| Hydrogen energy is a kind of clean and efficient energy,but it is easy to produce explosion danger.Hydrogen is easy to accumulate on the top of the application scene and is not easily detected.Its combustion concentration range is large,ignition energy is small,and it is easy to ignite and cause an explosion accident.Liquid hydrogen is often used as high energy and ultralow temperature liquid fuel in the engine field.Liquid hydrogen leakage is a common cause of low-temperature hydrogen production.When leakage occurs in liquid hydrogen production workshops,storage tanks,transportation pipelines and other places,the potential fire accident risk is very high.In this paper,on the basis of liquid hydrogen leakage accident,the actual problem is simplified,the performance of the stable phase of low-temperature hydrogen jet combustion in different scenes is studied,and the law of the characteristics of jet fire with the change of leakage source parameters is analyzed.In this paper,numerical simulation was adopted and the CFD software FLUENT was used to simulate the steady-state jet fire of low-temperature hydrogen,to study the influence of leakage source parameters on the characteristics of low-temperature hydrogen jet fire in different scenes.(1)Change the leakage temperature to explore the change process of the characteristics of free space vertical hydrogen jet fire.The simulation results show that the temperature distribution in the calculated domain is affected by the change of the total volume of air in the range of 40 K to 240 K,and determine the effect of the change of positive buoyancy in this process.(2)In the scene of top opening structure,the parameters of leakage source were simulated by changing.The change of jet hole diameter determined the effect of bottom solid boundary on air entrapping in the whole process.The increase of jet velocity promoted the whole flame entrainment process.The influence of the leakage temperature on the flame morphology in this scene is strengthened compared with that of the free vertical jet.(3)In the scene of ceiling jet structure,when the diameter of jet hole is greater than 1mm,the diameter of jet hole affects the radial expansion of flame;the increase of jet velocity had little influence on the flame morphology in the ascending stage,but the thickness and temperature of the hot fluid layer at the top increased.The change in the leakage temperature causes the flame to move up significantly near the top due to the change in buoyancy.(4)In the scene of the semi-sealed space structure,due to the limitation of structure size,the process of flame escape from the stable vent and air entrapment by reflux is intensified as the diameter of jet hole increases;the increase of jet velocity affects the temperature distribution in front of jet axis.The leakage temperature changes the ratio of flame morphology in axial direction to height by affecting the buoyancy determined by density difference.(5)The transverse comparison of simulation results of three spatial geometry structures shows that the influence of jet velocity variation mainly concentrates in the area with a certain distance from the jet hole.The effect of jet hole diameter variation is determined by the influence of space constraint on air entrainment.The influence of leakage temperature change is reflected in the buoyancy and mass flow rate change caused by density difference. |
PDF Full Text Request