火灾工况下公路隧道竖井通风模式试验研究

为了建立火灾工况下有效的竖井通风模式,通过大比例火灾模型试验,对不同通风模式下,主隧道、风道及竖井内温度场的传播分布、烟流蔓延扩散规律进行了研究。试验模型隧道长100 m,内径1.8 m,设有直径1 m的送风竖井、排风竖井各一座。火源采用燃烧床盛放油料模拟,试验中设定了A、B、C三个火灾规模用以模拟实际隧道火灾场景,考虑了三个火灾位置:火灾位置I、II和III。试验结果表明随着通风风速、火灾规模、火灾位置的不同,隧道、通风道及竖井内温度场分布及烟流流动差异很大,而且随着时间的推移,其分布发生显著变化。这表明当隧道中发生火灾时,应根据火灾点与竖井的相对位置分阶段,实施不同的通风模式。基于试验结果,建议了秦岭隧道火灾时的有效通风模式。     

火灾时隧道火风压及其对通风影响的试验研究

文章借助大比例火灾模型试验,分析了在火灾情况下隧道火风压力的变化,探析了火灾规模、通风速度、隧道坡度、烟流蔓延长度等因素对火风压的影响,同时还分析了火灾对隧道通风系统的影响情况。试验表明隧道火风压会随着火灾规模、通风速度、隧道坡度、烟流蔓延长度等因素的增大而变大,并且火风压会对隧道的通风造成很大的影响。     

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。     

中梁山隧道火灾通风排烟的数值模拟

根据中梁山地铁区间隧道的实际情况确定最不利的通风排烟模式,利用FDS对火灾时的通风排烟进行模拟,分析隧道内不同时刻、不同截面位置的烟流特性参数。模拟结果显示,射流风机作用下火区上游通风风速为2.5 m/s,没有产生回流,起火列车人员能够安全疏散。烟流前锋面到达非起火列车的时间超过850 s,大于非起火列车人员疏散完成时间。     

小半径曲线隧道火灾通风数值模拟研究

以四川雅安至西昌高速公路干海子曲线公路隧道为工程背景,结合小半径曲线隧道特殊的边界条件,建立三维数值模型,开展小半径曲线公路隧道火灾烟气蔓延规律的数值模拟研究。研究小半径曲线隧道内发生火灾时不同通风风速条件下烟流温度、速度和浓度的分布特征及变化规律,给出了曲线隧道火灾事故紧急通风情况下的最小纵向通风风速。模拟结果表明,小半径曲率隧道的火灾烟气蔓延及温度分布与直线隧道存在明显差异,干海子曲线隧道抑制火灾烟气回流的最小纵向通风风速为4m/s。     

公路隧道火灾通风计算的改进

现有的公路隧道火灾通风计算方法,是按正常运营通风设计的风机配置,考虑火灾发生后一定数量风机的损坏,计算火灾情况下能够提供的隧道内风速,用该风速和阻止烟流逆流的临界风速比较来验算火灾时期通风的安全性。但在公路隧道的火灾过程中,火灾烟流阻力确实存在,且对隧道火灾时的烟气流动影响较大。本文将烟流阻力引进传统的公路隧道通风计算中,给出了公路隧道火灾通风时的改进计算公式。通过算例,证明了改进的计算方法更符合隧道火灾时实际概况,为隧道火灾时的通风控制提供了科学依据。     

烟囱效应下山岭隧道火风压特性模拟研究

为探究山岭隧道火灾模式下竖井内火风压的变化特性,采用数值模拟方法,选取火灾发生在竖井附近及远离竖井时的烟气流动特性为研究对象,分析烟气在纵向通风作用下竖井内火风压的变化规律。研究表明：与传统斜坡隧道火灾不同,由于烟气涡流影响,竖井内火风压在纵向通风作用下均呈现非单调的变化趋势,故隧道火风压理论模型不能直接用于竖井内火风压预测;竖井内火风压随纵向风速从0 m/s 增大至3.5 m/s 时呈现逐渐增加趋势,最大差值约为40 Pa;火源靠近竖井时比远离竖井时,竖井内火风压更大,纵向无风时,两者最大差值约为25 Pa。     

