斯特林发动机新型密封材料摩擦磨损性能研究

发布时间：2018-04-06 21:28

  本文选题：斯特林发动机　切入点：聚四氟乙烯　出处：《兰州理工大学》2017年硕士论文

【摘要】：斯特林发动机是一种依靠外部热源对密封在机器中的气体工质加热,使其不断热胀冷缩进行闭式循环,从而推动活塞做工的热气机。其中工质密封是斯特林发动机关键技术和最难解决的技术之一,气体工质的泄露将直接导致发动机功率和效率的降低,重则还会引发严重的安全问题。因此密封材料的耐磨性、自润滑性以及热稳定性与斯特林机的功率、效率和可靠性密切相关。研究密封材料的摩擦磨损特性对提升发动机的性能有至关重要的作用。本文对比了不同材料之间的特性,并从中选取纳米碳化硅(Nano-SiC)和聚酰亚胺(PI)为填料,以不同体积比含量与聚四氟乙烯(PTFE)在混料机中混合,再经过冷压成型和烧结等工艺,制成聚四氟乙烯复合材料。利用MRH-3型环-块摩擦实验机研究不同实验条件下复合材料的摩擦磨损性能并记录磨损表面温度变化。通过扫描电镜观察试样磨损表面和转移膜形貌,分析其磨损机理。结果表明:聚酰亚胺的填充对聚四氟乙烯的改性效果明显。当聚酰亚胺含量为5%时,复合材料摩擦系数减小为0.182,耐磨性得到较大提升。添加纳米粒子能进一步提升复合材料的机械性能和摩擦磨损性能,且含量为5%时,对复合材料摩擦磨损性能的提升最显著。纳米粒子填料的含量、对磨时载荷和速度的变化均会引起磨损表面温度发生变化,影响复合材料摩擦磨损特性,复合材料磨损表面形貌和转移膜形貌也随之改变;随着纳米粒子含量增加,摩擦温升更快进入平稳阶段,有利于降低复合材料磨损率;载荷由100 N增加至400 N,速度由1 m/s增加至4 m/s时,复合材料摩擦磨损特性大幅下降,磨损表面形貌和转移膜形貌有显著变化,重载和高速条件下复合材料磨损率高;环境温度在室温到135℃变化时复合材料摩擦性能变化不明显。
[Abstract]:Stirling engine is a kind of hot gas engine which relies on the external heat source to heat the sealed gas working fluid in the machine, which causes it to heat up and shrink continuously, thus pushing the piston to work.Working fluid seal is one of the key technologies and one of the most difficult technologies in Stirling engine. The leakage of gas working fluid will directly reduce the engine power and efficiency, and the heavy gas will lead to serious safety problems.Therefore, the wear resistance, self lubricity and thermal stability of sealing materials are closely related to the power, efficiency and reliability of Stirling machine.It is very important to study the friction and wear characteristics of sealing materials to improve the performance of engine.In this paper, the properties of different materials are compared, and Nano-SiCand polyimide (Pi) are selected as fillers, and different volume ratios and PTFEs are mixed in the mixer, and then they are formed and sintered by cold pressing.Polytetrafluoroethylene (PTFE) composite was made.The friction and wear properties of composites under different experimental conditions were studied by MRH-3 ring-block friction tester and the temperature change of wear surface was recorded.The morphology of wear surface and transfer film were observed by SEM, and the wear mechanism was analyzed.The results showed that the modification effect of polyimide on PTFE was obvious.When the content of polyimide is 5, the friction coefficient of the composite decreases to 0.182, and the wear resistance is greatly improved.The mechanical properties and friction and wear properties of the composites can be further improved by adding nano-particles, and when the content is 5, the friction and wear properties of the composites can be improved most significantly.The change of load and velocity of nano-particle filler will cause the change of wear surface temperature, which will affect the friction and wear characteristics of composite material, and the morphology of wear surface and transfer film will also change.With the increase of the content of nanoparticles, the friction temperature increases to a stable stage, which is beneficial to reduce the wear rate of composites, and when the load increases from 100 N to 400 N, the friction and wear characteristics of the composites decrease significantly when the velocity increases from 1 m / s to 4 m / s.The wear surface morphology and the transfer film morphology have obvious changes, the wear rate of the composites is high under heavy load and high speed, and the friction properties of the composites do not change obviously when the ambient temperature varies from room temperature to 135 鈩，

本文编号：1718998