Strength Analysis And Optimization Of Multi-layer Wrapped Pressure Vessels

Pressure vessels mainly include two types of structures: single layer and multi-layer,among which the multi-layer structure is further divided into multilayer wrapping type,winding type,and heat jacket type.As one of the more widely used and mature multi-layer structure vessels in the industrial field,multi-layer wrapped vessels have many special advantages.Compared to single layer thick wall vessels,multi-layer wrapped vessels can not only use different materials for the inner cylinder and the laminate,but also generate pre-stress in the cylinder during the manufacturing process,which can improve the bearing capacity of the cylinder.However,in the design of multi-layer wrapped vessels,the pre-stressing force has not been reasonably utilized,only used as a strength reserve.In addition,multi-layer wrapped cylinders can also produce interlayer clearances due to insufficient manufacturing accuracy.Therefore,studying the effects of pre-stress and interlayer clearance on the strength of multi-layer wrapped vessels is of great significance for ensuring the safe operation and improving the economy of the vessels.In this paper,combined theoretical analysis and numerical simulation was used to conduct strength calculation,optimal design,and application research on multi-layer wrapped vessels.The main contents and conclusions are as follows:(1)Based on Lame formula and strength theory,a formula for calculating the cylinder stress of the multi-layer wrapped vessel under working conditions was obtained.The stress distribution of the multi-layer wrapped pressure vessel was simulated with ANSYS.Both theoretical analysis and numerical simulation found that the pre-stress significantly reduces the internal stress level of the cylinder,and the working stress distribution along the wall thickness direction is more uniform.(2)For improving the load-bearing performance of the vessel,the design method of the pre-tension stress of the winding pressure vessel was applied to calculate the clamping force.In order to more quickly and accurately perform the stress calculation of multi-layer wrapped pressure vessel,a general software for stress calculation of multi-layer wrapped pressure vessel was developed by using Python.(3)The optimization design model was established,which takes the number of layers,the thickness of the inner cylinder and the thickness of the laminate as the design variables,the elastic failure criterion and the geometric range of variables as the constraints,and the minimum cost of materials required for the cylinder as the objective function.As an example,a multi-layer wrapped pressure vessel was optimized,and as a result,the economy of the vessel was effectively improved.Even for vessels with corrosive chemical,when the inner cylinder is replaced with stainless steel,the cost of the whole cylinder can be reduced after optimization.(4)Based on the mechanical equilibrium equations and von-Mises yield criterion of the micro-element of the multi-layer wrapped cylinder,the calculation expressions of the full yield limit load of the multi-layer wrapped vessel cylinder with or without pre-stress and with uniform interlayer clearance were derived respectively.According to the plastic collapse criterion,the limit load analysis of the multi-layer wrapped cylinder was carried out by using ANSYS.Both numerical simulation and theoretical calculation found that the pre-stress improves the elastic performance of the cylinder,but does not improve the ultimate bearing capacity of the vessel.The research also shows that the interlayer clearance between the laminates does not affect the ultimate bearing capacity of the vessel.The ultimate load of multi-layer wrapped high pressure vessels is only related to the material properties of the vessels,the thickness of the inner cylinder,the thickness of the laminates and the number of laminates.(5)The material selection,structural strength and health detection system design of a multi-layer wrapped high-pressure hydrogen storage vessel were completed.And the stress assessment and fatigue check of the multi-layer wrapped high-pressure hydrogen storage vessel under the design conditions and pressure conditions were carried out according to the design-by-analysis standard.