不同围堰下液氢泄放过程可燃区域对称偏移与分布研究

Study of Symmetry Shift and Distribution of Flammable Regions at the Release Process of Liquid Hydrogen under Different Fences

为研究围堰对液氢泄漏扩散过程中可燃区域对称偏移的影响,根据NASA大型液氢泄放实验建立了三维瞬态CFD模型,对比分析了无围堰、下风向半围堰、全围堰下的可燃区域分布和对称偏移规律。计算结果表明,可燃区域对称偏移的原因来自氢气云团外侧对沿途空气的卷吸。无围堰时可燃区域形成分叉状结构最早,半围堰和全围堰下可燃区域在分叉状结构之间形成较小的羽状结构。不论何种围堰类型,可燃区域体积在液氢泄放停止后均继续上升12 s至峰值约30000 m^(3)。在第80 s时无围堰和半围堰情况下可燃区域体积均已降低至0,而全围堰下由于上风向的半围堰内部存在涡流,仍残存体积为4.6 m^(3)的可燃区域,该隐患在实际的氢能应用场景下需要引起重视。

To study the influence of fences on the symmetric shift of the flammable region at a leakage and diffusion process of liquid hydrogen,a 3D transient CFD model was established based on the NASA large-scale liquid hydrogen release experiments,and the distribution of the flammable region and the symmetric shift law without fences,with a half fence in the downwind direction,and with a full fence were comparatively analyzed.The results show that the reason for the symmetric shift of the flammable region comes from the entrainment of the hydrogen cloud to the air along the path.The flammable regions form bifurcated structures the earliest when there is no fence,under the half fence and no fence conditions,small plumes form between the bifurcated structures.Regardless of the fence type,the volume of the flammable region continues to rise for 12 s after terminating the liquid hydrogen release to the maximum value of about 30 000 m^(3).The volume of flammable region in the case of no fence and half fence has been reduced to 0 at the 80 s,while in the case of a complete fence,due to the vortex near the half fence in the upstream direction,there remains a residual flammable region of 4.6 m^(3),which is a potential problem that needs to be paid attention to in the actual hydrogen energy application scenarios.