DYNAMIC ANALYSIS OF PIVOTED-PAD JOURNAL GAS BEARING AND ROTOR SYSTEM OF TURBO-COMPRESSOR FOR FUEL-CELL POWER PLANT

摘要

When applying a large size pivoted-pad gas bearing to a turbo-compressor, it is important to evaluate its load capacity, the stability of the pivoted-pad, and the stability of the bearing and rotor system. In this paper, static and dynamic characteristics of the hybrid pivoted-pad gas bearings that make use of not only hydrostatic effects but also self-acting effects were analyzed using matrix method. At first, single-pad load capacities, stiffness and damping coefficients were calculated using the first-order perturbation method around the equilibrium point. Secondly, stiffness and damping coefficients of the single-pad were converted into full-pad data. Then stability thresholds of a gas bearing and rotor system were calculated for various compressibility numbers and support spring stiffness, and the effect of a support spring to a stability threshold was shown.