Hydrogen Permeation Behavior of the Liner of Type IV Hydrogen Storage Cylinders Under Different Pressures

Type IV hydrogen storage cylinders are increasingly recognized as a prime solution for hydrogen storage in hydrogen fuel cell vehicles (HFCVs). Compared with other cylinders, this type of hydrogen storage cylinder is comprised of a polymer inner liner wrapped with carbon fiber composite material, offering advantages such as light weight, low cost, and fatigue resistance. Nonetheless, the polymer liner, typically fabricated from high-density polyethylene (HDPE) or polyamide (PA), exhibits notable hydrogen permeability, posing an increased risk of hydrogen permeation leakage. This constitutes a primary factor influencing the safety of its operational application in hydrogen storage contexts. In this paper, experiments on hydrogen permeation were executed under varied pressure conditions on two representative liner materials (HDPE and PA6) of Type IV hydrogen storage cylinders, aiming to scrutinize the relationship between hydrogen permeation performance of different liner materials and pressure, and to encapsulate the differences and consistencies between materials. Based on the test results, a finite element simulation was conducted on the hydrogen permeation behavior of the cylinder liner to probe into the effects of various liner high-pressure side pressures and liner thicknesses on the hydrogen permeation behavior, culminating in the formulation of the hydrogen permeation law of Type IV hydrogen storage cylinders. The outcomes of this study and the elucidated hydrogen permeation laws provide a fundamental reference for further research and design endeavors aimed at enhancing subsequent Type IV cylinder liners.