Dynamics of a rotor-aerostatic journal bearings system with asymmetric air feeding


Dal A., KARAÇAY T.

JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING, vol.44, no.8, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 44 Issue: 8
  • Publication Date: 2022
  • Doi Number: 10.1007/s40430-022-03601-z
  • Journal Name: JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Communication Abstracts, Compendex, INSPEC, Metadex, Civil Engineering Abstracts
  • Keywords: Asymmetric air supply, Pneumatic hammer instability, Self-excited vibration, Nonlinear rotor dynamics, Aerostatic journal bearings, PNEUMATIC HAMMER, THRUST BEARING, STABILITY, INSTABILITY, PERFORMANCE
  • Gazi University Affiliated: Yes

Abstract

In this study, the effect of the symmetric and asymmetric air feeding on the dynamics of a shaft-aerostatic journal bearing system is theoretically investigated. In this scope, the pressure distribution of the air in the clearance is modeled with Reynold's equation and the lubrication forces are calculated using this distribution. Then, equations of motion derived in four degrees of freedom are solved for different rotational speeds under symmetric and asymmetric air feeding conditions. To validate the simulation results, an experimental test rig comprised of a rotor, air bearings, and measurement equipment is set up and run for different rotational speeds. The nonlinear dynamic behavior of the imbalance responses of the bearing-shaft system is analyzed using bifurcation diagrams, Poincare map, waterfall, and orbit plots. The results of the presented study brought to light that the system has a nonlinear dynamic motion due to a pneumatic hammer. However, the pneumatic hammer frequency of an aerostatic bearing with asymmetric supply pressure condition is lower than an aerostatic bearing with the symmetric condition. And the results also showed that the bearing performance will be improved by asymmetric supply pressure conditions.