不同火源面积下隧道火灾温度场试验与数值模拟分析
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摘要
为了探究隧道内不同火源面积下温度场的分布规律,给隧道火灾救援提供科学的理论支持,为隧道防火设计提供参考,建立1∶9的缩尺寸模型隧道,对3种不同火源面积下,隧道火灾的热释放速率、拱顶及纵断面温度场分布特征、隧道洞口火溢流分布特点进行试验研究。同时采用大涡模拟方法对以上3种火灾场景进行了数值模拟计算,并利用试验对模拟结果进行对比分析。研究结果表明:当火源面积较小时,空气充足,燃烧主要以燃料控制型为主,隧道内最高温度位于火源正上方,并沿隧道纵向向两端逐渐减小,温度分布稳定、分层明显,此时通过火灾模拟软件FDS得到的数值模拟结果与试验较为吻合;当火源面积较大时,空气较为不足,燃烧主要以通风控制型为主,在稳定燃烧阶段,火源中部的燃烧因通风受限而受到抑制,其温度明显降低,而火源两侧燃烧相对剧烈,温度较高;当燃烧进入衰减阶段,由于两侧可燃蒸气减少,火源中部因助燃物充足而再次剧烈燃烧,此时,FDS数值模拟结果能够较好反映出该场景下的燃烧情况,但相对于试验,模拟计算所获得的温升速率较快,在充分燃烧阶段火源中心的抑制作用较试验更为明显;隧道洞口火溢流的模拟结果与试验结果相一致,数值模拟能够更好地给出火羽流的结构细节。
In this study,a 1/9 scaled tunnel was established,and experiments and numerical simulations were carried out using the LES method for three different fire source areas to investigate the distribution rules of temperature in a tunnel exposed to fire and provide a reference for tunnel fire protection design and rescue.The distribution characteristics of temperature along the tunnel ceiling and cross-section,as well as the heat release rate and the behaviors of fire overflow at the tunnel entrance were determined and analyzed.The experimental and numericalresults indicate that small area tunnel fire is mainly controlled by the fuel owing to the relatively abundant air,and the temperature at the center of the combustion region is significantly higher than the temperature at the two sides and it continues to decrease along the longitudinal direction.Furthermore,the temperature distribution is stable and obvious stratification occurs.It was found that the simulation results of FDS and the experimental results are in good agreement.For large area tunnel fire,the combustion is mainly controlled by the ventilation owing to the relatively abundant air supply,and the fire intensity at the middle of the combustion region decreased owing to limited ventilation and lack of oxygen;thus,the temperature decreased,while fire on both sides is relatively intense.As burning on both sides enters a weak phase,flammable vapors on both sides are reduced,and fuel in the middle of the combustion region burns intensely again owing to the abundant air supply.In this case,the simulation by FDS can also reflect the development of the fire.However,the simulation results indicate that the rate of increase of the temperature in the tunnel is higher and the combustion inhibition effect is more evident in the middle of the combustion region at the developing stage of the combustion.In addition,the growing trend of fire overflow of FDS is essentially consistent with the experimental results,and the simulation results can provide further details of fire overflow.
In this study,a 1/9 scaled tunnel was established,and experiments and numerical simulations were carried out using the LES method for three different fire source areas to investigate the distribution rules of temperature in a tunnel exposed to fire and provide a reference for tunnel fire protection design and rescue.The distribution characteristics of temperature along the tunnel ceiling and cross-section,as well as the heat release rate and the behaviors of fire overflow at the tunnel entrance were determined and analyzed.The experimental and numericalresults indicate that small area tunnel fire is mainly controlled by the fuel owing to the relatively abundant air,and the temperature at the center of the combustion region is significantly higher than the temperature at the two sides and it continues to decrease along the longitudinal direction.Furthermore,the temperature distribution is stable and obvious stratification occurs.It was found that the simulation results of FDS and the experimental results are in good agreement.For large area tunnel fire,the combustion is mainly controlled by the ventilation owing to the relatively abundant air supply,and the fire intensity at the middle of the combustion region decreased owing to limited ventilation and lack of oxygen;thus,the temperature decreased,while fire on both sides is relatively intense.As burning on both sides enters a weak phase,flammable vapors on both sides are reduced,and fuel in the middle of the combustion region burns intensely again owing to the abundant air supply.In this case,the simulation by FDS can also reflect the development of the fire.However,the simulation results indicate that the rate of increase of the temperature in the tunnel is higher and the combustion inhibition effect is more evident in the middle of the combustion region at the developing stage of the combustion.In addition,the growing trend of fire overflow of FDS is essentially consistent with the experimental results,and the simulation results can provide further details of fire overflow.
引文
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[20]MCDERMOTT R,MCGRATTAN K,HOSTIKKA S.Fire Dynamics Simulator(Version 5)Technical Reference Guide[M].Gaithersburg:NIST Special Publication,2008.
[2]OKA Y,OKA H,IMAZEKI O.Experimental Study on Temperature Property Along a Tunnel Axis with Flat Ceiling in Natural Ventilation[J].Fire Safety Science,2014,11(3):472-485.
