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Thermohydrodynamic Instability in Fluid-Film Bearings aims to establish instability criteria for a rotor-bearing system associated with fluid-film journal bearings. • It focuses on how the influencing factors such as rotor flexibility, manufacturing imperfections such as residual shaft unbalance, and service-related imperfections such as uneven wear affect the stability of a rotor-bearing system • It shows how the specific operating conditions such as oil inlet temperature, inlet pressure, and inlet position of a rotor-bearing system directly influence the system stability • General design guidelines have been summarized to guide the engineering system design and the correction of failure and/or malfunction
The lecture introduces the basic principles of hydrodynamic lubrication and the fundamental equation of Classical Lubrication Theory. The analysis proceeds to derive the static and dynamic performance characteristics of short length cylindrical journal bearings, with application to the dynamic forced performance of a rigid rotor supported on plain bearings. In a radial bearing, the Sommerfeld number defines a relationship between the static load and the journal eccentricity within the bearing. This design parameter shows the static performance of the bearing as rotor speed increases. Rotordynamic force coefficients are introduced and their effect on the stability of a rotor-bearing system thoroughly discussed. Cross-coupled force coefficients are solely due to journal rotation, and the magnitude (and sign) of the cross-stiffness determines rotordynamic stability. The whirl frequency ratio (WFR) relates the whirl frequency of subsynchronous motion to a threshold speed of instability. The desired WFR is null; however, plain cylindrical bearings show a whirl ratio of just 0.50, limiting the operation of rotating machinery to shaft speeds below twice the system first critical speed. The analysis concludes with a review of practical (in use) journal bearing configurations with highlights on their major advantages and disadvantages, including remedies to reduce or entirely avoid subsynchronous whirl instability problems.
Comprehensive coverage of fluid film lubrication Written by global experts in the field, this in-depth engineering resource discusses the theory, design, analysis, and application of fluid film lubrication, providing proven methods for reducing friction in rotating machinery components. The book thoroughly addresses all aspects of the topic, from viscosity and rotor-bearing dynamics to elastohydrodynamic lubrication and fluid inertia effects. Fully worked examples, analytical and numerical methods of solutions, practice problems, and detailed illustrations are included in this authoritative reference. Fundamentals of Fluid Film Lubrication covers: Introduction to tribology Viscosity and rheology of lubricants Mechanics of lubricant films and basic equations Hydrodynamic lubrication Finite bearings Thermohydrodynamic analysis of fluid film bearings Design of hydrodynamic bearings Dynamics of fluid film bearings Externally pressurized lubrication Fluid inertia effects and turbulence in fluid film lubrication Gas-lubricated bearings Hydrodynamic lubrication of rolling contacts Elastohydrodynamic lubrication Vibration analysis with lubricated ball bearings Thermal effect in rolling–sliding contacts
The Phase 2 (1994) Annual Progress Report presents two major report sections describing the thermal analysis of tilting- and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings. A literature review on the subject of two-phase flow in fluid film bearings and part of the proposed work for 1995 are also included. The programs delivered at the end of 1994 are named hydroflext and hydrotran. Both codes are fully compatible with the hydrosealt (1993) program. The new programs retain the same calculating options of hydrosealt plus the added bearing geometries, and unsteady flow and transient forced response. Refer to the hydroflext & hydrotran User's Manual and Tutorial for basic information on the analysis and instructions to run the programs. The Examples Handbook contains the test bearing cases along with comparisons with experimental data or published analytical values. The following major tasks were completed in 1994 (Phase 2): (1) extension of the thermohydrodynamic analysis and development of computer program hydroflext to model various bearing geometries, namely, tilting-pad hydrodynamic journal bearings, flexure-pad cylindrical bearings (hydrostatic and hydrodynamic), and cylindrical pad bearings with a simple elastic matrix (ideal foil bearings); (2) improved thermal model including radial heat transfer through the bearing stator; (3) calculation of the unsteady bulk-flow field in fluid film bearings and the transient response of a point mass rotor supported on bearings; and (4) a literature review on the subject of two-phase flows and homogeneous-mixture flows in thin-film geometries. Sanandres, Luis Unspecified Center NASA-CR-197412, NAS 1.26:197412 NAG3-1434...
Insightful working knowledge of friction, lubrication, and wear in machines Applications of tribology are widespread in industries ranging from aerospace, marine and automotive to power, process, petrochemical and construction. With world-renowned expert co-authors from academia and industry, Applied Tribology: Lubrication and Bearing Design, 3rd Edition provides a balance of application and theory with numerous illustrative examples. The book provides clear and up-to-date presentation of working principles of lubrication, friction and wear in vital mechanical components, such as bearings, seals and gears. The third edition has expanded coverage of friction and wear and contact mechanics with updated topics based on new developments in the field. Key features: Includes practical applications, homework problems and state-of-the-art references. Provides presentation of design procedure. Supplies clear and up-to-date information based on the authors’ widely referenced books and over 500 archival papers in this field. Applied Tribology: Lubrication and Bearing Design, 3rd Edition provides a valuable and authoritative resource for mechanical engineering professionals working in a wide range of industries with machinery including turbines, compressors, motors, electrical appliances and electronic components. Senior and graduate students in mechanical engineering will also find it a useful text and reference.
Systematic treatment of the fundamentals of fluid film lubrication and fluid film bearings.