Oil film analysis and axial uniform distribution optimization for the sliding bearing in GTF engines

GTF滑动轴承润滑油膜分析与轴向分布优化

School of Mechanical Engineering, Northwestern Polytechnical University, Xi′an 710072, China

Received: 22 April 2024

Abstract

The journal bearings of planetary gear are the key technologies of the gearbox in geared turbo fan engine(GTF). GTF journal bearings are usually operated under high-speed, heavy-load, and large-eccentricity conditions. The harsh operating conditions results in high oil temperature and thermal deformations, non-uniform oil film thickness, journal inclination, and furtherly increase the failure risks. To improve the service life and operating safety of GTF journal bearings, the performance parameter of axial physical field homogenization was defined. The performance characteristics of GTF journal bearing were studied based on the thermal-elastohydrodynamic lubrication method under high-speed, heavy-load, and large-eccentricity conditions. The influence of journal inclination and thermal effect was included. The performance comparisons were conducted under various working conditions for journal bearings with four different journal profile, which were defined as R-profile, L-profile, convex profile, and linear profile. The effect of different journal profile on the bearing performance are studied. The performance of R-profile journal bearing is selected out and optimized by multi-objective optimization. The results indicated that the performance characteristics can be improved by the design of axial journal profile. The positive influence can be obtained with the increase of journal eccentricity and rotating speed. Besides, the improvement of R-profile journal bearing is the most significant, especially when considering the influence of journal inclinations. Then, the axial physical field homogenization, load carrying capacity, and oil film temperature were selected as optimization objectives. The multi-objective optimizations were carried out based on genetic algorithm for R-profile journal bearing. The bearing performance were significantly improved resulting from the optimization, which considering the influence of axial physical field homogenization. This study provides valuable guides for design of GTF journal bearings with high load carrying capacity and high performance reliability.

摘要

行星齿轮支承滑动轴承是齿轮传动涡扇发动机(geared turbo fan engine, GTF)主减速齿轮箱的关键技术之一, 其一般工作在高转速、高比压和大偏心工况下。苛刻工况加之特殊结构的影响, 使得GTF滑动轴承易出现轴端局部热变形过大、轴向油膜厚度分布不均、倾斜引发轴颈碰磨风险增大等问题, 进而影响滑动轴承及齿轮箱的使用寿命和运行可靠性。针对这一问题, 建立了高转速、高比压、大偏心工况下考虑轴颈倾斜的GTF滑动轴承热弹流润滑分析模型, 以4种不同轴颈轴向母线的滑动轴承为对象, 开展不同条件下的轴承性能对比分析。提出了滑动轴承油膜轴向物理场均匀化这一参数指标, 然后以油膜的温升、承载力、油膜轴向厚度均匀化为目标, 进行了R型轴颈轴向母线的滑动轴承多目标优化, 并对参数优化后的轴承性能进行了分析。结果表明: 通过轴颈轴向母线设计可以显著提升滑动轴承的润滑性能, 且其效果随着偏心率和转速的增大而增加; R型轴颈轴向母线对滑动轴承性能改善效果最明显, 且能降低轴颈倾斜对轴承性能的影响; 以油膜的承载力、温升、膜厚轴向均匀化为目标, 通过多目标优化获得R型轴颈轴向母线滑动轴承，其轴承性能及稳定性均较好。该研究为高承载力和高可靠的GTF滑动轴承设计提供了重要参考。