Air-oil mist lubrication of small bore ball bearings at high speeds

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Virginia Polytechnic Institute and State University


Deep groove and angular con tact 25 and 30 mm bore ball bearings were tested to high speeds using air-oil mist lubrication. Test conditions included cooling air flow rates of 1.5, 3.0, and 6.0 scfm (0.05, 0.10, and 0.20 kg/min), thrust loads of 50, 75, and 100 lb (222, 334, and 445 N), and a constant radial load of 25 lb (111 N). Steady-state bearing outer race temperature was recorded at various speeds under each set of test conditions.

Maximum ON values of 1.9 x 10⁶, 1.5 x 10⁶, 1.4 x 10⁶, and 1.26 x 10⁶ were achieved on the 30 mm deep groove, the 25 mm deep groove, the 25 mm angular contact, and the 30 mm angular contact bearings, respectively. Tests were usually terminated when the stabilized outer race temperature reached approximately 200°F (366 K) although the 30 mm deep groove bearing was operated to 240°F (389 K).

A cooling air flow rate of 1.5 scfm (0.05 kg/min) was judged not adequate for high speed bearing operation under the tested conditions.

An outer-race temperature prediction equation, based on a regression analysis of the test results, is presented for each test bearing.