Abstract:

In the launch vehicle with liquid oxygen and kerosene as propellants, the load-bearing sandwich bulkhead tank can shorten the length and lengthen the aspect ratio of the whole vehicle. And it can eliminate the segment between the liquid oxygen (LO₂) tank and the kerosene tank, so as to reduce the structural mass. The bulkhead is required to have good thermal insulation properties while bearing the bi-directional pressure load of the LO₂ and kerosene tank. The unsteady temperature distribution of the tank, including the liquid nitrogen (LN₂) and the kerosene tank and the foam cored sandwich bulkhead, is analyzed with the CFD method when it is cooled down from room temperature to the moment the LN₂ filling is completed. The numerical model considers the effect of icing on the thermal boundary of the tank surface and the LN₂/vapor nitrogen (VN₂) phase change process due to heat leakage. The influence of whether the fork ring is wrapped or unwrapped PMI insulation material on the kerosene temperature and the LN₂ evaporation rate is especially analyzed. The calculation results show that the local minimum temperature of the kerosene is less than 240 K when the fork ring is wrapped with the insulation material, while it is greater than 260 K when the insulation material is not included. The calculation results provide reliable reference for the optimal design of LO₂ and kerosene bulkhead tank.

Key words: bulkhead tank, kerosene, foam, liquid nitrogen evaporation, phase change, CFD

摘要：

以液氧和煤油为推进剂的新一代运载火箭，承力式共底贮箱结构一方面可以缩短整个运载器长度，改善运载器长径比，二能取消液氧贮箱与煤油贮箱间的箱间段，减轻结构质量。但要求共底夹层需要良好的隔热性能，同时承受煤油箱和液氧箱双向压力载荷。获得加注过程共底夹层的温度非稳态分布是分析夹层隔热和应力性能的基础。基于CFD方法，模拟了液氮加注过程，共底贮箱包括液氮贮箱和煤油贮箱以及共底夹层，从室温到加注完成的非稳态温度分布。数值模型考虑了贮箱表面可能结冰时的热边界条件变化以及由于壁面漏热导致的液氮/氮蒸气相变蒸发。为了防止煤油局部温度过低，重点分析了叉形环处包裹或未包裹PMI绝热材料对煤油温度场和液氮蒸发率的影响。计算结果表明，叉形环处包裹绝热材料时在自然蒸发阶段煤油局部最低温度小于240 K，而未包裹绝热材料时局部最低温度大于260 K，满足设计要求。仿真结果为液氧和煤油共底贮箱的优化设计提供参考。

关键词: 共底贮箱, 煤油, 泡沫, 液氮蒸发, 相变, CFD