纵向通风与坡度对隧道竖井排烟影响数值模拟

以某公路隧道为研究对象,采用开启6个竖井的双向均衡排烟模式。利用FDS对纵向通风与坡度影响下的竖井排烟效果进行数值模拟,通过分析不同工况下竖井内的烟气扩散特性、温度场分布及烟气质量浓度变化,获得隧道内竖井排烟速率的变化规律。结果表明:火源位于隧道中间时,在无纵向通风和纵向风速较小时,竖井下方均会出现烟气层吸穿现象,排烟速率较低;风速增加,火源下游的竖井排烟速率较大;风速大于2.0 m/s时,火源下游的竖井出现边界层分离现象,排烟速率降低;改变隧道坡度并不影响竖井下方的自然排烟效果。     

跨线运营隧道火灾烟气分布特性研究

地铁网络化运营后,部分城市已开通跨线运营列车。本文针对列车跨线运营两线联络线火灾,建立了地铁正线和联络线隧道模型,采用三维CFD数值计算方法,模拟分析了不同排烟方向、隧道纵向通风风速和火源热释放速率下联络线隧道火灾烟气分布特性。结果表明：相比向正线下游排烟,向上游排烟时正线和联络线隧道烟气控制效果更好,更有利于人员逃生;正线隧道纵向通风风速对联络线隧道内烟气分布影响较弱;联络线隧道纵向通风风速增大,有利于联络线隧道内的烟气控制,但风速过大时,隧道内满足疏散能见度要求的位置与火源的距离增大,不利于疏散;火源热释放速率越小,越有利于正线隧道逃生。     

纵向通风与竖井自然排烟下隧道火灾烟气特性实验研究

中国逐渐发展成为世界上隧道和地下工程最多的国 家,其长隧道数量和长度跻身世界前列。据统计,火灾中85%的 人员死亡是由热烟气造成的,目前隧道中采用较为广泛的排烟系 统有纵向排烟系统、集中排烟系统和横向排烟系统,而针对长隧道 来说,我国广泛采用的是竖井式纵向通风,因此,研究纵向通风与 竖井排烟综合效应下隧道火灾烟气流动特性及温度分布规律具有 重要意义。本文建立了1：10 缩尺寸竖井隧道模型,主隧道长度 16.5 m,宽度1.3 m,高度0.65 m;竖井通过排烟横通道与主隧道 连接,排烟横通道设置在主隧道侧面中部,尺寸为1.2 m 长、0.6 m 宽、0.4 m 高;竖井横截面为半径0.6 m 的1/4 圆,高4.6 m。在 竖井隧道模型中开展了一系列油池火实验,选取2 种方形燃烧池 （20 cm×20 cm、23 cm×23 cm）作为火源,设置2 个纵向火源位置 （位置A：火源中心线与排烟横通道中心线距离0.375 m;位置B： 火源中心线与排烟横通道中心线距离1.375 m）,7 种纵向通风风 速（0,0.18,0.27,0.35,0.44,0.52,0.69 m/s）,定量分析不同工 况下温度分布及烟气逆流长度。研究结果表明：当无纵向通风时, 火焰与隧道地板垂直,且呈轴对称形态;当有纵向通风时,火焰向 下游偏移,且纵向通风风速越大,火焰向下游偏移越明显;当纵向 通风风速为0 m/s 时,由于竖井的存在,火源上、下游两侧烟气温 度分布并非对称,火源下游（竖井侧）烟气温度下降速度较快,与单 洞隧道烟气温度分布明显不同;随纵向通风风速增加,烟气逆流长 度和烟气温度减小,而最大温度偏移距离整体呈增加趋势;当无量 纲纵向通风风速v′＜0.19 时,主隧道最大温升△Tmax 与Q2/3/ Hef 5/3 呈正比,而当无量纲纵向通风风速v′＞0.19 时,主隧道最大 温升△Tmax 与Q? /(vb1/3Hef 5/3)呈正比,但常数系数均小于Li 等预 测模型中的常数系数;竖井隧道内无量纲纵向烟气温度分布符合 Fan 和Ji 等建立的纵向温度衰减模型,衰减系数k′在1.36~1.63 范围内变化,但其值明显大于单洞隧道纵向温度衰减系数k′;另 外,当火源位于位置A 时,最大烟气温度低于火源位于位置B 时 的最大烟气温度,无量纲纵向烟气温度衰减速度慢于火源位于位 置B 时衰减速度。     

