利用电梯竖井的高层建筑排烟系统研究

发布时间：2018-09-06 09:52

【摘要】：烟气是建筑火灾中造成人员伤亡的主要原因,烟气的流动特性成为建筑防火设计中的研究热点。建筑火灾发生后,高层建筑中诸多竖井产生的“烟囱效应”是烟气竖向运动的主要驱动力,烟气进入竖井后通过开口或缝隙侵入楼层区域,从而造成烟气的蔓延。考虑到建筑竖井产生的“烟囱效应”,结合火灾烟气数值模拟的方法,对高层建筑利用电梯竖井的排烟系统进行分析研究。鉴于建筑竖井产生的“烟囱效应”,可以考虑利用建筑竖井进行排烟。遵循火灾烟气从高压区向低压区流动的规律,针对高层建筑中电梯竖井与楼梯竖井分开设置的情况,本文提出了高层建筑利用电梯竖井进行排烟的研究课题。《高层民用建筑设计防火规范》(GB50045-2005)8.1条中提到了可利用建筑竖井有组织地自然排烟,但建筑竖井占地面积较大,一般情况下设计者很难接受,所以近年来很少采用。电梯竖井是一个将整栋建筑物上下连接的通道,截面积较大,具有作为排烟竖井的可能性。从实践上看,若将消防楼梯间与电梯间作平面分离,分别作为人员逃生和火灾烟气排出的通道,则可以考虑在电梯竖井顶部设置排烟口进行排烟。《高层民用建筑设计防火规范》尚未明确规定针对电梯竖井具体的防排烟措施,本文主要针对高层建筑利用电梯竖井的排烟系统进行研究。在数学模型研究方面,主要利用网络模型对高层建筑火灾烟气的流动规律进行数值计算。传统的网络模型对着火房间火灾过程的处理比较简单,未考虑烟气与壁面的换热,且忽略了烟气流动摩擦阻力损失,计算结果势必与实际火灾烟气流动规律相差较大。基于传统网络模型,提出一种改良的网络模型：在着火房间采用双区模型；考虑了火灾烟气与建筑竖井壁面之间的对流换热与辐射换热；考虑了火灾烟气在建筑竖井内的流动摩擦阻力损失,以修正竖井烟气上升阻力及竖井排烟能力。在模型验证方面,对改良的网络模型中各子模型的准确性进行验证：所编写传统网络模型与着火房间双区模型程序分别与CONTAM软件、FDS (Fire Dynamic Simulator)软件的计算结果进行对比；对竖井内烟气的传热进行了缩尺模型实验,并采用盐水模型实验对竖井内的烟气流动进行了直观演示。基于上述各子模型建立的改良网络数学模型及求解方法,为高层建筑火灾烟气的流动规律提供了研究手段。在应用研究方面,本文利用改良的网络模型对高层建筑利用电梯竖井的自然排烟进行了数值计算,详细分析了电梯竖井顶部开口面积、着火层常闭排烟口尺寸、电梯门缝宽度与竖井壁面摩擦阻力系数对电梯竖井自然排烟的影响。在数值计算过程中,防烟楼梯间作为人员逃生通道,采用机械加压送风方式阻止烟气侵入,着火层内未考虑机械排烟。为了比较不同工况下的排烟效果,主要考虑电梯竖井中和面位置、电梯竖井排烟量与从着火层进入电梯竖井的烟气量,提出了电梯竖井综合排烟系数的概念；利用正交实验方法得到了各影响因素在计算范围内的重要程度,并分析了不同着火楼层下利用电梯竖井自然排烟的效果。对着火层以上各楼层进行加压送风,利用改良的网络模型对电梯竖井的排烟进行数值计算,得到了不同的加压送风量对电梯竖井排烟效果的影响；分析了着火楼层不同时,对着火层以上各楼层加压送风对电梯竖井排烟效果的影响。结合遗传算法,对某高层建筑利用电梯竖井排烟进行了优化计算,得到了电梯竖井顶部开口面积比、加压送风量、电梯门缝宽度与着火层常闭排烟口尺寸在计算范围内优化,电梯竖井能够达到较好的排烟效果。
[Abstract]:The flue gas is the main cause of casualties in building fires, and the flue gas flow characteristics become the research hotspot in building fire protection design. Considering the "chimney effect" produced by building shaft and combining with the method of fire smoke numerical simulation, the smoke exhaust system of elevator shaft in high-rise building is analyzed and studied. According to the law of pressure zone flowing to low pressure zone and the situation that the elevator shaft and the staircase shaft are separated in high-rise buildings, this paper puts forward the research subject of smoke exhaust by elevator shaft in high-rise buildings. The elevator shaft is a passage connecting the whole building up and down, with a large cross-section area, and it is possible to be used as a smoke exhaust shaft. Fire smoke exhaust passage can be considered in the top of the elevator shaft for smoke exhaust. has not clearly defined specific smoke prevention and exhaust measures for elevator shaft, this paper mainly for high-rise buildings using elevator shaft smoke exhaust system. The traditional network model is simple in dealing with the fire process of a high-rise building. It does not consider the heat transfer between the smoke and the wall, and ignores the friction loss of the smoke flow. An improved network model is proposed based on the traditional network model: a two-zone model is used in the fire chamber; the convective and radiative heat transfer between the fire smoke and the wall of the building shaft is considered; and the friction loss of the fire smoke in the building shaft is considered to correct the rising resistance of the shaft smoke and the smoke exhaust capacity of the shaft. In the aspect of model validation, the accuracy of each sub-model in the improved network model is verified: the traditional network model and the two-zone model program of the fire room are compared with the results of CONTAM software and FDS (Fire Dynamic Simulator) software respectively; the scale model experiment of flue gas heat transfer in the shaft is carried out, and salt is used. The water model experiment demonstrates the smoke flow in the shaft directly. The improved network mathematical model and solving method based on the above sub-models provide a research method for the smoke flow law of high-rise building fire. In the aspect of application research, this paper uses the improved network model to study the nature of high-rise building using the elevator shaft. The influence of the opening area at the top of the elevator shaft, the size of the smoke outlet at the normal closure of the fire layer, the width of the elevator door gap and the friction coefficient of the shaft wall on the natural smoke exhaust from the elevator shaft is analyzed in detail. In order to compare the smoke exhaust effect under different working conditions, the position of the neutral plane of the elevator shaft, the smoke exhaust volume of the elevator shaft and the smoke volume from the ignition layer into the elevator shaft were mainly considered, and the concept of the comprehensive smoke exhaust coefficient of the elevator shaft was put forward. The importance of the calculation range is analyzed, and the effect of natural smoke exhaust by elevator shaft under different fire floor is analyzed. The influence of pressurized air supply on the smoke exhaust effect of elevator shaft is studied when the fire floor is different. Combining with genetic algorithm, the smoke exhaust effect of elevator shaft in a high-rise building is optimized. The ratio of the top opening area of elevator shaft, the pressurized air supply rate, the width of elevator door gap and the size of the smoke exhaust nozzle are calculated. Within the scope of optimization, elevator shaft can achieve better smoke exhaust effect.
【学位授予单位】：华北电力大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU976.5

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