The report presents the results of an investigation into the adequacy of presently available theory in predicting the dynamic behavior of a rotor supported in hydrostatic and hydrodynamic gas lubricated journal bearings. Measurements of critical speeds, threshold of instability speeds, gas flow rates, and rotor whirl frequencies for several rotors supported in hydrostatic and hydrodynamic journal bearings were made and compared to theoretical predictions. Variables investigated were bearing load, bearing supply pressure, bearing and gas temperature, and type of bearing supply gas. Good agreement between the experimental and theoretical results was obtained. (Author).

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The gas foil bearing (GFB) technology is a key factor for the transition to oil-free rotating machinery. Among numerous advantages, GFBs offer the unique ability to be lubricated with working fluids such as refrigerants. However, the computational analysis of refrigerant-lubricated GFB–rotor systems represents an interdisciplinary problem of enormous complexity. This work pushes forward existing limits of feasibility and establishes a new strategy that enables stability and bifurcation analyses.

A discussion of models for the behaviour of gas bearings, particularly of the aspects affecting the stability of the system. The text begins with a discussion of the mathematical models, identifying the stiffness and damping coefficients, and describing the behaviour of the models in unstable regions. It then turns to apply these results to bearings: static characteristics and stability of various rotor systems and an extensive discussion of air rings.