Study On Leakage Hazard Of Fuel Cell Locomotive Liquid Hydrogen Storage System

In order to reduce carbon emissions and solve the problem of frequent natural disasters caused by global warming,China put forward the double carbon peaking and carbon neutrality goals at the 75th United Nations General Assembly.One way to achieve this goal is to use zero-carbon energy and reduce carbon emissions.Hydrogen（H₂）is gaining increasing attention as a zero-carbon energy carrier.Compared with high-pressure H₂,low temperature liquid hydrogen（LH₂）has the advantage of higher energy density.High density LH₂significantly improves storage,transportation and distribution efficiency.Hydrogen-powered locomotives would likely be fully promoted if LH₂is used as fuel.However,LH₂has the characteristics of ultra-low temperature（storage temperature 20.324 K）,easy vaporization,combustion,explosion,etc.,with a wide range of explosion limits,it is easy to cause danger under certain conditions.Therefore,the extensive application of LH₂requires in-depth analysis of its safety.At present,the accident evolution and risk assessment methods of LH₂release in different application sites need to be further studied.In this thesis,the coupled integral model and computational fluid dynamics（CFD）numerical simulation technique are used to systematically evaluate the source term variation and diffusion scenarios.The law of LH₂release in the fuel locomotive in different application scenarios（completely enclosed area workshop,multi-part enclosed area tunnel and semi-enclosed area station）under the same conditions is studied,which is extremely important for the later application of relevant safety emergency and measures.Firstly,the LH₂in the locomotive hydrogen storage tank is released to form a liquid pool on the ground.The integral model is used to accurately predict the source information and obtain the change rule of the leakage source.The user-defined（UDF）boundary conditions of H₂diffusion are developed to serve as the basis for the later diffusion simulation.The effectiveness of the integral model is verified by comparison with experiments.Secondly,the H₂diffusion behavior in three different application scenarios was studied by CFD numerical simulation.Considering the influence of wind field,model and other factors,the diffusion behavior of H₂was revealed through the combination of theory and simulation,the variation law of H₂concentration distribution over time was studied,the cloud shape,duration and danger range during the growth and contraction of hydrogen cloud under different environments were analyzed.The accuracy of the CFD model was verified by comparing with the experiment.Because H₂clouds effectively mix with air to form"Gaussian clouds",they tend to burn under certain conditions.Finally,the non-premixed combustion model and DO radiation model are used to conduct numerical simulation of H₂combustion combined with the reaction mechanism of H₂19 step combustion.The influence of multiple factors on the flame combustion law is also considered.The results show that the total time of the accidental release of 6 kg LH₂from the gas storage tank to the ground is 2.8 s and the maximum radius of the LH₂pool is1.2 m.The fully diffusion time of LH₂from H₂pool into the environment is 4.7 s.Based on the different H₂diffusion behaviors in different flow fields,the relationship between ventilation conditions and diffusion is considered.It takes 140 s for a 150-m short tunnel and 100 s for a 1 600-m long tunnel to fully diffuse H₂to the outside of the building.It takes 210 s for the station and longer for the factory.Fully diffused H₂combustion causes high temperature in the building appliances,locomotives and the surrounding environment.Dangerous areas exist around the locomotives and on the top of the building.This study deepens the understanding of researchers on the release,diffusion and combustion phenomena of LH₂in different application scenarios.The research results are expected to guide the safety of LH₂storage and transportation system and promote the large-scale application of H₂as an alternative energy source.