Entrainment and Inlet Suction: Two Mechanisms of Hydrodynamic Lubrication in Textured Bearings

A new mechanism of hydrodynamic lubrication termed “inlet suction,” applicable to low convergence, micropocketed bearings, has been identified. In this, sliding of one of the bearing surfaces generates a subambient pressure in pockets close to the bearing inlet. Because this pressure is less than the external atmospheric pressure, lubricant is “sucked” into the bearing through the inlet land. This is quite a different mechanism from classical entrainment due to shear. In the current paper flow, hydrodynamic load support and friction are calculated using analytical solutions for simple pocketed bearings having a wide range of convergence ratios, including parallel surfaces. It is found that for the parallel case, inlet suction provides the only mechanism of hydrodynamic load support, and that inlet suction continues to play a major role in load support and friction reduction up to quite high convergence ratios. This mechanism of lubrication is believed to be responsible for the enhanced lubricant film formation and reduced friction of textured bearings, previously reported by a number of authors.