重点排烟模式下坡度隧道烟气控制优化研究

针对不同坡度隧道,对重点排烟模式下的烟气控制效果进行研究。以某三车道隧道为例,采用FDS对不同坡度、单向与双向重点排烟以及不同的排烟口开启方式等多工况进行模拟研究,分析烟气蔓延长度、能见度和隧道洞口自然补风风速等关键性判据的变化规律,提出重点排烟模式下不同坡度隧道的烟气控制优化建议。     

海底特长隧道利用横通道控烟技术研究

摘 要：为了解决特长海底隧道发生火灾时的排烟问题,提出利用服务通道和联络横通道辅助送风的通风方案。利用火灾动力学模拟软件（FDS）,建立隧道火灾通风模型,通过研究通风排烟时服务隧道内补风量与横通道开启数量对火灾烟气的控制效果,确定通风系统的技术参数。结果表明：火灾发生时,事故隧道内纵向通风风速2 m/s,同时开启火源上游3 个横通道,并在服务隧道两端各施加1.3 m/s 纵向通风风速,既可将烟气控制在火源一侧,同时不影响人员安全疏散,其控烟效果与通风网络解算结果一致。采用横通道辅助送风的通风方案,控制特长海底隧道内火灾烟气蔓延是具有理论可行性的。     

侧部重点排烟与水喷淋协同作用下隧道烟气运动研究

合理的水喷淋设计参数及排烟策略，可保证隧道有效排烟和烟气层的稳定性，为人员安全疏散提供有利环境。为研究侧部排烟模式下烟气失稳临界状态时最佳喷水流量和排烟口设计参数，采用FDS 对15 MW 火灾规模下，不同喷水流量、排烟量、排烟口间距及排烟口高度下19 组工况进行模拟计算。结果表明：喷淋流量越大，烟气层高度越高，隧道整体温度降低，改变喷水流量对控制烟气层的稳定性效益不大，隧道空间内有烟气滞留；排烟量为70 m3/s、排烟口间距为50 m、排烟口高度为3.2 m 或4.0 m 为烟气层稳定临界状态时的排烟口最佳参数，此时侧部抽吸力向上的分力与烟气的热浮力大于水喷淋拽曳力，烟气层较稳定，隧道空间内无旋涡烟气滞留，有利于排烟和人员疏散。     

液氮及排烟共同作用扑灭电缆火灾有效性研究

城市地下综合管廊电缆火灾危险性极大。运用FDS软件模拟液氮和机械排烟共同作用、仅有机械排烟以及无液氮和机械排烟3 种工况下,综合管廊内部电缆火灾蔓延情况。分析火灾发生后综合管廊内部烟气蔓延及温度分布,发现液氮和机械排烟的共同作用能迅速扑灭火灾从而减小由于发生火灾造成严重后果的危险程度。分析不同的注氮速度和机械排烟速度对扑灭综合 管廊电缆火灾的影响,发现适当增加注氮速度和排烟速度有利于扑灭电缆火灾。     

大纵坡双向行车公路隧道火灾控制风速研究

城万二级公路白芷山隧道和八台山隧道为双向行车的大纵坡公路隧道,火灾后烟流控制难。采用火灾动力学计算软件FDS对其进行了火灾三维数值模拟,分析了仅火风压作用及0.5 m/s、1 m/s和-0.5 m/s控制风速作用下的烟流扩散和能见度的分布规律。结果表明:在大纵坡隧道中,火灾后仅靠火灾效应能引起火灾烟流的流动,其流动的规律是烟流从火源点流向高洞口方向,火灾烟流能完全从高洞口排出,而烟流向火源点下坡方向的蔓延距离仅在100 m左右;当风速为0.5 m/s时,烟流在火源两侧基本呈对称状蔓延;下坡方向的隧道中的烟流也因风速较小,产生的扰动比较小,这种烟流控制是最为合理,有利于灾害情况下逃生。因此,建议将白芷山隧道和八台山隧道的火灾控制风速取为0.5 m/s左右,且该速度应为自然风速、火风压引起的风速和风机提供风速的合速度。     

