高层建筑竖向通道内烟气输运规律及着火房间火行为特性研究
发布时间：2018-09-11 09:34
【摘要】：近年来,我国兴建了越来越多的高层建筑,且伴随着高层建筑火灾事故频发,造成了大量的人员伤亡和财产损失,统计结果表明,火灾中有超过百分之八十的人员死亡是由于有毒烟气造成的。高层建筑由于建筑高,扑救和控制火势难度大,人员疏散困难。建筑内部的竖向通道(电梯井,楼梯井,管道井)容易成为火势迅速蔓延的重要途径。火灾烟气在高层建筑的竖向通道内运动主要驱动力有烟囱效应,湍流混合运动,热浮力,另外还容易受到外界风的影响。因此研究这几种驱动力作用下高层建筑火灾烟气的运动特性以及这几种作用力作用下房间内火源的燃烧,对于高层建筑火灾防治有着重要意义。 本文围绕烟囱效应,湍流混合作用,热浮力,外界风等作用力,采用实验研究与理论分析相结合的方式,利用大空间的1：3楼梯井实验台以及1：3火溢流实验台,开展了相应的研究。具体工作包括： 研究烟气前锋在顶部开放和顶部封闭的楼梯井内的上升时间,结合理论分析,得到烟气前锋上升无量纲时间与楼梯井无量纲高度的定量关系式,结果表明,开放楼梯井和封闭楼梯井内的烟气前锋上升时间分别与火源功率的三分之一次方成反比,与无量纲上升高度的1.227次方和2.135次方成正比,与烟气在竖井中的上升时间进行对比,发现烟气在楼梯井中上升比竖井中慢。开放楼梯井内的烟气温度在经历一段时间之后,会进入一个稳定的阶段,即楼梯井内的温度不随时间变化,分析稳定阶段楼梯井内温度的无量纲温升与无量纲高度的关系,发现无量纲温升随着无量纲高度的增加而指数衰减,衰减的系数近似与楼梯井内的烟气的质量流量成反比,并通过实验数据验证了这一点。分析楼梯井温度稳定分布情况下内外的压强差和楼梯井开口处空气和烟气的流速,得到了楼梯井内烟气流动的流动系数,流动系数的值表明,楼梯井的结构对楼梯井内烟气流动的阻力非常大。 研究了烟气在顶部封闭的竖向通道内湍流混合作用下的运动,前人研究封闭竖向通道内流体湍流混合运动时未考虑壁面传热,本文通过理论分析建立了考虑壁面传热的竖向通道内流体湍流混合运动方程。在1：3尺寸的楼梯井实验台中,开展了一系列火源产生的热浮力羽流在顶部封闭的楼梯井中湍流混合运动实验,并将实验数据与前人及本文推导的湍流混合运动方程的数值求解结果进行对比。对比结果表明,本文提出的湍流混合运动方程可以较好地模拟强热浮力羽流在顶部封闭的竖向楼梯井内的湍流混合运动,前人的模型计算的结果比实验值偏高。 研究了多个开口的楼梯井在火灾情况下中性面的位置,通过实验中测得的温度数据,风速数据以及拍摄的视频,判定了多开口楼梯井中性面的位置。结合楼梯井内的温度分布,利用流体静力学方程,伯努利方程和质量守恒方程,计算火灾情况下多个开口楼梯井的中性面位置,计算结果和实验得到的结果对比,发现两者符合得较好。结果表明在相同开口状况下,不同火源功率对楼梯井中性面位置的影响较小,火源功率较小时,楼梯井中性面高度会偏低。在三个开口的楼梯井中,楼梯井的中性面位置主要由楼梯井的开口状况决定。 利用1：3尺寸的火溢流实验台,研究了在着火房间热浮力作用下,着火房间外的溢流火焰形态,分析了溢流火焰在水平和竖直方向上的长度,建立了火焰尺寸与火源功率以及着火房间开口状况之间的耦合关系式,并分析了溢流火焰震动频率与房间开口状况之间的关系。研究了在外界风和着火房间热浮力共同作用下,着火房间内的通风状况,以及通风状态对着火房间内燃烧的影响。
[Abstract]:In recent years, more and more high-rise buildings have been built in China, and with the frequent fire accidents in high-rise buildings, a large number of casualties and property losses have been caused. Statistics show that more than 80% of the deaths in fires are caused by toxic fumes. It is difficult to evacuate people. Vertical passages (elevator shaft, stairwell, pipeline shaft) inside buildings are easy to become important ways of rapid fire spread. The main driving forces of fire smoke in vertical passages of high-rise buildings are chimney effect, turbulent mixing motion, thermal buoyancy, and also vulnerable to the influence of external wind. The motion characteristics of fire smoke in high-rise buildings under dynamic action and the combustion of fire sources in rooms under these forces are of great significance for fire prevention and control of high-rise buildings.
In this paper, the chimney effect, turbulent mixing, thermal buoyancy, external wind and other forces are studied by combining experimental research with theoretical analysis. The corresponding research is carried out by using the 1:3 stairwell test bench with large space and the 1:3 fire overflow test bench.
The rising time of flue gas front in open and closed stairwells was studied. Based on theoretical analysis, the quantitative relationship between the dimensionless rising time of flue gas front and the dimensionless height of stairwells was obtained. The results show that the rising time of flue gas front in open stairwells and closed stairwells is one third of the fire power, respectively. Comparing with the rising time of flue gas in the shaft, it is found that the rising speed of flue gas in the stairwell is slower than that in the shaft. The relationship between dimensionless temperature rise and dimensionless height is analyzed. It is found that the dimensionless temperature rise decreases exponentially with the increase of dimensionless height. The coefficient of attenuation is inversely proportional to the mass flow rate of flue gas in the stairwell. This is verified by experimental data. The flow coefficients of flue gas flow in stairwell are obtained by the pressure difference between inside and outside and the velocity of air and flue gas at the opening of stairwell. The values of flow coefficients show that the structure of stairwell has great resistance to flue gas flow in stairwell.
