimensionless heat release rates of fire source are modified and the flame length formulas are obtained under the two orientations of oil pool. The equation of the transverse temperature distribution under arched ceiling was obtained by modifying the lateral travelling distance of the plume.
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Abbreviations
- \(r_{l}\) :
-
Longitudinal flame length under ceiling (m)
- \(r_{t}\) :
-
Transverse flame length under ceiling (m)
- D p :
-
Equivalent diameter considering pool shape (m)
- \(Q_{{D_{p} }}^{*}\) :
-
Modified dimensionless heat release rate by Fan
- \(H_{ef}\) :
-
Effective height of the fire source to the ceiling (m)
- \(Q_{{l_{p} H_{ef} }}^{*}\) :
-
Modified dimensionless heat release rate by Ji
- L :
-
Total flame length (m)
- n :
-
Aspect ratio (the ratio of the long side to the short side)
- S :
-
Pool area (m2)
- H :
-
Height from the ground to the bottom of the pool (m)
- A :
-
Length of the long side of pool (m)
- B :
-
Length of the short side of pool (m)
- \(\dot{m}\) :
-
Mass loss rate of unburnt fuel before impingement (kg/s)
- \(\dot{m}_{up}\) :
-
Mass loss rate of unburnt fuel in upward direction after impingement (kg/s)
- \(\dot{m}_{down}\) :
-
Mass loss rate of unburnt fuel in downward direction after impingement (kg/s)
- \(\dot{m}_{leng}\) :
-
Mass loss rate of unburnt fuel in lengthwise direction after impingement (kg/s)
- \(\dot{m}_{loss}\) :
-
Mass loss rate (kg/s)
- \(\alpha\) :
-
Tangent angle at the flame impact point (°)
- \(\dot{m}^{\prime\prime}_{\infty }\) :
-
Asymptotic value for fuel mass loss rate per unit area (kg/(s m2))
- D :
-
Equivalent diameter (m)
- \(Y_{ox,l}\) :
-
Oxygen fraction feeding flame
- \(Y_{ox,o}\) :
-
Oxygen fraction in free burning
- \(\dot{q}^{\prime\prime}_{Ext}\) :
-
External heat feedback per area from environmental (kW/m2)
- \(L_{g}\) :
-
Heat of gasification (kJ/kg)
- a, b :
-
Constants
- \(\dot{m}_{e}\) :
-
Mass flow rate of entrainment (kg/s)
- \(Y_{{O_{2} ,\infty }}\) :
-
Mass fraction of oxygen in environment
- w :
-
Constant
- \(u_{e}\) :
-
Speed of entrainment (m/s)
- p :
-
Circumference of oil pool that can entrain (m)
- \(\dot{Q}\) :
-
Heat release rate (kW)
- \(c_{p}\) :
-
Specific heat of ambient air (kJ/(kg k))
- \(T_{a}\) :
-
Temperature of ambient air (°C)
- g :
-
Gravity acceleration (m/s2)
- \(l_{p}\) :
-
Length of pool side which is perpendicular to sidewall (m)
- \(Q_{{D_{p} H_{ef} }}^{*}\) :
-
New modified dimensionless heat release rate
- \(\Delta T\) :
-
Temperature rise (°C)
- d :
-
Transverse distance under the horizontal ceiling (m)
- l :
-
Arc length of plume travelling along arched ceiling (m)
- R :
-
Radius of the arched ceiling (m)
- \(\theta\) :
-
Central angle (°)
- \(\alpha\) :
-
Inclined angle (°)
- \(\rho_{a}\) :
-
Density of ambient air (kg/m3)
- \(\gamma\) :
-
Stoichiometric ratio
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Acknowledgements
The work was supported by the National Key Research and Development Program of China (No. 2016YFC0802900).
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Liu, X., Zhu, G., Pan, R. et al. Experimental Study on Flame Length of Sidewall Fire with Different Aspect Ratios and Orientations in an Arched Tunnel. Fire Technol 58, 3577–3596 (2022). https://doi.org/10.1007/s10694-022-01328-w
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DOI: https://doi.org/10.1007/s10694-022-01328-w