Study On Hydrogen Leakage And Diffusion Of High Voltage Cabin Of Fuel Cell Bus

Hydrogen energy is considered to be the most promising new energy carrier in the21st century.As a typical example of the practical application of hydrogen energy,fuel cell vehicles are getting the attention of industry and academia.Among them,fuel cell buses have the most application prospects due to low technical threshold and stable market.Fuel cell buses use hydrogen as the main fuel,however,hydrogen is very easy to leak,and it is flammable and explosive,which brings potential safety risks to the use of fuel cell buses.The study on hydrogen leakage and diffusion of fuel cell bus can acquire the rule of hydrogen leakage and diffusion,find out the influencing factors of hydrogen leakage accident,which can provide scientific guidance for hydrogen safety design of fuel cell bus.The high-voltage cabin of fuel cell bus is a relatively closed space where fuel cell stacks,power batteries,and other components are arranged.If there is a hydrogen leak in the cabin,there may be accidents such as combustion or explosion,causing serious consequences.And for that,the theoretical analysis and numerical simulation methods are used to study the hydrogen leakage and diffusion process in the high-voltage cabin under different ventilation conditions.A numerical model of hydrogen leakage and diffusion was established using FLUENT software,and the numerical simulation results were compared with the experimental data of others to verify the accuracy of the calculation model.Based on this,relevant research was carried out.The main research contents are as follows:（1）The effects of natural ventilation area,ventilation grill layout,layout location,and leakage time on hydrogen leakage and diffusion in the high-voltage cabin were explored.The results show that using reasonable natural ventilation measures can ensure that hydrogen concentration in the cabin is within a safe range,but it takes a certain time.While the total ventilation area is 0.096 m~2,it took 25 seconds.While the total ventilation area is 0.128 m~2,it took 21 seconds.When arranging natural ventilation,it must be placed on top or higher place of the cabin.When the total ventilation area is constant,compared with increasing the area of a single ventilation grille,increasing the number of ventilation grille in the vertical direction can make the leaked hydrogen diffuse out of the cabin more quickly and effectively.（2）The effects of the location and velocity of forced ventilation on hydrogen leakage and diffusion in the high-voltage cabin were explored.The results show that compared with natural ventilation,the use of forced ventilation can significantly accelerate the discharge of leaked hydrogen in the cabin and greatly reduce the potential hydrogen safety risks in the high-voltage cabin.The bottom of the high-voltage cabin which nears the fuel cell stack is the best position to arrange it.When the vent size is200×200mm,the ventilation speed is 15m/s.（3）Consider the effects of natural ventilation and forced ventilation on the hydrogen leakage and diffusion of the high-voltage cabin of a fuel cell bus and the factors affecting hydrogen leakage accidents,From the four aspects:ventilation system design,hydrogen safety monitoring system,necessary safety functions of hydrogen system,structural design and system arrangement,the guideline for hydrogen safety design of fuel cell buses was expounded.The study in this thesis can provide scientific and systematic guidance for the hydrogen safety design of fuel cell buses,and can ensure the safety of hydrogen use of fuel cell buses to the maximum extent.