Numerical Investigation of Leakage Height and Protective Wall Effects on High-Pressure Hydrogen Dispersion and Jet Flames

High-pressure hydrogen leakage can induce severe fire hazards and destructive overpressures. While protective walls are commonly employed as standard safety measures, most existing studies focus on either the effect of leakage height or the presence of protective walls individually. Systematic investigations on their combined influence remain limited, In contrast, the present study conducts a comprehensive analysis that explicitly considers the interaction between leakage height and the presence of protective walls, evaluating its subsequent effects on hydrogen dispersion, jet flame behavior and overpressure. A comprehensive investigation of this interaction is crucial for optimizing protective wall design and enhancing the safety of hydrogen facilities. Employing the Birch 1987 notional nozzle model, three-dimensional numerical simulations were performed to investigate the dispersion, jet flame morphology, and overpressure distribution of 35 MPa hydrogen leaks at varying heights. The results indicate that hydrogen jet flame reaches a peak temperature of approximately 2650 K within 1.1~1.2 m from the leakage orifice. Wall confinement promotes a broader accumulation of combustible gas clouds near the ground, thereby increasing the risk of delayed ignition. Low-altitude leaks generate near-ground jet flames, which bring the flame closer to the equipment and surrounding surface, potentially increasing local thermal exposure. Deterministic parametric analyses indicate that the installation of protective walls mitigates far-field overpressure by 76.5~89.5%. Crucially, as the leakage height approaches the wall height, the wall’s shielding effectiveness diminishes due to shock wave diffraction. These findings highlight that protective wall design must account for vertical leakage positioning to prevent localized safety failures.