共查询到19条相似文献,搜索用时 46 毫秒
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摘 要:超长海底隧道结构特殊,排烟补风成为制约超长海底隧道发展的关键因素。依托烟大海底隧道提出超长海底隧道无竖井排烟系统,并设计新型的海中无竖井排烟补风方案——采用离心式空气压缩机将火灾烟气高速加压后排到海水中,并通过压缩空气进行额外补风。采用FDS对不同排烟量和补风量下56组工况进行模拟,通过分析烟气层厚度、排烟效率和能见度,寻找最优的排烟补风方案。结果表明:排烟量在140~180,190~210 m3/s,补风量分别占排烟量的50%、70%时,系统排烟效果最优;其中,排烟量180 m3/s,补风量50%和排烟量200 m3/s,补风量70%情况下的排烟效果最优,且后者优于前者。实际工程应用中,可以考虑设计排烟量为200 m3/s,补风量为140 m3/s。 相似文献
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上海市的工程建设规范《建筑防排烟技术规程》中要求;需要补风的排烟区间,其补风量不应小于排烟量的50%。但是在实际设计过程中,如果简单地套用排烟量的50%作为补风风量,而不经过风量平衡的验证计算,很有可能遇到由于补风风量不足造成排烟量无法满足设计要求的问题。对于一些密封性能好,排烟量特别大的房间应由风量平衡计算来确定补风量。 相似文献
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通过数值模拟方法对推拉式排烟模式应用于地铁公共区的排烟效果进行了研究探讨。结果表明,推拉式排烟模式可将火灾烟气有效控制在起火防烟分区内,有效防止地铁公共区排烟死角现象的出现;当地铁公共区排烟设备负担两个或两个以上防烟分区时,火灾下关闭相邻防烟分区的排烟口,将两个或两个以上防烟分区的排烟量加到起火防烟分区内,补风量为排烟量的70%~90%,可取得良好的排烟效果。 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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摘 要:开展了不同火源间距(1.5D、1.75D、2D)和不同油盘直径(1.0,1.4,1.7 m)下户外多火源燃烧和单火源燃烧对比试验,试验中利用摄像机、电子天平、热电偶阵列分别监测了火焰高度、火源燃烧速率和几何中心温度。结果发现,四火源燃烧时各个火源的燃烧速率高于相同直径下单火源的燃烧速率,而且均在火源间距1.5D时发生了火焰融合现象,火焰融合高度高于相同直径下单火源的火焰高度,表明多火源燃烧危险性更大。四火源融合后,在连续火焰区、间歇火焰区、羽流区几何中轴线火焰温度随高度的指数变化分别为0.13、-1.02、-1.46,与普通浮力池火公认的中轴线温度变化基本保持一致,表明多火焰融合后形成了一个普通的浮力池火。 相似文献
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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。 相似文献
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Olivier Vauquelin 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2008,23(2):171-178
When a fire occurs in a long tunnel, smoke control is crucial for obvious reasons of safety. Ventilation and extraction systems have to be designed with accuracy in order to control the longitudinal motion of the fire-induced smoke and to extract it efficiently in a zone close to the fire source. This paper presents experimental investigations carried out on a small scale tunnel model (scale reduction is 1:20) to study the fire-induced smoke control by longitudinal and transverse ventilation systems. The experimental model is non-thermal and a buoyant release (a mixing of air and helium) is used to represent the fire smoke plume. The main objective of this model is to represent, as well as make possible, the duality between inertial forces (due to ventilation) and buoyant forces. Radiation and heat losses at the walls are not taken into account in this model. At first, the principle of the simulation is widely described. Then, some results are presented for both longitudinal and transverse smoke control by a mechanical ventilation. Finally, perspectives for future investigations are proposed. 相似文献
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When tunnel fire smoke is exhausted using a top central exhausting system, the air entrainment at the smoke-air interface has a significant effect on the overall mass flux. Using theoretical analysis, the air entrainment coefficient in one-dimensional horizontal smoke movement stage in central exhausting was obtained. Both heat release rate and smoke extraction rate have effects on the horizontal entrainment coefficient. The experimental results show that the entrainment coefficient in central exhausting is between 0.01 and 0.03 and the horizontal entrainment coefficient increases to 0.0181 with increasing heat release rate and becomes relatively stable afterwards. The entrainment coefficient increases with the smoke extraction rate increasing as the smoke extraction process will enhance the smoke momentum in the tunnel. 相似文献
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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. 相似文献
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在建筑的防排烟系统中,前室的防烟对于保证人员的安全疏散和顺利的消防扑救相当重要。文章时前室防烟的理念做了阐述,明确前室机械加压送风系统在火灾时只应开启着火层的送风口、针对我国及上海市现行的建筑防排烟规范,文中通过实例时前室机械防烟系统不同的送风量计算方法进行了对比分析。 相似文献
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The rail based urban transport system is being developed for national capital of India, New Delhi. The smoke control using
ventilation in case of fire inside the tunnel, similar to Delhi Metro corridor has been investigated using computational fluid
dynamics technique. A section of tunnel having dimensions 400 m long, 5.5 m wide and 6 m high is considered for simulation.
The analysis has been carried out by assuming a variable fire source with a peak heat release rate (HRR) of 16 MW, located
at the center of the tunnel. Ventilation ducts are located in the ceiling near the tunnel portals and are inclined at 10 degrees
to the plane of the ceiling through which fans discharge air. The influence of the fire HRR curve slope on the smoke flow
dynamics in a realistic tunnel model fitted with jet injection type longitudinal ventilation system has been investigated.
In case of fire two cases are studied: (1) fans activated immediately after detection, (2) fans activated at delayed times
to take into account the response time for the fans to achieve its maximum speed. The velocity of supply and exhaust fans
necessary to remove smoke in 30 s from the upstream direction is determined. The velocities of fan required to produce desired
critical velocity in the longitudinal direction for different HRR of fire is predicted. 相似文献
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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。 相似文献
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地铁站厅至站台楼梯口风速对火灾烟气运动的影响 总被引:1,自引:0,他引:1
地铁车站站台发生火灾,连接站厅与站台的楼梯口保持一定风速,可阻挡烟气向站厅蔓延并为人员疏散提供诱导气流。为研究楼梯口风速对车站火灾烟气运动的影响,试验对不同排烟模式下楼梯口风速进行测量,建立数值计算模型进行模拟。结果表明:火灾场景下楼梯口风速大于无火源场景下风速,因此常规楼梯口风速校核设计方法由于没考虑真实火灾情况下各种因素的复杂作用,需进一步改进;楼梯口附近起火,烟气易从挡烟垂壁溢出向站厅层蔓延,站台火灾时站厅层为送风状态,存在溢出烟气时站厅层烟浓度可增至大于站台层;站台公共区着火,增开隧道风机,能够增 相似文献