【作者】 张军；

【导师】 汪箭； 冯卫；

【作者基本信息】 中国科学技术大学 ， 能源与环保（专业学位）， 2020， 博士

【摘要】 近年来,我国在经济高速发展的支撑下,特大型城市规模日趋扩大,高层建筑越来越多,建筑结构越来越复杂。虽然高层建筑占地面积小、土地利用率高,但是建筑内的火灾隐患多、危害性大,一旦起火,火灾的快速扑救和人员的安全疏散也是一个巨大的挑战。高层建筑内有很多竖向通道,火灾发生后容易成为热烟气的主要蔓延通道,造成火灾危害区域扩大。在以往的研究中,由于实验条件所限,研究者多采用比例模型实验来探究发生火灾时高层建筑楼梯井内的烟气流动与温度分布规律,缺乏与全尺寸楼梯井实验的对比。比例模型的实验结果具有一定的参考意义,但是仍具有一定局限性。因此本文采用理论分析、全尺寸实验和数值模拟相结合的方法,来探究开口形式、火源位置、火源功率等不同因素对楼梯井内烟气流动和正压送风方式的影响,主要包括以下三个方面的内容:一、通过全尺寸实验和数值模拟相结合研究了不同开口形式(高度和开闭状态)下楼梯井烟气流动特性和参数分布,研究所得结论如下,随着开口位置的升高,开口位置上下层烟气温度差和开口楼层处楼梯井内竖向速度分量的绝对值在不断降低,而楼梯井内中性面高度则是先增大后减小的。受热烟气影响的区域和CO浓度的最大值则是随着开口位置的升高在逐渐的增大。顶部和底部开口的开闭情况会对前室火行为和楼梯井内的温度分布产生影响。当顶部开口关闭时,楼梯井内温度曲线的衰减系数较大,约为顶部开口工况的两倍,当底层开口开启时,楼梯井内的温度曲线的衰减系数则会减小。二、采用数值模拟的方法研究了不同火源位置(横向和竖向)下楼梯井烟气的流动特性和参数分布,研究所得结论如下,同一楼层火源位于门口处时,前室顶棚处温度要比火源位于靠墙处时低。楼梯井内温度从大到小排列分别是楼梯门口,前室门口,前室中心,正对楼梯门口,正对前室门口。不同火源横向位置下楼梯井内的压力分布的趋势都是相同的。火源位置离楼梯门口越远,中性面的高度越低。前室顶棚温度分布和顶棚内最高温度的位置会随着火源高度的改变而发生变化。相同火源高度,楼层开口全部打开时,前室顶棚温度分布比1、21层及着火楼层打开时更为均匀,并且温度更低。开口楼层全部打开时,楼梯井内最高温度随着火源位置的升高逐渐增加,而衰减系数却是呈先增大后减小的趋势,此时压力分布基本不受火源位置影响。而1、21层及着火楼层打开时,楼梯井内最高温度和最大压力都是随着火源位置的升高不断降低,温度衰减系数也是呈递减趋势。通过引入火源高度因子,提出了不同开口方式下最高温度与火源高度因子的关系式。三、针对发生火灾时楼梯井单独加压送风的情况,采用数值模拟的方法研究不同影响因素对正压送风系统有效性的影响。研究所得结论如下:加压送风量对正压送风系统阻挡烟气侵入能力的影响较大,送风量越大,阻挡烟气流入楼梯井的能力越强。通过对楼梯井温度和压力分布进行分析,可以将送风量分为三个区段:未克服热压区,基本克服热压区和完全克服热压区。楼梯井内各送风口的气流质量流量随着加压送风量的增加基本呈线性增长,并且送风口的高度越低,其增长速率越高。开口位置的不同也会对正压送风系统的送风效果产生影响。随着开口高度的增加,楼梯井内的温度是先升高后降低的,烟气所能达到的最高位置也是先升高后降低的。开口楼层的升高会增加正压系统在着火楼层处产生的正压值,从而提高正压系统抵御烟气入侵的能力。楼层开口打开时会使该区域内送风口的质量流量显著增大,而底部着火楼层区域送风口的质量流量则会随着开口高度的升高而减小。火源位置对正压送风系统的送风效果影响较小。在正压送风的风量较小的情况下,不同火源位置下正压送风系统所产生的正压均不能抵挡烟囱效应所产生的热压。着火楼层的存在将压力曲线分成了两个部分:着火楼层下部区域和着火楼层上部区域。着火楼层下部区域内,压力随着火源位置的升高在逐渐增大,而上部区域则是与之相反,随着火源位置的升高在逐渐降低。更多还原

