OIL DROP FORMATION AT THE OUTLET OF AN ELASTOHYDRODYNAMIC LUBRICATED POINT-CONTACT

The loss of lubricant from grease-lubricated bearing surfaces is deter mined by a number of different mechanisms such as side-flow out of the contacts, evaporation, drop formation, oxidation etc. Some of the dro ps formed behind a rolling element in a bearing will be enrolled by th e next rolling element but some will be lost from the bearing. This lo ss of lubricant is dependent to a high degree on the speed of the air flow through the bearing and is one of the reasons for early failure o f grease lubrication in bearings operating in strong, axial air stream s. To evaluate the most important parameters in drop formation, the dr oplets being thrown out from the outlet of an elastohydrodynamic con t act were analyzed using picture processing and statistical methods. An empirical model has been built to describe mathematically the princip al factors involved in the volume flow thrown out into the air at the outlet side of the Hertzian contact area. For example, drops in a ball bearing will contribute to the inlet feed of oil for the next ball if it is not lost by sideways flow out from the bearing.