【作者】 张伟；

【导师】 彭伟；

【作者基本信息】 安徽理工大学 ， 安全科学与工程， 2025， 硕士

【摘要】 隧道多火源火灾中,火焰合并使热释放速率增加30%～50%,顶棚温度呈"双驼峰"分布,显著提升火灾风险。火源高程的差异化会直接影响空气卷吸路径和受限程度,进而影响火焰合并概率、羽流运动特性及温度场分布。然而,现有研究多基于火源与地面齐平的假设或将火源设置在既定高程上,未考虑实际火灾中车辆燃烧部位(如车体、轮胎、货物)的高程差异对火灾燃烧行为的影响,对火源高程这一关键参数的影响机制缺乏系统性探讨,尤其是自然通风条件下双火源高程对火焰合并及温度分布的定量规律尚不明确。本文以自然通风公路隧道为研究对象,通过缩尺寸实验、理论分析与数值模拟相结合的方法,从以下三个方面开展研究:首先,研究了双火源高程对火焰耦合作用机制的影响,重点包括以下四个方面:火焰合并概率分布规律、火焰合并点高度、火焰偏离中心线角度演变特征以及火焰长度特征。实验结果表明:双火源高程的增大会显著降低火焰合并概率,阐述了火焰合并概率的变化规律,得到了火焰合并的临界判定标准;利用火焰合并情形下的火焰合并点高度量化了火焰合并程度,得到归一化火焰合并点高度的经验公式;分析了各火源高程工况下倾斜角度随火源间距的变化趋势;通过量纲分析对火焰长度进行归一化处理,得到无量纲火焰长度的表达式,并和前人数据进行对比,进一步验证了公式的准确性。其次,运用数值模拟手段建立全尺寸隧道模型,从温度分布和火焰合并点高度角度验证了数值模拟和缩尺寸试验的一致性。从速度场、压力场和空气卷吸系数这三个角度开展了隧道内双火源对火源间空气流动特性的研究。结果表明,由于火源的阻挡效应和对称效应,横向速度分量与双火源的相互作用程度和合并状态密切相关,压力和速度均相对于火源纵向阵列中心对称;火源高程下方的空气均向上被卷吸从而参与燃烧,而在火源高程高度处时,除火源上方区域为负压区域外,其他区域均呈现正压,说明火源上方区域的燃烧所需空气均由火源高程下方的空气提供,火源上方空气未参与燃烧;通过测量不同高度X-Y平面上的气体质量通量获得不同高度的空气卷吸率,得出空气卷吸率与离地高度之间的变化趋势。最后,对顶棚下方最大温升和温度衰减趋势进行了实验研究,探讨了前人关于隧道内顶棚下方最大温升对本研究数据的适用性,最后得出了包含火源高程参数在内的最大温升的归一化经验公式;针对双火源产生的羽流在各火源高程、热释放速率、火源间距下撞击顶棚的行为特点,分为单撞击点和两个撞击点时两种情形对纵向温度分布进行分析,得到适用性更高的归一化纵向温度分布经验公式。本研究揭示了不同火源高程下双火源火焰形态特征,火源间空气流动特性和隧道顶棚下方温度温度场分布特性,对隧道内消防设计与灭火救援具有一定的指导意义。图[72]表[10]参[107]更多还原

【Abstract】 In tunnel multi-source fires,flame merging increases the heat release rate by30%～50%,and the temperature distribution under the ceiling shows a"double hump"characteristic,which significantly increases the fire risk.Differences in fire source elevation directly affect the air entrainment path and the degree of restriction,which in turn affects the probability of flame merging,plume motion characteristics,and temperature field distribution.However,most of the existing studies are based on the assumption that the fire source is flush with the ground or the fire source is set at a given elevation,without considering the influence of the elevation differences of the burning parts of the vehicle(such as the vehicle body,tires,and cargoes)on the combustion behavior of the fire,and there is a lack of systematic discussion on the mechanism of the influence of the key parameter of the elevation of fire source,especially the quantitative law of the dual fire source elevation on the flame merging and the temperature distribution under the condition of natural ventilation is not clear yet.In particular,the quantitative law of dual fire source elevation on flame merging and temperature distribution under natural ventilation conditions is not clear.In this paper,the natural ventilation road tunnel is taken as the research object,and the following three aspects are carried out through the combination of size reduction experiment,theoretical analysis and numerical simulation.Firstly,the influence of the dual source elevation on the flame coupling mechanism was investigated,focusing on the following four aspects:the distribution law of flame merging probability,the height of the flame merging point,the evolution of the flame deviation angle from the centre line,and the flame length characteristics.The experimental results show that:the increase of dual fire source elevation will significantly reduce the flame merging probability,and the change rule of the flame merging probability is elaborated,and the critical determination standard of flame merging is obtained;the flame merging point height under the flame merging scenario is used to quantify the degree of the flame merging,and the empirical formula of the normalised flame merging point height is obtained;the trend of the change of the tilting angle with the fire source spacing is analysed for the working conditions of each fire source elevation;the change of the flame length is normalised to the flame length by means of magnitude analysis.The normalisation of the flame length is carried out by means of magnitude analysis,and the expression for the dimensionless flame length is obtained,which is compared with the previous data to further verify the accuracy of the formula.Secondly,numerical simulation was used to establish a full-size tunnel model,and the consistency between numerical simulation and downsizing tests was verified from the perspectives of temperature distribution and the height of the flame merging point.The study of the air flow characteristics between two fire sources in a tunnel was carried out from three perspectives:velocity field,pressure field and air entrainment coefficient.The results show that,due to the blocking effect and symmetry effect of the fire source,the transverse velocity component is closely related to the interaction degree and merging state of the two sources,and the pressure and velocity are symmetric with respect to the centre of the longitudinal array of the fire source;the air below the fire source elevation is sucked upwards to participate in the combustion,and the air required for the combustion is supplied by the air from the fire source elevation,while at the height of fire source elevation,the air above the fire source is suppressed by the air from the fire source.At the height of the fire source,except for the area above the fire source,which is a negative pressure area,all the other areas show positive pressure,which means that the air required for combustion in the area above the fire source is provided by the air below the height of the fire source,and the air above the fire source is not involved in combustion.The air entrainment rate at different heights was obtained by measuring the gas mass flux in the X-Y plane at different heights to derive the trend between the air entrainment rate and the height above the ground.Finally,the experimental study of the maximum temperature rise and temperature decay trend under the ceiling was carried out,and the applicability of the previous research on the maximum temperature rise under the ceiling in the tunnel to the data of this study was discussed,and finally the normalized empirical formula of the maximum temperature rise including the elevation parameters of the fire source was obtained.According to the behavior characteristics of the plume generated by the double fire source hitting the ceiling under the elevation,heat release rate and spacing of each fire source,the longitudinal temperature distribution is analyzed in two cases:single impact point and two impact points,and the normalized longitudinal temperature distribution empirical formula with higher applicability is obtained.This study reveals the morphological characteristics of the flame of the dual fire sources under different fire source elevations,the air flow characteristics between the fire sources and the temperature field distribution characteristics under the tunnel ceiling,which has certain guiding significance for the fire protection design and fire fighting and rescue in the tunnel.Figure[72]Table[10]Reference[107]更多还原