Rotordynamics of Gas-Lubricated Journal Bearing Systems

ISBN-13: 9780387986777 / Angielski / Twarda / 1999 / 152 str.

Krzysztof Czolczynski

Opis

Gas bearings have been used to support rotating parts in a wide range of applications - from magnetic recording heads in computer disk drives to gyroscopes and special machine tools. The advantage of gas bearings is the very low viscosity of air compared to that of most oils used in lubrication. As a result, not only is there much less frictional heat to dissipate, but the bearing remains very nearly isothermal. Gas bearings can thus support rotors spinning at much higher rotational velocities than those lubricated with liquids. This book discusses models for the behavior of gas bearings, particularly of the aspects affecting the stability of the system. It begins with a discussion of the mathematical models, identifying the stiffness and damping coefficients, and describing the behavior 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.

Spis treści

I Theory.- 1. Mathematical Model of a Gas Journal Bearing.- 1.1. Reynolds Equation.- 1.2. Numerical Solution of the Reynolds Equation.- 1.3. Equations of Mass Flow through Feeding System.- 1.4. “Orbit” Model of Gas Bearing.- 2. Identification of Stiffness and Damping Coefficients.- 2.1. Free Vibrations.- 2.2. Step-Jump.- 2.3. Harmonic Forcing.- 2.4. Harmonic Motion of the Shaft.- 2.4.1. Accuracy of the Method.- 2.4.2. Estimation of the Coefficients for any ? andV— Interpolation.- 3. Mathematical Model of Rotor-Gas Bearing System.- 3.1. Equations of Motion — Symmetrical System.- 3.2. Reduced System.- 3.3. Method of Calculation of Eigenvalues.- 3.4. Equations of Motion — Unsymmetrical System.- II Applications.- 4. Gas Bearings.- 4.1. Static Characteristics of Gas Bearings.- 4.2. Stiffness and Damping Coefficients of Gas Bearings.- 4.2.1. Self-Acting Bearings.- 4.2.2. Bearings with the Direct Feeding System.- 4.2.3. Bearings with the Chamber Feeding System.- 4.2.4. Conclusions.- 5. Stability of Rotor — Gas Bearing System.- 5.1. Stability of Rotor with Unmovable Bushes.- 5.2. Stability of Rotor with Elastically Mounted Bushes — Symmetrical (Reduced) System.- 5.2.1. How to Design the Rotor Support.- 5.3. Stability of Unsymmetrical Rotor with Elastically Mounted Bushes.- 5.3.1. Stability of the Homogeneous Shaft Supported in Two Bearings.- 5.3.2. Stability of the Rotor with Concentrated Mass of the Shaft.- 5.3.3. Stability of the Unsymmetrical Rotor with the Unsymmetrical Support of the Bushes.- 5.3.4. An Influence of the Mass of the Bushes on the Size of Always-Stable Loops.- 6. Air Rings.- 6.1. Air Rings with the Direct Feeding System.- 6.2. Air Rings with the Chamber Feeding System.- 6.2.1. Air Hammer.- 6.2.2. Stiffness and Damping Coefficients of Air Rings.- 7. Stability of the Rotor — Bearing — Air Rings System (Applications)..- 7.1. Application 1.- 7.2. Application 2.- 7.3. Application 3.- 7.4. Application 4.- References.- Notation.