亚毫米三维槽机械密封跨尺度液膜超高速稳定性与空化抽吸控漏机制

Mechanical seal is one of key components of turbopumps. It is prone to fail due to the vaporization instability of the over-heating lubrication film when operating in the ultra-high speed condition. To solve this problem, a new concept of submillimeter 3D groove mechanical seals (SMG-MS) is proposed. The ultra-high speed stability and leakage control method of the trans-scale lubrication film will be investigated in this project. (1) The theoretical model of the lubrication film in the ultra-high speed condition will be established based on the turbulent lubrication theory. The mechanism of the turbulence, inertia and film pressure jump will be clarified. The flow of the lubrication film in the 3D grooves will be investigated. The film formulation and working mechanism will be disclosed. (2) The dynamic characteristics and the dynamic response behavior of the mechanical seals will be studied based on the established dynamic model of the SMG-MS. The instability mechanism of the lubrication film in the ultra-high speed condition will be clarified. The stability criteria of the SMG-MS will be established. The method will be proposed to improve the ultra-high speed stability. (3) A new concept of the cavitation aspiration in the fluid film is proposed to control the leakage. The leak law of the SMG-MS will be studied. The mechanism of flow control by the cavitation in the fluid film will be disclosed. The influence of submillimeter grooves and cavitation ones on stability will be studied. The composite grooves structure of the submillimeter ones and the cavitation ones will be optimized to harmonize the load carrying cpacity and leakage control. The study results from this project will not only fill a gap in the design theory of the ultra-high speed mechanical seals for the turbopumps, but also contribute to the turbulent lubrication theory.

机械密封是涡轮泵的关键基础部件，在超高速工况下端面间润滑液膜易过热而汽化失稳并导致密封失效。为解决此问题，项目提出亚毫米三维槽机械密封概念，针对其跨尺度润滑液膜的超高速稳定性和泄漏控制方法开展研究：(1)基于湍流润滑理论，建立超高速工况下润滑液膜的理论模型，阐明湍流、惯性力和压力跃变的作用机理，探索亚毫米深槽内液膜的流动规律，揭示机封的成膜机理和工作机制；(2)建立湍流工况亚毫米深槽机封动力学模型，研究机封动力学特性和动态响应行为，阐明超高速条件下润滑液膜的失稳机制，建立密封稳定性判据，探索提高润滑液膜超高速稳定性的方法；(3)提出基于液膜空化抽吸原理的泄漏控制理念，研究密封泄漏规律，揭示液膜空化控漏机理，研究亚毫米深槽和空化槽结构对稳定性的影响规律，实现复合型槽稳定承载与控漏的协调优化。该研究不仅可以弥补涡轮泵用超高速机封设计理论的缺失，而且对于补充和完善湍流润滑理论具有重要的科学贡献。

机械密封是航空航天和海洋特种装备动力源-超高速涡轮泵的关键基础部件。随着涡轮泵向更高转速发展，近乎苛刻的工况条件使机械密封端面液膜过热而汽化失稳，导致密封失效，这为机械密封的设计带来严峻挑战。为解决上述问题，项目提出了亚毫米三维槽机械密封概念，针对超高速工况下跨尺度润滑液膜润滑湍流、惯性和空化作用机制，亚毫米深槽润滑液膜流动规律和泄漏机理，基于液膜空化抽吸的超高速大膜厚控漏机制三大科学问题，开展了如下的理论和试验研究：（1）建立了超高速机械密封跨尺度润滑液膜的湍流润滑稳态模型，采用有限单元法实现了模型的数值求解，获得了超高速机械密封润滑液膜的流动规律、揭示了湍流、惯性、空化和粘性剪切热对密封性能的影响作用机制；（2）建立了基于湍流润滑模型的跨尺度液膜三维动力学模型，探索了湍流、空化和粘性剪切热对液膜动态刚度系数和阻尼系数的影响规律，研究了提高液膜稳定性的方法；（3）研究了液膜的空化抽吸控漏机制，分析了起泄漏控制作用的空化槽与起承载作用的亚毫米槽交互关联作用关系，探索了复合槽型内流体的流体规律，成膜特性和协同工作机制，提出了基于水平集的动压沟槽形状优化方法，获得了优化的动压型槽结构。上述湍流润滑理论的建立可为超高速跨尺度润滑液膜的润滑力学的研究提供了一定的理论基础，复合槽型的交互作用机制和槽型优化设计方法的提出可为超高速涡轮泵用机械密封的设计提供了理论指导。