水力机械端面密封内部微尺度流动与密封润滑机理研究

Moving seal is one of the difficult problem in the hydro machinery field. Study on the lubrication mechanism of mechanical seals with facial geometry structure is the key point to obtain the high performance seal. Based on the requirement of zero-leakage and non-contact, a new type of fluid mechanical seal with combination of micro lubrication pores and macro pumping grooves on the seal ring face is introduced for the first time in this research project.Scientific problems such as viscous dissipation, heat diffuse, physical characteristics , boundary layer transfer of fluid near to the wall and cavitation form, etc, will be studied to build the mathematic relation of viscous-temperature model and double electric layer to establish the new theoretical model which truly describes the heat and flow mechanism in the seal.Theoretical analysis, multi-coupling numerical simulation and experimental research is applied to study the flow field structure, cavitation characteristics, pressure fluctuation frequency and dynamic pressure effect, to obtain the main factors and their internal laws, to deeply analysis the mechanism of seal lubrication mechanism.At the same time, the optimal design method for the mechanical seal with facial geometry structure is researched, as well as the new type laser micro processing technical, to provide necessary modification and verification for theoretical and experimental research, and finally to establish the new technology of zero-leakage and non-contact fluid mechanical seal.This research project will provide new approach for high performance seal technology in the hydro machinery field.

水力机械的动密封是本行业难题之一，端面微造型机械密封的密封润滑机理研究是获得高性能密封的关键。本项目根据零泄漏非接触要求首次提出具有宏观槽和微凹腔形貌组合表面的新型液体机械密封，拟在研究其微尺度区域内粘性耗散、热扩散、近壁流体物理特性、边界层诱导和空化形态等问题，进而获得粘温模型、双电层等微尺度效应数学关系和凹腔空化模型的基础上，建立真实描述密封内部热流体行为的理论模型。通过理论分析、多重耦合数值模拟和试验研究相结合，着重研究不同密封工况、不同形貌参数组合条件下的热变形、润滑膜流场结构、压力脉动频率特性及其与动压效应、泵送效应的关系，获得影响润滑膜特性的因素及内在规律性，深入分析密封润滑机理。同时，研究密封端面跨尺度组合形貌优化设计方法，探索新型激光微造型工艺，为试验研究和理论模型的修正、验证提供保证，并形成零泄漏非接触液体机械密封新技术。本研究旨在为水力机械行业高性能密封技术提供新途径。

机械密封是旋转介质输送设备的关键部件，为获得高性能机械密封，本项目针对非接触式机械密封的密封润滑机理进行研究。通过密封微间隙内部流动微尺度效应的研究，获得了边界滑移、表面粗糙度对密封润滑性能的影响关系，为具有微间隙流动理论模型的建立提供依据；首次将动网格技术引入机械密封性能研究中，开展了密封微间隙液膜空化机理、发展过程和空化热效应研究，得到了转速、压力和气核含量对空化效应的影响以及空化效应对液膜压力、开启力、液膜刚度、泄漏量和摩擦扭矩等密封性能的影响规律，初步探索了空化效应和热效应引起的动压润滑失效机制；实现了密封双向流固热多场耦合研究，获得密封环热-力变形规律及其与密封润滑性能的关系，尤其是密封环变形对液膜流场瞬态特性的影响关系；拓展了化工输送泵用中温高粘性介质机械密封热特性、热变形、冲洗参数优化和密封端面改型的研究，为密封性能提升和节能降耗提供了理论参考依据；基于两相流体的连续介质理论，利用Mixture模型，拓展了密封微间隙液膜内部流固两相流动特性及其对密封性能的影响研究，得到间隙内部颗粒分布规律及其与膜压、开启力和摩擦扭矩的关系，为把握密封磨损机理和获得减磨途径提供参考；对密封微间隙液膜流场瞬态特性、动压机理、润滑特性、热特性，以及槽深渐变、槽腔耦合方式、槽型改进等进行研究，为密封微间隙流场及性能的系统研究和端面形貌设计提供了参考依据；开展了密封端面几何形貌参数与密封性能的多目标优化研究以及密封端面宏微观几何形貌设计、激光加工和性能对比试验，获得了高性能机械密封设计理论、方法和密封端面几何形貌加工方法。研究成果为水力机械行业高性能密封技术的开发和应用提供了理论参考依据和新途径。