Numerical Simulation Study Of Leakage And Diffusion Of Liquid Hydrogen Supply System For Fuel Cell Vehicles

As an efficient and environmental energy carrier,hydrogen has attracted wide attention.With the development and progress of technology,hydrogen fuel cell vehicles have begun to enter the public view.Because hydrogen has the characteristics of wider ignition range,lower ignition energy,easier leakage,higher flame propagation speed and easier explosion,it may cause more serious safety problems after leakage.Therefore,it is an urgent and important subject to study the safety of hydrogen in service.In this paper,the leakage and diffusion process of liquid hydrogen after vehicle-mounted liquid hydrogen supply system leakage is studied,and the diffusion trend of liquid hydrogen and hydrogen after accidental leakage of hydrogen fuel cell vehicle is predicted.The research on leakage of on-board liquid hydrogen supply system has certain engineering application value for the use of hydrogen fuel cell vehicle technology and has important academic value for the research subject of hydrogen safety.The research object of this paper is the hydrogen fuel cell semi-trailer traction truck.The on-board liquid hydrogen supply system and body structure are analyzed,the multiphase flow model and turbulence model used in the simulation process are selected,the mathematical model of liquid hydrogen leakage and diffusion process is established,and the hydrogen fuel cell vehicle and different spatial models are established.The process and influencing factors of liquid hydrogen leakage and diffusion in vehicle-mounted liquid hydrogen supply system in open space were studied.The physical process of phase transition after liquid hydrogen leakage in open space is described and safety analysis is carried out for different leaking locations.The results show that when the direction of hydrogen leakage points to the rear of the vehicle,the dangerous area is mainly distributed behind the leaking vehicle.When the direction of leakage points to the head,a large range of combustible hydrogen cloud is generated near the cab,endangering the driver’s personal safety.In this paper,according to the limit of combustible hydrogen concentration as a reference,the dangerous distance after liquid hydrogen leakage is proposed.In order to study the influence of environmental factors on liquid hydrogen leakage and diffusion process,the process of liquid hydrogen leakage and diffusion under different wind directions,different wind speeds and different environmental temperatures was analyzed.The results show that the environmental wind has a significant influence on the process of liquid hydrogen leakage and diffusion.When the wind direction is consistent with the direction of leakage,it is beneficial to the diffusion of liquid hydrogen and hydrogen.The diffusion process and influencing factors of liquid hydrogen leakage in vehiclemounted liquid hydrogen supply system in tunnel space are analyzed.The process of liquid hydrogen leakage while driving in tunnels is simulated numerically and the influence of different leak locations on the diffusion process of liquid hydrogen leakage is analyzed.The results show that when the leak direction is opposite to the driving direction,the dangerous area is distributed behind the leaking vehicle.When the leak direction is the same as the driving direction,the flammable hydrogen cloud surrounds the body of the leaking vehicle.Combustible hydrogen clouds and cold zones form at the left door of the cab.When the vehicle is stationary in the tunnel and the leaking direction of liquid hydrogen points to the rear of the vehicle,the combustible hydrogen cloud in the tunnel distributes in the rear space of the leaking vehicle and accumulates at the top of the tunnel.When the leaking direction points to the vehicle head,a low temperature area will appear near the cab,and the accumulation of combustible hydrogen cloud will occur at the top space of the tunnel above the vehicle body.As the leaking time increases,The distribution of combustible hydrogen clouds is also expanding to both sides of the tunnel.When medium-sized passenger cars become obstacles in the tunnel,hydrogen will accumulate near the passenger cars and diffuse to other vehicles.At this time,it is necessary to open the tunnel ventilation device in time to promote the diffusion of hydrogen and avoid danger.