不同类型火源下烟气在大空间内的充填特性研究

在大空间火灾试验厅内采用沙发作为火源，研究了烟气层的发展过程，并将得出的烟气层温度、烟气层下降曲线与油池火对比。结果表明：不同的火源条件下，烟气的温升曲线和烟气层下降曲线是不同的，对于稳定的油池火，烟气层下降曲线是光滑的，对于非稳定火源，烟气层下降曲线存在跳变现象；烟气层厚度较小时，火源热释放速率的大小对烟气层的温度、烟气层的下降速率有着重要影响；对于变热释放速率情况下的烟气充填，可以采用对热释放速率的分段近似来进行模拟分析。     

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。     

纵向通风下隧道长度对临界风速的影响分析

临界风速可有效控制烟气蔓延,是隧道防灾通风重要参数。为分析隧道长度对临界风速的影响,采用量纲分析法构建临界风速与隧道长度关系公式,并分别在5 MW和30 MW火源热释放速率下,对不同长度隧道的火灾进行数值模拟以量化研究隧道长度对临界风速的影响。结果表明,隧道长度对临界风速具有影响,且不同火源释放速率时影响也有所不同:无量纲火源热释放速率小于0.15时,临界风速随隧道长度增大呈现1/41次方增长关系;无量纲火源热释放速率高于0.15时,临界风速随隧道长度增大呈现1/25次方增长关系。进而建立了考虑隧道长度的无量纲临界风速计算公式。     

大断面道路隧道火灾初期规律足尺试验研究

为研究火灾初期时大断面道路隧道内温度及烟气流动特性,在三车道大断面试验隧道内进行了足尺火灾试验。试验考虑了0.5 MW、1 MW及5 MW三个等级的火灾规模;试验纵向风速范围为0~2 m/s。试验结果表明:在火灾发展初期,火灾规模和纵向风速是影响大断面道路隧道内温度场分布及烟气扩散的重要因素;隧道火灾产生的高温烟气趋于向拱顶扩散,故隧道横截面高温区域分布于隧道上部空间,靠近地面的空间温度则较低。火灾规模越大,隧道横截面的高温区域范围越大。大断面隧道因隧道内空间较大,有利于烟气扩散和人员逃生。然而,火灾预警的角度考虑,大断面隧道需多在关键截面上设置温度传感器和摄像头,以获得更为有效的火情信息来组织灵活的疏散逃生方案。     

分布式排烟管对侧向排烟效率提升效果分析

为了进一步提高隧道火灾侧向排烟效率,以港珠澳大桥海底沉管隧道为研究对象,利用FDS数值模拟软件进行等尺寸建模,将火源热释放速率设置为10,20,50 MW,排烟速率设置为4,6,8,10 m/s,宽高比设置为1:2、1:1、2:1、3:1,共计48组工况,在各个侧向排烟口处加装"分布式排烟管",通过控制变量法分析分布式...     

通风对竖井型隧道火灾烟气特性影响试验研究

通过隧道火灾模型试验,研究纵向通风对竖井排烟效果及隧道内纵向烟气温度分布的影响。试验考虑不同火源热释放速率和纵向风速。结果表明：纵向风速对正庚烷池火热释放速率存在影响,对于较小正庚烷池火（≤11 cm）,火源热释放速率基本不随纵向风速而改变;对于较大正庚烷池火（≥14 cm）,火源热释放率随风速的增加先降低后基本保持恒定。此外,当隧道内风速较小时,竖井内烟气附壁排出,竖井后方烟气温度较低,控烟效果较好;当隧道内风速较大时,竖井内烟气出现边界分离,竖井后方温度升高,烟气蔓延距离增加,竖井排烟效果较差。因此,建议当竖井型隧道内发生火灾时,应尽量采用自然通风或较低的内部通风,避免较高风速。     

商业建筑火灾场景设计的试验研究

当前,建筑防火设计规范向性能化方向发展。性能化防火设计所做的主要工作是火灾风险评估,而火灾场景设计是火灾风险评估的基础。以火灾荷载调查数据为基础进行典型商业建筑火灾场景设计的试验研究,设计大型购物中心内快餐店和运动休闲店两类店铺的燃料包并进行ISO 9705实体房间火试验,用于确定燃料包的燃烧特性,如热释放速率、毒性气体产生速率等。试验结果表明:快餐店和运动休闲店两个燃料包的火灾增长率处于中速火和快速火之间,并且偏向于快速火,两个试验的热释放速率的峰值都达到1MW左右,平均热释放速率快餐店为139kW,运动休闲店为191kW。试验结果可以为建筑设计师和消防工程师在火灾风险评估中设计火灾场景提供参考。     

