液氢贮箱在轨排气的闪蒸特性与热力态调节规律研究

doi:10.11949/0438-1157.20251202

摘要/Abstract

摘要：

火箭末级在轨长时间滑行后，要求低温推进剂的温度品质须满足发动机二次点火入口要求，可通过低温贮箱在轨排气实现推进剂压力与温度调控。针对微重力下液氢贮箱在轨排气造成的流体热力态瞬变特性预示难题，建立了CFD仿真模型，预测了排气过程液体闪蒸阶段的汽化速率与箱内气液两相流的温度变化规律。采用“半人马”上面级液氢贮箱飞行数据对模型进行了验证，表明所建立模型预测误差小于5%。对比分析了液氢贮箱在轨排气过程中壁面蓄热和排气管径对推进剂热力态的影响。结果表明，排气闪蒸研究中需要考虑壁面蓄热对排气压降速率和蒸发损失的影响。当排气管径为50 mm时，相较于不考虑壁面蓄热的情况，考虑壁面蓄热的贮箱压降速率降低了10.3%，总蒸发损失增加了2.8%。增大排气管径会加剧微重力闪蒸中的液面上升幅度，但有利于缩短排气时长和降低推进剂的蒸发损耗。当液氢充灌率为17.2%时，排气管径由30mm增加至50mm，液面上浮高度由0.576 m增加至0.932 m，对应液相空泡份额由51.8%增至83.9%；而排气时长则由283.4 s缩短至67.3 s，推进剂消耗由37.52 kg降至36.42 kg。

关键词: 液氢, 在轨排气, 相变, 闪蒸, 数值模拟

Abstract:

The long-time on-orbit coast phase of the rocket's upper stage demands the temperature quality of cryogenic propellant meeting the engine's restart requirements. On-orbit venting in cryogenic tanks has been demonstrated to regulate ullage pressure and propellant temperature. Aiming at transient evolutions of fluid thermodynamic states caused by on-orbit venting of liquid hydrogen tanks under microgravity conditions, a CFD simulation model was established to predict the flash vaporization of liquid hydrogen as well as the temperature variations of gas-liquid two phase flow in the tank during the venting process. The model was validated using flight data from the liquid hydrogen tank of the Centaur upper stage, showing that the prediction deviation of the established model was less than 5%. A comparative analysis was conducted on the effects of heat stored in the tank wall and venting pipe diameter on the thermal state of the propellant. The findings suggest that it is necessary to account for the effect of the heat stored in the tank wall on depressurization rate and flash evaporation. For a 50 mm venting pipe, compared to scenarios disregarding the wall heat storage, the depressurization rate decreased by 10.3% and the total evaporation losses increased by 2.8% relative to the scenarios considering the wall heat storage. Enlarging the venting pipe diameter could exacerbate the rise in liquid level during microgravity flash, but is advantageous for shorten the total venting time and mitigating propellant consumption. An increase in pipe diameter from 30 mm to 50 mm resulted in a notable rise in the liquid level from 0.576 m to 0.932 m as well as in the void fraction in liquid phase from 51.8% to 83.9%. Concurrently, the venting time was reduced from 283.4 to 67.3 s and the propellant vaporization consumption exhibited a decline from 37.52 kg to 36.42 kg.

Key words: liquid hydrogen, on-orbit venting, phase change, flash evaporation, numerical simulation

中图分类号:

V 511.6

梁鸽, 李鹏, 李轲, 孙培杰, 王磊, 厉彦忠. 液氢贮箱在轨排气的闪蒸特性与热力态调节规律研究[J]. 化工学报, DOI: 10.11949/0438-1157.20251202.

Ge LIANG, Peng LI, Ke LI, Peijie SUN, Lei WANG, Yanzhong LI. Study on flash evaporation characteristics as well as thermodynamic variation performance in liquid hydrogen tank during on-orbit venting[J]. CIESC Journal, DOI: 10.11949/0438-1157.20251202.

图/表 14

图 1 液氢贮箱排气闪蒸过程示意图

Fig. 1 Schematic diagram of flashing during venting process in liquid hydrogen tank

图 2 结构化网格模型

Fig. 2 Structured mesh model

图 3 三维和二维气枕压力与推进剂损失对比

Fig. 3 Comparison of three-dimensional and two-dimensional models on ullage pressure and propellant loss

图 4 三维与二维气液相与温度分布云图对比

Fig. 4 Comparison of three-dimensional and two-dimensional models on phase and temperature distributions

图 5 网格无关性验证

Fig. 5 Grid independence verification

图 6 仿真与实验气枕温度对比

Fig. 6 Comparison of simulation and experiment on ullage temperature

图 7 流固温度变化与气液相分布

Fig.7 Fluid-solid temperature variation and gas-liquid phase distribution

图 8 有无壁面工况的参数对比

Fig.8 Parameter comparison with and without wall conditions

图 9 排气结束时刻气液相图（左）和速度云图（右）

Fig. 9 Phase distribution (left) and velocity counters (right) at the end time of venting

表 1 管径对液面上浮高度和液相空泡份额的影响

Table 1 The influence of tube diameter on the surface height and void fraction of liquid

管径	30mm	40mm	50mm
/m	0.576	0.742	0.932
/%	51.8	66.8	83.9

图 10 排气管径对液相平均温度的影响

Fig. 10 Influence of tube diameter on liquid average temperature

图 11 排气管径对推进剂蒸发速率的影响

Fig. 11 Influence of tube diameter on the vaporization rate of propellant

表 2 平均压降速率与最大闪蒸速率

Table 2 Average depressurization rate and maximum flashing mass flow rate

管径	30mm	40mm	50mm
平均压降速率/Pa·s	176	411	743
最大闪蒸速率/kg·s^-1	0.251	0.477	0.774

图 12 不同排气管径下排气时间和蒸发损失对比

Fig. 12 The venting time and propellant loss at different tube diameter

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