Advancements in the Performance of Aerodynamic Foil Journal Bearings: High Speed and Load Capability

Heshmat, H. “Advancements in the Performance of Aerodynamic Foil Journal Bearings: High Speed and Load Capability,” ASME Paper No. 93-Trib-32, STLE/ASME Tribology Conference, October 24-27, 1993 New Orleans, Louisiana, (1994) Journal of Tribology, Volume 116 (2), pp. 287-295.

An advanced-design, aerodynamic, air-lubricated foil journal bearing achieved a landmark speed of 2200 cps (132,000 rpm) and a major breakthrough in load performance of 673.5 kPa (97.7 psi).  At 20ºC (68ºF) room temperature, normal ambient pressure 995 cps (59,700 rpm) rotor speed, and with bearings projected pad area of 1081 mm2 (1.675 in2), the bearing demonstrated a load capacity of 727.8 N (163.6 lb).  The bearing also exhibited low heat generation, with about 40ºC (104ºF) average side leakage temperature rise.  For this demonstration, a high-speed spindle utilizing a pair of 35-mm (1.375-in) bearings and supporting a test rotor with a mass of 1.545 kg (weighing 3.41 lb) and overall length of 211 mm (8.3 in.) was successfully taken to the limiting speed of the test apparatus.  This speed was set by the maximum sound velocity (Mach 1) in the spindle’s turbine wheel.  The rotor/bearing speed of 4.62 x 106DN is beyond the capability of any advanced oil-lubricated ball bearings or conventional gas-lubricated bearings.  The net results is a highly stable baring at high operating speed.  This paper presents the development of this air-lubricated foil journal bearing, the operational procedures used during testing, test results (dynamic analyses), and load performance characteristics. 


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