多变工况动静组合型机械密封自适应机理及变形特性研究

A mechanical seal with the macro-porous and cone is a research object in this project, in order to solve the problems of the seal failure and poor liquid film stability when the static pressure and dynamic pressure effect of the end faces liquid film constantly change under the different working conditions. The adaptive capacity of anti-variable operating conditions and anti-change mechanism of the combination mechanical seal with the macro-porous and cone are researched, considering the cavitation of the liquid film between the end surfaces under the different working conditions, and combining with JFO mass conservation boundary conditions. A three-dimensional model of the multi-field and multi-body and fluid, solid, thermal coupling is established, which is very close to the actual working status. The finite element method and the finite difference method are combined to precisely simulate the end faces deformation and temperature distribution of the sealing rings and liquid film. The force deformation and thermal deformation of the mechanical seal with the macro-porous and cone are studied, and also, the liquid film pressure distribution after the end faces deformation and the sealing performance are analyzed. It is playing a crucial role for controlling the end face deformation of the seal rings, and achieving deformation compatibility, and optimizing the performance of the sealing device, to discuss which the macro-size of the seal rings impacts on the adaptive ability to resist variable conditions. The correctness of the theoretical results of the mechanical seal with the macro-porous and cone and feasibility of the optimal geometric parameters are validated by using the experimental method.

本项目以大孔径-锥面动静压组合型机械密封为研究对象，旨在解决多变工况条件下端面液膜的静压效应、动压效应时刻发生变化极易导致密封失效和液膜稳定性差的问题。考虑不同工况下端面内液膜的空化现象，结合JFO质量守恒边界条件，研究大孔径-锥面组合型机械密封抗变工况的自适应能力及抗变机理；构建非常接近实际工作状态的多场、多体三维流、固、热耦合的物理模型，采用有限差分法和有限元法离散方程，通过计算机语言自行编程与有限元商用软件有机结合，对密封端面的变形和温度场分布情况进行类似智能化的理论模拟；研究大孔径-锥面机械密封的力变形、热变形以及端面变形后的液膜压力分布规律和密封性能，并探讨密封环宏观尺寸对抗多变工况自适应能力的影响程度，对于实现控制密封环的端面变形，达到变形协调，优化密封装置的性能起到了至关重要的作用；用实验的方法验证大孔径-锥面机械密封理论成果的正确性以及最佳几何参数的可行性。

密封机构是机器中重要组成元件，在运行时有可能处于复杂的工况中，当环境条件发生变化时密封端面将产生不同形式的变形，进而改变其摩擦润滑状态，或者引起密封环端面的部分加载，造成严重摩擦与磨损，从而引起密封的失效，使腔体介质泄漏到装置外，不仅会造成大量污染，还将使机械设施与人员安全造成到极大危害。因此为解决多变工况条件下端面液膜的静压效应、动压效应时刻发生变化极易导致密封失效和液膜稳定性差的问题，研究大孔径-锥面组合型机械密封抗变工况的自适应能力及抗变机理。基于不同工况下端面内液膜的空化现象，结合JFO质量守恒边界条件，给出新型锥-孔组合型端面密封结构模型，考虑液膜压场的变化规律与环受热力变形的相互作用关系，构建机械密封3D流、固热力耦合数学模型，并给出相关的数值计算方法，获得了膜压、温度分布规律及端面变形情况，分析锥面结构参数在各工况下对密封性能的影响规律。结果表明：由织构孔所引起的动压效应可使端面产生周向和径向波状变形，而静压效应随锥度、锥宽比和O型圈轴端位置等的变化，在端面区域范围内所起作用也发生相应变化；对压强较低和低、中转速设备，应选取锥度为5.0~6.0或2.0~4.0的收敛锥面密封，锥宽比为0.8~1。对高压和高速设备，应选用锥度为2~3的收敛锥面密封，锥宽比为1或0.2；通过改变锥面结构可有效改变机械密封的特性参数，实现密封运行中的自动调节，特别适合变工况条件。另外，由于锥面结构的变化所引起O型圈轴端位置和膜厚的变化，低速时可弥补动压效应较小的缺陷，获得较大开启力，也可在大膜厚下工作，故可降低密封端面对平整度和光洁度的要求。并通过实验研究，可知在供液充分条件下具有合适孔型、孔深和锥度的菱形孔织构端面，可极大地改善摩擦副的润滑性能，能够有效地降低摩擦系数，并对其机理进行了详细的分析，同时也验证大孔径-锥面机械密封理论成果的正确性以及最佳几何参数的可行性。