Experiment And Simulation Studies On Annular Flow And Lubrication Properties In Oil-air Lubrication System

Oil-air lubrication and traditional oil lubrication are quite different. One of the differences between them is that lubricant in oil-air lubrication is transported in the form of annular flow which drove by high-speed air. As a result, oil supply in the oil-air lubrication is more accurate, more constant, and lubrication property of the oil-air lubrication is better than the traditional oil lubrication. A special working condition is essential to the formation of annular flow in the pipe, and stable transportation of the annular flow is also associated with many parameters of the system. Therefore, thorough research of the formation, the transportation and the lubrication property of annular flow is of practical importance.Experiments and simulations, aimed at the annular flow’s formation in the oil-air mixer, stability in the transportation of the pipe and lubrication property for high-speed rolling bearings, are done in this thesis. The main research work and conclusions are as follows,(1) Property evaluation experiments of oil-air annular flow, according to the actual conditions in oil-air lubrication, are designed, and a self-developed oil-air lubrication experimental rig and the ECT detection technology are employed in experiments.(2) Property experiments for the oil-air annular flow in horizontal pipes in the self-developed oil-air lubrication experimental rig are done. The influences of oil’s quantity and air’s pressure on oil film’s thickness and oil film’s speed are studied. The results show that, with the small to large quantity of oil supply, the oil film’s thickness changes along a S-type curve and the oil film’s speed changes along an inverted U-type curve; with the increase of air’s pressure, the thickness of oil film tend to be thin and the speed of oil film tend to be stable. There is a supply interval of oil’s quantity and air’s pressure, in which the oil-air annular flow is the most stable.(3) Property experiments of oil-air mixer are done. The thickness ratio of upper to lower oil film and the oil content of annular flow at the export pipeline near the oil-air mixer are chosen as property evolution indexes of the oil-air mixer. The influences of oil’s quantity and air’s pressure on the mixing property are studied. The results show that reasonable parameters of lubrication can significantly improve the mixing property of mixer.(4) According to the actual condition of oil-air lubrication, a unique inlet nozzle of oil-air annular flow is designed, and thermal-fluid coupling simulation of rolling bearing with oil-air lubrication is done. Simulation with traditional oil lubrication is done in the same working condition, to compare with the result of oil-air lubrication. The results show that the highest temperature of the rolling bearing under oil-air lubrication is much lower than the one under the traditional oil lubrication, in the condition of high rotational speed.