超高海拔隧道火灾燃烧与烟气温度现场模型试验研究

随着我国川藏铁路和高原公路的不断修建,超高海拔地区“三低”环境特征将对高原隧道火灾燃烧和烟气扩散特性产生严重影响。文章采用移动模型隧道火灾试验平台对成都平原、海拔3544m、4103m超高海拔山区在相同油盘尺寸和燃料体积条件下,火灾燃烧和烟气温度分布进行现场试验研究。研究结果表明：随着海拔高度的增加,火灾热释放率和火源区拱顶温度不断下降,燃烧时间明显增长;与平原地区相同火灾规模相比,超高海拔隧道火源区拱顶温度略有下降;超高海拔地区拱顶纵向温度衰减速率显著低于平原地区,火灾高温烟气热浮升力效应在超高海拔隧道内更突出。     

压缩空气泡沫喷淋系统在水下隧道的应用研究

搭建模型开展隧道油池火灾模拟试验,研究压缩空气泡沫与汽油火作用过程中的温度、烟气、热释放速率、热辐射强度等火灾参数变化规律,考察压缩空气泡沫喷淋系统对油池火的灭火性能。结果表明:在5 L/(min·m2)供给强度下,压缩空气泡沫喷淋系统结合A类泡沫灭火剂对于汽油池火具有优异的灭火性能,且泡沫性能稳定;在压缩空气泡沫作用下,隧道顶部及侧壁100℃以上高温持续时间不超过2 min,并且油池火周围的热辐射强度可在30 s内将降至1 kW/m2以下;压缩空气泡沫对于隧道内高温烟气层扰动很小,不影响人员逃生疏散。     

在受限和通风防火分区内对燃烧速率特性的试验研究

在核安全研究框架内对在受限和通风防火分区内油池火燃烧速率进行了试验研究。在实体火灾试验基础上，此研究为在受限和通风火灾场景下的燃烧速率机理提供了新的信息。描述了在自由条件和空气受限条件下所进行的试验，对试验装置、仪器以及火源进行了详细叙述。在相同场景（0．4m^2TPH油池火）下，对自由条件和空气受限条件的试验情况下的燃烧速率进行了对比。在空气受限情况下，燃烧速率与时间的变化曲线显示出三个不同阶段：自由条件和受限燃烧速率相同；不稳定阶段，空气受限条件下燃烧速率高于自由条件下的燃烧速率;稳定阶段。从图像分析看，不稳定阶段显示，动荡和间歇火焰大大提高了燃烧速率。介绍了通风速率和油池面积对此现象的影响。试验结果为理解有限区域内燃烧速率提供了新的试验信息。     

Smoke spreading characteristics during a fire in a shallow urban road tunnel with roof openings under a longitudinal external wind blowing

A series of fire experiments was conducted using a 1:12 scale model of a shallow urban road tunnel with roof openings to clarify the flow structure of smoke and fresh air during a fire with a longitudinal external wind blowing above the roof openings. The model tunnel consisted of two road tubes separated by a pillar-type median structure. Five fire test cases were conducted by changing the heat release rate as the experimental parameter. When the smoke produced by a fire in the tunnel tube was exhausted by natural ventilation through the roof openings of the tunnel tube, fresh air was sucked in from the roof openings of the opposite tunnel tube. The flow of exhausted smoke and sucked-in fresh air created a complex three-dimensional flow structure inside the tunnel tubes. Stratified smoke that had formed under the ceiling of the tunnel tube was disturbed by the flow of sucked-in fresh air and was diffused on the upstream side of the fire. Compared to the condition without a longitudinal external wind, when a longitudinal external wind blew over the tunnel with the pillar median structure, the smoke spreading distance on the upstream side was longer than that without the external wind due to the diffusion of smoke. On the other hand, the smoke spreading distance on the downstream side of the fire was shorter than that without the external wind due to the improved smoke extraction performance by the Venturi effect of the longitudinal external wind. Furthermore, the smoke spreading distance on the downstream side was nearly constant and independent of the heat release rate of the fire, within the scope of our experimental conditions.     

公路隧道动态火灾规模及人员疏散研究

为了确定城市公路隧道阻塞场景下火灾蔓延时的动态火灾规模和人员疏散方案,基于临界辐射热通量理论计算车辆引燃时间,并运用FDS研究动态火灾规模和同时打开两侧横通道与只打开一侧横通道两种工况下的温度与可视度分布规律,通过Pathfinder计算人员疏散时间。结果表明：初次引燃需要250 s,二次引燃分别需要615、650 s,共计11辆车参与燃烧,最大热释放速率高达39.1 MW;两种工况下的温度与可视度分布规律基本相同,但同时打开两侧横通道的疏散时间仅为390 s,较后者减少了320 s;建议四洞公路隧道发生火灾时,宜同时打开两侧横通道,且应在10 min内及时采取措施防止车辆发生二次引燃。     

A New Methodology of Design Fires for Train Carriages Based on Exponential Curve Method

Design fires have great influences on the fire safety concepts and safety measures, and are the basis for any assessment and calculation in tunnel fire safety design. A new methodology of design fires for individual train carriages is proposed based on the exponential design fire curve method and state-of-the-art fire research. The three key parameters required for construction of a design fire are the maximum heat release rate, time to maximum heat release rate, and energy content. An overview of the full scale train carriage fire tests is given and the results show that the maximum heat release rate is in a range of 7 MW to 77 MW and the time to reach the maximum heat release rate varies from 7 min to 118 min. The method could be employed to one single train carriage or several carriages, and alternatively one carriage could be divided into several individual sections. To illustrate the use of the methodology, several engineering applications are presented, including design fires for a metro train carriage with a maximum heat release rate of 77 MW, a double-deck railway train carriage with a maximum heat release rate of 60 MW and a tram carriage with a maximum heat release rate of 28 MW. The main objective is to provide practicing engineers with a flexible and reliable methodology to make design fires for individual train carriages in performance-based tunnel fire safety design.     

