Study On The Influence Of Longitudinal Ventilation On Hydrogen Leakage Diffusion And Fire Characteristics In The Tunnel

As the key route and control node on the traffic road,it is of great significance to use longitudinal ventilation to prevent and control the harm of tunnel vehicle fire.With the continuous consumption of oil resources and the increasing maturity of hydrogen energy technology,hydrogen-fueled vehicles entering tunnels will become the norm which increases the risk of high-pressure hydrogen leakage accidents in tunnels.At the same time,hydrogenfueled vehicles have completely different power sources from ordinary vehicles and the highpressure hydrogen leakage accidents are diverse.It is unclear whether the existing longitudinal ventilation velocity can effectively solve the safety problem from high-pressure hydrogen leakage of hydrogen fueled vehicles in the tunnel.Therefore,in this thesis,a 100 m long square tunnel is selected as the research object,and Fluent software is used to numerically simulate the fire and hydrogen leakage diffusion process of hydrogen fueled vehicles in the tunnel to study the influence of longitudinal ventilation on the diffusion and fire characteristics of high-pressure hydrogen jet in the tunnel.Firstly,the influence of longitudinal ventilation on the fire characteristics of highpressure hydrogen jet fire in tunnel is discussed.The main conclusions are as follows:(1)Affected by the longitudinal ventilation velocity and heat release rate,there are three typical bending states of the non impact hydrogen jet flame in the tunnel,and the inertia force of hydrogen jet is the main influencing factor.(2)Longitudinal ventilation could effectively control the diffusion and accumulation of residual hydrogen in tunnel high-pressure hydrogen jet fire.(3)There is a critical ventilation velocity that effectively hinders the return of hot smoke from tunnel hydrogen jet fire,and increases with the heat release rate,and finally tends to be stable.The critical ventilation velocity corresponding to the leakage shape with smaller leakage area and aspect ratio tending to 1:1 would be larger.Then,comparing the differences between the characteristics a hydrogen-fueled vehicle fire and a ordinary vehicle fire in the tunnel with and without longitudinal ventilation,the main conclusions are as follows:(1)The high-temperature area of the hydrogen-fueled vehicle fire in the tunnel mainly exists on the hydrogen jet flame,and exceeds 2300 K,and the hot smoke propagation velocity was faster,while the high-temperature area of the ordinary vehicle fire in the tunnel is concentrated near the ceiling of the burning vehicle,and the hot smoke stratification is narrower and more obvious.(2)The traditional prediction formula of critical ventilation velocity for tunnel fires is no longer applicable to tunnel hydrogen-fueled vehicles fires.In the working conditions studied in this thesis,the critical ventilation velocity of the tunnel ordinary vehicle fire is 2.0 m/s and that of the tunnel hydrogen-fueled vehicles fire is6.0 m/s.Under the critical ventilation velocity,the escape environment of the hydrogen-fueled vehicle fire does not meet the safety control standard,and there is no obvious improvement after continuing to increase the longitudinal ventilation velocity,so other fire-fighting measures should be supplemented.Finally,based on the overpressure hazard classification of combustible hydrogen cloud explosion,the influence of longitudinal ventilation on the diffusion hazard of high-pressure hydrogen jet in the tunnel was analyzed.The main conclusions are as follows:(1)The possibility and hazard degree of explosion caused by high-pressure hydrogen jet diffusion in the tunnel gradually decrease with the increase of longitudinal ventilation velocity,but can not be completely eliminated.(2)The recommended ventilation velocity for preventing and controling the high-pressure hydrogen leakage accident of a hydrogen-fueled vehicle in the tunnel is 8.0 m/s.Under the recommended ventilation velocity,the hazards of fire and highpressure hydrogen jet diffusion from a hydrogen fuel vehicle in the tunnel could be well controlled.