地铁列车对区间隧道火灾逆流烟气输运特性影响的研究

发布时间：2018-08-09 20:27

【摘要】：鉴于地铁隧道发生火灾时后果的严重性,研究地铁隧道火灾的特征与规律,对于保障乘客的生命财产安全,维护地铁的日常安全运营,减小由火灾造成的各项损失具有重要的意义。本文以揭示不同长度的地铁列车对区间隧道火灾逆流热烟气输运特性的影响机制为研究目标,采用数值模拟、小尺寸实验和理论分析相结合的研究方法,从以下几个方面进行了研究工作:一、使用火灾数值模拟软件FDS搭建了全尺寸的地铁区间隧道计算模型,通过在区间隧道内紧邻火源上游设置不同长度的地铁列车,研究了在不同纵向通风速率条件下火源上游隧道顶棚下逆流热烟气的温度纵向分布规律。研究结果表明,当火灾热烟气的逆流长度超过地铁列车的长度时,逆流热烟气的温度分布曲线在列车长度处出现一个明显的拐点,导致温度的变化趋势发生改变。将逆流热烟气的温度进行无量纲化处理以后发现:当地铁列车长度相同时,逆流热烟气温度衰减系数会随着纵向通风速率的增大而增大,且在地铁列车堵塞区域内的温度衰减系数要比上游非堵塞区域内的大;而当纵向通风速率相同时,两个区域内逆流热烟气的温度衰减系数没有明显变化,说明此时不同长度的地铁列车对逆流热烟气温度衰减系数的影响不明显。二、利用小尺寸隧道模型实验台研究了不同长度的地铁列车对区间隧道火灾热烟气逆流长度的影响。通过将地铁列车模型放置在区间隧道模型中模拟了地铁列车发生火灾无法继续行驶停靠在区间隧道的情景,研究了区间隧道内停靠有不同长度的地铁列车时,火灾烟气逆流长度随火源燃烧功率和纵向通风速率的变化规律。实验结果显示,逆流热烟气会出现超越地铁列车继续向上游蔓延和无法超越地铁列车这两种现象。将热烟气的逆流长度进行无量纲化处理发现:无量纲烟气逆流长度l*在地铁列车堵塞区域和上游未堵塞区域内随无量纲火源--风速组合量ln(Q*1/3/V*)的增长率不相同。理论分析可知,地铁列车的存在,导致列车堵塞区域内的纵向风速要比上游未堵塞空间内的大,造成列车堵塞区域内的纵向通风阻力比较大,抑制了火灾热烟气的逆流蔓延。根据上游逆流热烟气的温度衰减规律,采用基于温度衰减的虚拟火源法,建立了不同长度地铁列车影响下的区间隧道火灾烟气逆流长度预测模型。三、利用火灾数值模拟软件FDS搭建了全尺寸的地铁区间隧道,研究了不同长度的地铁列车对区间隧道火灾临界纵向通风速率的影响。地铁列车的存在改变了区间隧道内纵向通风流场的结构特征,对隧道火灾的临界纵向通风速率产生了影响。研究结果表明:无量纲的临界纵向通风速率主要受到障碍物堵塞率因子(1-φ)和无量纲火源功率Q*1/3的影响。通过对比有无地铁列车时的隧道纵向通风流场图可知,地铁列车的存在导致地铁堵塞区域内的纵向通风速率变大,从而使得地铁列车存在时临界纵向通风速率减小;而地铁列车障碍物长度比较长,速率增大的纵向通风在到达火源上部空间抑制烟气逆流之前已经达到相对稳定状态,导致当地铁列车长度超过20 m时,临界纵向通风速率几乎不会随着列车长度的增大而发生明显变化。在数据分析的基础上,提出了地铁区间隧道中含有不同长度的地铁列车时火灾临界纵向通风速率的预测模型。
[Abstract]:In view of the seriousness of the consequences of a subway tunnel fire, the study of the characteristics and laws of the subway tunnel fire is of great significance for ensuring the safety of the life and property of the passengers, maintaining the daily safe operation of the subway and reducing all the losses caused by the fire. The influence mechanism of the gas transport characteristics is the research goal, and the research method combining the numerical simulation, the small size experiment and the theoretical analysis is carried out from the following aspects. First, the full size subway interval tunnel calculation model is built by using the fire numerical simulation software FDS, which is close to the upstream of the fire source in the interval tunnel. The longitudinal distribution of the temperature distribution of the hot flue gas under the roof of the upper tunnel under the different longitudinal ventilation rate is studied under different longitudinal ventilation rates. The results show that the temperature distribution curve of the countercurrent heat smoke appears at the length of the train when the counter current length of the fire hot smoke exceeds the length of the subway train. It is found that the temperature attenuation coefficient of the counter current hot gas will increase with the increase of the longitudinal ventilation rate, and the temperature attenuation coefficient in the blockage area of the subway train is more than that in the upstream. When the longitudinal ventilation rate is the same, the temperature attenuation coefficient of the hot flue gas in the two regions does not change obviously when the longitudinal ventilation rate is the same. It shows that the influence of the subway trains with different lengths on the temperature attenuation coefficient of the countercurrent hot flue gas is not obvious. Two, the subway train with different lengths is studied by the small size tunnel model test bench. In the interval tunnel model, the subway train model is placed in the interval tunnel model to simulate the situation that the subway train can not continue to stop in the interval tunnel. The fire smoke countercurrent length with the fire source power is studied when the subway trains with different lengths in the interval tunnel are stopped. The experimental results show that there are two phenomena that the counter current hot flue gas will surpass the subway train to continue to spread to the upper reaches and cannot exceed the subway train. The non dimensionless treatment of the counter current length of the hot flue gas is found that the non dimensional backflow length l* is in the block area of the subway train and the unblocked area in the upper reaches. The growth rate of the wind velocity combination ln (Q*1/3/V*) in the domain is different with the non dimensional fire source. The theoretical analysis shows that the existence of the subway train causes the longitudinal wind speed in the area of the train jam to be larger than the unblocked space in the upstream. The longitudinal ventilation resistance in the area of the train blockage is larger, which inhibits the backflow spread of the fire hot smoke. The temperature attenuation law of upstream countercurrent hot flue gas, using the virtual fire source method based on the temperature attenuation, established the prediction model of the interval tunnel fire smoke counterflow length under the influence of the subway trains with different lengths. Three, the full size subway tunnel is built by the fire numerical simulation software FDS, and the different length of the subway train pair area is studied. The influence of the critical longitudinal ventilation rate on the tunnel fire. The existence of the subway train changed the structural characteristics of the longitudinal ventilation flow in the tunnel, and influenced the critical longitudinal ventilation rate of the tunnel fire. The results show that the dimensionless critical longitudinal ventilation rate is mainly affected by the obstacle blocking rate factor (1-) and the dimensionless fire. The influence of source power Q*1/3. By comparing the longitudinal ventilation flow field of a tunnel with or without subway trains, the existence of the subway train leads to a larger longitudinal ventilation rate in the subway blockage area, thus reducing the critical longitudinal ventilation rate in the existence of the subway train, while the length of the subway train obstacles is longer and the rate increases in the longitudinal passage. The wind has reached a relatively stable state before reaching the upper fire source and restraining the backflow of the flue gas. When the subway train length exceeds 20 m, the critical longitudinal ventilation rate will hardly change obviously with the increase of the length of the train. On the basis of data analysis, the subway trains with different lengths in the subway tunnel are proposed. Prediction model of critical longitudinal ventilation rate for vehicle-time fire.
【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】：2017
【分类号】：U458;U231.96

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