Single-structured zero-bias hybrid gas-magnetic bearing and its rotordynamic performance

A single-structured hybrid gas-magnetic bearing (HGMB) has been proposed for frequent start/stop occasions, which eliminates foil structures or static pressure systems by using the closed magnetic poles of the active magnetic bearing (AMB) as the bushing of the gas bearing. This allows the proposedbearing to realize the functions of both AMB and gas bearing with a single bearing structure. In this paper, the bias currents of AMB, aimed for enhanced load capacity and dynamic characteristics, are omitted to reduce power consumption and heat. The combination of zero-bias AMB and rigid self-acting gas bearing in a single bearing structure is therefore proposed. The rotor orbits of gas bearing, AMB, single-structured HGMB, and single-structured zero-bias HGMB in conditions of varied horizontal and vertical external loads are simulated. The dynamic performances during the run-up processes of AMB, HGMB, and zero-bias HGMB are investigated. The electromagnetic forces of each kind of bearing are compared. Numerical results demonstrate that by applying the single-structured zero-bias HGMB, the power consumption can be significantly reduced in contrast with pure AMB and single-structured HGMB. The reduced load capacity and dynamic characteristics of zero-bias AMB can be compensated by the rigid self-acting gas bearing, making the single-structured zero-bias HGMB an ideal candidate for cryogenic, ultra-high speed as well as frequent start/stop occasions.