隧道近火源烟气热参数理论研究与数值模拟

发布时间：2018-04-16 15:31

本文选题：理论模型 + 数值模拟　；参考：《山东建筑大学》2015年硕士论文

【摘要】：近年来,集中排烟模式因兼顾纵向通风、局部排烟等诸多优点,在隧道建设中得到广泛应用。究其物理本质,其火羽流的发展过程可抽象为上游垂直风流与排风诱导斜向风流耦合作用下的受限扩散问题。本文以此为研究重点,对隧道内近火源烟气热参数进行深入研究,为隧道火灾安全设计提供理论依据和技术参考。在分析送风和排烟耦合作用的基础上,提出等效风速的概念。建立火源热烟羽理论模型和等效风速作用下热烟羽偏转模型,预测烟气温度、密度、羽流速度、羽流半径、羽流轨迹及偏移距离等近火源烟气热参数,进而得到火羽流发展过程详尽的参数描述。结合某长大隧道工程实例,以顶板下方烟气最大温升及烟气羽流纵向偏移距离为例,对近火源烟气热参数进行理论分析。将理论分析结果与已有火灾实验结果对比,发现两者具有较好的一致性,证明理论模型是可靠的。进一步回归整理得到顶板下方烟气最大温升、偏移距离的无量纲准则关联式。结合集中排烟隧道系统设计,针对天然气火灾,借助CFD模拟预测15种工况横流作用下火羽流轴线偏移轨迹、火焰结构分区、顶板下方烟气最大温升等火羽流状态参数。结果表明模拟火焰与自由火焰结构分区规律类似,但自由火焰分区转折点与火灾强度无关,而模拟火焰分区转折点随火灾强度增大不断减小。将模拟结果与已有火灾实验结果对比分析,进一步完成了模拟结果验证。对火羽流3个分区轴线温升进行了风速修正,回归整理得到轴线温升及顶板下方烟气最大温升的无量纲准则关联式。最后,对下一步研究工作的方向和内容进行了简要讨论。
[Abstract]:In recent years, centralized smoke exhaust mode has been widely used in tunnel construction because of its advantages of longitudinal ventilation and local smoke exhaust.In terms of its physical nature, the development process of fire plume can be abstracted as a constrained diffusion problem under the coupling of vertical air flow and exhaust wind induced oblique wind flow.In this paper, the thermal parameters of the flue gas near the fire source in the tunnel are deeply studied, which provides the theoretical basis and technical reference for the fire safety design of the tunnel.The concept of equivalent wind speed is put forward on the basis of analyzing the coupling effect of air supply and smoke exhaust.The theoretical model of fire source heat plume and the model of heat plume deflection under the action of equivalent wind speed are established to predict the heat parameters of smoke near fire source, such as flue gas temperature, density, plume velocity, plume radius, plume trajectory and offset distance.Then the detailed parameter description of the fire plume development process is obtained.Taking the maximum temperature rise of flue gas under the roof and the longitudinal offset distance of flue gas plume as examples, the thermal parameters of flue gas near the fire source are analyzed theoretically with an example of a long tunnel project.By comparing the theoretical analysis results with the existing experimental results, it is found that there is a good agreement between the two results, and it is proved that the theoretical model is reliable.The dimensionless correlation formula of the maximum temperature rise and offset distance of flue gas under the roof is obtained by further regression analysis.Combined with the design of centralized exhaust gas tunnel system, aiming at the natural gas fire, CFD simulation was used to predict the fire plume state parameters, such as the offset track of the fire plume axis, the division of the flame structure, and the maximum temperature rise of the smoke under the roof.The results show that the simulated flame is similar to the free flame structure, but the free flame zone turning point is independent of the fire intensity, while the simulated flame zoning turning point decreases with the increase of the fire intensity.The simulation results are compared with the existing fire experiment results, and the simulation results are further verified.In this paper, the temperature rise of three regional axes of plume is corrected, and the dimensionless correlation formula of temperature rise of axis and maximum temperature rise of flue gas under roof is obtained by regression analysis.Finally, the direction and content of the next research work are briefly discussed.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U458.1

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