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High-speed jet engine ball bearings operate under challenging operating conditions, such as high speeds, loads, and temperatures. In addition, they have to meet the highest reliability standards. Thus, they require advanced materials, designs, and cooling systems. Though new materials, heat treatments, and component designs have been developed to meet these challenging requirements, the design of the raceway curvature ratio mainly follows the classical rolling bearing life theory, which is based on subsurface fatigue. But the frictional heating in the contact zone due to the phenomenon of microsliding is not considered in the design of high-speed ball bearings. This article presents the results obtained from rig testing with a state-of-the-art high-speed jet engine ball bearing with various curvature ratios on the inner and outer races. The influence of the curvature ratio on the bearing ring temperatures and the bearing power loss is demonstrated. [ABSTRACT FROM AUTHOR]

The distribution of lubricating oil in the bearing cavity is of great significance to bearing lubrication and cooling. A new idea is provided to further study the ball bearings lubrication, to achieve effective lubrication of bearings. The flow field of oil injection lubrication ball bearings is studied by the moving particle semi-implicit (MPS) method. The accuracy of the numerical calculation method is verified by experiments. The oil distribution of the bearing lubrication flow field and churning torque of the ball and cage at different speeds are analyzed. The research results show the maximum oil content in the bearing cavity is distributed in the range of about 90° to 120°. As the increase of rotating speed, the number of particles in the bearing cavity decreases. The churning torque decreases with the increase of rotating speed and increases with the increase of the oil viscosity. This study provides a new numerical calculation method for the lubrication flow field of ball bearings. [ABSTRACT FROM AUTHOR]

Next-generation aircraft engines will have to face more stringent requirements for reliability, thrust to weight, efficiency, environment protection, and profitability. These requirements affect all engine modules and components, including rolling element bearings. To cope with the above-mentioned requirements, next-generation aircraft engine main shaft bearings will operate under higher loads, speeds, and temperatures and increased reliability. In addition, lighter weight components are desirable. Hence, new material and cooling technologies including weight- and stress-optimized designs need to be developed. In this article, the experimental investigation results of a novel main shaft ball bearing featuring ceramic balls, direct outer ring cooling, squeeze film damping, as well as surface-nitrided raceways are presented. Bearing rig testing under typical aircraft engine flight conditions has been performed. Savings for oil flow quantity of more than 45% and for power loss of more than 15% were identified. Outer ring temperature reductions of more than 20 K were achieved due to the use of ceramic ball material and the direct outer ring cooling concept. The ultra-high-speed capability of the bearing was demonstrated. Rotational speeds of 24,000 rpm were achieved at bearing temperatures below 200°C. The fundamental experimental results including oil and bearing temperature distribution, power dissipation, and bearing efficiency are presented. In addition, experimental power loss and temperature results are compared with data for a conventional all-steel bearing. [ABSTRACT FROM AUTHOR]

When a ball bearing is designed with thin rings or is mounted in a flexible housing, the assumption of rigid rings is not true anymore. In this article, an experimental study is presented and a comparison with a numerical model is performed. The numerical approach is based on the coupling between a semi-analytical code and a finite element (FE) model that computes the deformation of the rings and housings. The numerical model accounts for ring ovalization, raceway opening, change of conformity, and structural displacements of the whole assembly. The experimental setup allows investigation of the load–displacement behavior of a four-point contact ball bearing submitted to a static thrust loading. Displacements are measured by an optical method (stereo-correlation) that enables comparison of the surface deformation of the two tested bearings and computation of the rigid-body displacement of the inner ring with respect to the outer ring. A comparison between experimental results, numerical results, with and without consideration of ring and housing stiffness, is presented. The numerical results show the importance of the housing stiffness in the modeling, even with standard ball bearings with relatively large and thick rings. Good agreement between measured quantities and numerical results was found. This permits the prediction of the real nonlinear bearing stiffness (load–displacement curve) with a reasonable margin of error. [ABSTRACT FROM PUBLISHER]