纵向风对隧道柴油池火影响的试验研究

在全尺寸隧道模型中开展了试验研究,采用柴油池火设计了2.8~12.2 MW共8组工况,考查了油盘面积2~5 m~2、纵向风速0.2~2.0 m/s条件下隧道火灾烟气层形态、热释放速率和火源燃烧速率的变化规律。研究发现,各工况在该区域附近的烟气分层效果较好,纵向风速对各工况中火源区烟气分层影响不明显。热释放速率经验计算值比测量值普遍高7%~30%,但当火源面积较大、纵向风速较高时经验计算值显著低于测量值。火源平均燃烧速率表现出与热释放速率一致的变化规律,随隧道纵向风速增大而增大。在纵向风作用下,3 m~2和5 m~2柴油池火的燃烧速率比无风环境下分别高出18.4%和25.1%。     

胶州湾海底隧道防排烟设计探讨

分析海底隧道火灾烟气的特点及危害.结合青岛胶州湾海底隧道情况,运用FDS模拟分析海底隧道半横向通风在各种情况下的排烟效果,通过改变排烟口数量、排烟量以及隧道内纵向风速等参数研究烟气运动规律.结果表明,排烟量相同时,开启的排烟口越少,越有利于控制烟气向两端蔓延;存在纵向风时,火源上游排烟口越少,烟气抑制效果越好,烟气运动速率随纵向风速的增大而减小.     

公路隧道纵向通风对火灾烟气分层影响研究

纵向通风目前是我国长隧道使用最多的通风排烟方式。通过1∶ 10隧道模型火灾排烟试验,利用激光片光观测火灾烟气分层结构,分析了纵向通风对火灾烟气分层结构的影响;通过数值模拟,研究了隧道采用纵向通风排烟的效果。结果表明:在无风情况下,火灾初期烟气能够较好地维持在隧道顶部,与空气分层界限明显;开启纵向排烟后,能够有效抑制火灾烟气向火源上游蔓延,但烟气分层结构遭到破坏并随着风速增加逐渐消失,火源下游区域能见度下降;纵向排烟风速维持在临界风速及以下,可降低纵向风对烟气分层的影响。     

排烟模式对隧道火灾烟气控制影响研究

以某海底隧道为例,建立1∶4的缩尺物理模型,分析不同火灾场景、纵向与横向排烟模式下的热释放速率、烟气蔓延长度和高度、行车道和排烟口的温度分布和风速分布情况。结果表明,纵向排烟可以减少烟气回流,控制烟气向火源下游蔓延;横向排烟可以减少烟气在隧道内聚集;纵向排烟与横向排烟相结合的模式能够将两种排烟模式的优点有机结合起来,烟气控制效果能满足相关规范要求。     

纵向通风及坡度对隧道池火燃烧速率影响实验研究

采用1∶15的缩尺模型隧道,隧道坡度范围为0～10%,进行纵向通风风速为0～2.5 m/s的乙醇和正庚烷池火实验,研究坡度与通风风速对油池火燃烧状态的影响。油池采用厚度1 mm的不锈钢板打造,边长为8 cm和10 cm。随着纵向通风风速的增加,乙醇池火的燃烧速率先下降后上升,正庚烷池火在水平隧道和坡度为5%的情况下,燃烧速率也呈现先下降后上升的趋势。但在隧道坡度为10%的情况下,正庚烷的燃烧速率单调增加。火焰倾斜角随风速的增大先迅速增加后缓慢增加。     

区间隧道火灾临界风速和温度特性

为了研究地铁区间隧道火灾临界风速和温度变化规律,建立了西安某地铁站区间隧道模型,采用FDS模拟软件对不同纵向通风条件下烟气流动和温度分布进行模拟。介绍模型的基本参数,根据Froude相似性原理建立了各个燃烧参数的相似性关系。利用FDS模拟不同火灾功率、不同通风速度时的温度和烟气速度分布。对比分析5、6、7、8、9、10 MW火灾功率下的临界风速变规律化并提出预测模型。结果表明:纵向通风风速设为3m/s时对防止9 MW以下的火源功率火灾烟气回流效果明显;热释放速率不大于10 MW时,隧道火灾中烟气温度不大于250℃,火源下风侧烟气流动速度不大于4 m/s。     

纵向通风与侧壁开口竖井自然排烟协同作用下烟气运动模拟

为探究山岭隧道火灾烟气运移特性,采用数值模拟的方法,选取两种典型火源功率(20 MW及50 MW),分析不同纵向风速下火源位置对隧道顶棚下方沿程温度分布规律、烟气运移速率及竖井内烟气质量流量的影响规律.研究结果表明,纵向风速低于3m/s时,不同火源位置时,火源上游沿程温度均随纵向风速增加逐渐降低,而下游沿程温度随纵向风...     

