Numerical study on the flow characteristics of pressurized hydrogen leaking into the confined space through different shaped orifices

Abstract

The safety concerns associated with accidental hydrogen leakage remain a challenge. Although numerous studies have been carried out on the flow behavior of compressed hydrogen leaking in unconfined spaces, the knowledge of the flow characteristics when it leaks into confined spaces through irregular holes is lacking. Therefore, this study uses the three-dimensional Large-Eddy Simulation (LES) model to simulate high-pressure hydrogen leakage in a confined space. Effects of the leakage hole shape on the flow features are investigated, including the circle, square, and triangle with the same equivalent area. Results indicate that the Mach disk shows circular, hexagonal, and octagonal shapes depending on the leakage port geometry. When the leak hole shape is square and triangular, the distribution of pressure waves deflects 45° and 60° near the hole, respectively. It means that non-circular holes affect the pressure distribution after hydrogen leakage. In addition, changing the shape of the leak hole results in a difference in hydrogen jet morphology. Compared to circular jets, in square and triangular jets, the jet boundary narrows along the diagonal plane and the gravity plane, respectively. It indicates that leakage ports with sharp corners can complicate the flow. Therefore, it is essential to consider the influence of the leakage port shape when performing a risk assessment of high-pressure hydrogen leaks in confined spaces.