高温高速旋转轴接触式密封材料研制及其密封性能研究

发布时间：2018-02-23 21:31

本文关键词： 高速高温工况接触式密封 PTFE复合材料摩擦磨损密封性能　出处：《哈尔滨工业大学》2014年博士论文　论文类型：学位论文

【摘要】：航空发动机中的密封、轴承等典型摩擦学部件的滑动摩擦副需要工作在高速、高温、低温和高低温交变等趋近当前材料使用极限的苛刻工作条件下，密封等摩擦副常因表面接触应力过高、摩擦生热加剧及润滑失效而发生磨损加剧现象，从而导致密封失效。为了满足航空发动机向着大推重比、高可靠性和长寿命的趋势发展的需要，密封等零部件的材料特性及其结构需要不断的改进。因此，开展高速高温复合材料摩擦学特性的研究，揭示苛刻工况下复合材料的增强规律和失效机理，以指导新材料的设计和评价，发展航空摩擦学设计规范体系，对推动航空发动机密封技术的发展有重要理论和实际应用价值。本文以小型高速发动机泵用接触式动密封的高速高温工况为背景，结合发动机封严密封介质，完成密封材料配方设计，对密封材料在苛刻环境下的磨损行为进行试验研究，研究填料、温度、速度对密封材料的影响规律，优化耐高温高速密封材料配方；建立密封材料磨损模型，研究密封在不同润滑状态下唇口结构、接触特性的变化关系；建立密封泄漏模型，分析结构参数、材料特性对泄漏的影响，研究密封失效原因。利用M-200摩擦磨损试验机测试了复合材料在常温低速干摩擦条件下的摩擦学性能，利用冲击强度测量仪、邵氏D硬度计、拉伸试验机测试了复合材料力学性能，通过对基本摩擦学和力学性能分析，初步确定了含有碳纤维、球形石墨和鳞片石墨的动密封材料配方及其成型工艺；研制了高速高温滑动磨损试验装置，，利用该试验装置，研究了线速度、温度及增强体含量对复合材料磨损率的影响规律，发现速度、温度和鳞片石墨对磨损率有显著影响。利用扫描电子显微镜分析了常温低速、高速、高温高速复合材料磨损表面形貌及断口形貌，在此基础上研究了增强体的增强机理，发现碳纤维提高了复合材料的强度和韧性，同时在高温的条件下，能够起到骨架、阻止基体软化后流动的作用；球形石墨降低了复合材料的摩擦系数；鳞片石墨提高了复合材料的导热性能，增强了复合材料的热稳定性，同时降低了材料基体之间的结合强度。通过对Archard粘着磨损公式和基于分形理论的W-M磨损公式的分析，建立了密封材料磨损数学模型，模拟了开关机、加压、稳定运行阶段在不同润滑状态下磨损过程，分析了唇口结构及其接触特性随磨损时间的变化规律。结果表明由结构带来的接触应力不均匀现象消失，高速密封稳定运行阶段处于流体润滑状态。通过对“表面效应及泵吸作用”唇形密封机理的研究，建立了密封泄漏及回油的数学模型，分析稳定运行阶段密封泄漏量及回油量随磨损时间的变化规律。同时进行了发动机工况适应性试验研究，在给定的运行时间内，密封未出现明显泄漏。
[Abstract]:The sliding friction pairs of typical tribological components such as seals and bearings in an aeroengine need to work under harsh working conditions such as high speed, high temperature, low temperature and high and low temperature alternating to the current limit of material use. Due to the high surface contact stress, the friction heat generation and the lubrication failure, the sealing and equal friction pairs often cause wear and tear, which leads to the seal failure. In order to satisfy the large ratio of thrust and weight of the aero-engine, Due to the trend of high reliability and long life, the material characteristics and structure of sealing and other parts need to be improved continuously. Therefore, the tribological properties of high speed and high temperature composite materials are studied. It is of great theoretical and practical value to reveal the reinforcement law and failure mechanism of composite materials under harsh working conditions, to guide the design and evaluation of new materials and to develop the aviation tribology design code system, which is of great theoretical and practical value in promoting the development of aero-engine sealing technology. In this paper, based on the high temperature working condition of contact dynamic seal for small high-speed engine pump, combined with the sealing medium of engine seal, the formula of sealing material is designed, and the wear behavior of sealing material under harsh environment is studied experimentally. The effects of packing, temperature and speed on sealing materials were studied, and the formula of high temperature and high speed sealing materials was optimized, and the wear model of sealing materials was established to study the change of lip structure and contact characteristics under different lubricating conditions. The leakage model of seal is established, the influence of structural parameters and material characteristics on leakage is analyzed, and the reason of seal failure is studied. The tribological properties of composites under normal temperature and low speed dry friction were tested by M-200 friction and wear tester. The mechanical properties of composites were tested by impact strength tester, Shao's D hardness tester and tensile tester. Based on the analysis of basic tribological and mechanical properties, the formula and forming process of dynamic sealing materials containing carbon fiber, spherical graphite and flake graphite were preliminarily determined, and a high speed and high temperature sliding wear test device was developed. The effects of linear velocity, temperature and reinforcement content on the wear rate of composites were studied. It was found that velocity, temperature and flake graphite had significant effects on the wear rate of composites. The wear surface morphology and fracture surface morphology of composites at room temperature and low speed, high speed and high temperature were analyzed by scanning electron microscope (SEM). On the basis of this, the reinforcement mechanism of composites was studied. It was found that carbon fiber enhanced the strength and toughness of composites. At the same time, at high temperature, it can play the role of skeleton to prevent the flow of matrix after softening; spherical graphite reduces the friction coefficient of composites; flake graphite improves the thermal conductivity of composites and enhances the thermal stability of composites. At the same time, the bonding strength between the matrix is reduced. Based on the analysis of Archard adhesive wear formula and W-M wear formula based on fractal theory, a mathematical model of sealing material wear is established, and the wear process of switch machine, pressurized machine and stable running stage under different lubrication states is simulated. The changes of lip structure and its contact characteristics with wear time are analyzed. The results show that the non-uniform contact stress caused by the structure disappears and the high speed seal is in the state of fluid lubrication at the stable operation stage. Based on the study of the mechanism of "surface effect and pump suction" lip seal, a mathematical model of seal leakage and oil recovery is established. The variation law of seal leakage and oil return with wear time in stable operation phase is analyzed. At the same time, the experimental study on engine operating condition adaptability is carried out, and no obvious leakage appears in the seal under given operating time.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB42

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