共查询到19条相似文献,搜索用时 125 毫秒
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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。 相似文献
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文章基于CFD软件FLUENT,对某直线隧道进行数值模拟,研究了长度为300 m的直线隧道在火灾下的临界风速和烟气流动。采用RNG k-ε湍流模型进行数值模拟,结果当隧道内发生规模约为5 MW火灾时,火灾烟气控制的临界风速为2.3 m/s。当风速低于临界风速时,隧道内会出现烟气回流,不利于人员逃生。火灾下游靠近火源的断面烟气紊乱,距离断面较远的断面则具有较好的分层性。 相似文献
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《地下空间与工程学报》2021,17(z1):469-473
针对城市隧道日益增多的引流渐扩段,利用数值模拟分析渐扩段发生火灾时,烟气回流长度、临界风速、火风压等纵向排烟关键参数特征。研究表明为控制渐扩隧道烟气回流,需考虑火源处风速——有效风速,入口处临界风速可根据最宽截面处发生火灾,即最不利工况时的有效临界风速进行折算。在相同有效风速下,渐扩隧道烟气回流长度更短,回流长度差距最大的情况可达到60 m左右,对消防设计和火灾救援产生明显的影响。渐扩隧道火风压会随有效风速的增大,先增大后减小,当有效风速增大到临界风速后趋于稳定的数值。由于隧道渐扩段烟气回流速度更快,烟气的惯性力项越大,火风压也越大。 相似文献
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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。 相似文献
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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。 相似文献
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《Planning》2016,(7)
为了探究火灾发生后风机启动时间对地铁区间烟气控制的影响,现以内径为5.5m圆形盾构地铁区间隧道为研究对象,采用数值模拟方法研究不同火源功率(5、7.5、10 MW)下隧道内烟气的温度分布,分析了4种火灾工况下隧道顶部最高温度值以及出现位置,研究了风机延迟启动时间对隧道内烟气温度分布的影响。结果表明,隧道顶部最高温度随火源功率增大而增高;纵向通风风速会造成隧道顶部最高烟气温度区域向通风方向偏移,但随着火源功率增加,排烟风速的影响会逐渐减弱;延迟启动风机会破坏烟气层的稳定性,导致烟气沉降到列车的车厢位置,从而会影响乘客安全疏散。 相似文献
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采用试验与数值模拟研究隧道双火源火灾临界风速变化,重点研究双火源功率和火源间距对临界风速的影响。结果表明:随着火源间距增加,临界风速逐渐降低,当两火源间距达到极限距离时,临界风速不再变化;当进风口侧火源功率确定时,在极限间距内出风口侧火源功率增大时,临界风速增大,说明出风口侧的火源对进风口侧的烟气回流有促进作用;在极限间距内,临界风速随火源间距增加呈二次方递减到一个稳定值;两火源总功率越大,临界风速随着间距增加降低的幅度越明显。并得到了临界风速的预测公式。 相似文献
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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。 相似文献
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Due to the small width and the large train blockage ratio in subway tunnel, the smoke back-layering will be different from that in the wider road tunnel with small vehicle blockage ratio. In the train blockage region of tunnel, the velocity of longitudinal ventilated air-flow interacting with the back-flowed smoke gas is different from that in the upstream tunnel without train blockage. Then the back-flowed smoke gas might be prevented in the train blockage region with higher ventilation velocity, otherwise it would be stopped in the upstream tunnel without train blockage but with lower ventilation velocity. They were taken into consideration separately and an equivalent fire source was introduced by dividing the dimensionless heat release rate of fire source into two parts in the cases where the smoke back-layering length is longer than metro train length. A series of full-scale numerical simulations are carried out with FDS to investigate the smoke back-layering length in subway tunnel with different train lengths and longitudinal ventilation velocities. The simulation results indicate that the influence of metro train length on the smoke back-layering is great and cannot be ignored any more. A global correlation model is proposed based on the dimensionless analysis and simulation results. 相似文献
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火灾时隧道内烟流流动状态试验研究 总被引:6,自引:1,他引:6
通过大比例火灾模型试验,研究火灾时隧道内烟流流动状态、烟流速度变化以及通风对烟流流动状态的影响。试验模型隧道长100m,内径1.8m。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。试验结果表明,点火后,隧道内火区、火区下游烟流速度在2~8min内增加很快,明显大于点火前风速,且其增幅随通风风速、火灾规模的不同而变化。同时,随着火势的逐渐减弱隧道内烟流速度也逐渐减小,并趋于初始风速。试验结果建议对于一般的限制或禁止油罐车通行的隧道,火灾时,隧道内应尽快建立起2~3m/s的纵向风流以抑止烟气的逆流。 相似文献
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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。 相似文献
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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. 相似文献
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Heat exhaust coefficient of transversal smoke extraction system in tunnel under fire is studied by experimental means with a 1:10 model tunnel using Froude scaling. Heat exhaust coefficient is defined as the proportion of the heat exhausted by individual exhaust inlet, smoke duct and exhaust fans in total heat released by the fire in the tunnel, respectively. Results of a series of fire tests in a model tunnel are presented. Heat exhaust coefficient of single exhaust inlet and the smoke duct are strongly influenced by the configuration of the exhaust inlets. Heat exhaust coefficient of the exhaust fans varies in the range of 13–20% and is smaller than the heat exhaust coefficient of the smoke duct which varies from 17% to 83% and tends to be about 35% with the increase of the total area of the exhaust inlets. Activating small number of the exhaust inlets is beneficial for enhancing the heat exhaust coefficient of the smoke duct. The heat exhaust coefficient of the smoke duct and exhaust fans is high when the exhaust inlets are set close to the fire. Due to the cooling effect of the solid boundaries on the smoke while traveling in the tunnel and smoke duct, the heat exhaust coefficient of the exhaust fans in unilateral exhaust mode is slightly smaller than that in bilateral exhaust mode. 相似文献