Sealing Performance of 70 MPa Type IV Hydrogen Storage Cylinders Based on Multifield Coupling

Abstract The reliability of sealing structures is critical to ensuring the safe operation of high-pressure hydrogen storage cylinders. To investigate the sealing performance of a 70 MPa hydrogen storage cylinder, tensile and compressive tests were conducted on fluororubber seals under high-temperature conditions to obtain their constitutive models. A thermo-mechanical coupled numerical simulation model of the sealing structure was established to analyze the influence of structural dimensions on sealing performance and to optimize the design. The effect of hydrogen-induced expansion on the sealing performance was also evaluated. Results indicate that both the chamfer of the seal groove and the clearance between mating surfaces affect rubber extrusion at the gap. Rounded corners at the groove bottom effectively mitigate stress concentration. An insufficient compression ratio fails to ensure sealing performance, while an excessive ratio increases the risk of strength failure. The maximum stress (i.e., the maximum Von Mises equivalent stress, used to characterize the comprehensive stress state under multi-axial loading), maximum shear stress, and maximum contact pressure of the seal ring all decrease with increasing cylinder temperature. Under high-temperature conditions, the maximum reduction in contact pressure at 70 MPa hydrogen pressure reaches 5.18%. Hydrogen-induced expansion causes additional deformation of the seal ring, influencing its sealing behavior. When hydrogen absorption is considered, the maximum stress, maximum shear stress, and maximum contact pressure all exceed those under nonabsorption conditions, with increases of 3.64%, 6.54%, and 3.69%, respectively, at 70 MPa. Although hydrogen-induced expansion can enhance sealing performance, the concomitant rise in shear and stress reduces the service life of the seal ring. These findings provide a theoretical basis for the design of sealing structures in high-pressure hydrogen storage cylinders.