Comparison of Power Losses and Temperatures between an All-Steel and a Direct Outer Ring–Cooled, Hybrid 133-mm-Bore Ball Bearing at Very High Speeds

ABSTRACT

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.

KEYWORDS:

• Aircraft engines
• gas/jet turbines
• rolling bearings
• ball bearings
• ceramics
• friction
• power loss

Funding

The authors express their acknowledgment to the Federal Ministry for Economic Affairs and Energy for financial support within the cooperative project “Eff_ÖLS–Effective Oil Systems” FKZ 20T1101B, Research Program “Luftfahrtforschungsprogramm IV, 2012–2015 (LuFo)”.