Overview of hydrogen-resistant alloys for high-pressure hydrogen environment:on the hydrogen energy structural materials

With the progressive expansion of hydrogen fuel demand,hydrogen pipelines,hydrogen storage cylinders and hydrogen refuelling stations(HRSs)are the primary components of hydrogen energy systems that face high-pressure hydrogen environments.Hydrogen embrittlement(HE)is a typical phenomenon in metallic materials,particularly in the high-pressure hydrogen environment,that causes loss of ductility and potentially catastrophic failure.HE is associated with materials,the service environment and stress.The primary mechanisms for explaining the HE of materials are hydrogen-enhanced decohesion,hydrogen-induced phase transformation,hydrogen-enhanced local plasticity,adsorption-induced dislocation emission and hydrogen-enhanced strain-induced vacancy.To reduce the risk of HE for metallic structural materials used in hydrogen energy systems,it is crucial to reasonably select hydrogen-resistant materials for high-pressure hydrogen environments.This paper summarizes HE phenomena,mechanisms and current problems for the metallic structural materials of hydrogen energy systems.A research perspective is also proposed,mainly focusing on metal structural materials for hydrogen pipelines,hydrogen storage cylinders and hydrogen compressors in HRSs from an application perspective.

Seal contact performance analysis of soft seals on high-pressure hydrogen charge valves

The charge valve is an important element in the charging port of a high-pressure hydrogen storage cylinder(HP-HSC).It is normally closed after the HP-HSC is filled with hydrogen.If the seal of the charge valve is damaged,it will seriously affect the stable operation of the hydrogen supply system and may even cause safety problems.Therefore,the seal performance of the charge valve is important.In this paper,finite element analysis(FEA)is carried out to analyze the seal contact performance of hydrogenated nitrile rubber(HNBR)gaskets in the seal pair of a charge valve.The effects of different pre-compressions,seal widths,and hydrogen pressures on the seal contact performance of the charge valve are analyzed.The contact pressure on the seal surface increases with the increase of pre-compression.With a pre-compression of 2.5 mm,the maximum contact pressure without and with hydrogen pressure are 68.51 and 107.38 MPa,respectively.A contact gap appears in the inner ring of the seal surface with pre-compression below 0.15 mm.The contact gap occurs between the entire seal surface with a seal width of1 mm.The contact pressure on the seal surface and the width of the separation area between the seal surfaces increase with the increase of the seal width.The contact gap between the seal surfaces is zero with a width of 2.5 mm.The width of the separation area between the seal surfaces decreases with the decrease of the hydrogen pressure.The width of the separation area is reduced from 0.5 mm at 35 MPa to 0.17 mm at 15 MPa.This work can be useful for improvement of the seal performance and of the design of the charge valve used in the HP-HSC.