车库内氢气扩散和分布状态的数值模拟

为研究车库内氢气连续性泄漏的浓度分布和聚集状态,采用ICEM-CFD软件建模,利用Fluent软件对氢气连续性泄漏过程进行了模拟。通过分析监测点氢气物质的量分数、氢气分布和可燃性区域体积分数,研究了横梁及其间距(L)、自然通风、通风口面积(A)对车库内氢气的扩散和分布状态的影响。结果表明:在密闭状态下,无横梁时可燃性区域最小,L=3 m时可燃性区域最大;当A=0.5 m2时,在自然通风的作用下,车库底部氢气物质的量分数明显下降,但车库中部和上部氢气物质的量分数与密闭时相近;当A=1 m2时,虽然初始阶段氢气物质的量分数上升很快,但很快就趋于稳定,监测点氢气物质的量分数均在爆炸下限以下,此时自然通风能够消除氢气爆炸的风险。

Numerical simulation for the hydrogen dispersion and distribution behaviors in the garage context

This paper is aimed at simulating the continuous hydrogen leakage process and making exploration of the hydrogen concentration distribution and accumulation behaviors.To achieve the above purpose,we have established a physical model for garage application by ICEM-CFD and simulated the process of continuous hydrogen leakage in the species transportation model of the fluent,by meshing the computational domain into the nonhomogeneous hexahedrons.And,next,local grid refinement has been employed for the leakage point,ventilation opening,and crossbeams.The effects of crossbeams,distance between the crossbeams (L),natural ventilation and vent area (A) on hydrogen dispersion and concentration distribution behaviors have been studied by analyzing the hydrogen concentration of monitors,hydrogen distribution,and the volumetric ratio of the flammable region.The numerical results indicate that there exist three concentration layers from the top to the bottom of the garage.Moreover,the top layer has had the maximum hydrogen concentration,whereas the bottom layer has gained the minimum hydrogen concentration.Under the tightly shut-up condition,the crossbeam may have effects on the hydrogen dispersion and concentration distribution behavior.For example,when L =6 m,the dispersion velocity of hydrogen to the two sides of the crossbeam tends to be accelerated after impinging the crossbeam.But little effect has been found by the crossbeam on the hydrogen distribution behaviors in the middle and lower parts of the garage.Besides,when L =3 m,the hydrogen dispersion has been found nearly blocked by the bilateral crossbeams to the lateral sides.What's more,the bilateral crossbeams tend to have downward acceleration effects on the hydrogen.On the contrary,the flammable volume can be reduced to the minimum value where and when there is no crossbeam.Therefore,the crossbeam can also have negative effects on the hydrogen dispersion.Besides,it can be assumed that the best approach to the garage building is perhaps to have no crossbeams at all.We have also found that hydrogen accumulation can be mitigated by the natural ventilation.For instance,when A =0.5 m2,the hydrogen concentration at the lower part tends to be reduced noticeably by the natural ventilation.However,the hydrogen concentration in the middle and the upper part can be found somewhat affected by the natural ventilation.And,in turn,if A =1 m2,the hydrogen concentration would be reduced sharply and lowered than the lowest flammable limit and should even be ignored,so that the risk of hydrogen explosion can be got relieved of by the natural ventilation.Thus,it can be seen that the results of the present paper can be taken as a guide for the garage design for hydrogen vehicles to be put in so as to get rid of hydrogen leakage accidents.