Friction

, 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

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.

Keywords

oil droplet spreading elastohydrodynamic lubrication optical interferometry 

Nomenclature

a

diameter of Hertz contact, m

D

width of spreading layer, m

Dini

initial droplet diameter, m

hlayer

thickness of spreading droplet layer, m

K

constant

Ls

distance between the droplet center and the contact center, m

p

pressure, Pa

ΔPL

left side pressure of liquid, Pa

ΔPR

right side pressure of liquid, Pa

ΔP

capillary pressure, Pa

R

radius of droplet, m

RL

left side curvature of the lubricant layer, m

RR

right side curvature of the lubricant layer, m

t

time, s

T

time ratio

ta

actual lubrication time, s

tn

nominal lubrication time, s

ue

entrainment speed, m/s

usp

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

Notes

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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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 (http://creativecommons.org/licenses/by/4.0/), 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

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