Session: 01-13: Thermal Management and Aero-engine Oil Systems II

Submission Number: 177816

Mechanism Analysis and Parametric Influence on Oil Capture Performance in Under-Race Lubrication of Aero-Engine Bearings 

Aero-engines are high-speed rotating thermomechanical systems whose main shaft bearings operate under extreme conditions characterized by high rotational speeds, heavy loads, and elevated temperatures. Efficient lubrication and cooling are not only critical to ensuring long bearing life and high reliability but also fundamental to the safe and stable operation of the engine. With the continuous increase in engine thrust and power output, the bearing DN value (the product of bearing diameter and rotational speed) rises correspondingly, leading to a significant increase in heat generation. To achieve long-term stable bearing operation, the lubrication system must deliver an appropriate amount of lubricant oil to effectively reduce friction and wear while removing the generated heat in a timely manner. The lubrication methods commonly employed in aero-engines include direct jet lubrication and under-race lubrication. In the direct jet configuration, airflow resistance and centrifugal forces hinder oil penetration into the bearing, thereby limiting lubrication and cooling effectiveness. In contrast, under-race lubrication utilizes an oil scoop, which rotates with the main shaft to capture oil discharged from the oil jet nozzle. The captured oil is then conveyed through oil passages to the inner race of the bearing, where it enters the rolling element region via inner race oil holes under the action of centrifugal force, achieving efficient lubrication and cooling. This method offers distinct advantages in thermal management by significantly reducing the inner race temperature. However, during the oil capture process, intense shear and impact interactions occur between the oil, the high-speed airflow, and the rotating oil scoop, generating a complex two-phase oil-air flow. As a result, part of the supplied oil cannot be effectively captured, which deteriorates the oil capture performance. In actual operation, aero-engines experience highly variable working conditions, and the oil supply parameters (such as flow rate and temperature) vary considerably under different operating states. These variations further influence the oil-air two-phase flow characteristics and the oil capture efficiency. Therefore, elucidating the effects of oil supply parameters on oil capture performance in under-race lubrication is of great scientific significance and practical engineering value.

To investigate the underlying mechanisms of oil-air two-phase flow and the evolution of oil capture performance, this study combines experimental testing with numerical simulation to conduct a systematic analysis of the internal flow behavior and oil capture characteristics in under-race lubrication. The discrepancy between experimental and numerical results for oil capture performance was within 15%, and the predicted two-phase flow distributions showed good agreement with experimental observations, confirming the validity of the experimental design and the numerical model. On this basis, experimental results were used to reveal the variation trends of oil capture performance with changing oil supply parameters, while numerical analyses were employed to elucidate the corresponding flow mechanisms. The results indicate that, under constant oil flow rate or supply pressure, increasing the oil temperature enhances both the captured oil mass flow rate and oil capture efficiency. In particular, at constant supply pressure, the reduction in oil viscosity improves the flow characteristics of the oil jet nozzle, leading to a more pronounced improvement in oil capture performance. The oil capture efficiency increased by more than 20%, while the captured oil mass flow rate more than doubled. Furthermore, to enable efficient prediction of oil capture performance, a high-accuracy surrogate model was developed using a neural network approach. The predicted oil capture performance exhibited a root mean square error of less than 0.1, with a maximum prediction error below 2.0%, demonstrating that the proposed model provides an effective tool for optimizing the design and parameter matching of under-race lubrication systems in aero-engine bearings.

Presenting Author: Le Jiang Northwestern Polytechnical University

Presenting Author Biography: Jiang Le is a Professor at the School of Power and Energy, Northwestern Polytechnical University. His research primarily focuses on the mechanical systems of aero-engines, with an emphasis on the fundamental study and engineering applications of gas-liquid two-phase flow and heat transfer. He has participated in the development of several key aero-engine models and has served as the principal investigator or lead researcher for multiple national research projects, including sub-topics of the National Science and Technology Major Project and projects funded by the National Natural Science Foundation of China. As the first or corresponding author, he has published more than twenty SCI/EI-indexed papers in high-impact international and domestic journals, and he holds over ten authorized invention patents and software copyrights.

Authors:

Le Jiang Northwestern Polytechnical University
Wenjun Gao Northwestern Polytechnical University
Yaguo Lyu Northwestern Polytechnical University
Yewei Liu Northwestern Polytechnical University
Yankun Hou Northwestern Polytechnical University
Chi Zhang Northwestern Polytechnical University