Experimental Studies On The Lubrication Films With Minimal Quantity Oil Feeding

Oil/air lubrication is an advanced lubrication technology. In fact, in the oil/airlubrication，it is discrete tiny oil droplets that enter into the tribo-pairs and formlubricating oil films.This thesis experimentally investigated the static spreading of asmall oil droplet arround a ball-on-disc contact and dynamic lubricating film generationcharacteristics under pure rolling. The main work includes:(1) Experimental observation of the spreading of micro liquid droplets in thetiny-gaps of a ball-on-disc static contact.Micro droplets will spread around the contact region due to capillary force and itwill definitely have an affect on the lubricating film generation. Studies were carried outto investigate the static spreading process, and the spreading time, the spreadingdistance and the spreading speed of a micro-droplet have been revealed under differentloads, droplet sizes and interfaces.The results show that with the increase of its size, thedroplet’s spreading speed increase. Along with the increase of the viscosity, the droplet’sspreading velocity decreases. Micro droplets show large spreading speeds on the solidsurface of high energy. With the surface tension decreases of the solid surface thedroplet initial spreading radius decreases and the spreading distance significantlyreduced,and moreover, the second-spreading behaviuor appears.(2) Study on the dynamic EHL film generation under lubricant supply withoil-droplets.The lubricant supply in air/oil lubrication is actually realized by some smalloil-droplets.The study on the dynamic process of lubricant film formation by microoil-droplets is of great significance for the development of the oil-gas lubricationtechnology. Studies have been carried out to investigate the lubrication precess with asingle oil droplet supply (the volume is0.1μl), and the relation of the lubricating timeand the speed is the main concern. Experiments have also been carried out and the resultshows that the lubrication time decreases with the increase of the entrainment velocity,and the droplet size also has a dominating influence on the formation of lubricant film. (3) Measurement of the starved lubrication under minimum quantity lubrication.The nature of micro-oil-droplet lubrication is lubrication under starvedconditions. Studies have been carried out to investigate the dynamic lubricant filmshape for a long run undner starved conditions. The results show that the starvation ismore serious as the entrainment velocity increase.The numerical simulation results areconsistent with the experimental results.