Release of high-pressure hydrogen into the air
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Hydrogen as an energy carrier is one of the available alternatives to fossil fuels fordecarbonizing the global energy system. Regarding to the very low volumetric energycontent of gaseous hydrogen, for practical and economical storage, it has to be eitherpressurized at ambient temperature (Compressed Gaseous Hydrogen – CGH2) orliquefied 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 transportationor as storage tanks, for instance, in local hydrogen refueling stations is the commonapproach.Having a leakage in such a high-pressure reservoir will form shock waves in front of thereleased hydrogen causing a temperature rise which may be intensified by existingobstacles in that environment; the presence of these obstacles and confinement may alsoenhance 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 regionscould last as long as the hydrogen-air induction time. In this thesis, it is tried tonumerically investigate the possibility of this kind of scenario. In order to simulate a 70 − ???????????? hydrogen release into the air (treated as a dual pseudospecies), in the initial attempts, the USN-FLIC code was tried, but because the resultswere 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 solversalong with new thermophysical models are used to be able to overcome the so-calledRiemann 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 arecompared with available data of similar cases.According to the results, potentially hazardous regions are formed in the domain that aremostly related to the interaction of the reflected, rarefaction, and normal shock wavesinside the flow field. Although there are some inconsistencies between the results of thesimulations in estimating the flow properties, generally, the risk of hydrogen auto-ignitionin these regions is quite high. But for having a better understanding about the effects ofdistances between wall boundaries, it is shown that the simulation should be done in threedimensions.