公路隧道火灾模拟试验弗劳德准则试用范围

发布时间：2018-06-12 00:16

本文选题：隧道火灾 + 弗劳德准则　；参考：《兰州交通大学》2017年硕士论文

【摘要】：随着社会经济和道路交通的发展,公路隧道数量和公里数不断增加,车流密度加大,行车速度加快,各类隧道事故发生的数量和频率也相应增加。其中,隧道火灾由于其环境的封闭性和逃生救援的困难性,往往造成严重的人员伤亡和财产损失。尤其长大隧道和交通量大的隧道,火灾发生的概率也会相对较大。目前,公路隧道火灾模型试验设计中通常采用弗劳德准则,但理论分析结果表明,火源远区烟气流动过程中浮力作用减小,弗劳德准则不适用。为确定弗劳德准则的适用范围,有必要结合模型试验结果,采用数值模拟方法进行分析研究。本文采用数值模拟和模型试验结合的方法,以单向交通公路隧道为例,分别针对无风和2m/s自然风条件下燃烧热释放速率为5MW和10 MW规模火灾的烟气速度(场)和温度(场)进行对比分析。预备试验中,用毕托管测量同一断面上36个点的速度值,以求出该断面平均风速,共测量5个断面,用以求得隧道模型的阻力系数。模型试验时,使用PT100温度传感器和JY-GD2型风速传感器,分别对5MW和10MW火灾规模下燃烧60s及120s时,无风条件的温度分布和2m/s风速条件的断面速度分布进行了测量。数值模拟使用Gambit软件对隧道原始尺寸建立几何模型和划分网格,并通过FLUENT软件采用标准k-ε模型和PDF模型对无风和2m/s风速条件下燃烧热释放速率5MW和10 MW规模的火灾进行模拟,得到了与60s和120s相对应的285.7s和571.4s时各工况下不同断面的温度云图和速度云图,以及与模型试验各测点相对应点处的温度值与速度值。首先通过预备试验,求出了隧道变态模型的沿程阻力系数λ'_m为0.033,进而求出了该试验所用隧道模型变态后模型与原型的纵向长度比尺为1:29.7;之后对阻力隔栅进行试验,计算出了隔栅的阻力系数ζ_λ为0.412,进而得到了阻力隔栅等效的正态模型长度和等效的原型长度。然后基于数值模拟和试验研究结果,通过对无风条件下各测点相应时间的温度模拟值与试验测量值的对比,确定数值模拟模型及计算方法。通过对2m/s风速条件下相对应位置处相应时间的速度数值模拟结果与模型试验测量数据的对比,验证了弗劳德准则在距火源不同距离处的适用性,得出了该隧道火灾模型试验中弗劳德准则适用于下风方向距火源120m-170m范围内。通过对比相同燃烧热释放速率,无风和2m/s风速情况下数值模拟所得弗劳德准则适用距离的范围得出,2m/s风速时的适用距离比不通风时的适用距离短。通过对比相同通风条件下,5MW和10 MW两种不同燃烧热释放速率火灾时数值模拟所得弗劳德准则适用距离的范围得出,燃烧热释放速率5MW时的适用距离比10MW时的适用距离短。
[Abstract]:With the development of social economy and road traffic, the number of highway tunnels and the number of kilometers are increasing, the traffic density is increasing, the driving speed is speeding up, and the number and frequency of all kinds of tunnel accidents are also increasing accordingly. Among them, tunnel fire often causes serious casualties and property losses because of its closed environment and difficulty of escape and rescue. Especially large tunnels and large traffic tunnels, the probability of fire will be relatively large. At present, the Froude criterion is usually used in the design of highway tunnel fire model test. However, the theoretical analysis results show that the buoyancy decreases in the process of flue gas flow in the far area of the fire source, and the Froude criterion is not applicable. In order to determine the application range of Froude criterion, it is necessary to use numerical simulation method to analyze and study the model test results. In this paper, the method of numerical simulation and model test is used to take one-way traffic highway tunnel as an example. The flue gas velocity (field) and temperature (field) of 5 MW and 10 MW scale fire under the condition of no wind and 2m/s natural wind were compared and analyzed respectively. In the preliminary test, the velocity values of 36 points on the same section were measured with Beetown, and the average wind speed of the section was calculated. Five sections were measured, and the resistance coefficient of the tunnel model was obtained. In the model test, the temperature distribution without wind condition and the cross section velocity distribution of 2m/s wind speed condition were measured by using PT100 temperature sensor and JY-GD2 wind speed sensor under the fire scale of 5 MW and 10 MW for 60 s and 120 s, respectively. Gambit software is used to build geometric model and mesh the original size of tunnel, and standard k- 蔚 model and PDF model are used to simulate the fire with 5 MW and 10 MW combustion heat release rate without wind and 2m/s wind speed by fluent software. The temperature cloud map and velocity cloud map of different sections under different working conditions were obtained at 285.7 s and 571.4 s corresponding to 60 s and 120 s, as well as the temperature and velocity values at the corresponding points of the model test. First of all, through the preliminary test, the drag coefficient 位 _ p _ m of the abnormal tunnel model is calculated to be 0.033, and then the longitudinal length ratio of the model to the prototype is 1: 29.7. then the resistance barrier is tested. The drag coefficient 味 _ 位 is 0.412, and the equivalent normal model length and the equivalent prototype length are obtained. Then, based on the results of numerical simulation and experimental research, the numerical simulation model and calculation method are determined by comparing the temperature simulation values of the corresponding time of each measuring point under the condition of no wind with the measured values. The applicability of the Froude criterion at different distances from the fire source is verified by comparing the numerical simulation results of the corresponding time at the corresponding position with the measured data of the model test under the condition of 2m/s wind speed. It is concluded that the Froude criterion is applicable to the 120m-170m range from the downwind direction to the fire source in the tunnel fire model test. By comparing the same combustion heat release rate and the range of the applicable distance of Froude criterion obtained by numerical simulation without wind and 2m/s wind speed, it is concluded that the applicable distance of 2 m / s wind speed is shorter than that of unventilated wind speed. By comparing the range of applicable distance of Froude criterion obtained from numerical simulation of different combustion heat release rates under the same ventilation conditions at 5 MW and 10 MW, it is concluded that the applicable distance of 5 MW combustion heat release rate is shorter than that of 10 MW.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U458

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