高速低温气液混合润滑动静结合型机械密封机理及动力行为研究

以液体火箭发动机高速涡轮泵轴端机械密封为背景，针对前期在试验过程中发现的此类高速低温动静结合型机械密封在运行中存在的两相润滑问题和微幅颤振问题，开展低温液氧/液氢（以液氮为模拟介质）被密封介质在高速运转过程的气液两相润滑模型、混合介质润滑下的密封热流固力多场耦合模型、混合介质下密封动力学特性及低温高速运转试验研究。提出低温气液混合模型及其在密封模型中的应用方法，揭示存在可压缩流体特殊工况下的密封机理；发展混合介质下密封的动力学系数求解方法，并构建高速密封转子动力学模型，以其获取气液混合流体激励诱发的动力行为及系统动力学特征演变规律；开展高速低温工况的模拟和运转试验，验证气液混合润滑密封多场耦合模型的正确性，同时测试高速阶段存在气液混合润滑下密封的振动特性，理论和试验对比揭示密封的颤振机制。研究将为长寿命、高可靠性、高稳定性的高速涡轮泵用新型动静结合型机械密封的设计及应用提供理论和试验基础。

In view of the problems of the liquid-vapor mixture lubrication and the slight flutter in the high-speed cryogenic hydrodynamic mechanical seal of the high-speed turbopump for the liquid rocket engine, revealed by a series of previous experimental studies, a study is carried out on the liquid-vapor (cryogenic LOX, LH2 and using liquid nitrogen as simulation lubricant) mixture lubrication model, the integration of the thermo-elastic-hydrodynamic-mechanical multi-field coupling seal model and the mixture lubrication model, the seal dynamics under the mixture lubrication conditions and the high-speed cryogenic experimental test. The method for integrating the liquid-vapor mixture lubrication model into the seal model is developed, and the integrated model is built to discover the mechanics of the hydrodynamic mechanical seal under the working-condition with compressible fluid. The method for solving the dynamic characteristics coefficients of the seal is proposed and the dynamics model of the turbopump seal-rotor system is advanced. Therefrom, the dynamics behavior induced by liquid-vapor mixture fluid and its evolving features are obtained. The experiments using liquid nitrogen and working lubricants are implemented to verify the mixture lubrication model and the multi-field coupling seal model; the vibration data of the seal-rotor system under the high-speed stable-running stage are gathered, and the seal’s flutter mechanism is revealed with the comparison of the theoretical and experimental data. This study will provide the theoretical and experimental basis for the design and application of the long-life, high-reliability, high-stability hydrodynamic mechanical seal used in the cryogenic high-speed turbopump.