Comparative Analysis of Fixed and Tilting Pad Bearings in Rotordynamic Applications

Bearings constitute one of the most critical components in turbo and rotating machinery today. Bearings are fundamental elements in rotating machinery such as turbines, compressors, motors, and pumps, as they support the rotor, control vibration, and influence system stability. Their stiffness and damping properties critically affect rotordynamic behaviour, including critical speeds and overall stability. Among the various types, fluid film bearings are widely used due to their ability to separate surfaces with a thin lubricant film, providing near-infinite life when properly maintained. Operating regimes range from dry friction and mixed lubrication to full hydrodynamic lubrication, with the latter playing the most significant role in rotordynamic performance. Fluid film bearings exist in fixed-geometry (sleeve) and variable-geometry (tilting pad) configurations. Fixed-geometry bearings are simpler and provide higher damping but are more susceptible to instability, while tilting pad bearings offer superior stability by eliminating cross-coupling effects, albeit at higher cost and complexity. The orientation (loadon-pivot vs. load-between-pivots), preload, and design parameters of tilting pad bearings strongly influence stiffness, damping, and thermal behaviour. This paper highlights the rotordynamic implications of bearing design, configuration, and operating regimes, emphasizing their role in vibration control, stability enhancement, and overall machine reliability.