【作者】 涂锐；

【导师】 钟委；

【作者基本信息】 郑州大学 ， 安全技术及工程， 2013， 硕士

【摘要】 随着城市化进程加快,交通问题日益严峻,地铁以其方便快捷、高效节能等诸多优点成为解决城市拥堵问题的有效途径,但同时也带来了严重的火灾防治问题。由于车站埋于地下,空间相对封闭,人员高度集中,一旦发生火灾将会蓄积大量有毒有害的高温烟气。在列车活塞风的作用下,站内烟气流动速度增大,分层特性也会遭到破坏,进而影响人员疏散,造成灾难性的后果。统计结果表明,火灾伤亡中有超过85%的人死于烟气中毒。因此,必须控制火灾烟气在地铁站内的蔓延以保障人员安全疏散。当火灾发生在区间隧道内时,由于隧道净空较低,火焰很容易形成顶棚射流火焰,这与开放空间下自由扩散火焰的燃烧机理有着本质区别。对于自然扩散火焰,决定其质量燃烧速率的主要因素是火羽流对燃料表面的热反馈,决定其燃烧状态的是羽流竖直上升过程中对空气的卷吸；而对于顶棚射流火焰,决定其燃烧速率的是火羽流及其射流火焰对可燃物表面的热反馈,决定其燃烧状态的是射流火焰对空气的卷吸。然而目前相关实验数据不仅缺乏,而且尚未系统地考虑隧道空间结构和起火高度对火焰特征参数的影响。本文采用流体动力学软件FLUENT模拟了列车运动产生的活塞风对地铁车站流场结构的影响,分别将活塞风与站台火灾和站厅火灾相结合,进一步分析车站内的烟气流动状态和分层现象受活塞风影响的变化过程。模拟发现受活塞风的影响现有车站防排烟系统无法将起火站台层或起火站厅层的烟气限制在本层内。为了达到上述目的,本文提出通过增加安全门高度,增大站厅层送风量、降低楼梯口周围挡烟垂壁高度以及增设活塞风竖井和迂回风道等措施,取得了较好的效果。针对受限空间下车辆火灾顶棚射流火焰发展特性,设计并开展了小尺寸模型实验。采用了液面恒定的燃料供应装置,研究了不同截面宽度、不同起火高度下隧道内火焰燃烧特性及其特征参数随火源功率的变化关系,建立了相应的无量纲预测模型。研究发现,当考虑火源功率随时间的变化时,开放空间下火焰高度与火源功率呈线性关系；受限空间下在顶棚射流火焰形成之前,火焰高度与火源功率呈二次函数关系,受限空间下当火焰形成顶棚射流状态后,射流长度截断比与火源功率之间呈线性关系。本文选取尺寸L作为单一尺寸油盆下火源功率的无量纲特征尺寸,并建立了火焰振荡频率与特征尺寸之间的预测模型。更多还原

【Abstract】 With the accelerating of urbanization process, the traffic problem is increasingly serious. Subway, with its advantages of convenient and quick, high efficiency and energy saving, has been becoming an effective way to solve traffic congestion. However, it also caused serious fire safety problems. Due to the station buried underground, space relatively closed and crowd concentrated, a lot of poisonous and high-temperature smoke will be accumulated when a fire starts. Under the influence of piston wind, the smoke flow will be accelerated and distribution will be destroyed and evacuation will be arrested. According to the statistical data, more than85%casualties have died of toxic smoke in fire.When a fire breaks out in metro tunnel, the flame will be easy to form the ceiling jet state because of low headroom, which is essentially different from free diffusion flame in the open space. For the free diffusion flame, the thermal feedback of fire plume on the surface of fuel is the main factor to determine the mass burning rate while the air entrainment by vertical rise plume decides the combustion state. For ceiling jet flame, the thermal feedback of fire plume and jet flame on the fuel decide the mass burning rate while the air entrainment by jet flame is the main factor to determine the combustion state. However, the relevant experimental data is scarce.The influence of the piston wind produced by train movement on airflow structure of subway station was simulated by fluid dynamics software FLUENT. Piston wind was combined with platform fires and station hall fires separately to analysis the impact on smoke flow state and stratification. Result shows that the existing station smoke control system is not able to confine the smoke in platform or station hall layer. For this purpose, active measures, such as increasing screen door height, enlarging air supply, reducing the height of smoke barrier, adding piston wind shaft and bypass and so on, were taken and achieved good results.In allusion to the study on development characteristics of ceiling jet flame of tain, the model experiments were designed and carried out. A fuel supply device with a constant Liquid level was adopted to study the flame characteristic parameters changed with the fire power under different cross section and fire source location. The dimensionless prediction models were established. The study found that, considering fire power changes over time, the relationship between flame height and fire power in open space is linear. Before the ceiling jet flame has been formed in the limited space, the relationship between flame height and fire power is of a quadratic function. After the ceiling jet flame has been formed in the limited space, the relationship between the jet length and fire power is linear. The feature size Lwas taken as the dimensionless parameter of fire power. The prediction models between flame oscillation frequency and feature size were established.更多还原