LNG储罐内翻滚现象临界判据的数值模拟

Numerical simulation on critical criteria of rollover phenomenon in LNG tank

利用Fluent软件分别对160 000、30 000和5 000立方米LNG储罐内的翻滚现象进行了数值模拟,并将翻滚过程中的密度变化幅值与翻滚时间的比值定义为翻滚系数来表征翻滚的剧烈程度,得到了不同罐容LNG储罐内的翻滚现象随初始密度差的变化规律。研究结果发现:不同罐容的LNG储罐均存在一个翻滚的临界密度差,当初始密度差小于临界密度差时,储罐内相邻两层LNG的混合过程较为平稳;当储罐中相邻两层LNG的密度差大于临界密度差时,翻滚有明显的加速趋势。计算结果表明160 000立方米储罐的临界密度差区间为0.78—0.82千克每立方米,30 000和5 000立方米储罐的临界密度差区间为4—5千克每立方米。这些临界密度差区间值可作为不同罐容储罐的分层与翻滚判据,用于指导储罐设计和实际工程操作。

The rollover phenomenon in LNG tank with 160 000,30 000 and 5 000 cubic meters was simulated by Fluent CFD software respectively. The ratio of density change amplitude and the rollover time during the rollover progress was defined as rollover coefficient, which was used to describe the intensity of rollover in LNG tank. The effects of the initial density difference of the adjacent LNG layers in LNG tank on the rollover were presented. It is found that a critical density difference exists with every LNG tank. When the density difference of adjacent LNG layers in tank is smaller than cirtical value, the mixing progress of the adjacent LNG layer is smoothly. However, when the density difference of adjacent LNG layers in tank is larger than cirtical value, the rollover of adjacent LNG layers becomes more violent. In addition, the calculated results show that the range of the cirtical density difference of 160 000 cubic meters LNG tank is between 0.78 - 0.82 kg per cubic meters, while the range of critical difference values of 30 000 and 5 000 cubic meters LNG tank are both in the range of 4 -5 kg per cubic meters.