InfluEnce of Structural Parameters of Combined Bump Foil Radial Air Bearings on Rotor Dynamic Performance

Taking the rotor system supported by the combined bump foil air bearings proposed previously by the authors as the research object, this paper carries out an investigation on its dynamic performance. A fluid–structure interaction model for the combined bump foil air bearings is established by simultaneously solving the Reynolds equation and the deformation equation of the foil structure. The perturbation method is adopted to solve the dynamic Reynolds equation and compute the dynamic performance coefficients of the foil bearings. A lumped-parameter model for the bearing–rotor system is established, and the Riccati transfer matrix method is applied to analyze its dynamic characteristics. The accuracy of the model is verified by comparing the first six modal frequencies obtained from hammer impact tests with those from model calculations. On this basis, numerical calculations are performed to explore the effects of bearing structural parameters—such as radial clearance, top foil thickness, bump foil thickness, and half-length of bump arches—on rotor-dynamic performance, including critical speed and unbalance response. Within a certain range, increasing radial clearance and decreasing top foil thickness helps improve system stability. By contrast, reasonable selection of bump foil thickness and half-length of bump arches can reduce the amplitude of unbalance response and further promote system stability. This study can offer theoretical guidance for the structural design of combined bump foil air bearings and matching rotors.