超低温流体迷宫密封过程中，密封间隙节流压降引发的流体空化现象致使超低温流体动密封性能变化规律和物理机理十分复杂，但目前尚缺乏可预测动密封参数的数学模型，为此开展超低温流体迷宫密封理论与实验研究具有重要意义。为揭示空化作用下的迷宫密封机理，以直通型迷宫结构为研究对象，构建考虑相间热质传递的两相流控制方程，建立迷宫齿隙微小空间内两相流流场变量稳态解析模型，提出超低温流体空化起始位置判别依据，形成空化前后多相态流体齿隙压力与泄漏率解析计算方法，实现超低温流体迷宫密封齿隙流场演变规律的定量描述。结果表明，该解析模型依赖于各级齿隙中两相流含气率，稳态时超低温流体被空化起始齿隙分割成液相流与两相流两部分，其中两相流压力变化趋势与流体饱和压力曲线一致，压降很小；与仿真和实验数据相比，中低转速和压力条件下解析模型预测精度高于85%，空化现象可降低超低温流体质量泄漏率，文中工况下最大降幅达到19.43%。本文研究工作改善了超低温环形动密封缺乏预测模型的现状，可为超低温流体迷宫密封机理揭示、结构设计与性能研究提供理论依据。

Fluid cavitation phenomenon inside the seal clearance caused by throttling pressure drop makes the performance and mechanism of cryogenic dynamic sealing very complex in the process of cryogenic fluid labyrinth sealing， but there is a lack of mathematical model to predict the dynamic sealing parameters. Therefore， it is of great significance to carry out theoretical and experimental research on cryogenic fluid labyrinth sealing. To reveal the cryogenic labyrinth sealing mechanism under cavitation effect， a straight-through labyrinth structure is taken as the research subject， A two-phase flow control equation considering heat and mass transfer between phases are established. Steady-state analytical models of two-phase flow variables inside the limited-space of labyrinth clearance are developed. A criterion of the cavitation starting position of cryogenic fluid in the labyrinth seal is proposed. An analytical calculation method for tooth-clearance pressure and leakage rate of multi-phase fluid is formed to realize the quantitative description for evolution laws of flow field inside labyrinth seal clearances. The results show that the analytical models depend on gaseous phase fraction of two-phase flow in each clearance. Cryogenic fluid is divided into the liquid-phase flow in non-cavitation tooth cavities and the two-phase flow in cavitation tooth cavities by the cavitation starting tooth clearance in the steady state. The pressure change trend of the two-phase flow is consistent with the fluid saturation pressure curve， and its pressure drop is very small. Compared with simulation and experimental data， the prediction accuracy of these two-phase flow analytical models is higher than 85% at low speed and low pressure conditions. The leakage mass-flow rate can be reduced by cavitation， and the maximum reduction is 19.43% under the conditions in this paper. The study can improve the situation with lack of prediction models for cryogenic annular dynamic sealing， and can provide theoretical basis for revealing the mechanism of cryogenic fluid labyrinth sealing， as well as for the structural design and performance research.