Study On Oil Scavenge Characteristics Of Aero-engine Bearing Chamber

Aero-engine bearing chamber is the cavity of rotor bearing operation,which plays a vital role in aero-engine lubrication system.The mixed flow of oil and gas in bearing chamber affects the recovery of lubricant,and the recovery efficiency of lubricant is a key factor affecting the service life of bearings and even engine operation.Aiming at the low efficiency of lubricant recovery in bearing chamber,taking simplified structure of bearing chamber as the research object,the influencing factors of lubricant flow and recovery in bearing chamber of aero-engine were deeply studied by combining theoretical analysis,numerical simulation and test verification.The main research work and achievements are as follows:1.Based on high-speed photography system,a visual bearing chamber test rig was built,and a simplified bearing chamber was designed.The influence laws of rotational speed,oil supply flow rate and return ratio on oil-gas two-phase flow pattern and oilreturn performance(amount of retained lubricant,oil-gas ratio at return outlet and oilreturn ratio)of the bearing chamber were studied.The test shows that with the increase of rotor speed,oil droplets accumulate as oil film adheres to the outer wall,thus reducing oil retention,oil outlet ratio and oil/gas ratio at the scavenge port.The increase of oil supply flow increases the retained lube oil and decrease the oil outlet ratio and oil return ratio.An increase in the return ratio significantly reduces the droplets in the chamber,resulting in a decrease in retention,return ratio and oil/gas ratio.2.Based on VOF model and RNG k-ε Based on the model,the numerical calculation method of bearing chamber was established,and the distribution and motion law of two-phase flow in bearing chamber under different conditions were studied.Clear influence factors of oil-gas mixture interface and oil-return characteristics in bearing chamber were obtained.The results show that the oil is symmetrically distributed along the central axis of the bearing chamber and concentrated in the lower part of the chamber.Lubricating oil accumulates film near the scavenge port of chamber,which affects the discharge of lubricating oil.With the increase of rotational speed,the retention decreases,and the oil film shows a rather uneven serrated distribution along the circumference of the bearing chamber.At the same time,the oil in the upper part of the bearing chamber gradually disappears,the oil-gas ratio in the scavenge port increases and the proportion of oil returns decreases.With the increase of oil supply flow,the accumulation of oil film is more and the ratio of oil to gas at outlet increases exponentially,but the proportion of oil returned first increases and then decreases.With the increase of intake air flow,the oil retention decreases,the oil film becomes thinner and the ratio of oil to gas at outlet and oil return decreases.3.Scavenge sump of different sizes(pool depth,width and thickness)are designed at the bottom of the bearing chamber to improve the low return efficiency of the bearing chamber.Based on the numerical calculation method,the influence of the size of the sump on the two-phase flow pattern and return characteristics of the bearing chamber is systematically studied.The research shows that adding the structure of sump can improve the oil return performance of bearing chamber to a certain extent.The deeper the sump,the less oil retention,the slightly higher the oil return ratio,but at the same time,the lower the oil-gas ratio;Increasing the width of the sump increases the oil/gas ratio at the outlet,but causes the oil retention to increase gradually and the oil return ratio to decrease.The thickness of sump has little influence on oil return ratio and oilgas ratio.When it is smaller than the thickness of bearing chamber,the oil retention increases gradually with the increase of sump thickness.