In tunnel fire, smoke is a great threat to successful emergency escapes, and its spreading patterns at high altitude tunnel may differ. Therefore, the impact of ambient pressure on the stability of smoke layers and maximum smoke temperature under ceiling in ventilated tunnels were investigated in this study. Results show that the temperature of smoke layer is negatively correlated with the longitudinal velocity and ambient pressure. Besides, the influence of longitudinal velocity at different ambient pressures on the shear velocity between the smoke and air layers was further studied. Using Richardson number (Ri) and Froude number (Fr), smoke flow can be classified into three patterns, namely stable and obvious smoke stratification (Ri>3.2 or Fr < 0.38), a stable smoke layer but with blurred interface (2.3 < Ri < 3.2 or 0.38 < Fr < 0.53) and a completely unstable smoke stratification (Ri < 2.3 or Fr > 0.53). Furthermore, a model has been developed to predict maximum smoke temperature under the tunnel ceiling, which agrees well with previous studies at standard atmospheric pressure. The results of the present work provide information for tunnel structure protection and safe evacuation in fire accidents at different ambient pressures.
LiJMLiuSSLiYFChenCCLiuXYinCC.Experimental study of smoke spread in titled urban traffic tunnels fires. Procedia Eng2012; 45: 690–694.
2.
LiYFBianJLiJM.Research on smoke flow in a tunnel fire of subway system. Procedia Eng2014; 71: 390–396.
3.
YaoYZZhangSGShiLChengXD.Effects of shaft inclination angle on the capacity of smoke exhaust under tunnel fire. Indoor Built Environ2019; 28(1): 77–87.
4.
XieBCHanYXHuangHChenLNZhouYFanCGLiuXP.Numerical study of natural ventilation in urban shallow tunnels: impact of shaft cross section. Sust Cities Soc2018; 42: 521–537.
5.
AwadASCalayRKBadranOOHoldoAE.An experimental study of stratified flow in enclosures. Appl Therm Eng2008; 28: 2150–2158.
6.
OkaYOkaHImazekiO.Ceiling-jet thickness and vertical distribution along flat-ceilinged horizontal tunnel with natural ventilation. Tunn Undergr Space Technol2016; 53: 68–77.
7.
NymanHIngasonH.Temperature stratification in tunnels. Fire Saf J2012; 48: 30–37.
8.
TangFChenLChenYHPangHP.Experimental study on the effect of ceiling mechanical smoke extraction system on transverse temperature decay induced by ceiling jet in the tunnel. Int J Therm Sci2020; 152: 106294.
9.
HanJQLiuFWangFWengMCWangJ.Experimental study on the effect of ceiling mechanical smoke extraction system on transverse temperature decay induced by ceiling jet in the tunnel. Int J Therm Sci2020; 149: 106165.
10.
TaiCMTianGSLeiWJWangJW.A field measurement of temperature and humidity in a utility tunnel and a brief analysis of the exhaust heat recovery system. Indoor Built Environ2021; 30(4): 487–501.
11.
LiYZLeiBIngasonH.The maximum temperature of buoyancy-driven smoke flow beneath the ceiling in tunnel fires. Fire Saf J2011; 46: 204–210.
12.
HuLHTangFYangDLiuSHuoR.Longitudinal distributions of CO concentration and difference with temperature field in a tunnel fire smoke flow. Int J Heat Mass Transfer2010; 53: 2844–2855.
13.
HuLHHuoRPengWChowWKYangRX.On the maximum smoke temperature under the ceiling in tunnel fires. Tunn Undergr Space Technol2006; 21: 650–655.
14.
TangFCaoZLPalaciosAWangQ.A study on the maximum temperature of ceiling jet induced by rectangular-source fires in a tunnel using ceiling smoke extraction. Int J Therm Sci2018; 127: 329–334.
15.
ZhangSChengXYaoYZhuKLiKLuSZhangH.An experimental investigation on blockage effect of metro train on the smoke back-layering in subway tunnel fires. Appl Therm Eng2016; 99: 214–223.
16.
ZengZKangXLuXLWengMCLiuF.Study on the smoke stratification length under longitudinal ventilation in tunnel fires. Int J Therm Sci2018; 132: 285–295.
17.
LemaireTKenyonY.Large scale fire tests in the Second Benelux Tunnel. Fire Technol2006; 42: 329–350.
18.
YanGFWangMNYuLTianY.Effects of ambient pressure on the critical velocity and back-layering length in longitudinal ventilated tunnel fire. Indoor Built Environ2020; 29(7): 1017–1027.
19.
GannouniSZinoubiJRejebBM.Numerical study on the thermal buoyant flow stratification in tunnel fires with longitudinal imposed airflow: effect of an upstream blockage. Int J Therm Sci2019; 136: 230–242.
