Study On Cryo-Compressed Hydrogen Releases And Explosions

Hydrogen is considered a good alternative energy source for the transportation sector because of its advantages of easy production,cleanliness,and high energy density per unit mass.Many industrial countries are strongly prompting hydrogen energy research and increasingly investing in hydrogen energy infrastructure.In the future,hydrogen energy will be widely used in the fields of transportation and energy storage.Hydrogen storage and transportation are essential parts of the hydrogen industry chain.As a very promising way of hydrogen storage,cryo-compressed hydrogen(CcH2)storage has attracted more and more attention.However,hydrogen leakage accidents pose great safety concerns to the public.In-depth and systematic hydrogen safety studies are required to ensure the safety use of hydrogen.Existing hydrogen safety studies mainly focus on the room temperature high-pressure hydrogen,with only a few studies on the CcH2.There are few accurate experimental data,and the existing data has plenty of numerical noise,which cannot be used directly.There is a lack of research on leakages and explosions of CcH2 refueling stations.Therefore,this paper presents a series of studies focusing on the CcH2,including experimental data processing,numerical model validation,and leakage and explosion modeling of a CcH2 refueling station.This paper first introduces the experimental system and related test technologies of the CcH2 jet experiment.Firstly,a three-stage cooling method using liquid nitrogen,cryogenic helium,and liquid helium for hydrogen liquefaction is described.Secondly,the principle of laser Raman scattering measurement and the design of the test system is introduced.Thirdly,the calculation method of the CcH2 properties based on the Helmholtz energy function is introduced.The measured CcH2 jet concentrations and temperatures had much numerical noise because of the background noise of the test environment and the experimental equipment itself and the scattering caused by the condensed air components.This paper developed an image denoising algorithm based on the far-field data features and the wavelet decomposition method to denoise the measured CcH2 concentrations and temperatures.The data shows that the jet temperature increases along the jet centerline.The centerline concentration increases with the jet pressure.The radial distribution of jet parameters conforms to the Gaussian distribution.The concentration and temperature data show the same similarity as the room temperature hydrogen if properly normalized.The concentration and temperature fields of CcH2 jets were calculated using FLACS for four conditions.The results show that the predictions agree well with the experimental data,which demonstrates that the numerical models are suitable for modeling the CcH2 jets.An actual size CcH2 refueling station was modeled.The consequences of hydrogen leakage and explosion accidents were studied for a pipeline rupture under the cryogenic storage tank.Some protective wall configurations were studied to show that the protective wall can effectively reduce the damage of high-temperature and overpressure caused by the explosion and delay the time of explosion shock wave reaching a given location.The protective wall with a proper height and distance from the leaking tank can effectively reduce the risks.For a given wall height,the farther the wall is from the leaking tank,the worse the protection effect is.For a given distance,increasing the height of the wall can only reduce the high-temperature damage behind the wall,but cannot effectively reduce the overpressure damage.Therefore,both factors should be considered to find a height with the best protection effect.The present study will help to enrich the content of hydrogen safety research,fill the gaps in cryogenic hydrogen leakage and diffusion studies,and provide scientific bases for developing and updating the corresponding safety codes and standards.