Studies on tribology.
Bottom Line: Oil whip is one of such vibrations due to oil film action of journal bearing.Some mechanisms of wear are introduced for better understanding of tribo-layer.In the last part of this paper, the mechanisms of generating static friction are shown for the cases of plastic contact and elastic contact, which is the base for understanding the mechanism of initiation of macroscopic sliding.
Affiliation: Kanazawa Institute of Technology, Tokyo, Japan.
In high speed rotating machines such as turbines and generators, vibrations of a rotating shaft often hinder the smooth operation of the machine or even cause failure. Oil whip is one of such vibrations due to oil film action of journal bearing. Its mechanism and preventive method is explained and proposed in this paper. Further theoretical and experimental analyses are made for considering heat generation and temperature rise in hydrodynamic lubrication. The usefulness of the lubrication theory based on the k-epsilon model is also shown for bearings with high eccentricity ratios. In the latter half of this paper, water lubrication, nitrogen gas lubrication and tribo-coated indium lubrication are shown as new promising methods, and their mechanisms are discussed and the importance of tribo-layer is explained. Some mechanisms of wear are introduced for better understanding of tribo-layer. In the last part of this paper, the mechanisms of generating static friction are shown for the cases of plastic contact and elastic contact, which is the base for understanding the mechanism of initiation of macroscopic sliding.
Related in: MedlinePlus
Mentions: Figure 14 shows a comparison of the experimental and theoretical temperature distribution at the middle cross section of the bearing metal.6) For the measurement of temperature distribution, 144 copper-constantan thermocouples were embedded in the bearing metal. Operating conditions are: rotating speed N = 2502 rpm, load on the journal P = 5.61 kN, oil supply pressure Pin = 98 kPa, oil supply temperature Tin = 40.0 °C, ambient temperature Ta = 29.2 °C. Dimensions of the bearing used were: inner diameter D = 100 mm, length L = 70 mm, length and width of axial oil groove l × w = 60 mm × 8.7 mm, clearance ratio c/R = 0.00157. The lubricating oil was #90 turbine oil. The eccentricity ratio was κ = 0.7 and the attitude angle was θ = 43°. Experimental and theoretical isotherms are in good agreement which shows the validity of the theoretical treatment.