SEMI-EMPIRICAL CHARACTERIZATION OF FLOATING-RING BEARING FOR IMPROVED HIGH-SPEED TURBOMACHINERY PERFORMANCE

Abstract

Floating-ring bearings (FRBs) play a crucial role in high-speed turbomachinery by providing improved rotordynamic stability and load-bearing capacity. This study presents a semi-empirical characterization of FRB performance, focusing on the relationships between ring eccentricity, speed ratio, and force coefficients. Results indicate that the ring's eccentricity (ε2) is strongly influenced by the journal eccentricity (ε1) in low clearance ratios (c2/c1), but this dependence weakens as c2/c1 increases. The ring-to-journal speed ratio (NR/NJ) is primarily governed by the inner film Sommerfeld number (Sn1), exhibiting a sharp decline with increasing Sn1 due to variations in rotor speed and bearing load. The evaluation of FRB force coefficients reveals that direct stiffness components (Kxx, Kyy) vary non monotonically with Sn1, while cross-coupled stiffness terms (Kxy, Kyx) become significant at near-centre operations, posing potential instability risks. The direct damping coefficients (Cxx, Cyy) demonstrate high sensitivity to Sn1 and ε1, with Cyy exhibiting particularly strong damping effects in light-load, high-speed conditions, thereby enhancing overall stability. These findings provide valuable insights for optimizing FRB design and operation in turbomachinery, ensuring improved rotordynamic performance, stability, and efficiency.