, Volume 4, Issue 4, pp 359–368 | Cite as

Behaviors of a micro oil droplet in an EHL contact

  • Xinming Li
  • Feng Guo
  • Shaopeng Wang
  • Chenglong Liu
  • Wenzhong Wang
Open Access
Research Article


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.


oil droplet spreading elastohydrodynamic lubrication optical interferometry 



diameter of Hertz contact, m


width of spreading layer, m


initial droplet diameter, m


thickness of spreading droplet layer, m




distance between the droplet center and the contact center, m


pressure, Pa


left side pressure of liquid, Pa


right side pressure of liquid, Pa


capillary pressure, Pa


radius of droplet, m


left side curvature of the lubricant layer, m


right side curvature of the lubricant layer, m


time, s


time ratio


actual lubrication time, s


nominal lubrication time, s


entrainment speed, m/s


spreading speed, m/s


velocity of liquid, m/s


volume of droplet, m3


average velocity of liquid, m/s


applied load, N

x,y, z

coordinates, m


surface tension, N/m


viscosity, Pa·s


contact angle, degree



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).


  1. [1]
    Tret’yakov E I, Yurchenko N A, Lysyak A A. Improving oil-air lubrication systems. Metallurgist 48(7–8): 414–416 (2004)CrossRefGoogle Scholar
  2. [2]
    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)CrossRefGoogle Scholar
  3. [3]
    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)CrossRefGoogle Scholar
  4. [4]
    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)CrossRefGoogle Scholar
  5. [5]
    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)CrossRefGoogle Scholar
  6. [6]
    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)CrossRefGoogle Scholar
  7. [7]
    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)CrossRefGoogle Scholar
  8. [8]
    Spikes H. Sixty years of EHL. Lubr Sci 18(4): 265–291 (2006)CrossRefGoogle Scholar
  9. [9]
    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)CrossRefGoogle Scholar
  10. [10]
    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)CrossRefGoogle Scholar
  11. [11]
    Pemberton J, Cameron A. A mechanism of fluid replenishment in elastohydrodynamic contacts. Wear 37: 185–190 (1976)CrossRefGoogle Scholar
  12. [12]
    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.Google Scholar
  13. [13]
    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)CrossRefGoogle Scholar

Copyright information

© The author(s) 2016

Open Access:The articles published in this journal are distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  • Xinming Li
    • 1
  • Feng Guo
    • 1
  • Shaopeng Wang
    • 1
  • Chenglong Liu
    • 1
  • Wenzhong Wang
    • 2
  1. 1.School of Mechanical EngineeringQingdao University of TechnologyQingdaoChina
  2. 2.School of Mechanical EngineeringBeijing Institute of TechnologyBeijingChina

Personalised recommendations