【Abstract】 In recent years,with the rapid development of economy,the large-scale cities in China have been expanding in size.There are more and more high-rise buildings and the high-rise buildings have more and more complex structures.Although high-rise buildings have the advantages of saving urban land and enriching space,they also have problems such as high fire hazard and it has difficulty in fighting and evacuation.There are many vertical passages in the high-rise buildings.After the fire broke out,it would become the main propagation channel of hot smoke,which caused the fire hazard area to expand,resulting in suffocation and casualties of people away from the fire floor.In the previous research,due to the limitations of experimental conditions,researchers used the experimental method of proportional model to explore the flow characteristic and temperature distribution of smoke in the stairwell in the event of fire,and the reaserch is lack of comparison with the full-scale stairwell experiment.The experimental results of the proportional model had certain reference significance,but still had limitations.Therefore,this thesis combined theoretical analysis,full-scale experiment and numerical simulation to explore the effects of different forms such as opening form,heat release rate and positon of fire on smoke flow and positive pressure ventilation system in the stairwell.The thesis is mamly composed of three parts.First,through the combination of full-scale experiment and numerical simulation,the flow characteristics and parameter distribution of smoke under different opening forms(height and open and closed state)were studied.The conclusions obtained from the study are as follows.As the height of the opening position increases,the temperature difference of smoke which is located in upper and lower floors of the opening position and the absolute value of the vertical velocity in the stairwell at the open floor are continuously decreasing,while the height of the neutral plane in the stairwell first increases and then decreases.The maximum area affected by the smoke and the concentration of CO is gradually increasing as the position of the opening increases.The opening and closing of the top and bottom openings affects fire behavior in the atria and the temperature distribution within the stairwell.When the top opening is closed,the attenuation coefficient of the temperature in the stairwell is twice larger than the top opening condition.When the bottom opening is opened,the attenuation coefficient of the temperature in the stairwell reduces.Secondly,the numerical simulation method was used to study the flow characteristics and parameter distribution of smoke in the stairwell under different fire posiiton(horizontal and vertical).The conclusions of the study are as follows.When the fire source is at the door,the temperature at the ceiling of the atria is lower than that when the fire source is at the wall.The temperature in the stairwell is arranged from the large to the small is the position at stairwell door,the positon at atria door,the positon in the center of atria,the positon by the side of wall which facing stairwell door and the positon by the side of wall which facing atria door.The trend of pressure distribution in the stairwell under different horizontal positions of fire sources is the same.The farther the fire source is away from the doorway,the lower the height of the neutral surface is.The temperature distribution under the ceiling of the atria and the position of the highest temperature will change as the height of fire source changes.The same fire source height,when the floor doors are all open,the temperature distribution of the atria is more uniform than the conditon when the door of 1th and 21th fire floors are open,and the temperature is lower.When the floor door is fully opened,the maximum temperature in the stairwell increases gradually with the increase of the fire source position,while the attenuation coefficient increases first and then decreases.At this time,the pressure distribution is basically not affected by the fire source position.When the door of 1th,21th and fire floors are open,the maximum temperature and maximum pressure in the stairwell are decreasing with the increase of the fire source position,and the temperature attenuation coefficient is also decreasing.By introducing the fire source height factor,the relationship between the maximum temperature and the fire source height factor under different opening states is proposed.Third,the numerical simulation method is used to study the effects of different influencing factors on the ventilation effect of the stairwell when the fire occurs.The conclusions obtained from the study are as follows.The volume of pressurized air supply has a great influence on the ability of the positive pressure ventilation system to block the intrusion of smoke.The larger the air supply volume,the stronger the ability to block the flow of smoke into the stairwell.By analyzing the temperature and pressure distribution of the stairwell,the air supply volume can be divided into three sections:the zone which hot pressure is not overcome,the zone which hot pressure is basically overcome,and the zone hot pressure is completely overcome.The mass flow rate of each air supply outlet in the stairwell increases linearly with the increase of the pressurized air supply volume,and the lower the height of the air supply outlet,the higher the growth rate.The position of open doors also affects the ventilation effect of the positive pressure ventilation system.As the height of the opening door increases,the temperature and the highest position that the smoke can reach in the stairwell both rises first and then decreases.The increase of the opening height will make increase the positive pressure at the fire floor increase,thereby improving the ability of the PPV system to resist the intrusion of smoke.When the upper floor is open,the mass flow rate of the air outlet in this area will be significantly increased,while the mass flow rate in the fire floor area will decrease as the opening height increases.The location of the fire source has little effect on the ventilation effect of the PPV system.In the case of a small volume of positive air supply,the positive pressure generated by the PPV system under different ignition sources cannot withstand the hot pressure generated by the stact effect.The fire floor divides the pressure curve into two parts:the lower part and the upper part.In the lower part,the pressure gradually increases as the height of the fire source increases,while the upper area decreases as the height of the fire source increases.更多还原