Abstract: It is important to investigate the oil vapor leakage and emission from external floating-roof tanks for the loss evaluation and potential danger control. The oil vapor leakage from the annular space between the rim and the tank shell is one of the major sources for the evaporation loss. The vapor leakages from the rim of the single-tray floating roof are simulated numerically using FLUENT and measured experimentally. The effects of tank diameter, roof level and wind speed v on the pressure distribution above the roof surface are investigated. The results are as follows. (1) Numerical results agree with the experimental data. (2) When the ratio of the distance h between floating-roof and tank top to the tank diameter D, h/D, is greater than 1/4, the vapor is more likely to leak from the two opposite sides of the annular space perpendicular to wind direction and the side of the annular space in the upwind. (3) Tank diameter has little effect on the pressure distribution above the roof surface, while h/D and v affect the pressure distribution. Larger h/D lowers the wind pressure of roof center, and smaller h/D lowers the upwind pressure above the roof. When h/D varies from 1/20 to 1/2, the upwind and downwind pressures are negative, and with the decrease of h/D, the differential pressure above the roof increases. API loss formula for external floating-roof tank is recommended to consider the effect of ratio h/D to improve the accuracy in loss evaluation.

Key words: external floating-roof tank, oil vapor leakage, numerical simulation, wind pressure distribution, evaporation, diffusion

摘要： 外浮顶罐油气泄漏扩散规律的研究对其油品蒸发损耗的评估及潜在危险的控制都具有重要意义。外浮顶罐油品蒸发损耗的一个主要途径是油气从浮盘边圈密封处泄漏。为此，对单浮盘环形密封圈的油气泄漏规律进行了数值模拟与实验对比，同时考察了罐直径、浮盘位置和风速大小对浮盘上风压分布的影响。研究结果表明：（1）油气泄漏的模拟结果与实验相吻合。（2）浮盘距罐顶的距离h与罐直径D的比值大于1/4时，垂直风向的浮盘两侧和上风侧最易泄漏。（3）浮盘上的风压分布规律受罐直径影响不大，但浮盘上方空间的高径比h/D和风速大小对其有较大影响。h/D较大时，浮盘中部的风压较低；h/D较小时，浮盘上风侧的风压较低；h/D在1/20～1/2范围内时，浮盘上下风侧风压均为负压；浮盘上的压差随着h/D比值的减小而增大。最后建议API外浮顶罐油气蒸发损耗评估公式中考虑h/D比值的影响。

关键词: 外浮顶罐, 油气泄漏, 数值模拟, 风压分布, 蒸发, 扩散