| With the construction of clean,efficient,safe and sustainable modern energy system by national energy development strategy,clean fuels such as natural gas,petroleum gas and hydrogen have become more and more important in the optimization of energy structure.Gas fuels are usually liquefied and stored under pressure or low temperature,so they have obvious pressure-reducing and heat-sensitive characteristics.Once their storage equipment breaks down,they will rapidly boil and spray,resulting in steam explosion,fireball and even tank area explosion accidents.Fracture accidents of liquefied gas storage tanks have attracted wide attention from scholars at home and abroad.The macro-laws of tank fracture accidents have been obtained through the research work carried out.The understanding of crack propagation behavior during tank fracture under the influence of stress response of solid materials at high temperature and accumulation of medium energy in tank is still insufficient.In this paper,the cracking behavior of tank under high temperature and high pressure is studied from the aspects of high temperature degradation of metal material properties and stress response under non-uniform wall temperature distribution.The main work and conclusions are as follows:(1)Based on engineering analysis software FLUENT and ABAQUS,a calculation model describing the thermal response and solid mechanical response process of liquefied gas storage tank is established.The thermal response model includes the solution of the heat transfer inside the tank solid wall,the heat transfer between the tank wall and the medium inside the tank,and the mass transfer between the medium inside the tank.The solid mechanical response model includes the stress response of storage tank under high temperature and pressure and the solution of crack propagation process.(2)Through the hydrodynamic simulation of the tank heating process,the thermal response behavior of propane medium and tank wall in the fire environment was studied.The law of pressure rise in the tank under fire was obtained,and the non-uniform distribution characteristics of medium and tank wall temperature in the tank were revealed.The results show that under the condition of unilateral heating,the liquid medium in the tank can form strong natural convection,and the temperature stratification is not obvious;the gas phase wall temperature is much higher than the liquid phase wall,which affects the formation of distinct temperature stratification in the gas phase space,and the maximum wall temperature appears on the top of the tank and distributes unevenly;the wall temperature of the gas phase area without flame heating is similar to the liquid phase wall temperature.(3)The cracking behavior of the solid wall was simulated by using the extended finite element method.Through the analysis of stress field and plastic deformation field at crack tip,the propagation characteristics of initial crack under non-uniform wall temperature were revealed.The numerical simulation results of crack propagation process of three-dimensional storage tank agreed well with the final crack morphology of Birk's experiment.Based on the results of thermal response of storage tank,the causes of partial cracking and integral cracking in Birk's tests of 04-6 and 04-1 were demonstrated respectively.The results show that the crack propagation is greatly influenced by the temperature distribution on the top of the tank wall.In the 04-1 experiment,the initial crack of the tank occurred at lower pressure because of the high peak value of the top wall temperature,while the crack propagation is limited due to the large difference of the top wall temperature along the axis,and only a local crack is formed.In the 04-6 test,the top wall temperature was relatively lower under the influence of wind,so the safety valve was opened first.With the continuous injection loss of the medium,the gas wall temperature rose as a whole,and finally,after the formation,the crack expanded rapidly until the whole crack. |
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