隧道内顶棚和侧向机械排烟效果对比

为了比较顶棚机械排烟和侧向机械排烟在隧道火灾中的排烟效果,采用数值模拟的方法对隧道火灾中两种排烟方式的温度分布、流场分布、排烟量、排热量以及排烟效率进行对比.结果表明,两种排烟方式的流场分布与烟气吸入方式差别较大;侧向机械排烟更容易发生吸穿;顶棚机械排烟的排烟量和排热量更高,排烟效果更好;侧向机械排烟由于更容易发生吸穿...     

重点排烟坡度隧道纵向机械补风量研究

合理的纵向机械补风量,可有效保障重点排烟隧道火灾烟气控制效果。基于有效排烟和人员疏散安全两大原则,将烟气蔓延长度、最小清晰高度处能见度以及排烟效率作为判定合理纵向机械补风量的关键性判据。采用FDS6.2对1%、3%和6%坡度隧道下不同排烟量和补风量组合下的80组工况进行模拟计算。结果表明:当隧道坡度为1%、3%和6%时,机械补风量分别占排烟量的50%～70%、70%～100%及90%～120%;坡度小于1%时,坡度隧道与水平隧道的合理补风量和排烟量间比例关系基本一致,当坡度大于1%时,两者合理比例关系随坡度的增大呈现线性增长趋势,与水平隧道时相比其坡度修正系数K_Q可取0.8+0.2λ。     

公路隧道集中排烟道排烟阀结构设计参数研究

针对某大断面公路盾构隧道火灾烟气控制工程实际,为了优化设计公路隧道集中排烟模式下排烟阀结构参数,采用火灾动力学模拟软件FDS构建了隧道数值模型,并根据公路隧道的通行车辆种类、火灾类型和火灾规模,选择了隧道火灾典型场景,设计了集中排烟模式下单向及双向排烟时相应的火灾工况,通过提取隧道顶隔板下方温度场、行车道2 m高处能见度以及排烟阀流速等数据,分析了双向排烟时特定排烟阀面积下不同排烟阀结构形状对隧道火灾排烟效果的影响,进而探讨了单向排烟方式下不同排烟阀面积时的隧道火灾排烟效果。在此基础上,获得了隧道集中排烟模式下合理的排烟阀面积、排烟阀结构形状等设计参数。     

Numerical simulation of fire in a tunnel: Comparative study of CFAST and CFX predictions

The mathematical modeling of fire growth and smoke movement in any enclosure is a formidable task. Two types of deterministic models are in vogue, zone models and field models (popularly known as CFD technique). CFAST is a popular zone model used for modeling of fires in enclosures. Likewise, CFX is a general purpose CFD code used for various purposes including modeling of fires. In the present paper, a tunnel of length 150 m having a rectangular cross-section of 80 m² has been considered for analyzing the temperature and velocity profiles generated by fire, placed at a distance of 20 m from one end of portal, by both CFAST and CFX. The simulation by CFAST has been carried out by dividing the tunnel into 1, 2, 5, 8, 10, 12 and 15 compartments of equal size, where these compartments are joined by openings or vents having same cross-section as that of the tunnel. In case of tunnel divided into 15 compartments the fire source position lies at the position of vent; CFAST predicted very high temperatures. The simulations have also been carried out by dividing tunnel into unequal sized compartments such that position of fire was at the center of the compartment. It was found that for accuracy of results, location of fire source inside compartment is an important factor. Computational difficulty was experienced when tunnel was divided into more than 15 compartments. In this paper, a comparative study of temperatures predicted by CFAST and CFX has been done. The CFX and CFAST predictions show that smoke temperature changes with a pattern roughly similar to that of heat release rate. The temperature profiles at selected positions cannot be predicted by CFAST unlike CFX. The detailed features like flame tilt, flow field can only be observed from CFX predictions.     

