Experimental And Simulative Research On Thermal Response Characteristics Of Diesel Fuel Tank Exposed To Fire

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.