ISSN   1004-0595

CN  62-1224/O4

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微量油辅助水润滑成膜特性的研究

Film-Forming Characteristics of Assisted Water Lubrication with Small Quantity Oil

  • 摘要: 由于水的润滑膜建立能力较差,本文中研究了微量环保型润滑油辅助水润滑的润滑膜建立机制. 利用滚子-盘接触润滑膜测量仪,研究了水环境下2种黏度的环保型润滑油作为第二介质的辅助润滑特性,并通过荧光标记对油的流动进行了观测. 结果表明,水环境下滚子-盘接触区的润滑油主要来源于入口油池和侧油脊. 与在空气中不同,水环境使油在固体表面的润湿性变低,接触区供油易受外界干扰,膜厚易发生波动. 低速下侧油脊更容易向接触区回流,从而改善供油;在高速下水的逆流推动侧油脊回流的油远离接触区,导致入口供油变差. 此外,环块试验机结果表明微量环保型润滑油辅助水润滑具备良好的减摩抗磨能力.

     

    Abstract: Water lubrication has became immensely popular due to its environmental friendliness and low cost. However, the challenge lies in achieving an effective lubrication film with water’s low viscosity. Usually water-lubricated bearings could suffer from wear and noise under tough working conditions, such as low running speeds at start up/shut down/dynamic positioning, and heavy dynamic loads when subjected to waves. In fact, new bearing structure and new bearing materials have been studied to protect the water-lubricated bearings under the tough cases. It is certainly good to find alternative solutions beyond the existing schemes. The author’s research group designed a new way for water lubrication assisted by a small amount of secondary lubricant, and it was found that a short-term supply of a small amount of emulsifying oils or silicone oils was conducive to reducing friction and wear of water-lubricated bearings. In order to further explore the mechanism of lubrication with a small amount of lubricant under water environment, a roller-on-disc lubrication film test rig was used to directly measure the film formation behaviour when a small quantity of oil was injected. Two environmentally friendly lubricants, Bio-oil A of low viscosity and Bio-oil B of high viscosity were provided by a micropette (1 μL/s, total 10 s) under the load of 2 N at various speeds. The film thickness in the contact area after a short-term supply of lubricant was recorded, and therefore the assistant lubrication characteristics of two lubricants as the second medium in the water environment were revealed. Moreover the fluorescent approach was used to observe oil flow. The results showed that the water lubrication assisted by a small amount of lubricant was beneficial to improve the film-forming capacity of the contact area, and the lubricant supply of the roller-disc contact area mainly came from the inlet oil pool and the side-oil ridges. Wettability of the oil on the disc surface decreased in the water environment compared to those in air, making the oil supply susceptible to external interference and leading to fluctuation in film thickness. The instability of the side oil- ridge and the inlet pool was the main reason for the fluctuation of film thickness. At lower disc-speeds, the side oil-ridge was more likely to flow back to the lubrication track, which could improve the oil supply, and it was showed that the oil with lower viscosity demonstrated more reflow. At higher disc-speeds, the oil was pushed away at the inlet area by both mechanical diversion from the contact and water adverse flow, resulting in a poor inlet oil-supply. It was more difficult for Bio-oil B with higher viscosity to be replenished into the contact area than Bio-oil A with lower viscosity. In addition, the results of the block-on-ring tribometer showed that the water lubrication assisted with a small amount of lubricant presented obvious reduction of friction and wear. The higher the speed, the greater the influence of reverse flow. Bio-oil B, which had a higher viscosity had a better friction reduction effect.

     

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