隧道火灾发展特性及竖井自然排烟方法研究
发布时间：2019-05-17 00:01
【摘要】：为了应对经济建设快速发展和城市现代化进程,各种隧道不断涌现出来。通常情况下,在这类狭长空间中,一旦发生火灾,扑救将十分困难,很容易造成大量的人员伤亡和财产损失。近年来国内外发生了多起重特大隧道火灾,引起了极为广泛的社会关注。目前,在隧道火灾研究领域,已有不少国内外学者开展了相关研究。基于隧道火灾研究现状中存在的问题和不足,本文在以下几个方面开展了研究： 开展小尺寸实验研究了火焰没有撞击到隧道顶棚的较小火灾中,横向火源位置对顶棚下方烟气最高温度和温度分布的影响。结果表明隧道侧壁的限制作用会使顶棚下方最高温升相比火源在非受限空间和隧道纵向中心线时的有所增加。随着火源到侧壁的距离减小,最高温升开始几乎不变,在其距离减小到某一值时大幅度增加。建立了顶棚下方烟气最高温升与火源到隧道侧壁距离关系的预测公式。发现对于各种火源尺寸和横向位置的工况,顶棚下方烟气温升随着到火源纵向距离的增大而呈指数减小,并建立了预测模型。建立了考虑横向火源位置的预测顶棚下方烟气温升横向分布的模型。 开展小尺寸实验研究了火焰撞击到隧道顶棚的较大火灾中,隧道侧壁对火焰形态、燃烧速率和顶棚火焰长度的影响。结果表明当火源距离侧壁较近时,由于侧壁对火焰卷吸空气的限制,火焰会向侧壁倾斜,同时竖向火焰体积减小,顶棚火焰长度增加。随着火源到侧壁距离的减小,由于被火焰加热的侧壁和顶棚火焰对燃料的辐射热反馈增加,相对于火源在隧道中心的工况,燃烧速率会增加。然而,对于各种形状(长宽比)的火源,最大燃烧速率并没有出现在火源紧贴壁面时,而是火源到侧壁有一定距离时。这是因为在火源贴壁的工况中,由于火焰形状改变(因侧壁对其卷吸空气的限制),竖向火焰部分对燃料的辐射反馈减小。顶棚下方横向火焰长度和纵向火焰长度的比值随着火源到侧壁的距离减小而减小,在火源贴壁和最大火焰长度的工况,此比值下降到0.5,恰好符合镜像原理。由于侧壁的影响并非是单调的,所以在较高燃烧速率的工况下顶棚火焰长度未必较大。建立了顶棚火焰长度与火源功率、火源尺寸的关系式。 开展小尺寸实验研究了隧道横截面尺寸(隧道宽度和高度)对火灾特性的影响。发现对于火焰撞击到隧道顶棚的正庚烷池火,隧道宽度对处于燃料控制(通风良好)的火灾的火源功率几乎没有影响,而较低的隧道高度会导致较大的火源功率。各尺寸隧道中正庚烷池火的火源功率达到开放空间的3倍左右。对于燃料控制的木垛(木垛／塑料)火灾,隧道中的火源功率可达开放空间的1.25倍,而且不受隧道宽度和高度及纵向风速的影响。而在通风控制(通风不良)的条件下,隧道中的火源功率会小于开放空间的。对于小尺寸实验中较大的隧道火灾,顶棚下方最高温度是火源功率和纵向风速的弱函数,受隧道宽度的影响也比较小,而随着隧道高度的减小而明显增大。这是由于在较低隧道中,顶棚更加靠近持续火焰区的基部,导致顶棚下方温度更大。对于正庚烷和木垛火灾,总体来说,火源下游顶棚下方的烟气温度随着隧道横截面面积的增大而减小。对于顶棚下方温升衰减率,火源功率也是一个影响其变化的重要参数,因而引入一个无量纲火源功率,建立了考虑隧道横截面尺寸和火源功率的温升衰减公式。火源下游地面处的热流与顶棚下方的烟气温度有着密切的关系,较大的隧道横截面面积会导致地面处较小的热流。 开展小尺寸实验研究了竖井自然排烟作用下的空气卷吸模式。发现竖井排烟会对烟气层和空气层分界面处造成剧烈扰动,使得烟气层下方的部分空气被直接吸入竖井,即发生吸穿现象。通过数值模拟方法发现纵向风会对隧道内的烟气分层稳定性产生明显的影响,进而影响竖井中的排烟过程。当纵向风速较小时,竖井中会形成较强的烟囱效应,导致吸穿现象的发生。当纵向风速较大时,在竖井与隧道顶棚的连接位置会发生烟气的边界层分离现象,使得竖井中产生大量的漩涡。存在一个纵向风速的临界值,可以避免吸穿现象的发生,同时边界层分离现象也不明显,可以得到较好的排烟效果。对于多竖井的设置问题,在竖井总横截面面积不变的情况下,各竖井的总排烟量随着竖井数量的增多而增大。而对于竖井数量相同的工况,纵向风速最大时的各竖井的总排烟量最小,这是由于大部分竖井中发生了明显的边界层分离现象。在隧道顶部均匀设置多个横截面较小的竖井能够分散和减弱吸穿和边界层分离现象对排烟的不利影响。通过小尺寸实验发现竖井高度较低时,边界层分离现象会在竖井内左侧(上游)区域引起大尺度漩涡。由于竖井越高,产生的烟囱效应越大,所以漩涡的尺寸随着竖井高度的增加而减小。把竖井侧壁与隧道顶棚的直接连接改为斜角连接,可以抑制边界层分离现象的发生。通过数值模拟方法发现在不同角度的斜角竖井中,都没有漩涡的存在。在竖井高度较低时,斜角竖井的排烟优势更加明显,三种斜角竖井的排烟量相近。
[Abstract]:In ord to cope with that rapid development of economic construction and the process of urban modernization, various tunnel have been emerging. In general, in such an elongated space, it is very difficult to put out a fire once a fire has occurred, and it is easy to cause a large number of casualties and property damage. In recent years, a large number of heavy tunnel fires have taken place at home and abroad, which has caused great social concern. At present, many domestic and foreign scholars have carried out relevant research in the field of tunnel fire research. Based on the existing problems and shortcomings in the present situation of tunnel fire research, this paper studies the following aspects: The small-size experiment is carried out to study the effect of the position of the transverse fire source on the highest temperature and temperature distribution of the flue gas under the ceiling in the small fire without the tunnel ceiling. The results show that the limiting effect of the side wall of the tunnel can increase the maximum temperature rise below the ceiling compared with the fire source in the non-confined space and the longitudinal center line of the tunnel. plus. As the distance between the fire source and the side wall is reduced, the maximum temperature rise starts to be almost constant, and is greatly increased when the distance is reduced to a certain value The prediction of the relationship between the maximum temperature rise of the flue gas under the ceiling and the distance between the fire source and the side wall of the tunnel is established. It is found that the temperature rise of the smoke under the ceiling decreases exponentially with the increase of the longitudinal distance of the fire source and the prediction mode is established for the working conditions of the size and the lateral position of the fire source. The model of the horizontal distribution of the temperature rise of the smoke under the ceiling with the position of the transverse fire source is established. The flame shape, the burning rate and the flame length of the ceiling were studied by small-size experiments in a large fire that hit the ceiling of the tunnel. The results show that when the fire source is close to the side wall, the flame will be inclined to the side wall due to the restriction of the side wall on the air to the flame, while the vertical flame volume is reduced and the ceiling flame is long As the distance between the fire source and the side wall decreases, the heat feedback of the fuel by the side wall and the ceiling flame heated by the flame is increased, and the combustion rate is increased with respect to the working condition of the fire source in