设排烟道隧道的烟气逆流长度与临界风速研究

隧道火灾是运营公路隧道的主要灾害。为有效控制隧道火灾,采用理论分析和数值模拟相结合的方法研究了设排烟道隧道的火灾烟气逆流长度与临界风速。以国内常见的双车道隧道尺寸建立模型,分析了排烟速率和纵向通风速率对烟气逆流长度的影响,提出了临界风速的预测模型。并将其通风效果与常规未设排烟道的纵向通风做了比较。结果表明:未设排烟道时,纵向风速还未达到临界风速时,火灾下游烟气的层化状态就已破坏。设排烟道能及时排出火灾产生的烟气,有利于保持烟气的层化状态,有效改善火灾时的隧道环境,为火灾下游人员的疏散救援提供了有利条件。同时,设置排烟道有利于减小逆流长度和临界风速。随着排烟速率的增大,相应的临界风速呈指数函数递减的特性。     

The influence of longitudinal ventilation systems on fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study investigating the influence of forced longitudinal ventilation on car fires, pool fires and heavy goods vehicle fires in tunnels. A Bayesian probabilistic approach is used to refine estimates, made by a panel of experts, with data from experimental fire tests in tunnels. Results are presented and the implications are discussed. The influence of longitudinal ventilation on heavy goods vehicle fires is predicted to be much larger than the experts’ estimates, causing a fire to grow ten times larger than if natural ventilation was used. The effect of ventilation on a pool fire in a tunnel depends on the size of the pool; the heat release rate of small pool fires may be reduced by forced ventilation, whereas it may be enlarged for large pool fires. The size of a car fire is not expected to be greatly affected by forced ventilation at low ventilation velocities.     

Effect of cross section and ventilation on heat release rates in tunnel fires

Model scale fire tests were performed in tunnels with varying tunnel widths and heights in order to study the effect of tunnel cross-section and ventilation velocity on the heat release rate (HRR) for both liquid pool fires and solid fuel fires. The results showed that for well ventilated heptane pool fires, the tunnel width nearly has no influence on the HRR whilst a lower tunnel height clearly increases the HRR. For well ventilated solid fuel fires, the HRR increases by approximately 25% relative to a free burn test but the HRR is not sensitive to either tunnel width, tunnel height or ventilation velocity. For solid fuel fires that were not well ventilated, the HRRs could be less than those in free burn laboratory tests. In the case of ventilation controlled fires the HRRs approximately lie at the same level as for cases with natural ventilation.     

灭火救援专业知识智能匹配算法

摘 要：基于当下灭火救援领域中的突发事件,提出灭火救援专业知识智能匹配算法,该算法基于自然语言处理和注意力机制计算案件描述和消防预警信息之间的语义关系,从而实现相关灭火救援专业知识的匹配。首先基于自然语言处理的方法学习句粒度级别的语义信息,然后基于注意力机制学习词粒度级别的语义信息,最后基于两个级别语义信息的交互,根据信息之间局部差异推断两个句子之间的关系。试验结果表明：该算法具有优异的性能,能够同时从词和句两个粒度上更准确地理解句子,实现基于案件描述的灭火救援专业知识智能匹配。     

Studies on buoyancy driven two-directional smoke flow layering length with combination of point extraction and longitudinal ventilation in tunnel fires

This paper investigates the buoyancy-driven smoke flow layering length (both upstream and downstream) beneath the ceiling with combination of point extraction and longitudinal ventilation in tunnel fires. A theoretical model is developed based on previous back-laying model with only longitudinal ventilation, with modified actual heat release rate, as well as modified upstream and downstream opposing longitudinal air flow velocities by the induced flow velocity due to point extraction. Experiments are carried out in a reduced scale model tunnel with dimensionless of 72 m×1.5 m×1.3 m. A LPG porous gas burner is used as fire source. The smoke flow layering length both upstream and downstream are identified based on temperature profiles measured along the ceiling, for different experiment conditions. CFD simulations with FDS are also performed for the same scenarios. Results show that with combination of point extraction and longitudinal ventilation, the smoke flow layering length is not symmetric where it is longer downstream than that upstream. The upstream smoke layering length decreases, while the downstream layering length increases with increase in longitudinal ventilation velocity; and they both decrease with increase in point extraction velocity. The predictions by the proposed theoretical model agree well with the measurements and simulation results.     

