73 research outputs found

    A bibliography /with abstracts/ on gas-lubricated bearings Interim report

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    Gas lubricated bearings - annotated bibliograph

    Fundamentals of fluid lubrication

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    The aim is to coordinate the topics of design, engineering dynamics, and fluid dynamics in order to aid researchers in the area of fluid film lubrication. The lubrication principles that are covered can serve as a basis for the engineering design of machine elements. The fundamentals of fluid film lubrication are presented clearly so that students that use the book will have confidence in their ability to apply these principles to a wide range of lubrication situations. Some guidance on applying these fundamentals to the solution of engineering problems is also provided

    Thermal-hydrodynamic behaviour of coated pivoted pad thrust bearings: Comparison between Babbitt, PTFE and DLC

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    The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study is to build a parametric, iterative algorithm in order to perform a complete thermal and hydrodynamic lubrication analysis for pivoted pad thrust bearings with coatings. The analytical model is mainly based on the energy, continuity and Navier-Stokes equations, which are solved numerically with the Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC) method. The analysis focuses on a single pivoted pad of the thrust bearing. The thermal properties of the coating material are taken into account and the resulting thermal and flow fields are solved. The basic hydrodynamic and tribological characteristics are calculated for an uncoated, a Babbitt coated, a PTFE coated and a diamond like carbon (DLC) coated pivoted pad thrust bearing. The pressure and the film thickness distribution, as well as the load capacity and the frictional forces, are determined for several pad positions and velocities of the rotor. A mineral oil lubricant is used to estimate the shear thinning or thickening effects on the pad tribological performance. The results indicate that pads coated with PTFE and DLC show lower friction forces compared to the common steel and Babbitt applications. At the same time, the DLC coating seems to affect the bearing's flow and thermal fields less than the PTFE, making it more suitable for thrust bearings applications

    The status of gas-lubricated bearings

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    The idea of gas-lubricated bearings was suggested as far back as 1854 by Hirn, but it is only very recently that they have aroused a great amount of interest. The interest is centered on the advantages of gas-bearings for the following major applications: High temperature lubrication where ordinary liquid or grease lubrication fails. Bearings operating in radio-active atmospheres where conventional lubrication may break down. Applications sensitive to contamination where fouling from lubricating oil becomes serious. Low-friction devices--an especially important advantage because of the trend to high speed machinery. Applications where positional accuracies down to micro-inches are required. As a result of the increasing interest, many people are working in this field and gas bearings have been used for a variety of purposes, both in the laboratory and in industry on a small scale. There is a definite lack of published information relating to their systematic design. It is possible to design a gas bearing for a particular purpose and to make it function satisfactorily, but it is often difficult to achieve the optimum design from the standpoint of maximum load, minimum friction, economic gas flow and maximum stability. It is the purpose of this thesis to collect all possible literature with a view of finding out what has been done up to this time, so that further theoretical and experimental investigations may be carried out with a view of formulating a complete theory for the design and operation of gas bearings in par with the liquid and grease lubricated bearings. The subject has been divided into two main parts, because the basic principles underlying the two are quite different: Hydrodynamic or Self-acting Bearings. Hydrostatic or Pressurized Bearings. In each part an attempt has been made to cover the following topics: Basic Theory. Experimental Results and Their Comparison with Theoretical Predictions. Stability. Effects of Various Parameters on the Performance. Some Practical Aspects --Introduction, pages 9-10

    Fundamentals of Fluid Film Journal Bearing Operation and Modeling

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    TutorialTutorial 14: Widely used in turbomachinery, the fluid film journal bearing is critical to a machine’s overall reliability level. Their design complexity and application severity continue to increase making it challenging for the plant machinery engineer to evaluate their reliability. This tutorial provides practical knowledge on their basic operation and what physical effects should be included in modeling a bearing to help ensure its reliable operation in the field. All the important theoretical aspects of journal bearing modeling, such as film pressure, film and pad temperatures, thermal and mechanical deformations and turbulent flow are reviewed. Through some examples, the tutorial explores how different effects influence key performance characteristics like minimum film thickness, Babbitt temperature as well as stiffness and damping coefficients. Due to their increasing popularity, the operation and analysis of advanced designs using directed lubrication principles, such as inlet grooves and associated starvation issues, are also examined with several examples including comparisons to manufacturers’ test data

    Fundamentals of Fluid Film Journal Bearing Operation and Modeling

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    TutorialWidely used in turbomachinery, the fluid film journal bearing is critical to a machine’s overall reliability level. Their design complexity and application severity continue to increase making it challenging for the plant machinery engineer to evaluate their reliability. This tutorial provides practical knowledge on their basic operation and what physical effects should be included in modeling a bearing to help ensure its reliable operation in the field. All the important theoretical aspects of journal bearing modeling, such as film pressure, film and pad temperatures, thermal and mechanical deformations and turbulent flow are reviewed. Through some examples, the tutorial explores how different effects influence key performance characteristics like minimum film thickness, Babbitt temperature as well as stiffness and damping coefficients. Due to their increasing popularity, the operation and analysis of advanced designs using directed lubrication principles, such as inlet grooves and associated starvation issues, are also examined with several examples including comparisons to manufacturers’ test data

    Nuclear Brayton turboalternator-compressor (TAC) conceptual design study

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    A comprehensive analysis and conceptual design study of the turboalternator-compressor components was performed using HeXe as the working fluid. Individual turbine, alternator, compressor, and bearing and seal designs were evaluated. Six turboalternator-compressor TAC configurations were completed. One TAC configuration was evaluated to calculate its performance when operating under new cycle conditions,namely, one higher and one lower turbine inlet temperature and one case with krypton as the working fluid. Based on the results, a TAC configuration that incorporated a radial compressor, a radial turbine, a Lundell Alternator, and gas bearings was selected. A new layout of the TAC was prepared that reflects the cycle state points necessary to accommodate a zirconium hydride moderated reactor and a 400 Hz alternator. The final TAC design rotates at 24,000 rpm and produces 160 kWe, 480V, 3-phase, 400 hertz power

    Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings

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    A thermohydrodynamic analysis is presented and a computer code developed for prediction of the static and dynamic force response of hydrostatic journal bearings (HJB's), annular seals or damper bearing seals, and fixed arc pad bearings for cryogenic liquid applications. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility and thermal effects. The analysis and computational model devised allow the determination of the flow field in cryogenic fluid film bearings along with the dynamic force coefficients for rotor-bearing stability analysis
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