长大隧道火灾安全疏散研究

在调研分析国内外长大隧道疏散模式的基础上,以虹梅南路隧道为研究对象,采用CFD软件对不同排烟方式下隧道火灾进行数值模拟,结果表明:不同的排烟方式下隧道内烟雾和温度场纵向分布扩散规律不同,采用单侧排烟时,烟雾向火源下游聚集,温度升高很快,有害气体浓度升高,无法提供合适的逃生环境;而采用双侧排烟时,烟雾向两侧蔓延,浓度和温度较小,满足火灾通风要求。最后,通过数值模拟人员疏散过程,计算结果表明,现有的排烟措施能够满足疏散安全要求。     

Impact of Air Velocity on the Detection of Fires in Conveyor Belt Haulageways

A series of large-scale experiments were conducted in an above-ground fire gallery using three different types of fire-resistant conveyor belts and four air velocities for each belt. The goal of the experiments was to understand and quantify the effects of air velocity on the detection of fires in underground conveyor belt haulageways and to determine the rates of generation of toxic gases and smoke as a fire progresses through the stages of smoldering coal, flaming coal, and finally a flaming conveyor belt. In the experiments, electrical strip heaters, imbedded approximately 5 cm below the top surface of a large mass of coal rubble, were used to ignite the coal, producing an open flame. The flaming coal mass subsequently ignited 1.83-m-wide conveyor belts located approximately 0.30 m above the coal surface. Gas samples were drawn through an averaging probe for continuous measurement of CO, CO₂, and O₂ as the fire progressed. Approximately 20 m from the fire origin and 0.5 m below the roof of the gallery, two commercially available smoke detectors, a light obscuration meter, and a sampling probe for measurement of total mass concentration of smoke particles were placed. Two video cameras were located upstream of the fire origin and along the gallery at about 14 m and 5 m in order to detect both smoke and flames from the fire. This paper discusses the impact of ventilation airflow on alarm times of the smoke detectors and video cameras, CO levels, smoke optical densities and smoke obscuration, total smoke mass concentrations, and fire heat release rates, examining how these various parameters depend upon air velocity and air quantity, the product of air velocity, and entry cross-section.     

Full-scale experimental study on smoke flow in natural ventilation road tunnel fires with shafts

Three full-scale burning tests were conducted in a natural ventilation city road tunnel with shafts. Fire sources were placed to be at different locations but its peak release heats were all around 5 MW. Results showed that large amounts of smoke and heat were released through shafts. The maximum smoke temperatures under the ceiling were below than 100 °C, and being lower than 110 °C at the safe height farther 3 m away from fires. The maximum smoke spreading horizontal lengths were less than 240 m both in the upwind and downwind. During the late stages, many smoke particles descended from the ceiling and downdraught occurred at shafts due to low smoke temperatures, but the visibility was not very bad and people needn’t evacuate. All These results are valuable for fire protection and construction of natural ventilation road tunnel with shafts.     

地下交通联系隧道典型火灾场景的烟气控制研究

本文针对北京市CBD地下交通联系隧道的结构特点和通风设计条件,在环形主隧道中设置典型火灾场景,采用数值模拟软件模拟了设定火灾场景下不同排烟工况时的烟气蔓延规律。而后,以临界风速作为主要判断标准,并以有限的烟气蔓延范围为控制要求,确定了该场景的合理烟控方案。     

防火分隔及排烟措施对综合管廊电缆火灾烟气蔓延的影响

以某综合管廊为研究背景,利用PyroSim模拟软件建立的仿真计算模型,研究了设立挡烟垂壁、改变防火门开启程度、增设排烟设施等情况下的烟气蔓延规律.研究发现:在烟气未充满管廊时,挡烟垂壁会使烟气蔓延速度降低,烟气蔓延速度与挡烟垂壁高度成反比;防火门打开会使火灾烟气蔓延至相邻防火分区,烟气蔓延速率与防火门开启程度成正相关;...     

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.     

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.     

