Effects of Air-ring Bearing Parameters on the Dynamic Stability of Rotor Air-ring Bearing System

An examination of the dynamic stability of an air-ring journal air-bearing, also known as an air-ring bearing (ARB), under external pressurization is presented for a lightweight, rigid, and balanced rotor. Using a two-degrees of freedom solution approach, the dynamic coefficients (DCs) of the ARB are determined at various angular velocities and angular frequencies of vibration of the journal in its range of operation. The dynamic stability of the rotor ARB system (RARBS) against self-excited vibrations is then predicted using these DCs. The verification of dynamic stability is achieved through the solution of the RARBS free-vibration equations. When compared to direct DCs, the effects of cross-coupled DCs on the dynamic stability of RARBS are negligible. Among all the parameters studied, including air-bearing clearance, air-ring (AR) clearance (cAR), feed-hole (FH) orifice diameter, FH chamber diameter, FH chamber depth, and supply air pressure (ps), it was found that cAR and ps had greater effects on DCs. As cAR increases or ps decreases, the ARB's DCs decrease, and RARBS's dynamic stability is attained.