Finite Element Modeling And Structure Optimization Of Fixed Device For Hydrogen Tank Of Onboard Hydrogen Supply System

The onboard hydrogen supply system is an important part of the fuel cell bus,and its main function is to provide hydrogen gas for the fuel cell stack.Once the structure of the hydrogen supply system is damaged,hydrogen leakage may occur,resulting in insufficient energy supply for fuel cell stacks.Leaking hydrogen is liable to cause fire and threatens the safety of people and property,so the safety of hydrogen supply system structure is the key to the normal operation of fuel cell bus.Based on the analysis of the structural characteristics of the onboard hydrogen supply system,a three-dimensional model of fixed device for hydrogen tank of hydrogen supply system is established by using the software Pro/E.According to the conditions of emergency start,emergency braking,sharp turning and bumping,etc.often encountered during the driving process of the vehicle,the static finite element simulation model of fixed device for hydrogen tank is established by Hyper Mesh.According to GB/T 29126-2012 Fuel cell electric vehicle-Onboard hydrogen system-Test methods?GB/T 26990-2011 Fuel cell electric vehicles-Onboard hydrogen system-Specifications the strength and stiffness of fixed device for hydrogen tank are checked.The simulation results show that the stiffness of the existing fixed device for hydrogen tank structure meets the requirements while the strength cannot meet the requirements.The maximum stress occurs near the bolt holes at the bottom of the permanent seat and the stress distribution is concentrated around the bolt holes.According to the results of structural strength analysis of fixed device for hydrogen tank,the thickness and arrangement of inner reinforcement plate of permanent seat are redesigned by using Opti Struct based on SIMP variable density topological optimization.A single loading case topological optimization finite element model is established with the remaining volume percent of the structure as constraints and the minimum strain energy as objectives,and the appropriate optimum volume percent is determined.On the basis of single loading case topological optimization model,multiple loading cases topological optimization of permanent seat is carried out by taking the minimization of weighted strain energy as the objective function with linear weighting method.After topology optimization,the structure of the permanent seat can meet the requirements of strength and stiffness.Based on the results of topology optimization,the size of permanent seat structure is optimized by Opti Struct.The plate thickness of each part of the permanent seat is selected as the initial design variable of size optimization,and the final optimized design variable is determined according to the sensitivity analysis results;The size of the permanent seat is optimized.The mass of the optimized permanent seat structure is reduced by 16.1% on the premise of meeting the stiffness and strength requirements.The modal comparison of fixed device for hydrogen tank before and after the structural optimization is carried out.The results show that the first six natural frequencies of the optimized fixed device for hydrogen tank structure are greatly increased,which can avoid resonance.This paper provides a basis for the selection of structural safety evaluation scheme of fixed device for hydrogen tank of onboard hydrogen supply system.At the same time,the combined optimization method of topology optimization and size optimization is adopted,which provides a useful reference for the structural optimization of other fixed devices or brackets.