正向风作用下的对开口腔室火灾行为  

Compartment fire behavior with two opposite openings under crosswind

作　　者：段君瑞 何明铭 胡皓玮 纪杰[1] DUAN Junrui;HE Mingming;HU Haowei;JI Jie(State Key Laboratory of Fire Science,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]中国科学技术大学火灾科学国家重点实验室,合肥230026

出　　处：《清华大学学报（自然科学版）》2023年第10期1502-1511,共10页Journal of Tsinghua University(Science and Technology)

基　　金：国家自然科学基金面上项目(51976211)。

摘　　要：为了系统揭示正向风作用下对开口腔室火灾行为的演化机理,该文建立了更符合实际的腔室火灾场景,开展了相应的数值模拟和理论分析,研究了正向风风速对迎风侧、背风侧的火溢流行为、腔室内部温度以及腔室气体流动方式的影响。结果表明:随着风速的增加,通风控制下腔室迎风侧的火溢流会逐渐消失。之后,背风侧的火溢流也会逐渐消失。火溢流发生的临界判据为全局当量比等于0.645。当全局当量比小于等于0.645时,燃烧只发生在腔室内部;当全局当量比大于0.645时,腔室外部开始出现火溢流。在燃料控制状态下,腔室内部的平均温度随着风速的增大不断降低。结合腔室内外的能量守恒方程,通过量纲分析,建立了正向风作用下燃料控制状态腔室内平均温升模型。基于迎风侧和背风侧与腔室内的压差,建立了腔室气体由双向流动转化为单向流动的临界风速表达式。当风速小于临界风速时,腔室两侧开口气流存在双向流动;当风速大于等于临界风速时,腔室两侧开口气流为单向流动。[Objective]External wind almost always exists around high-rise buildings.Due to the superimposed or competitive effect of wind pressure,buoyancy,and thermal expansion,the fire behaviors in high-rise building enclosures with two openings exhibit more complex dynamic evolution characteristics than those without external wind effects.In situations with such effects,new models are required to systematically analyze the fire behavior evolution mechanism.[Methods]In this study,we established a more practical compartment fire scenario and performed numerical analyses using the computational fluid dynamics(CFD)code,fire dynamics simulator(FDS),to study the evolution of the fire behavior of a compartment with two opposite openings.A total of 48 simulations were performed,wherein different wind speeds and heat release rates were considered.The fire source was a propane burner in the center of the compartment.The simulation duration was set at 350 s.The use of numerical simulations opened up the potential for a direct evaluation of a wide range of variables(e.g.,the mass rate of inflow and outflow through openings and temperature)and even more complex quantities(e.g.,the heat release rate within predefined volumes such as windward side space,leeward side space,and space inside the compartment).To obtain accurate simulations,sensitivity analysis was performed.The impact of crosswind speed on the behavior of fire spill plume on the windward and leeward sides,the temperature inside the compartment,and the flow pattern across the two openings were analyzed.Combined with the energy conservation equation,the average temperature rise model inside the compartment at over-ventilated conditions under the crosswind was established based on dimensional analysis.A critical wind speed(vc)was determined for the conversion of gas from bidirectional to unidirectional flow according to the pressure differences among the windward side,the compartment,and the leeward side.[Results]This study finds that a uniform mesh size of 2 cm is sufficient

关 键 词：腔室火 正向风 腔室温度 热释放速率 火溢流 

分 类 号：X93[环境科学与工程—安全科学]