Stability analyses and experiments of spindle system using new type of slot-restricted gas journal bearings

A new type of slot-restricted gas journal bearing with non-uniform slot clearance in the circumferential direction is proposed in this paper. The stability characteristics of the new type of slot-restricted gas bearing are obtained by solving linear equations of motion of rotor with two degrees of freedom supported by one bearing to prove that the proposed new type of the slot-restricted gas journal bearing is much more stable than a conventional slot-restricted bearing. For comparisons with experimental results, the stability characteristics of four degrees of freedom rotor-bearing system are judged by the non-linear transition analyses. The instability threshold speed tests of the rotor-bearing system are performed. The instability threshold speed experimentally obtained is compared with theoretical results to confirm the validity of the numerical analyses. As a result of the analysis and experiment, it was shown that the proposed new type of slot-restricted gas journal bearing is much more stable than a conventional slot-restricted bearing due to non-uniform slot clearance. (C) 2004 Elsevier Ltd. All rights reserved.