On The Modelling Of Hybrid Aerostatic - Gas Journal Bearings

Stefano Morosi (Invited author), Ilmar Santos (Invited author)

Research output: Contribution to journalConference articleResearchpeer-review


Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more conventional oil bearings, carrying capacity and dynamic characteristics of passive systems are generally poorer. In order to enhance these characteristics, one solution is to combine the hydrodynamic effect with the addition of external pressurization. The present contribution presents a detailed mathematical modeling for hybrid lubrication of a compressible fluid film journal bearing. Additional forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving this equation, stiffness and damping coefficients can be determined. A multibody dynamics model of a global system comprised of rotor and hybrid journal bearing is built in order to study the lateral dynamics of the system. Campbell diagrams and stability maps are presented, showing the main advantages and drawbacks of this special kind of hybrid fluid film bearing.
Original languageEnglish
JournalProceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology
Issue number7
Pages (from-to)641-653
Publication statusPublished - 2011
EventNORDTRIB 2010: Nordic Tribology Conference - Luleå University of Technology, Storforsen, Sweden
Duration: 8 Jun 201011 Jun 2010


ConferenceNORDTRIB 2010
LocationLuleå University of Technology


  • Fluid Film Bearings
  • Rotodynamics
  • Reynolds Equations

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