Dynamic Behavior of the Spherical Squeeze-Film Hybrid Bearing

The stability and vibration response of a spherical squeeze-film hybrid bearing were analyzed theoretically. Since the squeeze frequency is typically much higher than the vibration frequency, the asymptotic analysis for large squeeze number can be applied here. Perturbation solutions about the radially concentric position were obtained for small vibration amplitudes and small radial displacement. There is no limitation, however, in the values of vibration number (so long as it is small in comparison with the squeeze number), compressibility number, axial displacement ratio, and excursion ratio. Dynamic bearing reactions were computed based on the perturbation solutions. Results indicate that a spherical squeeze-film bearing is always stable in the axial direction. In the radial direction, however, instability about the radially concentric position is possible when there is journal rotation, the frequency of instability is exactly one half of the rotational frequency; the system would be stable if the mass is kept below the critical value. The analysis can be readily extended to compute the response to vibratory excitation in either the axial or the radial direction.