高海拔双向行车公路隧道火灾控烟风速研究

雀儿山隧道为高海拔双向行车公路隧道,发生火灾后需要兼顾火灾点两侧人员的疏散,烟气控制较单向行车隧道复杂。采用FDS软件对雀儿山隧道进行火灾三维数值模拟,研究了高海拔双向行车公路隧道火灾时的烟气流动规律和能见度分布规律。研究结果表明:高海拔隧道火灾烟气流动比低海拔隧道速度快;纵坡隧道发生火灾时,若不采取任何控烟措施,烟流在火风压效应的作用下会从高洞口排出,而烟流沿下坡方向的蔓延距离仅在10 m左右,火灾烟气沿火灾点两侧蔓延极不对称;当隧道高洞口控制风速过大或横通道内控制风速过小时,易出现烟气蔓延对称性不佳或烟气窜入横通道,故二者应合理取值;当隧道高洞口施加0.5 m/s的风速、横通道施加1.0 m/s的风速时,烟气在火灾点两侧基本呈对称蔓延,且火灾两侧的能见度也基本对称;建议类似于依托工程的单洞双向行车公路隧道火灾疏散救援阶段,隧道高洞口风速控制在0.5 m/s左右、横通道内风速控制在1.0 m/s左右,以利于人员逃生。     

纵向风速对隧道细水雾灭火效果影响探讨

摘 要：为了探究细水雾和纵向通风共同作用下隧道内烟气运动情况,确定配置有细水雾灭火系统的隧道最佳通风策略。采用FDS建立了隧道细水雾数值模拟模型,分别计算了不同纵向风速情况下隧道内温度、有害气体浓度及辐射热通量的变化情况。结果表明：30 MW火灾规模下,烟气层在火源上风向15 m的喷雾区开始出现逐渐层降,烟气层下降至2 m以下;至300 s灭火结束时,上风向150 m内,烟气层全部下降至2 m以下。故火灾发生5 min后,人员疏散距离应大于150 m。对比相同通风风速下（1 m/s）细水雾施加前后辐射热通量变化情况得出,开启细水雾灭火系统25 s后,火源下游5 m处热辐射强度由6 kW/m2降至0。建议开启细水雾灭火系统时尽量保持隧道内1 m/s的通风风速。     

公路隧道火灾温度场的分布规律研究

隧道火灾随着通风风速和火灾规模不同 ,其温度场也发生了变化 ,本文对五种不同风速下的三种火灾规模进行了试验 ,研究了火区内和火区下游最高温度的变化规律、温度随时间的变化规律、温度沿隧道纵向分布规律、温度沿隧道横断面分布规律等 ,这对公路隧道防灾减灾设计有现实的指导意义。     

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。     

Performance validation of a hybrid ventilation strategy comprising longitudinal and point ventilation by a fire experiment using a model-scale tunnel

We examined the exhaust performance of a hybrid ventilation strategy for maintaining a safe evacuation environment for tunnel users in a tunnel fire. The hybrid ventilation strategy combines the longitudinal ventilation strategy with the point ventilation strategy which is a type of transverse ventilation strategy. The model tunnel developed by this study was scaled to 1/5 the size of a full-scale tunnel. The model-scale experiment was performed taking into consideration Froude's law of similarity. Measurement items were the distribution of temperature and concentration of smoke inside the tunnel, longitudinal wind velocity, mass flow of smoke in the point ventilation duct, and the heat release rate of the fire source. The following main conclusions were obtained. The smoke height was constant even when varying the extraction rate of smoke from the ceiling vent. The backlayering length and critical velocity of the smoke flow in the hybrid strategy could be predicted by the methodology developed by using the longitudinal strategy. The hybrid strategy maintained a safe evacuation environment on both sides of the tunnel fire.     

Experimental study of the effectiveness of a water system in blocking fire-induced smoke and heat in reduced-scale tunnel tests

A water system, consisting of several water mist nozzles, has been installed in a reduced-scale tunnel. Its effectiveness in blocking fire-induced smoke and heat is tested, with and without longitudinal ventilation. A total of 14 fire tests have been carried out, with 250 ml methanol in an iron tray (25 cm × 20 cm) as fuel. Temperatures have been measured by 30 thermocouples, located upstream and downstream of the fire location. The aim is to assess the effectiveness of the water system in preventing smoke spread and in reducing the temperature in the tunnel. Interaction of the water with the fire is avoided. The impact of water pressure, ventilation velocity and nozzle arrangement on the effectiveness in smoke blocking and temperature reduction is discussed. The result confirms that the water system effectively reduces the temperatures and prevents smoke spreading in the absence of longitudinal ventilation. However, strong longitudinal ventilation (0.8 m/s ventilation velocity in the reduced-scale tunnel, corresponding to critical velocity in full-scale (1:10) tunnel) reduces the effectiveness in blocking the smoke spreading by the water system, although the temperature reduction downstream the water system remains in place. Higher water pressure makes the cooling effect stronger, because more and smaller water droplets are injected into the tunnel. For a given level of water pressure level, the impact of the nozzle row configuration is small in the tests.     

