Finite Element Analysis And Research Of Composite LNG Cylinder

In recent years,with the rapid development of automobile industry,the total number of automobile has increased dramatically and the exhaust emissions of automobile have become an important factor in urban environmental pollution.Therefore,Liquefied Natural Gas Vehicle(LNGV)has been promoted vigorously by the government and achieved rapid development and application.Liquefied Natural Gas(LNG)cylinder is one of the key components of LNGV and it is a kind of insulating cryogenic pressure vessel.Due to the complex structure,heavy weight and other factors,stainless steel LNG cylinder increases the whole weight of the automobile greatly,which not only reduces the economy of the car,but also greatly limits the application in small vehicles.However,the cryogenic composite cylinder is conducive to the integration molding,which can not only greatly reduce the number of parts and the complexity of manufacturing,but also significantly reduce the whole weight,so,there is a very broad development and application prospect of the cryogenic composite cylinder.So far,the research on the cryogenic mechanical properties and permeability resistance of composite has been extensively studied.However,there are still few studies on the structure design and analysis of cylinder.Therefore,based on ANSYS software,the Finite Element Analysis and research of the composite LNG cylinder under the thermo-mechanical coupling load were carried out in this paper.The contents and results are as follows:(1)Based on the ANSYS software,the finite element model of the composite cylinder body used for stress analysis under thermo-mechanical coupling loads was established.The effects of lay-up angle,thickness of single layer and the change of material properties with temperature on the performance of cylinder were studied.The results showed that,the numerical analysis of cryogenic composite cylinder needs to take the change of material properties with temperature into consideration.When the [902/±?2]S lay-up was adopted in the composite LNG cylinder,the lay-up angle ? should be in the range of 10 to 30.The effect of thickness of single layer on the stress analysis of cylinder under thermo-mechanical coupling load can be negligible.Then,considering molding conditions of cylinder,the optimal winding scheme of the composite LNG cylinder was determined.(2)Based on the Hashin failure criterion,the stress distribution of composite LNG cylinder under working conditions,test conditions,cryogenic load and internal pressure load were studied respectively.The results showed that,matrix cracking and fiber breakage wound not happen in the composite LNG cylinder either under the working conditions or under the test conditions,and it met the working and design requirements.Both the connection of bottleneck and head and the connection of body and head of the cylinder were stress-concentrated areas,which need be strengthened during manufacturing process.The partial circumferential stress produced by cryogenic load and internal pressure load canceled each other,and the maximum circumferential stress of cylinder under thermo-mechanical coupling load reduced.Due to limits of the axial displacement at both ends of the cylinder body,both the cryogenic load and internal pressure load caused axial tensile stress of the cylinder body,and the axial stress of cylinder under thermo-mechanical coupling load increased.The cryogenic load had little effect on the displacement of cylinder,while the internal pressure load was the main factor which induced displacement of cylinder.