[3]CALIENDO C,CIAMBELLI P,DE GUGLIELMO M L,et al.Simulation of Fire Scenarios Due to Different Vehicle Types with and Without Traffic in a Bi-directional Road Tunnel[J].Tunnelling and Underground Space Technology,2013,37(37):22-36.
[4]VIANELLO C,FABIANO B,PALAZZI E,et al.Experimental Study on Thermal and Toxic Hazards Connected to Fire Scenarios in Road Tunnels[J].Journal of Loss Prevention in the Process Industries,2012,25(4):718-729.
[5]CHEN F,LEONG J C.Smoke Flow Phenomena and Turbulence Characteristics of Tunnel Fires[J].Applied Mathematical Modelling,2011,35(9):4554-4566.
[6]INGASON H,LI Y Z.Model Scale Tunnel Fire Tests with Longitudinal Ventilation[J].Fire Safety Journal,2010,45(6/7/8):371-384.
[7]INGASON H.Design Fire Curves for Tunnels[J].Fire Safety Journal,2009,44(2):259-265.
[8]ROH J S,YANG S S,RYOU H S,et al.An Experimental Study on the Effect of Ventilation Velocity on Burning Rate in Tunnel Fire-heptane Pool Fire Case[J].Building and Environment,2008,43(7):1225-1231.
[9]BLANCHARD E,BOULET P,DESANGHERE S,et al.Experimental and Numerical Study of Fire in a Midscale Test Tunnel[J].Fire Safety Journal,2012,47(1):18-31.
[10]TIAN X L,ZHONG M H,SHI C L,et al.Fullscale Tunnel Fire Experimental Study of Fire-induced Smoke Temperature Profiles with Methanol-gasoline Blends[J].Applied Thermal Engineering,2017,116:233-243.
[11]CHEN C K,ZHU C X,LIU X Y,et al.Experimental Investigation on the Effect of Asymmetrical Sealing on Tunnel Fire Behavior[J].International Journal of Heat and Mass Transfer,2016,92:55-65.
[12]康恒.重载铁路隧道火灾特征试验及数值模拟研究[D].长沙:中南大学,2014.KANG Heng.Experimental and Numerical Simulation Research on the Characteristics of Heavy Haul Railway Tunnel Fire[D].Changsha:Central South University,2014.
[13]JI J,FAN C G,ZHONG W,et al.Experimental Investigation on Influence of Different Transverse Fire Locations[J].International Journal of Heat and Mass Transfer,2012,55(17/18):4817-4826.
[14]纪杰,霍然,胡隆华,等.长通道内排烟口与火源相对位置对机械排烟效果的影响[J].工程力学,2009,26(5):234-238.JI Jie,HUO Ran,HU Long-hua,et al.Influence of Relative Location of Smoke Exhaust Opening to Fire Source on Mechanical Smoke Exhaust Efficiency in a Long Channel[J].Engineering Mechanics,2009,26(5):234-238.
[15]王亚琼,夏丰永,谢永利,等.特长公路隧道双洞互补式通风物理模型试验[J].中国公路学报,2014,27(6):84-90.WANG Ya-qiong,XIA Feng-yong,XIE Yong-li,et al.Physical Model Experiment on Complementary Ventilation of Extra-long Highway Tunnel[J].China Journal of Highway and Transport,2014,27(6):84-90.
[16]纪杰,霍然,张英,等.长通道内烟气层水平蔓延阶段的质量卷吸速率实验研究[J].中国科学技术大学学报,2009,39(7):738-742.JI Jie,HUO Ran,ZHANG Ying,et al.Experimental Study on the Entrainment Mass Flow Rate Across the Smoke Layer Interface during Horizontal Spread in a Long Channel[J].Journal of University of Science and Technology of China,2009,39(7):738-742.
[17]周勇狄,夏永旭,王永东.公路隧道火灾消防救援安全研究[J].中国公路学报,2008,21(6):83-89.ZHOU Yong-di,XIA Yong-xu,WANG Yong-dong.Research on Safety of Fire Rescue in Highway Tunnel[J].China Journal of Highway and Transport,2008,21(6):83-89.
[18]钟委,李兆周,吕金金,等.FDS6对隧道火灾温度场模拟的适用性研究[J].郑州大学学报:工学版,2014,35(6):35-38.ZHONG Wei,LI Zhao-zhou,LU Jin-jin,et al.Study on Applicability of FDS6to Simulate the Fire in Horizontal Long Tunnel[J].Journal of Zhengzhou University:Engineering Science,2014,35(6):35-38.
[19]MCGRATTAN K,HOSTIKKA S,FLOYD J E.Fire Dynamics Simulator(Version 5),User’s Guide[M].Gaithersburg:NIST Special Publication,2010.
[20]MCDERMOTT R,MCGRATTAN K,HOSTIKKA S.Fire Dynamics Simulator(Version 5)Technical Reference Guide[M].Gaithersburg:NIST Special Publication,2008.