Optimization of Emergency Ventilation Strategies in a Roadway Tunnel

In order to evaluate the effectiveness of in-place emergency ventilation strategies to control smoke spread in the event of a fire in a section of a roadway tunnel, both numerical and experimental studies were performed. The experimental study was conducted to provide the necessary initial and boundary conditions for the numerical phase of the investigation. A fire heat release rate of 1 MW was used in all fire tests. This fire heat release rate was selected to minimize the risk of damage to the tunnel and its associated systems while producing reliable data for visualizing the smoke movement in the tunnel. The numerical study used Computational Fluid Dynamics, Fire Dynamic Simulator version 4.0 to investigate smoke removal in the tunnel for large fire of 30 MW (bus or truck on fire). In total, four field fire tests and seven numerical simulations were conducted. Based on the study results, recommendations were made to optimize the ventilation scenarios in the tunnel section. This article presents the details of the study as well as the recommendations made.     

超大断面水平隧道纵向通风临界风速CFD分析

首先介绍了临界风速研究的基本思路及国内外主要研究成果.结合国内某长大公路隧道设计,建立一长300m、水力高度10.64m的水平隧道模型,通过CFD模拟确定超大断面隧道临界风速的影响因子及相应的准则关联式.模拟表明:与火灾热释放速率相比,环境温度的影响可以忽略不计;与Atkinson(模型试验)及Buxton(大尺度试验)相似,临界风速随热释放速率的变化分为两个区域,与低热释放速率时不同,一旦热释放速率超过40MW,临界风速的变化明显趋于缓慢.     

活塞风作用下超长公路隧道火灾烟气蔓延特性研究

汽车在隧道中行驶时会产生活塞风,有效利用活塞风可降低机械排烟系统的成本和能耗。本文首先进行了理论分析,然后通过计算流体动力学软件对活塞风作用下公路隧道的火灾烟气蔓延特性进行研究。数值模拟探究了不同活塞风速对于隧道中不同火源功率（10、30、50 MW）情况下烟气层运动、温度场和流速场分布的影响。研究结果表明,近期、远期的活塞风速衰减模型在不同火源功率时,烟气层运动、温度场和流速场变化规律基本相同,随着火源功率增大,烟气回流到隧道入口的时间更短,隧道内流速场发生变化的时间越晚。     

ETFE薄膜屋面材料大尺寸火灾试验研究

设计了ETFE薄膜的大尺寸火灾试验,研究了在4 MW火灾规模下ETFE薄膜的燃烧特性,并探讨了在标准试验和大尺寸火灾试验条件下ETFE膜材燃烧是否出现熔滴现象.结果表明:在4 MW火灾规模下,ETFE薄膜在火焰可以接触到的位置发生软化及烧穿,并有滴落物,在火源无法接触到的位置保持完整性,未发生火蔓延;符合GB 8624...     

Characteristics of smoke extraction by natural ventilation during a fire in a shallow urban road tunnel with roof openings

The characteristics of the spread of smoke were investigated for a fire occurring in a shallow urban road tunnel with roof openings in its ceiling. In this type of tunnel, the smoke produced by a fire is ventilated through the openings in the ceiling given the natural buoyancy of hot smoke. A fire experiment was conducted using a 1/12 scale model tunnel to ascertain whether natural ventilation via the roof openings was sufficient to maintain a safe evacuation environment for tunnel users. The distance from the fire to the tip position of the spreading smoke and the thickness of smoke layers along the ceiling were investigated by changing the heat release rate and using two types of median structure as experimental parameters. The two types of median structure dividing the tunnel into two road tubes were pillars and walls. It was clarified that the smoke spreading distance was constant and independent of the heat release rate of the fire under our experimental conditions. Moreover, it was confirmed that the thickness of the smoke layers in the tunnel thinned out quickly due to the natural ventilation.     

隧道内火灾大小和火灾蔓延模拟研究

隧道内火灾的热释放速率对火灾蔓延和烟气生成起着关键作用。影响热释放速率的关键参数包括：燃烧物特性、隧道形状、通风条件以及车辆流量。综述了几年来热释放速率对这些参数的依赖性所做的研究成果。设计了贝页斯概率模型来模拟火灾热释放速率受隧道形状以及纵向通风的影响，设计了定性模型来模拟火灾在类似海底隧道内从一个物体蔓延到另一个物体的情况，通风条件同样是纵向通风，并给出了此次研究的初步成果。