Studies on hydrogen leakage have mainly focused on the influences of location and geometrical configuration on the distribution of the hydrogen in various spaces. The present study developed a simplified model for the leakage diffusion of hydrogen in an enclosed cuboid space with two vents, at the top and at the bottom, respectively. The effect of different leakage positions on the diffusion of the hydrogen was analyzed. The results showed that when hydrogen diffused vertically from the bottom to the top of the space, the farther the leakage position was from the vent on the side wall, the more hydrogen accumulated. When the hydrogen leaked in the vertical direction from the floor, the distance between the leakage position and the bottom vent had little effect on the horizontal diffusion speed of the hydrogen at the top of the space. The diffusion speed for the leakage in the horizontal direction was faster than that in the vertical direction. When the hydrogen leaked in the horizontal direction from the side wall, the height of the leakage had little effect on the horizontal diffusion speed of the hydrogen at the top of the space. Stratification occurred for models set up in the present study whenever the envelope of 1% mole fraction, or 4% mole fraction, of hydrogen extended to the whole ceiling.

Hydrogen fuel cell vehicles (HFCVs) represent an important breakthrough in the hydrogen energy industry. The safe utilization of hydrogen is critical for the sustainable and healthy development of hydrogen fuel cell vehicles. In this study, risk factors and preventive measures are proposed for on-board hydrogen systems during the process of transportation, storage, and use of fuel cell vehicles. The relevant hydrogen safety standards in China are also analyzed, and suggestions involving four safety strategies and three safety standards are proposed.

This study investigates the feasibility of utilizing a flow-induced vibration actuator as a potential energy source using piezoelectric energy harvesting. The focus is on exploring the behavior of piezo films configured as cantilever beams subjected to flow-induced vibration, which can be induced with fluid or wind streams. The primary objective is to maximize the harvested energy from the vibrating structure. This paper develops theoretical models to analyze the resonant frequencies and energy-harvesting potential of the piezo films in the context of flow-induced vibration. Experimental validations are conducted to verify the theoretical predictions. The findings indicate that higher operating frequencies in the second mode offer improved energy harvesting efficiency compared with lower modes. With the strategic adjustment of resonant frequencies using attached masses on individual piezo films, the harvestable energy output of a single film can be significantly increased from less than 1 μW to approximately 18 μW. However, the phase differences among individual piezo films can impact frequency measurements, necessitating careful fine-tuning of the physical conditions of individual components. To optimize energy harvesting, this study emphasizes the importance of implementing efficient charging mechanisms. By identifying suitable environmental vibration sources, the required charging duration for a synthesized energy harvesting array can be reduced by 25% as well. Despite certain challenges, such as phase deviations and turbulence, this study demonstrates the promising potential of flow-induced vibration resonators as sustainable energy sources. This work lays the foundation for further advancements in energy harvesting technology, offering environmentally friendly and renewable energy solutions.