Analysis of oil supply phenomena by sintered porous reservoirs

Different ways of supplying a liquid film with lubricant initially containe d in a porous structure have been investigated experimentally: centrifugati on, creeping by roughness or thermal effects. Observations and measurements concerning sintered porous materials (polyimide, stainless steel) impregna ted with conventional lubricants for space applications (MAC or PFPE) are p resented and discussed in this paper. Centrifugation caused the release of lubricant from the porous structure when a threshold in relational speed ha d been reached, proving consistent with an analytical model in which the th reshold is a function of oil surface tension and pore radius. We also obser ved some leakage from porous samples deposited on rough stainless-steel sub strates. But the lost volume did nor depend on surface roughness. On the ot her hand, a temperature gradient representative of the temperature distribu tion in running ball bearings proved unable to make the oil spread out from the tank, although capillary effects due to roughness did.