Influence of air pressure and ventilation speed on flashover of cable fire in long-narrow confined spaces

doi:10.16265/j.cnki.issn1003-3033.2025.07.0562

Abstract

Abstract:

In order to investigate the influence of air pressure and ventilation speed on the flashover critical conditions of cable fires in long-narrow confined spaces under plateau environments, a functional equation between the flashover critical ceiling temperature and air pressure and ventilation speed was derived based on dimensional analysis. A cable fire model in a long-narrow confined space was established using Fire Dynamics Simulator (FDS) to study the critical flashover temperature during fire development under different air pressures (101, 90, 77, and 65 kPa) and ventilation speeds (0, 0.5, 1.0, and 1.5 m/s). The results show that the flashover critical ceiling temperature of cable fires in long-narrow confined spaces is relatively high, ranging from 720.7 to 877.3 ℃. The flashover critical ceiling temperature follows a power-law relationship with air pressure and ventilation speed, while showing a decreasing trend with increasing pressure and ventilation speed. The established model provides reasonable predictions for the flashover critical ceiling temperature of cable fires in long-narrow confined spaces under both natural ventilation and longitudinal ventilation scenarios. The model prediction results agree well with the numerical simulation results.

Key words: air pressure, ventilation speed, long-narrow confined space, cable fire, flashover, flashover critical temperature

CLC Number:

X928.7火灾与爆炸事故

AN Weiguang, XUE Jingyun, WANG Tao, GU Mengbin, WANG Meng, WANG Zhe. Influence of air pressure and ventilation speed on flashover of cable fire in long-narrow confined spaces[J]. China Safety Science Journal, 2025, 35(7): 75-81.

Figures/Tables 7

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编号	物理量	符号	单位	量纲
1	轰燃临界顶棚温度	t_c	℃	Θ
2	电缆热释放速率	$\stackrel{·}{Q}$	kW	L²MT^-3
3	环境温度	t₀	℃	Θ
4	空气密度	${\rho }_{\infty }$	kg/m³	ML^-3
5	定压比热容	c_p	kJ/(kg·℃)	L²T^-2Θ^-1
6	重力加速度	g	m/s²	LT^-2
7	狭长受限空间高度	H	m	L
8	通风风速	U_m	m/s	LT^-1
9	气压	P	kg /(m·s²)	ML^-1T^-2

通风风速/ (m·s^-1)	关系式	R²
0.0	$\begin{array}{l}{t}_{c2}^{}=\frac{{t}_{c}}{{t}_{0}}=58.618{\left(\frac{{\stackrel{·}{Q}}^{}P}{{\rho }_{\infty }gH}\right)}^{-0.108}=\\ 58.618{P}_{2}^{*-0.108}\end{array}$	0.94
0.5、1.0	$\begin{array}{l}{t}_{c1}^{}=\frac{{t}_{c}}{{t}_{0}{\stackrel{·}{Q}}^{}}=0.124{\left(\frac{{U}_{m}P}{{\rho }_{\infty }{g}^{3/2}{H}^{3/2}}\right)}^{-0.795}=\\ 0.124{P}_{1}^{*-0.795}\end{array}$	0.97
1.5	$\begin{array}{l}{t}_{c1}^{}=\frac{{T}_{c}}{{T}_{0}{\stackrel{·}{Q}}^{}}=0.286{\left(\frac{{U}_{m}P}{{\rho }_{\infty }{g}^{3/2}{H}^{3/2}}\right)}^{-0.861}=\\ 0.286{P}_{1}^{*-0.861}\end{array}$	0.99