Abstract
Oil–air lubrication supplies lubricants in the form of droplets to elastohydrodynamic lubrication (EHL) contacts, such as those in high-speed spindle bearings. However, there is a paucity of information related to understanding the lubrication behaviors of oil droplets within EHL contacts. In this study, behaviors of lubricant droplets, in terms of spreading around a static contact as well as passing through a rolling contact, were studied with an optical ball-on-disk EHL test rig. Influences of oil droplet size, viscosity, and surface tension on droplet spreading were examined. Lubricating film formation was also investigated when droplets traveled through the EHL contact region. The results indicated that droplet size and running speed significantly influenced film profiles. With increasing entrainment speeds, a small droplet passed through the contact without spreading and generated films with a significant depression in the central contact region.
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Abbreviations
- a :
-
diameter of Hertz contact, m
- D :
-
width of spreading layer, m
- D ini :
-
initial droplet diameter, m
- h layer :
-
thickness of spreading droplet layer, m
- K :
-
constant
- L s :
-
distance between the droplet center and the contact center, m
- p :
-
pressure, Pa
- ΔP L :
-
left side pressure of liquid, Pa
- ΔP R :
-
right side pressure of liquid, Pa
- ΔP :
-
capillary pressure, Pa
- R :
-
radius of droplet, m
- R L :
-
left side curvature of the lubricant layer, m
- R R :
-
right side curvature of the lubricant layer, m
- t :
-
time, s
- T :
-
time ratio
- t a :
-
actual lubrication time, s
- t n :
-
nominal lubrication time, s
- u e :
-
entrainment speed, m/s
- u sp :
-
spreading speed, m/s
- v :
-
velocity of liquid, m/s
- V :
-
volume of droplet, m3
- v′:
-
average velocity of liquid, m/s
- w :
-
applied load, N
- x, y, z :
-
coordinates, m
- γ :
-
surface tension, N/m
- η :
-
viscosity, Pa·s
- θ :
-
contact angle, degree
References
Tret’yakov E I, Yurchenko N A, Lysyak A A. Improving oil-air lubrication systems. Metallurgist 48(7–8): 414–416 (2004)
Höhn B R, Michaelis K, Otto H P. Minimised gear lubrication by a minimum oil/air flow rate. Wear 266(3–4): 461–467 (2009)
Dudorov E A, Ruzanov A I, Zhirkin Y V. Introducing an oil-air lubrication system at a continuous-casting machine. Steel in Translation 39(4): 351–354 (2009)
Jeng Y R, Gao C C. Investigation of the ball-bearing temperature rise under an oil-air lubrication system. Proc Inst Mech Eng Part J: J Eng Tribol 215(2): 139–148 (2001)
Wu C H, Kung Y T. A parametric study on oil/air lubrication of a high speed spindle. Precis Eng 29(2): 162–167 (2005)
Jiang S H, Mao H B. Investigation of the high speed rolling bearing temperature rise with oil-air lubrication. ASME J Tribol 133(2): 021101 (2011)
Moon J H, Lee H D, Kim S I. Lubrication characteristics analysis of an air-oil lubrication system using an experimental design method. Int J Prec Eng Manuf 14(2): 289–297 (2013)
Spikes H. Sixty years of EHL. Lubr Sci 18(4): 265–291 (2006)
Damiens B, Venner C H, Cann P M E, Lubrecht A A. Starvation lubrication of elliptical EHD contacts. ASME J Tribol 126: 105–111 (2004)
Guo F, Wong P L. A multi-beam intensity-based approach for thin lubricant film measurements in non-conformal contacts. Proc Inst Mech Eng J Eng Tribol 216: 281–291 (2002)
Pemberton J, Cameron A. A mechanism of fluid replenishment in elastohydrodynamic contacts. Wear 37: 185–190 (1976)
Jocord B, Pubilier F, Cann P M E, Lubrecht A A. An analysis of track replenishment mechanisms in the starved regime. In Proceedings of the 25th Leeds-Lyon Symposium on Trib, 1999: 483–492.
Liu X, Guo D, Liu S, Xie G, Luo J. Interfacial dynamics and adhesion behaviors of water and oil droplets in confined geometry. Langmuir 30: 7695–7702 (2014)
Acknowledgement
The authors would like to express their thanks to the financial supports from the Natural Science Foundation of China (No. 51405525), Doctoral Scientific Fund Project of the Ministry of Education of China (No. 20133721110002) and Outstanding Young Scientist in Shandong Province (No. BS2014ZZ004).
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Feng GUO. He got his Ph.D. degree in mechanical engineering from the City University of Hong Kong in 2003. He is now employed as a full-time professor in Qingdao University of Technology. His main work is concentrated on fundamental research and university education in tribology. His research interests include numerical computation of liquid film lubrication, optical interferometry for lubricating film measurement, interfaces in tribology, and new lubrication techniques.
Xinming LI. He got his Ph.D. degree in School of Mechanical Engineering, Qingdao University of Technology in 2012. He is now employed as a full-time associate professor in Qingdao University of Technology. His recent research interests include bearing lubrication mechanisms, lubricant rheology, and lubrication approaches of machine elements.
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Li, X., Guo, F., Wang, S. et al. Behaviors of a micro oil droplet in an EHL contact. Friction 4, 359–368 (2016). https://doi.org/10.1007/s40544-016-0132-8
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DOI: https://doi.org/10.1007/s40544-016-0132-8