20.
WuYGaoNPWangLHWuXP.A numerical analysis of airflows caused by train-motion and performance evaluation of a subway ventilation system. Indoor Built Environ2014; 23: 854–863.
21.
ChowWKGaoYZhaoJHDangJFChowCLMiaoL.Smoke movement in tilted tunnel fires with longitudinal ventilation. Fire Safety J2015; 75: 14–22.
22.
ChowWKWongKYChungWY.Longitudinal ventilation for smoke control in a tilted tunnel by scale modeling. Tunn Undergr Space Technol2010; 25:122–128.
23.
YangDHuLHHuoRJiangYQLiuSTangF.Experimental study on buoyant flow stratification induced by a fire in a horizontal channel. Appl Therm Eng2010; 30: 872–878.
24.
HuLHHuoRLiYZWangHBChowWK.Full-scale burning tests on studying smoke temperature and velocity along a corridor. Tunn Undergr Space Technol2005; 20: 223–229.
25.
LiangQLiYFLiJMXuHLiKY.Numerical studies on the smoke control by water mist screens with transverse ventilation in tunnel fires. Tunn Undergr Space Technol2017; 64: 177–183.
26.
FengSLiYFHouYSLiJMHuangYB.Study on the critical velocity for smoke control in a subway tunnel cross-passage. Tunn Undergr Space Technol2020; 97: 103234.
27.
LiuCZhongMSongSXiaFTianXYangYZengL.Experimental and numerical study on critical ventilation velocity for confining fire smoke in metro connected tunnel. Tunn Undergr Space Technol2020; 97: 103296.
28.
ZhangSGYaoYZZhuKLiKYZhangRFLuSChengXD.Prediction of smoke back-layering length under different longitudinal ventilations in the subway tunnel with metro train. Tunn Undergr Space Technol2016; 53: 13–21.
29.
ChenLHuLZhangXZhangXZhangXYangL.Thermal buoyant smoke back-layering flow length in a longitudinal ventilated tunnel with ceiling extraction at difference distance from heat source. Appl Therm Eng2015; 78: 129–135.
30.
MengNLiuBBLiXJinXNHuangYJWangQ.Effect of blockage-induced near wake flow on fire properties in a longitudinally ventilated tunnel. Int J Therm Sci2018; 134: 1–12.
31.
TangFHuLHYangLZQiuZW.Longitudinal distributions of CO concentration and temperature in buoyant tunnel fire smoke flow in a reduced pressure atmosphere with lower air entrainment at high altitude. Int J Heat Mass Transfer2014; 75: 130–134.
32.
JiJGuoFYGaoZH.Numerical investigation on the effect of ambient pressure on smoke movement and temperature distribution in tunnel fires. Appl Therm Eng2017; 118: 663–669.
33.
LeeSRRyouHS.A numerical study on smoke movement in longitudinal ventilation tunnel fires for different aspect ratio. Build Environ2006; 41: 719–725.
34.
LiuCZhongMTianXZhangPXiaoYMeiQ.Experimental and numerical study on fire-induced smoke temperature in connected area of metro tunnel under natural ventilation. Int J Therm Sci2019; 138: 84–97.
35.
YaoYLiYZIngasonHChengX.Numerical study on overall smoke control using naturally ventilated shafts during fires in a road tunnel. Int J Therm Sci2019; 140: 491–504.
36.
McgrattanKHostikkaSMcdermottRFloydJWeinschenkCOverholtK.Fire dynamics simulator user’s guide. Gaithersburg, MD: National Institute of Standards and Technology, 2016.
37.
JiangXLiuMWangJLiK.Study on air entrainment coefficient of one dimensional horizontal movement stage of tunnel fire smoke in top central exhaust. Tunn Undergr Space Technol2016; 60: 1–9.
38.
McGrattanKHostikkaSMcDermottRFloydJ.Fire dynamics simulator (version 6) user’s guide. Gaithersburg, MD: National Institute of Standards and Technology, 2013.
39.
HeYFernandoALuoM.Determination of interface height from measured parameter profile in enclosure fire experiment. Fire Saf J1998; 31: 19–38.
40.
YanZGGuoQHZhuHH.Full-scale experiments on fire characteristics of road tunnel at high altitude. Tunn Undergr Space Technol2017; 66: 134–146.
41.
IngasonHWerlingP.Experimental study of smoke evacuation in a model tunnel. FOA-R—99-01267-311—SE. Tumba, Sweden: FOA Defence Research Establishment, 1999.
LesserNI.Memorial tunnel fire ventilation test program. Test report BN-97-6-2. Cambridge, MA: Massachusetts Highway Department and Federal Highway Administration, 1995.
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
