Running performance of an aerodynamic journal bearing with squeeze film effect

• Both numerical and experimental results of the air journal bearing running without and with squeeze film ultrasonic levitation are presented.
• Squeeze film ultrasonic levitation could improve dynamic stability of an air bearing running at speed under very light load.
• The bearing with squeeze film ultrasonic levitation had its instability speed increased four times.

Results of theoretical and experimental studies concerning the performance of an aerodynamic journal bearing of which running is assisted by squeeze film ultrasonic levitation (SFUL) are presented in this paper. The SFUL mechanism not only can separate journal from the bearing at the start and stop phases of operation but also can significantly contribute to the dynamic stability of the bearing when it runs at speed. Computer calculations and validating experimental testing of a prototype device were carried out. It was found that the SFUL mechanism, when combined with aerodynamic lift, significantly extends the threshold speed at which bearing's instability occurs comparing to that of a bearing operating without SFUL. Typically, in numerical calculations the bearing running without SFUL became unstable at the speed of 300 rpm while with the SFUL the speed at which instability became apparent was 10,000 rpm. This capability of the SFUL mechanism on the dynamic stability was also experimentally confirmed.