Release of high-pressure hydrogen into the air

Hydrogen as an energy carrier is one of the available alternatives to fossil fuels for decarbonizing the global energy system. Regarding to the very low volumetric energy content of gaseous hydrogen, for practical and economical storage, it has to be either pressurized at ambient temperature (Compressed Gaseous Hydrogen – CGH2) or liquefied at cryogenic temperatures (Liquid Hydrogen – LH2). On the subject of CGH2, using high-pressure hydrogen reservoirs from 250 ???????????? up to 70 ???????????? is conventional; and among these, utilizing 70 − ???????????? hydrogen reservoirs as fuel cells in transportation or as storage tanks, for instance, in local hydrogen refueling stations is the common approach. Having a leakage in such a high-pressure reservoir will form shock waves in front of the released hydrogen causing a temperature rise which may be intensified by existing obstacles in that environment; the presence of these obstacles and confinement may also enhance the hydrogen-air mixing. Because of the wide flammability range of hydrogen, this might lead to its spontaneous ignition if these high-temperature, well-mixed regions could last as long as the hydrogen-air induction time. In this thesis, it is tried to numerically investigate the possibility of this kind of scenario. In order to simulate a 70 − ???????????? hydrogen release into the air (treated as a dual pseudo species), in the initial attempts, the USN-FLIC code was tried, but because the results were not convincing, it was decided to use the OpenFOAM software as an alternative. Considering the restrictions of the solvers of OpenFOAM (v.7), combinations of solvers along with new thermophysical models are used to be able to overcome the so-called Riemann problem of shock waves in a non-ideal, multi-component, non-reacting mixture. Furthermore, to validate this method, the shock-tube problem is solved and the results are compared with available data of similar cases. According to the results, potentially hazardous regions are formed in the domain that are mostly related to the interaction of the reflected, rarefaction, and normal shock waves inside the flow field. Although there are some inconsistencies between the results of the simulations in estimating the flow properties, generally, the risk of hydrogen auto-ignition in these regions is quite high. But for having a better understanding about the effects of distances between wall boundaries, it is shown that the simulation should be done in threedimensions