The basic laws of friction. Fluid Film Bearings. Basic Operational Principles. Hydrodynamic and Hydrostatic Bearing Configurations. Example of rotordynamic study. Performance objectives.
The fundamental assumption in Lubrication Theory. Derivation of thin film flow equations from Navier-Stokes equations. Importance of fluid inertia effects in thin film flows. Some fluid physical properties
Reynolds equation for cylindrical journal bearings. Kinematics of motion and film thickness. Distinction between fixed and rotating coordinates. The pure squeeze velocity vector. Examples of journal motion.
The long and short bearing models. Pressure field and fluid film forces on short length journal bearings. Equilibrium condition, load capacity and the Sommerfeld number.
Equations of motion of a rigid rotor. The concept of force coefficients. Derivation of stiffness and damping coefficients for the short bearing. Stability analysis and the effect of cross-coupled stiffness. Effect of rotor flexibility on stability and imbalance response.
Evaluation of dynamic force coefficients in finite length bearings using a perturbation of the flow equations. Finite Element models: basic equations and their solution.
The nature of turbulence. Turbulence equations in thin film flows. Turbulence flow models. The bulk-flow model of turbulence, Hirs’ and Moody’s friction factors.
When fluid inertia effects are important. Bulk-flow model for inertial flows. Turbulence and inertia in short length journal bearings and open end dampers.
The complete set of bulk-flow equations for the analysis of turbulent flow fluid film bearings. Importance of thermal effects in process fluid applications. A CFD method for solution of the bulk-flow equations.
Floating ring seals for compressors: leakage and force coefficients, seal lock up and effect on rotor stability, recommendations to reduce seal cross-coupled effects. Long oil seals as pressure barriers in industrial mixers: leakage and force coefficients, effect on rotor stability, recommendations for grooved seals with reduced leakage and lesser cross-stiffnesses.
The mechanism of centering stiffness in seals. Force coefficients for short-length pressure seals. Design of annular seals: swirl brakes, impact on rotordynamics. Hydrostatic bearings in modern applications. The principle of hydrostatic lubrication. Effects of recess volume-fluid compressibility on force coefficients for operation at low and high frequencies. Applications of hydrostatic bearings
Appraisal of the art. Design considerations. Force Coefficients. Lubricant cavitation and air entrainment in SFDs. Response of a Rigid Rotor Supported on open-ended SFDs. (*) Digital video clips showing air entrainment in a SFD available at http://rotorlab.tamu.edu/TRIBGroup
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