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Lubricant oil is crucial to the rolling bearings as the main medium of lubricating, cooling, cleaning, and so on. The oil starvation in and around the contacts is harmful to the performance and fatigue life of rolling bearings. Therefore, it is of necessity to understand the behaviors of oil transfer and the patterns of air–oil two-phase flow in bearings, especially with the influence of different capillary properties. This work established a transient air–oil two-phase flow model in a ball bearing based on computational fluid dynamics (CFD). Groups of cases are implemented to investigate the behaviors of oil transfer and air–oil flow under different capillary conditions with speed, surface tension, and viscosity. Flow patterns are classified by the morphological features of the air–oil flow. Staged phenomena are analyzed with flow patterns and reach good agreements with the observations from experiments. It is found that the oil distribution and air–oil flow behaviors in a ball bearing are strongly related to the speed and the ratio of oil viscosity and air–oil surface tension (μoil/σ). The flow maps imply that the levels of capillary number (Ca) may be the boundaries and the critical points of flow pattern transition between the different flow patterns in bearing.


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Investigation on the oil transfer behaviors and the air–oil interfacial flow patterns in a ball bearing under different capillary conditions

Show Author's information Hongbai CHEN1He LIANG1Wenzhong WANG1( )Shengguang ZHANG2
School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
Aero Engine Academy of China, Beijing 101304, China

Abstract

Lubricant oil is crucial to the rolling bearings as the main medium of lubricating, cooling, cleaning, and so on. The oil starvation in and around the contacts is harmful to the performance and fatigue life of rolling bearings. Therefore, it is of necessity to understand the behaviors of oil transfer and the patterns of air–oil two-phase flow in bearings, especially with the influence of different capillary properties. This work established a transient air–oil two-phase flow model in a ball bearing based on computational fluid dynamics (CFD). Groups of cases are implemented to investigate the behaviors of oil transfer and air–oil flow under different capillary conditions with speed, surface tension, and viscosity. Flow patterns are classified by the morphological features of the air–oil flow. Staged phenomena are analyzed with flow patterns and reach good agreements with the observations from experiments. It is found that the oil distribution and air–oil flow behaviors in a ball bearing are strongly related to the speed and the ratio of oil viscosity and air–oil surface tension (μoil/σ). The flow maps imply that the levels of capillary number (Ca) may be the boundaries and the critical points of flow pattern transition between the different flow patterns in bearing.

Keywords: bearing, computational fluid dynamics (CFD), flow pattern, oil transfer

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Publication history

Received: 24 July 2021
Revised: 23 November 2021
Accepted: 19 December 2021
Published: 20 May 2022
Issue date: February 2023

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© The author(s) 2021.

Acknowledgements

This work was supported by National Key R&D Program of China (2018YFB2000604) and the National Natural Science Foundation of China (51805031) and (JSZL2019213B001).

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