本文選題：斯特林發(fā)動機(jī)　切入點(diǎn)：聚四氟乙烯　出處：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：斯特林發(fā)動機(jī)是一種依靠外部熱源對密封在機(jī)器中的氣體工質(zhì)加熱,使其不斷熱脹冷縮進(jìn)行閉式循環(huán),從而推動活塞做工的熱氣機(jī)。其中工質(zhì)密封是斯特林發(fā)動機(jī)關(guān)鍵技術(shù)和最難解決的技術(shù)之一,氣體工質(zhì)的泄露將直接導(dǎo)致發(fā)動機(jī)功率和效率的降低,重則還會引發(fā)嚴(yán)重的安全問題。因此密封材料的耐磨性、自潤滑性以及熱穩(wěn)定性與斯特林機(jī)的功率、效率和可靠性密切相關(guān)。研究密封材料的摩擦磨損特性對提升發(fā)動機(jī)的性能有至關(guān)重要的作用。本文對比了不同材料之間的特性,并從中選取納米碳化硅(Nano-SiC)和聚酰亞胺(PI)為填料,以不同體積比含量與聚四氟乙烯(PTFE)在混料機(jī)中混合,再經(jīng)過冷壓成型和燒結(jié)等工藝,制成聚四氟乙烯復(fù)合材料。利用MRH-3型環(huán)-塊摩擦實(shí)驗(yàn)機(jī)研究不同實(shí)驗(yàn)條件下復(fù)合材料的摩擦磨損性能并記錄磨損表面溫度變化。通過掃描電鏡觀察試樣磨損表面和轉(zhuǎn)移膜形貌,分析其磨損機(jī)理。結(jié)果表明:聚酰亞胺的填充對聚四氟乙烯的改性效果明顯。當(dāng)聚酰亞胺含量為5%時,復(fù)合材料摩擦系數(shù)減小為0.182,耐磨性得到較大提升。添加納米粒子能進(jìn)一步提升復(fù)合材料的機(jī)械性能和摩擦磨損性能,且含量為5%時,對復(fù)合材料摩擦磨損性能的提升最顯著。納米粒子填料的含量、對磨時載荷和速度的變化均會引起磨損表面溫度發(fā)生變化,影響復(fù)合材料摩擦磨損特性,復(fù)合材料磨損表面形貌和轉(zhuǎn)移膜形貌也隨之改變;隨著納米粒子含量增加,摩擦溫升更快進(jìn)入平穩(wěn)階段,有利于降低復(fù)合材料磨損率;載荷由100 N增加至400 N,速度由1 m/s增加至4 m/s時,復(fù)合材料摩擦磨損特性大幅下降,磨損表面形貌和轉(zhuǎn)移膜形貌有顯著變化,重載和高速條件下復(fù)合材料磨損率高;環(huán)境溫度在室溫到135℃變化時復(fù)合材料摩擦性能變化不明顯。
[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，

本文編號：1718998