A new insight into hydrogen leakage phenomena: Visibly observable patterns of hydrogen leakage

As hydrogen energy systems move toward miniaturization and modularization, the low-pressure, low-flow hydrogen leakage problem, which is becoming more frequent and significantly harder to detect, leading to the formation of flammable or explosive hydrogen-air mixtures, is a key challenge, constraining the widespread deployment of hydrogen technologies. The concentration distribution directly determines the extent and severity of flammable zones, but its spatiotemporal evolution, governed by the laminar-to-turbulent transition of the leakage jet, remains elusive. In this study, a visualization method is employed to observe hydrogen leakage, enabling the first clear depiction of the transition point’s behavior in low-pressure hydrogen jets. The transition point is found to exhibit a dual nature, with a relatively certain average position accompanied by distinct spatial fluctuations. A full-field concentration distribution of hydrogen leakage is constructed based on the spatial characteristics and fluctuation patterns of the transition point, enabling an accurate description of the spatiotemporal variation in hydrogen concentration fields. This work provides new insight and visual confirmation of hydrogen leakage behavior, offering essential support for the transition of hydrogen’s societal role—from a hazardous chemical to a safe and manageable energy carrier.