Full-scale experiment and CFD simulation on smoke movement and smoke control in a metro tunnel with one opening portal

Three full-scale model experiments were conducted in a unidirectional tube, which is a part of a metro tunnel with one end connected to an underground metro station and the other end opened to outside in Chongqing, PR China. Three fire HRRs, 1.35 MW, 3 MW and 3.8 MW were produced by pool fires with different oil pan sizes in the experiments. Temperature distributions under the tunnel ceiling along the longitudinal direction were measured. At the same time, CFD simulations were conducted under the same boundary conditions with the experiments by FDS 5.5. In addition, more FDS simulation cases were conducted after the FDS simulation results agreed with the experimental results. The simulation results show that the smoke temperature and the decay rate of the temperature distribution under the tunnel ceiling along the longitudinal direction increase as HRR increases. The smoke exhausts effectively from the tunnel under mechanical ventilation system, whether the emergency vent is activated as a smoke exhaust or an air supply vent. The operation mode of the mechanical ventilation system depends on the evacuation route.     

高海拔隧道全尺寸火灾烟气及温度场特征试验研究

通过对海拔为4100m的高海拔隧道进行全尺寸火灾试验,揭示高海拔隧道火灾烟气下沉及温度场变化特征。试验采用三种不同尺寸火源(0.8m2、1.0m2、2.0m2),对隧道火灾烟气蔓延特征、火区最高温度、隧道拱顶纵向温度分布进行研究。试验研究结果表明：隧道火灾试验初期及燃烧稳定阶段,火源附近隧道上层烟气与下层冷空气分界明显,火灾后期烟气下沉严重;较小风速有利于高海拔隧道小规模火灾烟气逆流层纵向和垂向蔓延的控制。隧道火灾温度场研究表明：隧道火灾温升速率随火源热释放率增大而增加;火源附近20m范围内温度衰减速率较快,远火源区域隧道拱顶纵向温度衰减较慢,趋于平缓;通过对火源上方拱顶烟气温度分析,发现隧道火灾探测采用差温报警模式较定温报警模式更加有效,并得出10℃/min的温升速率可基本满足高海拔隧道小规模火灾的初期报警;隧道拱顶纵向温度分布规律导致火源远场烟气下沉严重而近火源区域烟气层化较好的特征。高海拔隧道火灾温度分布特性试验研究,可为高海拔隧道火灾动力特性研究提供依据,为高海拔隧道人员疏散逃生提供指导及建议。     

Critical velocity and burning rate in pool fire during longitudinal ventilation

Since the prediction of ‘critical velocity’ is important to control the smoke in tunnel fires, many researches have been carried out to predict critical velocity with various fire sizes, tunnel shape, tunnel slope, and so forth. But few researches have been conducted to estimate critical ventilation velocity for varied burning rate by longitudinal ventilation, although burning rate of fuel is influenced by ventilation conditions. Therefore, there is a need to investigate the difference of upstream smoke layer (e.g., backlayering) between naturally ventilated heat release rate and varied heat release rate by longitudinal ventilation.In this study, the 1/20 reduced-scale experiments using Froude scaling are conducted to examine the difference of backlayering between naturally ventilated heat release rate and varied heat release rate by longitudinal ventilation. And the experimental results obtained are compared with numerical ones. Three-dimensional simulations of smoke flow in the tunnel fire with the measured burning rates have been carried out using Fire Dynamics Simulator; Ver. 406 code, which is developed by National Institute of Standards and Technology. They show a good degree of agreement, even if some deviation in temperature downstream of the fire is evident. Since ventilation velocity had a greater enhancing effect on the burning rate of fuel due to oxygen supply effect, the critical ventilation velocity should be calculated on the basis of varied HRR by ventilation velocity.