Numerical study on the dynamic performance of rotor supported by combined bump foil air bearings

This study investigates the dynamic performance of a rotor supported by the combined bump foil air bearings previously proposed by the authors. A fluid-structure interaction model is developed for the air foil bearing through coupled solutions of the Reynolds equation and the foil structure deformation equation. The dynamic stiffness and damping characteristics of the air foil bearing are determined by solving the dynamic Reynolds equation using the perturbation method. A lumped parameter model of the bearing-rotor system is established, and its dynamic characteristics are investigated using the Riccati transfer matrix method. The model accuracy is validated through comparative analysis of the first 6 modal frequencies obtained from hammer tests and computational results. Building upon this foundation, a numerical study is conducted to examine the influence of foil structure parameters on the rotor's dynamic coefficients in a specific case. Furthermore, a comprehensive dynamic analysis of the bearing-rotor system is performed, including determination of critical speeds, vibration modes, and shaft center trajectory. The influence of rotor unbalance mass moment on rotor stability is numerically investigated, yielding consistent and systematic conclusions. This study establishes a theoretical foundation for the potential application of combined bump foil air bearings in rotor support systems.