Thermal Analysis And Seismic Analysis Of Steel LNG Storage Tank

With the rapid growth of the world economy,utilizing liquefied natural gas(LNG)has become more and more popular worldwide as a new energy form.Utilizing LNG has many advantages including more safety in transportation,more cleanness and less environmental pollution,more economy,more efficiency,and its flexibility and convenience.When leakage or earthquake damage occurs in the operation process of LNG storage tank,the tank breakage will lead to devastating secondary disasters.Therefore,it is significant to study the varying temperature field of LNG tank during leakage and to analysis seismic response of the tank when earthquake happened.In this thesis,a steel LNG storage tank as full container is taken as an object to study the leakage temperature field and seismic response.The main contents of the thesis are as follows:1.The FE model of LNG storage tank is established by using axisymmetric elements of ANSYS.At first,carrying out thermal analysis of the model in steady state,the temperature field of the tank under normal working conditions is calculated.In order to analyze transient thermal process of the tank leakage,a suitable LNG leakage model is selected,and then continuous changing temperature fields of the leaking tank is simulated.The results show that the temperature distribution of the storage tank is accord with expectations for each operating condition.The results reveal that,the insulation design plays good heat insulation function at several important locations of the tank,which are at the bottom of the heat-insulation layer,near the shell of the heat-insulation layer and at the top of the cotton fiber.The results also show that,the design of thermal corner protection structure can actually weaken thermal shock caused by LNG leakage,and can effectively reduce temperature gradient in the thickness direction near the bottom of the outer tank wall.2.A FE model for liquid-solid coupling vibration analysis of LNG tank is established by using ANSYS.The natural vibration characteristics of coupling system embeded interaction between LNG and elasic thin-walls are studied.The results show that,the distribution of natural frequencies is very crowded,for the influences of LNG liquid vibration.The main modes of fluid-solid coupling vibration are selected by determining and comparing each vibration mode participation coefficient.As a result of the above efforts,the vibration modes of beam-shaped with large contribution to modal vibration are found at the considered LNG tank,which are consistent with the prediction by Haroun-Housner theory.3.The seismic response analysis of the tank was carried out by using the response spectrum method.The structural stress-strain field of LNG storage tank under the excitation of horizontal SSE(safety shutdown earthquake)is calculated.The most dangerous location and possible failure mode of the tank structure are studied by analyzing the stress spacial distribution.It is shown that these results are in good agreement with the results of the earthquake damage investigation of "elephant foot".