the tunnel center it will increase. However, for fire sources of various shapes (aspect ratio), the maximum combustion rate does not occur when the fire source is in close contact with the wall surface, but rather the fire source to the side wall In case of a distance, this is because the vertical flame part is opposite to the radiation of the fuel due to the change in the shape of the flame due to the change in the shape of the flame (due to the restriction of the side wall to its roll-up air) during the condition of the source of the fire. Feed reduction. The ratio of the lateral flame length and the longitudinal flame length under the ceiling decreases as the distance between the fire source and the side wall decreases, and the ratio decreases to 0.5 at the conditions of fire source attachment and maximum flame length, just in accordance with the mirror if the effect of the side wall is not monotonic, the ceiling flame length is not The length of the flame of the ceiling and the power of the fire source and the size of the fire source are established. The relationship of the cross-sectional dimensions of the tunnel (tunnel width and height) to the fire is studied in a small-size experiment. the effect of the characteristics. It is found that the tunnel width has little effect on the source power of the fire that is in the fuel control (well-ventilated) fire for the n-heptane pool fire impinging on the tunnel ceiling, while the lower tunnel height can result in greater Fire source power. Fire source power of n-heptane pool fire in each size tunnel reaches the open space The fire in the tunnel can reach 1.25 times of the open space and is not affected by the width and height of the tunnel and the longitudinal direction. The effect of wind speed. In the case of ventilation control (poor ventilation), the fire source power in the tunnel will be less than Open space. For a large tunnel fire in small-size experiments, the highest temperature under the ceiling is a weak function of the power of the fire source and the longitudinal wind speed, and the influence of the width of the tunnel is also small, and as the height of the tunnel decreases this is due to the fact that in the lower tunnel the ceiling is closer to the base of the continuous flame zone, resulting in the ceiling in general, that temperature of the flue gas below the ceiling of the fire source follow the cross-sectional area of the tunnel As for the temperature rise decay rate under the ceiling, the power of the fire source is an important parameter which influences the change of the fire source, so a non-dimensional fire source power is introduced, and the temperature of the tunnel cross-sectional dimension and the power of the fire source is established. The heat flow at the ground at the downstream of the fire source is closely related to the temperature of the flue gas below the ceiling, and the larger cross-sectional area of the tunnel will result in the ground The small-size experiment is carried out to study the effect of the natural smoke exhaust of the shaft the air-rolling mode of the air is detected, and the smoke exhaust of the shaft can cause severe disturbance at the interface of the smoke layer and the air layer, so that part of the air below the smoke layer is directly sucked into the shaft, The method of numerical simulation shows that the longitudinal wind will have a significant effect on the stratified stability of the flue gas in the tunnel, and then the vertical wind will influence the vertical wind. The smoke exhaust process in the well. When the longitudinal wind speed is small, a strong chimney effect will be formed in the shaft, resulting in when the longitudinal wind speed is large, the boundary layer separation phenomenon of the smoke is generated in the connecting position between the shaft and the tunnel ceiling, so that the shaft A large number of vortices are generated. There is a critical value of a longitudinal wind speed, which can avoid the occurrence of the phenomenon of suction and wear, and the phenomenon of boundary layer separation is not obvious and can be obtained. Good smoke exhaust effect. For multi-shaft setting problem, the total smoke exhaust of each shaft will increase with the shaft number if the total cross-sectional area of the shaft is not changed. The increase in the amount of shaft increases. For the same condition as the number of shafts, the total smoke exhaust of the shaft at the maximum longitudinal wind speed is the smallest, which is due to the obvious occurrence of most of the shaft the boundary layer separation phenomenon is characterized in that a plurality of vertical shafts with small cross sections are uniformly