挡烟垂壁作用下狭长通道内烟气输运特征研究
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摘要
为揭示挡烟垂壁对狭长通道火灾烟气特征及温度分布的影响,运用火灾动力学软件FDS,研究了狭长通道内不同高度挡烟垂壁下火灾烟流运动行为,重点探讨了密度跳跃过程及近火源区烟气特征参数变化。结果表明:挡烟垂壁增加了密度跳跃中翻滚区的长度,缩小了卷吸空气范围,造成烟气质量流率相应减少;挡烟垂壁对烟气垂直速度分布的影响主要作用在挡烟区,且与垂壁高度有关;垂高大于0.3 m,受挡烟垂壁高度影响,在垂直高度1.5~2 m位置出现一定速度的烟气逆流,速度分布曲线呈现与无挡烟垂壁不同的凹陷区,非挡烟区烟气垂直速度服从高斯分布;与无挡烟垂壁相比,挡烟垂壁上游顶棚附近温度普遍增高,下游温度衰减速率随挡烟垂壁高度的增加而加快。
In order to reveal the influence of smoke barrier on the smoke characteristics and temperature distribution of fire in long-narrow channel,the fire smoke movement behavior under different smoke barrier heights in long-narrow channel was studied by using the fire dynamics software FDS,and the density jump process and the characteristic parameters variation of smoke near the fire source were discussed with emphasis. The results showed that the smoke barrier increases the length of the rolling zone in the density jump and reduces the range of air entrainment,resulting in a corresponding decrease in the mass flow rate of smoke. The influence of smoke barrier on the vertical velocity distribution of smoke is mainly in the smoke blocking area,being related to the height of smoke barrier. When the vertical height is greater than 0. 3 m,influenced by the height of smoke barrier,the reverse smoke flow with a certain velocity appear at the vertical height of 1. 5-2 m,thus the velocity distribution curve shows a depression area being different from that without smoke barrier. The vertical velocity of smoke in the area without smoke blocking obeys the Gauss distribution. Compared with that without smoke barrier,the temperature near the ceiling in the upstream of smoke barrier generally increases,while the temperature attenuation rate in the downstream becomes faster with the increase of smoke barrier height.
In order to reveal the influence of smoke barrier on the smoke characteristics and temperature distribution of fire in long-narrow channel,the fire smoke movement behavior under different smoke barrier heights in long-narrow channel was studied by using the fire dynamics software FDS,and the density jump process and the characteristic parameters variation of smoke near the fire source were discussed with emphasis. The results showed that the smoke barrier increases the length of the rolling zone in the density jump and reduces the range of air entrainment,resulting in a corresponding decrease in the mass flow rate of smoke. The influence of smoke barrier on the vertical velocity distribution of smoke is mainly in the smoke blocking area,being related to the height of smoke barrier. When the vertical height is greater than 0. 3 m,influenced by the height of smoke barrier,the reverse smoke flow with a certain velocity appear at the vertical height of 1. 5-2 m,thus the velocity distribution curve shows a depression area being different from that without smoke barrier. The vertical velocity of smoke in the area without smoke blocking obeys the Gauss distribution. Compared with that without smoke barrier,the temperature near the ceiling in the upstream of smoke barrier generally increases,while the temperature attenuation rate in the downstream becomes faster with the increase of smoke barrier height.
引文
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[2]杨云春,何嘉鹏,周汝,等.垂向射流与挡烟垂壁组合控制烟气蔓延研究[J].消防科学与技术,2011,30(7):574-576.YANG Yunchun,HE Jiapeng,ZHOU Ru,et al.Research on combination of vertical jet flow and smokescreen in control ling the spread of smoke[J].Fire Science and Technology,2011,30(7):574-576.
[3]杨培培,石必明,穆朝明,等.建筑物条形走廊烟气运动特性研究[J].中国安全生产科学技术,2012,8(7):11-15.YANG Peipei,SHI Biming,MU Chao ming,et al.Numerical simulation of the fire smoke flue in a buildingcorridor[J].Journal of Safety Science and Technology,2012,8(7):11-15.
[4]Delichatsios,M.A.The flow of fire gases under a beamed ceiling[J].Combustion and Flame,1981,43(4):1-10.
[5]Reveg,A.,Hassid,S.,Poreh,M.Calculation ofentrainment in density jumps[J].Environmental Fluid Mechanics,2006,6(5):407-424.
[6]汤静,石必明,陈昆.典型结构走廊火灾烟气流场的数值模拟研究[J].中国安全生产科学技术,2015,11(10):33-37.TANG Jing,SHI Biming,CHEN Kun.Numerical simulation of fire smoke flow in typical structure of building corridor[J].Journal of Safety Science and Technology,2015,11(10):33-37.
[7]Yasushi Oka,Hideyuki Oka.Velocity and temperature attenuation of a ceiling-jet along a horizontaltunnel with a flat ceiling and natural ventilation[J].Tunnelling and Underground Space Technology.2016,56(6):79-89.
[8]ZHAO Weifeng ZONG Ruowen,Wei Tao,et al.The physical model and validation study of ceiling-jet flow in near-fieldof corridor fires[J].International Journal of Heat and Mass Transfer.2015,88(9):91-100.
[9]Hu,L.H.,Huo,R.,Peng,W.,et al.On the maximum smoketemperature under the ceiling in tunnel fires[J].Tunnelling and Underground Space Technology.2006,21(6):650-655.
[10]Qu,L.,Chow,W.K.,Numerical studies on density jump in a long corridor fire[J].Tunnelling and Underground Space Technology,2012,32(6):113-126.
[11]KEVIN Mcgrattan,SIMO Hostikka.Fire dynamics simulator(version5)technical reference guide[M].Washington:National Institute of Standards and Technology US Department of Commerce,2008:33-34.
[12]齐庆杰,王欢,董子文,等.矿井胶带运输巷火灾蔓延规律的数值模拟研究[J].中国安全科学学报,2016,26(10):36-41.QI Qingjie,WANG Huan,DONG Ziwen,et al.Numerical simulation of belt conveyorfire spreading law in coal mine[J].China Safety Science Journal,2016,26(10):36-41.
[13]R.L.Alpert,Turbulent ceiling-jet induced by large-scale fires,Combustion Science and Technology,1975,11(5):197-213.
[14]J.P.Kunsch,Simple model for control of fire gases in a ventilated tunnel,Fire Safety Journal,2002,37(1):67-81.
[15]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.