The influence of decreasing vehicle exhaust emissions on the standards for ventilation systems for urban road tunnels

The strengthening of vehicle emission standards in the Federal Republic of Germany has also served to reduce exhaust emissions in road tunnels. The effect of the stricter standards was investigated by STUVA [Research Association for Underground Transportation Facilities] (Cologne, Germany) and Schindler Haerter AG (Zurich, Switzerland) with regard to the influence of exhaust emissions on construction costs and the costs of operating ventilation systems. The study covered topics such as ventilation systems, vehicle exhaust emissions, fresh air requirements, dispersion of pollutants outside the tunnel, and fire safety standards. The research was sponsored by the Federal Ministry of Transport, Bonn, Germany. In the future, the fresh air requirement will be governed by the traffic states “congestion” and “at a standstill”, in addition to the exhaust components smoke and carbon monoxide. It is essential to introduce particle filters for diesel-engine, heavy-duty vehicles in order to reduce demands on the ventilation systems of tunnels (e.g., for number of fans and space for air ducts) at the planning stage, as well as to reduce power consumption and/or running times of existing ventilation systems. If particle filters are made obligatory by 1995, the fresh air requirement will decrease by about 30% to 45% by the year 2000. Vehicle emission factors are calculated for vehicle speeds of up to 100 km/h for the future design of ventilation systems, up to the year 2000. In the event of fire in tunnels lacking rescue/ escape facilities, the ventilation system must be capable of delivering 80 m³ (s·km) to 200 m³/(s·km) of fresh air, depending on the ventilation system. In such cases, recirculation of air must be strictly avoided.     

Simulation of smoke from a burning vehicle and pollution levels caused by traffic jam in a road tunnel

Detailed analyses of smoke movement from a burning vehicle in a road tunnel have been carried out for the westbound Melbourne City Link tunnel. The time-averaged equations for velocity, pressure, temperature, and mass fraction of emissions were solved for transient condition using the CFD software FLUENT 6.0. For the analysis, a burning bus was assumed to release an equivalent energy of burning 500 l of diesel in 6 min, with vehicles upstream of the fire at a standstill. On the other hand, the vehicles downstream of the fire had enough time to escape from the tunnel through the exit portal. Due to the action of jet fans, most of the smoke was pushed downstream of the fire. The smoke had also dispersed about 55 m upstream of the fire, putting the passengers in this region at great risk. The emissions released from the vehicles in the jam, with their engines running, also posed a threat to human health. Within 8 min after the fire had started, the mass concentrations of O₂, CO₂ and CO were in the ranges of 0.12–0.15, 0.08–0.11 and 0.0006–0.0014, respectively. Therefore, quick evacuation of the passengers is essential in the event of a fire in the tunnel.     

火源与排烟竖井的相对位置对重点排烟效果的影响研究

借助理论分析及数值模拟相结合的手段对某盾构城市地下道路火灾工况下,火源与排烟竖井的相对位置对重点排烟效果的影响进行模拟研究.研究结果表明单向排烟模式在一定的排烟量条件下,火源位置距离排烟竖井越近,排烟效果越好.当火源位于两个排烟竖井之间且偏向其中某一个竖井位置时,在排烟量允许的前提下,可以仅开启离火源位置较近的竖井风机...     

汕头海湾隧道消防减灾设计研究与应用

以汕头海湾隧道工程为依托,通过调研相关规范和工程实例、同步开展火灾实验和数值模拟分析,对消防减灾设计中的火灾规模、控烟排烟模式、自动报警及消防灭火措施等几个关键技术难题进行了应用研究。结果表明,当隧道设置自动灭火系统时,即使隧道允许货车拖车通行,火灾规模也可按50 MW进行设计;当隧道采用集中排烟模式时,隧道顶板温度低于900 ℃,烟气蔓延范围小于300 m,温度影响范围为火源两侧10 m,能见度影响范围为火源两侧5 m,CO体积分数小于临界危险值5×10-4,疏散环境良好;当隧道设置两种不同的火灾探测器时,60 s内可完成报警,水下长大隧道应设置消火栓、灭火器和自动灭火系统,优先采用泡沫-水喷雾联用灭火系统,消防时3个灭火分区同时动作。