arranged at the top of the tunnel to be capable of dispersing and reducing the absorption and the boundary layer separation phenomena, The adverse effect of smoke exhaust. The boundary layer separation phenomenon will be in the left (upstream) area of the shaft when the height of the shaft is low by the small-size experiment. The higher the shaft, the larger the chimney effect, the size of the vortex is as high as the shaft By changing the direct connection between the side wall of the shaft and the ceiling of the tunnel to an oblique angle, the boundary layer can be suppressed. the occurrence of the separation phenomenon is found in the oblique shaft at different angles by means of a numerical simulation method, There is no vortex. In the case of low shaft height, the smoke exhaust advantage of the bevel shaft is more obvious, and the three oblique angles are vertical.
【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】：2015
【分类号】：U458;U453.5
本文编号：2478654
[Abstract]:In ord to cope with that rapid development of economic construction and the process of urban modernization, various tunnel have been emerging. In general, in such an elongated space, it is very difficult to put out a fire once a fire has occurred, and it is easy to cause a large number of casualties and property damage. In recent years, a large number of heavy tunnel fires have taken place at home and abroad, which has caused great social concern. At present, many domestic and foreign scholars have carried out relevant research in the field of tunnel fire research. Based on the existing problems and shortcomings in the present situation of tunnel fire research, this paper studies the following aspects: The small-size experiment is carried out to study the effect of the position of the transverse fire source on the highest temperature and temperature distribution of the flue gas under the ceiling in the small fire without the tunnel ceiling. The results show that the limiting effect of the side wall of the tunnel can increase the maximum temperature rise below the ceiling compared with the fire source in the non-confined space and the longitudinal center line of the tunnel. plus. As the distance between the fire source and the side wall is reduced, the maximum temperature rise starts to be almost constant, and is greatly increased when the distance is reduced to a certain value The prediction of the relationship between the maximum temperature rise of the flue gas under the ceiling and the distance between the fire source and the side wall of the tunnel is established. It is found that the temperature rise of the smoke under the ceiling decreases exponentially with the increase of the longitudinal distance of the fire source and the prediction mode is established for the working conditions of the size and the lateral position of the fire source. The model of the horizontal distribution of the temperature rise of the smoke under the ceiling with the position of the transverse fire source is established. The flame shape, the burning rate and the flame length of the ceiling were studied by small-size experiments in a large fire that hit the ceiling of the tunnel. The results show that when the fire source is close to the side wall, the flame will be inclined to the side wall due to the restriction of the side wall on the air to the flame, while the vertical flame volume is reduced and the ceiling flame is long As the distance between the fire source and the side wall decreases, the heat feedback of the fuel by the side wall and the ceiling flame heated by the flame is increased, and the combustion rate is increased with respect to the working condition of the fire source in the tunnel center it will increase. However, for fire sources of various shapes (aspect ratio), the maximum combustion rate does not occur when the fire source is in close contact with the wall surface, but rather the fire source to the side wall In case of a distance, this is because the vertical flame part is opposite to the radiation of the fuel due to the change in the shape of the flame due to the change in the shape of the flame (due to the restriction of the side wall to its roll-up air) during the condition of the source of the fire. Feed reduction. The ratio of the lateral flame length and the longitudinal flame length under the ceiling decreases as the distance between the fire source and the side wall decreases, and the ratio decreases to 0.5 at the conditions of fire source attachment and maximum flame length, just in accordance with the mirror if the effect of the side wall is not monotonic, the ceiling flame length is not The length of the flame of the ceiling and the power of the fire