物性畸变作用下超临界CO2干气密封流体膜相态演化规律及其控稳性研究

随着超临界二氧化碳（sCO2）在布雷顿循环发电系统、页岩气开采和高效清洁驱油中的广泛应用，sCO2透平机械轴端密封采用干气密封已成为国际趋势，但是端面间流体膜相变引起的失效问题成为密封稳定可靠运行的瓶颈。sCO2干气密封端面间流体膜可能处于超临界相、液相、气相或气液混相共存的状态，而目前关于sCO2拟临界区内物性畸变对流体膜的相变演化规律、失稳机制和调控策略尚不明确。本项目在探讨拟临界区物性畸变作用下sCO2热质传递规律的基础上，通过建立干气密封端面间流体膜相态分布和相态动力学特性数值求解模型，结合实验测试分析，揭示物性畸变、多相共存和热力变形条件下流体膜相态的演化规律和失稳机制，获得影响流体膜相态分布的关键因素，构建密封相态稳定性的定量判据，并从除湿和控漏两个方面提出调控增稳流体膜相态的策略，完善干气密封设计方法，满足我国sCO2能源系统动力设备中关键密封技术的迫切需求。

With the wide application of supercritical carbon dioxide (sCO2) technology in Brayton cycle power generation system, shale gas exploitation and high-efficiency clean oil displacement, dry gas seals applied in sCO2 turbo equipment have become an international trend. However, failure caused by fluid film phase transition in fluid film has become a bottleneck problem restricting the stable operation of dry gas seal. The phase state in sCO2 fluid film of dry gas seal may be the combination of supercritical phase, liquid phase, gas phase and gas-liquid two-phase, while the CO2 phase state evolution law and instability mechanism under the action of physical property distortion near the critical point are still uncertain. On the basis of analyzing heat and mass transfer law of sCO2 fluid under the action of physical property distortion near the critical point, by establishing numerical models on simulating phase state distribution and phase state dynamic characteristics of sCO2 dry gas seal, together with the test results analysis, the phase evolution law and phase state transformation mechanism of sCO2 dry gas seal under the combined actions of physical property distortion, multi-phase state and thermal-mechanical deformation will be revealed. The key influence factors on fluid film phase state distribution of sCO2 dry gas seal will be obtained, quantitative criterion on judging phase state stability of sCO2 dry gas seal will be put forward. On this basis, the design strategies on adjusting and enhancing stable fluid film phase state of sCO2 dry gas seal will be proposed from the perspective of leakage control and dehumidification, which is expected to perfect the design method of dry gas seal and meet the urgent requirements of key components in sCO2 energy system.