Numerical and experimental investigation on two-phase flow and oil capture efficiency of under-race lubrication for high-speed bearings

The increasing rotational speed and temperature levels in modern aeroengines impose higher demands on the lubrication and cooling design of the roller bearings supporting the main shaft. To design a compact and efficient under-race lubrication system, a comprehensive understanding of the characteristics of oil-air two-phase flow and the variations in oil capture efficiency is necessary. This study experimentally investigated the oil capture efficiency and employed numerical simulations to elucidate the mechanisms of oil-air two-phase flow. The results reveal a favorable consistency between the numerical simulations and experimental findings, both in terms of the oil capture efficiency and the oil-air distribution. The decreasing trend of oil capture efficiency gradually stabilizes when the jet distance exceeds 10 mm. To ensure stable and effective testing results for oil capture efficiency, the jet distance should be maintained within the range of 10-14 mm during experiments. Under different operating conditions, there exists an optimal jet angle that maximizes the oil capture efficiency. The corresponding optimal jet angle becomes smaller with lower oil supply pressure and higher rotational speed of the radial oil scoop. Within a momentum flux ratio range of 5-870, an innovative predictive correlation for the optimal jet angle is derived, with a maximum relative error between predicted and experimental values being 4.0%. The proposed correlation provides theoretical support and methodological basis for refining the design of radial under-race lubrication in aeroengines.