Optimization and Property Analysis of the Sealing Structure of Type IV Cylinder for High-Pressure Hydrogen Storage

Composite overwrapped pressure cylinders with plastic liner (type IV) have a broad application prospect in high-pressure gaseous hydrogen storage due to their excellent properties, such as lightweight, corrosion resistance, fatigue resistance and low cost. Heterogeneous materials sealing is an important issue during the connection structure design between the plastic liner and the metal valve, where a rubber O-ring was often set for the sealing of hydrogen with high pressure. In this work, a finite element model (FEM) of the bottle mouth structure of composite overwrapped pressure cylinder composed of a plastic liner and a metal boss was established using the ABAQUS software, and the influences of boss shape and thickness of liner on the deformation and contact stress of rubber O-ring were analyzed. As a result, the shape and sizes of the metal boss and the liner were optimized and the connection structure between the liner and metal boss was determined. Based on the optimization, the effects of compression ratio, hydrogen pressure, backup ring and the temperature variation during the filling of composite overwrapped pressure vessel on the sealing performance of rubber O-ring were determined. The results of this work can provide guidance for the tightness analysis and lightweight design of composite overwrapped pressure vessels with plastic liners.