论文部分内容阅读
对于特长公路隧道,当火灾发生时,隧道内部的烟气扩散特征和诸多因素相关,如隧道纵坡、隧道横截面大小、火源功率大小、阻塞比、纵向通风风速等,不同因素对其烟气运动产生的影响各不相同,根据实际项目自身特点,确定其模拟仿真的数值参数,进行不同因素的影响分析对于分析隧道火灾特征有很重要的现实意义。结合米溪梁特长公路隧道设计参数文件确定PyroSim软件的隧道模型,分析了不同因素对隧道火灾临界风速、温度分布、烟气扩散的影响,发现火源功率越大所需的临界风速越大,当火源功率大于70MW时临界风速增长缓慢,当大于100MW时临界风速维持在4.3m/s不变。随着隧道负坡坡度的增加临界风速显著增大,随着隧道正坡坡度的增大临界风速逐渐减小。阻塞比对临界风速有一定影响。当阻塞比为0~20%时,随着阻塞比的增大临界风速显著下降,由3.2m/s降到2.6m/s;当阻塞比为20%~40%时,随着阻塞比的增大,临界风速缓慢下降由2.6m/s降为2.4m/s,当阻塞比大于40%时,对临界风速基本没有影响。火灾发生时,隧道纵向温度分布呈先升高后减小的变化趋势,火源附近的温度梯度也是先增大后减小,通风和纵坡条件下,温度最高断面逐步向下游移动,出现最高点温度漂移现象。在坡度绝对值小于1.0%时浮力效应不太明显,在坡度大于等于1.5%时随着坡度的增大隧道的浮力效应比较明显,“烟囱效应”形成。
In the case of extra-long highway tunnels, when the fire occurs, the characteristics of smoke diffusion inside the tunnel are related to many factors such as the longitudinal slope of the tunnel, the size of the cross-section of the tunnel, the power of the fire source, the blocking ratio and the longitudinal ventilation velocity. The influence of gas movement varies. According to the characteristics of the actual project, the numerical parameters of its simulation are determined. The analysis of the influence of different factors is of great practical significance for analyzing the fire characteristics of the tunnel. Combined with the design parameters of MiXiLiang highway tunnel, the tunnel model of PyroSim software is determined, and the influence of different factors on the critical wind speed, temperature distribution and smoke diffusion is analyzed. The larger the critical wind speed is, The critical wind speed increases slowly when the source power is greater than 70MW, while the critical wind speed remains unchanged at 4.3m / s when the source power is greater than 100MW. With the increase of negative gradient of the tunnel, the critical wind speed increases significantly. As the slope of the tunnel increases, the critical wind speed decreases. The blocking ratio has a certain impact on the critical wind speed. When the blocking ratio is 0 ~ 20%, the critical wind speed decreases significantly from 3.2m / s to 2.6m / s with the increasing of the blocking ratio. With the blocking ratio of 20% ~ 40% And the critical wind speed decreases slowly from 2.6m / s to 2.4m / s. When the blockage ratio is more than 40%, the critical wind speed will not be affected. In the event of a fire, the longitudinal temperature distribution in the tunnel firstly increases and then decreases, and the temperature gradient near the fire source first increases and then decreases. Under the conditions of ventilation and longitudinal slope, the highest temperature section gradually moves downstream and appears the highest Point temperature drift phenomenon. When the absolute value of slope is less than 1.0%, the buoyancy effect is not obvious. When the slope is greater than or equal to 1.5%, the buoyancy effect of the tunnel is obvious with the increase of slope, and the “chimney effect” is formed.