地铁区间隧道火灾通风模式的数值分析

介绍了地铁区间隧道火灾常见的几种通风排烟模式,对其中一种最复杂的模式进行了数值分析。模拟分析得出,对于地铁实际工程中的单线盾构圆形隧道,在10 MW火灾强度下,着火区间隧道内2.6~2.9 m/s左右的纵向风速可以有效阻止烟气发生逆流;在着火区间隧道2.9 m/s的纵向风速下,未着火区间隧道两端对送送风速度为1~1.5 m/s时,联络通道内有风速为6 m/s左右的气流流向着火区间隧道,可有效抑制烟气通过联络通道向未着火区间隧道蔓延,保证人员的安全疏散。     

Experimental studies on fire-induced buoyant smoke temperature distribution along tunnel ceiling

Twelve tests were conducted to study the distribution of smoke temperature along the tunnel ceiling in the one-dimensional spreading phase, two tests in a large-scale tunnel and the other ten in full scale vehicular tunnels. The fire size and the height above the floor, the tunnel section geometry and longitudinal ventilation velocity varied in these tests. Experimental results showed that when the fire size was larger, the smoke temperature below the ceiling was higher, but it decayed faster while traveling down the tunnel. The longitudinal ventilation velocity seemed to take much influence on the smoke temperature decay speed downstream. A “barrier effect” was shown for the smoke temperature distribution of the upstream back layering. The smoke temperatures measured were higher upstream than downstream before the “barrier”, and were much lower and decreased faster along the tunnel ceiling after the “barrier”. The temperature and the traveling velocity of the upstream smoke flow decreased largely when the longitudinal ventilation velocity increased a bit. The dimensionless excess smoke temperature distributions along the tunnel ceiling in all tests fell into good exponential decay. But the decay speed along the tunnel seemed to be much larger in the large-scale tunnel than that in full-scale tunnels. The measured data on ceiling jet temperature decay along the tunnel was compared with predictions of Delichatsios's model, a model built based on small-scale tests, with hydraulic diameter introduced. Results showed that Delichatsisos’ model over estimated the decay speed of ceiling jet temperature for the downstream flow. However, good agreement was achieved between the measured data and the model predictions for the upstream back layering. All the experimental data presented in this paper can be further applied for verification of numerical models, bench-scale results and building new models on ceiling jet temperature distribution.     

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。     

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.     

火灾工程在厦门翔安隧道项目中的应用

近年来,许多国家都发生了不同程度的公路隧道火灾事故,在国际上引起了广泛的关注。因此,火灾工程分析方法在国际隧道防火设计上的应用越来越普遍。通过引入可维生环境的设计概念,当隧道内发生火灾时,利用纵向通风模式达到满足隧道内人员疏散逃生要求的目的。厦门翔安隧道是国内第1条大断面海底隧道,全长约9 km,海底隧道长5.95 km。本文首先分析了厦门翔安隧道的特点,然后引入了国际上常用的进行火灾工程分析所使用的可维生环境概念,最后对该工程进行了火灾模拟分析。假定隧道内发生火灾的最大释热量为30 MW,分析后发现设计单位采用的2.5 m/s临界风速不能满足火灾工况下的烟控要求,烟气有回流现象发生。因此建议临界风速由2.5 m/s提高到3.0 m/s,确保烟气能被有效控制以保证隧道防火安全。在纵向风速为3.0 m/s的情况下,分析了火灾发展不同时刻的可维生环境参数,确保隧道内人员能安全疏散,从而提升厦门翔安隧道烟控、消防、防灾系统的整体设计水平。     

实体隧道火灾温度分布试验研究

建立实体隧道火灾现场试验系统及数据采集系统,通过在岩门界隧道开展的实体隧道火灾试验,测试了不同通风模式、不同火灾工况下隧道火源上、下游不同断面处的温度变化及隧道拱顶的温度变化。试验结果表明,与车行方向相同的1.8m/s机械通风能在一定程度上延缓烟气蔓延;有与车行方向相反的自然风时,火源下游温度较低,最高温度出现在火源上游;有机械通风时,温度随风向、风速而变化。