Anti Explosion Performance Analysis Of Double Steel Wall LNG Storage Tank Based On Multiphase Coupling

The liquid stored in LNG storage tank is easy to burn,explode and diffuse.The accidental ignition source after leakage will lead to combustion and explosion,which will not only have a serious impact on the environment,but also cause major accidents endangering people’s life and safety,such as fire and explosion,and bring huge losses.It can be seen that once an explosion occurs in the tank farm,the loss is very serious.In order to reduce the damage caused by explosion accident,the damage of steel double-layer LNG storage tank under external explosion load needs to be studied.Therefore,based on the finite element analysis,this paper will analyze the anti explosion performance of steel double-layer LNG storage tank based on multiphase coupling.The specific research work is as follows:(1)According to the amount of natural gas leakage from the low-pressure transmission pipeline of LNG storage tank,the leakage combustible gas cloud equivalent required in this paper can be obtained by TNT equivalent method.The multiphase coupling method of explosive load transfer of steel double-layer LNG storage tank was described in detail.In order to verify the accuracy of the multiphase coupling calculation method of explosive load of double-layer LNG storage tank established in this paper,the numerical simulation was compared with the experiment in reference.At the same time,considering the explosion shock wave transmission in the two states of integrity and crushing failure of cold insulation materials,the evaluation methods of external explosion strength and failure of storage tanks were described in detail from the two aspects of elastic-plastic stress analysis of storage tank materials and strain rate failure.(2)Considering the load transfer between the outer tank,the cold insulation material and the inner tank and the external explosion load of the fluid in the tank,a multiphase coupling finite element model of air tank structure fluid in the tank was established to explore the different states of the cold insulation material.The propagation law of the explosion shock wave in different media and the natural frequency,stress and deformation of the inner and outer tanks were obtained by the finite element calculation method.The results show that when the explosion shock wave reaches the outer tank and the inner tank,it is reflected,so that the pressure in the reflection area is about 3 times greater than the explosion pressure in the free air there;The complete cold insulation material forms a great resistance to the explosion shock wave.In the process of complete to complete crushing of the cold insulation material,the explosion reflection pressure gradually decreases,the deformation of the outer tank and the inner tank increases,and even damage occurs.The results of liquid sloshing modal analysis of outer tank and inner tank are compared with the theoretical calculation results respectively.The mass matrix coefficients of outer tank and inner tank(under half tank condition)are obtained through the classical Rayleigh damping calculation formulaαStiffness matrix coefficientβ。(3)The structural response and damage effects of different leaked combustible gas cloud equivalent and different initiation positions on the external explosion load were compared and analyzed.The results show that the larger the cloud equivalent of the leaked combustible gas is,the easier the inner and outer tanks are to be damaged,and once the outer tank is damaged,the inner tank will be more likely to be damaged.Under the condition of the initiation position of the tank top,the inner and outer tanks are easy to be damaged at the connection between the tank wall and the dome.Under the condition of the initiation position of the tank wall center,the inner and outer tanks are easy to be damaged at the center of the tank wall.Under the condition of the initiation position of the anchor belt,the inner and outer tanks are easy to be damaged at the bottom of the tank wall,or even the anchor belt.(4)The structural response and failure effects of different operation states and different tank structures on external explosion load were compared and analyzed,The results show that under the condition of half tank,the damage area of inner and outer tank is larger on one side and smaller on the other side.Under the condition of empty tank,the damage area of inner and outer tank is symmetrical,while under the condition of full tank,the inner and outer tank are not damaged.The damage and deformation area of inner and outer tanks under empty tank condition is larger than that under half tank condition.The inner and outer tanks under30000 m~3volume condition are easier to be damaged than those under 100000 m~3volume condition.The damage and deformation area of the inner and outer tanks under 30000 m~3volume condition is larger than that under 100000 m~3volume condition.In this paper,the structural response and failure influencing factors of steel double-layer LNG storage tank structure under external explosion load under different working conditions are calculated and analyzed,so as to provide reference for improving the anti explosion safety performance of storage tank,try to avoid accidents and reduce the losses caused by accidents.