Study on critical ventilation velocity induced by ejected fire of carriage in immersed tunnel

doi:10.16265/j.cnki.issn1003-3033.2023.02.0696

Abstract

Abstract:

For studying the critical velocity characteristics of smoke control induced by carriage fire plume under the synergy effect of longitudinal ventilation and lateral concentrated smoke extraction in immersed tunnel, a 1∶8 reduced-scale test model was firstly established. Based on 3 carriage opening sizes, 9 fire heat release rates and 2 states (on and off) of lateral smoke exhaust system, the smoke temperature under the immersed tunnel ceiling with different longitudinal velocity was collected. Meantime, the distribution characteristics of velocity and temperature field of ejected fire in immersed tunnel were simulated by FDS (Fire Dynamics Simulator). Finally, the physical influence mechanism of critical velocity evolution was analyzed. The results show that whether the lateral concentrated smoke extraction system is open or not, the smoke maximum temperature under ceiling decreases significantly, and the smoke back-layering length continues to shorten with the increasing longitudinal velocity. Moreover, the critical velocity shows the increasing section firstly and then remains unchanged trend with the increasing fire heat release rate of carriage fire in tunnel. Under the synergetic effect of lateral smoke exhaust and longitudinal ventilation, the critical velocity of carriage fire in immersed tube tunnel increases with the increasing heat release rate, which shows a piecewise function relationship of first increasing, then unchanged.

Key words: immersed tunnel, carriage fire plume, critical ventilation velocity, longitudinal ventilation, lateral concentrated smoke extraction

TANG Fei, LIU Ziwei, SUN Xiepeng, LIU Shuai, XU Tong. Study on critical ventilation velocity induced by ejected fire of carriage in immersed tunnel[J]. China Safety Science Journal, 2023, 33(2): 75-81.

Figures/Tables 9

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Tab.1

Test conditions

试验工况	v₁ /(m·s^-1)	v₂ /(m·s^-1)	车厢开口尺寸S/ (W × H: m × m)	$Q ·$ /kW
001—108	0 (关闭) 3 (开启)	0.57, 0.67,0.76, 0.85, 0.98, 1.05	0.15×0.15	15.5, 23.25, 31, 38.75, 46.5, 54.25, 62, 69.75, 77.5
109—216		0.62, 0.71, 0.78, 0.84, 0.88, 0.93	0.10×0.15
217—324		0.62, 0.71, 0.84, 0.92, 0.97, 1.01	0.15×0.10

Tab.1

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