The turbulent mixing motion of flue gas in a vertical channel with closed top was studied. The turbulent mixing motion in a vertical channel was studied without considering wall heat transfer. The turbulent mixing motion equation in a vertical channel with wall heat transfer was established by theoretical analysis. A series of experiments of turbulent mixing motion of thermal buoyancy plume generated by fire source in a closed stairwell were carried out and the experimental data were compared with the numerical results of previous studies and the equations of turbulent mixing motion derived in this paper. The turbulent mixing motion of plume in a vertical stairwell closed at the top is higher than the experimental results.
The location of the neutral surface of a stairwell with multiple openings under fire is studied. The location of the neutral surface of the stairwell with multiple openings is determined by the temperature data, wind speed data and video. Combining with the temperature distribution in the stairwell, the hydrostatic equation, Bernoulli equation and mass conservation equation are used to calculate the fire. The results show that under the same opening condition, the influence of different fire power on the position of the neutral surface of the stairwell is small, and when the fire power is small, the height of the neutral surface of the stairwell will be lower. In the well, the location of the neutral surface of the stairwell is mainly determined by the opening state of the stairwell.
By using a 1:3 scale fire overflow test rig, the shape of the overflow flame outside the burning room under the action of thermal buoyancy of the burning room is studied, the length of the overflow flame in horizontal and vertical directions is analyzed, the coupling relationship between the flame size, the power of the fire source and the opening condition of the burning room is established, and the vibration of the overflow flame is analyzed. The relationship between frequency and room opening condition is studied. The ventilation condition in the fire room under the combined action of external wind and thermal buoyancy of the fire room and the influence of ventilation condition on the combustion in the fire room are studied.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU998.1;TU972.4
本文编号：2236311
[Abstract]:In recent years, more and more high-rise buildings have been built in China, and with the frequent fire accidents in high-rise buildings, a large number of casualties and property losses have been caused. Statistics show that more than 80% of the deaths in fires are caused by toxic fumes. It is difficult to evacuate people. Vertical passages (elevator shaft, stairwell, pipeline shaft) inside buildings are easy to become important ways of rapid fire spread. The main driving forces of fire smoke in vertical passages of high-rise buildings are chimney effect, turbulent mixing motion, thermal buoyancy, and also vulnerable to the influence of external wind. The motion characteristics of fire smoke in high-rise buildings under dynamic action and the combustion of fire sources in rooms under these forces are of great significance for fire prevention and control of high-rise buildings.
In this paper, the chimney effect, turbulent mixing, thermal buoyancy, external wind and other forces are studied by combining experimental research with theoretical analysis. The corresponding research is carried out by using the 1:3 stairwell test bench with large space and the 1:3 fire overflow test bench.
The rising time of flue gas front in open and closed stairwells was studied. Based on theoretical analysis, the quantitative relationship between the dimensionless rising time of flue gas front and the dimensionless height of stairwells was obtained. The results show that the rising time of flue gas front in open stairwells and closed stairwells is one third of the fire power, respectively. Comparing with the rising time of flue gas in the shaft, it is found that the rising speed of flue gas in the stairwell is slower than that in the shaft. The relationship between dimensionless temperature rise and dimensionless height is analyzed. It is found that the dimensionless temperature rise decreases exponentially with the increase of dimensionless height. The coefficient of attenuation is inversely proportional to the mass flow rate of flue gas in the stairwell. This is verified by experimental data. The flow coefficients of flue gas flow in stairwell are obtained by the pressure difference between inside and outside and the velocity of air and flue gas at the opening of stairwell. The values of flow coefficients show that the structure of stairwell has great resistance to flue gas flow in stairwell.
The turbulent mixing motion of flue gas in a vertical channel with closed top was studied. The turbulent mixing motion in a vertical channel was studied without considering wall heat transfer. The turbulent mixing motion equation in a vertical channel with wall heat transfer was established by theoretical analysis. A series of experiments of turbulent mixing motion of thermal buoyancy plume generated by fire source in a closed stairwell were carried out and the experimental data were compared with the numerical results of previous studies and the equations of turbulent mixing motion derived in this paper. The turbulent mixing motion of plume in a vertical stairwell closed at the top is higher than the experimental results.
The location of the neutral surface of a stairwell with multiple openings under fire is studied. The location of the neutral surface of the stairwell with multiple openings is determined by the temperature data, wind speed data and video. Combining with the temperature distribution in the stairwell, the hydrostatic equation, Bernoulli equation and mass conservation equation are used to calculate the fire. The results show that under the same opening condition, the influence of different fire power on the position of the neutral surface of the stairwell is small, and when the fire power is small, the height of the neutral surface of the stairwell will be lower. In the well, the location of the neutral surface of the stairwell is mainly determined by the opening state of the stairwell.
By using a 1:3 scale fire overflow test rig, the shape of the overflow flame outside the burning room under the action of thermal buoyancy of the burning room is studied, the length of the overflow flame in horizontal and vertical directions is analyzed, the coupling relationship between the flame size, the power of the fire source and the opening condition of the burning room is established, and the vibration of the overflow flame is analyzed. The relationship between frequency and room opening condition is studied. The ventilation condition in the fire room under the combined action of external wind and thermal buoyancy of the fire room and the influence of ventilation condition on the combustion in the fire room are studied.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU998.1;TU972.4
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