Dilution of hydrogen vapor cloud formed by the liquid hydrogen spills under different spill amounts, spill rates and liquid mass fractions at the exit were numerically investigated. Three dimensional CFD simulations were performed with ANSYS FLUENT using Realizable k-ε turbulence model. Time variation of the maximum hydrogen concentration (t = 0 s at the end of the spill) is most sensitive to the liquid mass fraction, followed by the spill rate, and finally the spill amount. The dilution process is nearly unaffected by the spill amount. With the increment of spill rates, the dilution speed first decreases and then remains approximately unchanged, which can be attributed to the combined effects of the gaseous hydrogen generated per unit time and the source disturbances generated by the spill and evaporation process. In addition, the dilution accelerates with the increment of liquid mass fraction at the exit. The turbulence induced by the evaporation of liquid hydrogen promotes the mixing and dilution processes, while the temperature drop in the ground and the ambient air due to liquid evaporation has little influence on the overall dilution of the vapor cloud. The durations of detonation and flammability when the liquid mass fraction is 0% are 1.65 and 1.88 times of those when liquid mass fraction is 100%, respectively.

数值研究了在不同的溢流量，溢流速率和出口处的液体质量分数下，液态氢溢流形成的氢蒸气云的稀释度。使用可实现的k - ε湍流模型，利用ANSYS FLUENT进行了三维CFD仿真。最大氢浓度的时间变化（t 溢出结束时= 0 s）对液体质量分数最敏感，其次是溢出速率，最后是溢出量。稀释过程几乎不受溢出量的影响。随着溢流速率的增加，稀释速度首先降低，然后保持大致不变，这可以归因于单位时间内产生的气态氢与溢流和蒸发过程产生的源干扰的综合作用。另外，随着出口处液体质量分数的增加，稀释加速。液态氢蒸发引起的湍流促进了混合和稀释过程，而由于液态蒸发而导致的地面和周围空气中的温度下降对蒸气云的总体稀释几乎没有影响。