Researches On Large Volume Layered High-Pressure Hydrogen Vessels And Hydrogen Accumulation Characteristics In Metal

Hydrogen for its advantages of non-polluting, high combustion efficiency and renewable, has become the most promising secondary energy of the new century. Hydrogen can be obtained from other renewable energies which are of low energy density or poor stability, or difficult to store, therefore bridge up the gap for these energies’ direct usage.Economic, safe and reliable hydrogen storage is one of the key technologies for hydrogen industrialization. High pressure gaseous hydrogen storage, primarily for its technical simplicity and fast filling-releasing rate, has become the most popular and mature method. High pressure hydrogen storage vessel is the key for high pressure hydrogen storage system.The process for hydrogen changing from demonstration to industrialization is speeding up day by day. And high pressure storage vessels with larger volume, higher pressure and reliability are needed. Therefore, more and more attention should be paid on the issues such as optimal design of large volume high pressure hydrogen storage vessel and high pressure hydrogen embrittlement of metal.This research is supported by the National High Technology Research and Development Program of China (863Program)"Technology and equipment of high pressure hydrogen storage vessels"(No.2006AA05Z143) and "Key technology and equipment for70MPa high-pressure hydrogen storage and refueling system"(No.2009AA05Z118). For large volume layered high-pressure hydrogen vessels, problems such as the optimal design of the cylinder, the strength of the joint structure for head and reinforce ring, safety of the vessel and hydrogen accumulation characteristic in metal, are studied in this thesis. The main contents and conclusions are as follows:(1) Based on the effective normal stress in the ribbon wide direction and shear stress model, an elastic stress analysis method is developed in which the friction between ribbon layers are fully considered. Then, a calculation method for the pre-tension stress of the ribbon is established based on reverse recursive thinking, and the optimum design software (Registration No:2011SR060577) for large volume layered high-pressure hydrogen vessels is developed. Taken the self-developed hydrogen storage vessel with the design pressure of75MPa and the volume of2.5m3for example, compared with other methods, the pre-tension stress calculation method established in this thesis can fulfill equal strength along the vessel’s thickness direction, and at the same time keeps the inner shell with low-stress level, therefore with obvious advantage.(2) Experimental study has been taken on the strength of the joint structure for the vessel’s head and reinforce ring which is of the design pressure of75MPa and the volume of2.5m3. And the stress distribution around the area of the head, reinforce ring and their joint is obtained from experimental study. A finite element analysis model was established to study the deformation characteristics of the joint structures for the head and reinforce ring. Based on this model, the deformation characteristics of the joint structures for the cylinder and the head during over-pressure process, and the stability of the crack tips which is formed by the weld between the head and reinforce ring during cyclic loading process is studied. The results showed that the joint structures is of enough strength, so the empirical design method is fit for the reinforce ring’s design.(3) Various hazardous factors are indentified systematically through five aspects-medium, equipment, environment, operation and management, and some risk control policies are put forward accordingly. Considering the structural characteristics of the large volume layered high-pressure hydrogen vessels, the safety of the vessel is analyzed from the viewpoint of the key points of the design, the experience in the use and the development of standard. Based on the unique multi-layered structure characteristics and failure characteristics which is only leak but never burst, the leakage monitoring system is developed which can realize real time remote monitoring of the vessel’s safety status.(4) Based on the elastic-plastic fracture mechanics theory and the general law of diffusion, a sequentially coupled mass diffusion analysis method for hydrogen diffusion in metals under local stress fields has been established, and the influence of stress intensity factor, material interface and temperature on hydrogen diffusion and accumulation behaviors has been studied by this numerical analysis method. The mechanism of hydrogen accumulation at the interface of different materials has been revealed. And the reason why hydrogen will not accumulated at the interface of clad steel plate during working conditions has been analyzed. On the basis of above results, measures to prevent hydrogen accumulation in local areas have been proposed.