source and the size of the fire source are established. The relationship of the cross-sectional dimensions of the tunnel (tunnel width and height) to the fire is studied in a small-size experiment. the effect of the characteristics. It is found that the tunnel width has little effect on the source power of the fire that is in the fuel control (well-ventilated) fire for the n-heptane pool fire impinging on the tunnel ceiling, while the lower tunnel height can result in greater Fire source power. Fire source power of n-heptane pool fire in each size tunnel reaches the open space The fire in the tunnel can reach 1.25 times of the open space and is not affected by the width and height of the tunnel and the longitudinal direction. The effect of wind speed. In the case of ventilation control (poor ventilation), the fire source power in the tunnel will be less than Open space. For a large tunnel fire in small-size experiments, the highest temperature under the ceiling is a weak function of the power of the fire source and the longitudinal wind speed, and the influence of the width of the tunnel is also small, and as the height of the tunnel decreases this is due to the fact that in the lower tunnel the ceiling is closer to the base of the continuous flame zone, resulting in the ceiling in general, that temperature of the flue gas below the ceiling of the fire source follow the cross-sectional area of the tunnel As for the temperature rise decay rate under the ceiling, the power of the fire source is an important parameter which influences the change of the fire source, so a non-dimensional fire source power is introduced, and the temperature of the tunnel cross-sectional dimension and the power of the fire source is established. The heat flow at the ground at the downstream of the fire source is closely related to the temperature of the flue gas below the ceiling, and the larger cross-sectional area of the tunnel will result in the ground The small-size experiment is carried out to study the effect of the natural smoke exhaust of the shaft the air-rolling mode of the air is detected, and the smoke exhaust of the shaft can cause severe disturbance at the interface of the smoke layer and the air layer, so that part of the air below the smoke layer is directly sucked into the shaft, The method of numerical simulation shows that the longitudinal wind will have a significant effect on the stratified stability of the flue gas in the tunnel, and then the vertical wind will influence the vertical wind. The smoke exhaust process in the well. When the longitudinal wind speed is small, a strong chimney effect will be formed in the shaft, resulting in when the longitudinal wind speed is large, the boundary layer separation phenomenon of the smoke is generated in the connecting position between the shaft and the tunnel ceiling, so that the shaft A large number of vortices are generated. There is a critical value of a longitudinal wind speed, which can avoid the occurrence of the phenomenon of suction and wear, and the phenomenon of boundary layer separation is not obvious and can be obtained. Good smoke exhaust effect. For multi-shaft setting problem, the total smoke exhaust of each shaft will increase with the shaft number if the total cross-sectional area of the shaft is not changed. The increase in the amount of shaft increases. For the same condition as the number of shafts, the total smoke exhaust of the shaft at the maximum longitudinal wind speed is the smallest, which is due to the obvious occurrence of most of the shaft the boundary layer separation phenomenon is characterized in that a plurality of vertical shafts with small cross sections are uniformly arranged at the top of the tunnel to be capable of dispersing and reducing the absorption and the boundary layer separation phenomena, The adverse effect of smoke exhaust. The boundary layer separation phenomenon will be in the left (upstream) area of the shaft when the height of the shaft is low by the small-size experiment. The higher the shaft, the larger the chimney effect, the size of the vortex is as high as the shaft By changing the direct connection between the side wall of the shaft and the ceiling of the tunnel to an oblique angle, the boundary layer can be suppressed. the occurrence of the separation phenomenon is found in the oblique shaft at different angles by means of a numerical simulation method, There is no vortex. In the case of low shaft height, the smoke exhaust advantage of the bevel shaft is more obvious, and the three oblique angles are vertical.
【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】：2015
【分类号】：U458;U453.5
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