【作者】 王明艳；

【导师】 宗若雯；

【作者基本信息】 中国科学技术大学 ， 安全科学与工程， 2023， 硕士

【摘要】 油箱是车辆、飞机等运载工具的燃料储存设备,也是其燃油供给系统中较为薄弱的环节。一旦货运汽车、飞机以及油罐槽车等发生意外事故或处于高温环境中,极易导致油箱破裂,引发火灾爆炸事故,威胁人员的生命安全。因此,研究油箱在火灾作用下的热响应特性对油箱燃爆事故的预防、风险管理和应急救援具有重要指导意义。油箱遭受外部火灾侵袭时,壁面温度升高,材料性能下降。热量经壁面传递到内部介质,内部流体升温并产生温度分层现象,油箱内压力升高。高温环境导致油箱壁面产生局部温度梯度,从而引起热应力增大,当壁面热应力超过材料强度时,油箱易发生破裂,甚至引发沸腾液体扩展蒸气云爆炸(BLEVE)。爆炸事故的危害程度取决于油箱内介质储存的能量。现有研究工作表明,液体温度分层现象能有效降低火灾作用下容器失效风险和减轻爆炸事故危害,但油箱在火灾作用下的热响应机理尚未明确,仍需进一步研究。鉴于此,本文通过实验和数值模拟相结合的方法,探究柴油油箱在火灾作用下的热响应特性,能够为油箱爆炸事故的预测、预防和控制提供理论指导。主要开展工作及取得的成果如下:(1)以广泛使用的铝合金油箱为研究对象,内部燃料为0号柴油,设计并搭建了丙烷池火作用油箱实验平台,开展池火直接作用油箱实验和池火远距离辐射油箱实验,探究不同火灾作用下油箱的热响应行为。结果表明,池火直接作用油箱时,内部柴油未发生温度分层现象;而池火远距离辐射油箱时,内部介质出现温度分层现象,并且温度梯度随着火灾作用时间的持续而增大。(2)基于油箱火灾实验,对火灾作用下油箱内部介质的流体动力学和传热传质学原理进行深入分析,通过PyroSim火灾仿真软件建立了丙烷燃烧模型并求解油箱壁面热边界条件,通过Fluent流体仿真软件中用户自定义函数(UDF)建立了油箱内部介质的传热传质模型并求解油箱温度场和压力场的响应特性。将数值模拟结果与实验数据对比,结果表明两者吻合良好,仿真模型可用于研究火灾作用下油箱的热响应特性。(3)通过数值模拟探究了火灾作用位置、填充率和辐射距离对油箱热响应特性的影响,结果表明:火灾作用位置对液体温度分层现象的产生有直接影响。当火焰完全包围油箱时,内部液体温度趋于一致,气相介质存在温度分层,并且温度梯度随着填充率和辐射距离的增加而减小;当火焰只作用于油箱侧壁时,油箱内部气液介质均存在温度分层现象,并且介质温度随着垂直高度的增加而增加;当火焰只作用于油箱底面时,油箱内部气液两相介质温度趋于一致,将以沸腾的形式向上部液体传递热量。(4)在Fluent数值模拟的基础上,通过ANSYS Workbench平台求解了不同火灾工况下油箱壁面温度场、应力场和位移场的变化,深入探究油箱失效机理。结果表明,油箱外壁温度场受到火灾辐射热流和内部介质温度的耦合作用。当池火直接作用于油箱,火源功率为222 kW,填充率为18%时,热应力和位移快速增加,油箱将在239 s发生韧性断裂。更多还原

【Abstract】 The fuel tank is the fuel storage equipment for vehicles,aircraft and other transportation tools,and is also the weakest component of their fuel supply system.Once the freight truck,aircraft and tanker truck have an accident or in a hightemperature environment,it is very easy to cause the fuel tank to rupture,which can lead to fire and explosion accidents,threatening the human lives.Therefore,it is extremely significant to study the thermal response characteristics of fuel tanks exposed to fire for the prevention,risk management and emergency rescue of fuel tank combustion and explosion accidents.When the fuel tank is engulfed by fire,the wall temperature increases rapidly,which degrades the performance of the metal materials.The heat load received is transferred through the vessel walls into internal medium,causing the fluid to heat up and show temperature stratification phenomenon,while the internal pressure will increase.The high-temperature environment leads to local temperature gradients in the tank wall,which results in an increased thermal stress,when the thermal stress on tank wall exceeds the strength of material,the fuel tank is prone to rupture,or even provoke boiling liquid extended vapor cloud explosion(BLEVE).The degree of harm of the explosion depends on the energy stored in the tank medium.Available studies show that the liquid temperature stratification phenomenon can effectively reduce the risk of vessel failure engulfed by fire and mitigate the hazard of explosion accidents,but the thermal response characteristics of the fuel tank exposed to fire is not yet clear,which still needs further research.Therefore,this paper investigated the thermal response characteristics of diesel fuel tank under fire through a combination of experiments and numerical simulations,which can provide theoretical guidance for the prediction,prevention and control of fuel tank explosion accidents.The main work and results are as follows:(1)A propane pool fire experimental setup was designed and built,which can be used to carry out fire testing of widely used aluminum fuel tanks filled with 0#diesel.The experiments of diesel fuel tank directly engulfed by pool fires and radiated by pool fires at a distance were conducted to investigate the thermal behavior of the fuel tank under fires.The results showed that when the pool fire engulfs directly on the tank,no temperature stratification phenomenon occurs for the internal liquid;while when the pool fire is radiated to the fuel tank from a distance,temperature stratification phenomenon occurs for the internal medium,and the temperature gradient increases with the duration of the fire.(2)Based on the fuel tank fire experiments,the fluid dynamics and heat and mass transfer principles of the medium inside the tank under fire are analyzed in depth.The propane combustion model was built by PyroSim software to solve for the thermal boundary conditions at the fuel tank walls.The heat and mass transfer model of the medium inside the tank was implemented by the User Defined Function(UDF)code in the fluent software to solve the response characteristics of the temperature and pressure fields of the fuel tank.The numerical simulation results were compared with the experimental data,and the results showed that they are in good agreement,so the simulation model could be used to study the thermal response characteristics of the fuel tank exposed to fire.(3)The effect of fire location,filling level and radiation distance on the thermal response characteristics of the tank was investigated by numerical simulation.The results showed that the fire location has a direct effect on the generation of liquid temperature stratification.When flame completely engulfed the diesel fuel tank,temperature stratification appeared in the vapor space and gradually diminished with increasing filling level and radiation distance;however,the liquid phase could be considered isothermal.When the flame only engulfed the sides of the tank,the gas phase and liquid phase both showed temperature stratification phenomenon,and the medium temperature increases with the vertical height.When the flame only engulfed on the bottom of the fuel tank,the medium was approximately isothermal and transferred heat by boiling.(4)Based on the numerical simulation of Fluent software,the evolution of temperature field,stress field and displacement field of the fuel tank wall under different fire conditions were solved by ANSYS Workbench platform to investigate the failure mechanism of the fuel tank in depth.The results showed that the temperature field of the tank wall was subject to the coupling effect of the fire radiation heat flow and the internal medium temperature.When the pool fire engulfed directly on the fuel tank filled to 18%capacity with 0#diesel,the thermal stress and displacement increase rapidly,and the tank would undergo ductile fracture at 239 s.更多还原