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Sample records for fluid film bearing

  1. Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings

    Science.gov (United States)

    Andres, Luis San

    1993-01-01

    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.

  2. On the future of controllable fluid film bearings

    DEFF Research Database (Denmark)

    Santos, Ilmar

    2011-01-01

    This work gives an overview of the theoretical and experimental achievements of mechatronics applied to fluid film bearings. Compressible and uncompressible fluids are addressed. Rigid and elastic (deformable) bearing profiles are investigated. Hydraulic, pneumatic, magnetic and piezoelectric...... controllable fluid film bearings is to improve the overall machine performance by: controlling the lateral vibration of rigid and flexible rotating shafts; modifying bearing dynamic characteristics, such as stiffness and damping properties; increasing the rotational speed ranges by enhancing damping...... and eliminating instability problems, for example, by compensating cross-coupling destabilizing effects; reducing start-up torque and energy dissipation in bearings; compensating thermal effects. It is shown that such controllable fluid film bearings can act as “smart” machine components and be applied...

  3. Vibration Characteristics of Hydrodynamic Fluid Film Pocket Journal Bearings

    Directory of Open Access Journals (Sweden)

    N. S. Feng

    2010-01-01

    Full Text Available Theoretical analyses of hydrodynamic fluid film bearings with different bearing profiles rely on solutions of the Reynolds equation. This paper presents an approach used for analysing the so-called pocket bearings formed from a combination of offset circular bearing profiles. The results show that the variation of the dynamic bearing characteristics with different load inclinations for the pocket bearings is less than that for the elliptic bearing counterpart. It is shown that the natural frequencies as well as the critical speeds, and hence the vibrational behaviour, can also be significantly different for an industrial rotor supported by the different bearings.

  4. Mechanical design problems associated with turbopump fluid film bearings

    Science.gov (United States)

    Evces, Charles R.

    1990-01-01

    Most high speed cryogenic turbopumps for liquid propulsion rocket engines currently use ball or roller contact bearings for rotor support. The operating speeds, loads, clearances, and environments of these pumps combine to make bearing wear a limiting factor on turbopump life. An example is the high pressure oxygen turbopump (HPOTP) used in the Space Shuttle Main Engine (SSME). Although the HPOTP design life is 27,000 seconds at 30,000 rpms, or approximately 50 missions, bearings must currently be replaced after 2 missions. One solution to the bearing wear problem in the HPOTP, as well as in future turbopump designs, is the utilization of fluid film bearings in lieu of continuous contact bearings. Hydrostatic, hydrodynamic, and damping seal bearings are all replacement candidates for contact bearings in rocket engine high speed turbomachinery. These three types of fluid film bearings have different operating characteristics, but they share a common set of mechanical design opportunities and difficulties. Results of research to define some of the mechanical design issues are given. Problems considered include transient strat/stop rub, non-operational rotor support, bearing wear inspection and measurement, and bearing fluid supply route. Emphasis is given to the HPOTP preburner pump (PBP) bearing, but the results are pertinent to high-speed cryogenic turbomachinery in general.

  5. Mixed and Fluid Film Lubrication Characteristics of Worn Journal Bearings

    Directory of Open Access Journals (Sweden)

    Toshiharu Kazama

    2012-01-01

    Full Text Available The mixed and fluid film lubrication characteristics of plain journal bearings with shape changed by wear are numerically examined. A mixed lubrication model that employs both of the asperity-contact mechanism proposed by Greenwood and Williamson and the average flow model proposed by Patir and Cheng includes the effects of adsorbed film and elastic deformation is applied. Considering roughness interaction, the effects of the dent depth and operating conditions on the loci of the journal center, the asperity-contact and hydrodynamic fluid pressures, friction, and leakage are discussed. The following conclusions are drawn. In the mixed lubrication regime, the dent of the bearing noticeably influences the contact and fluid pressures. For smaller dents, the contact pressure and frictional coefficient reduce. In mixed and fluid film lubrication regimes, the pressure and coefficient increase for larger dents. Furthermore, as the dent increases and the Sommerfeld number decreases, the flow rate continuously increases.

  6. On Controllable Elastohydrodynamic Fluid Film Bearings

    DEFF Research Database (Denmark)

    Haugaard, Martin Asger

    This thesis gives a theoretical description of the active tilting-pad journal bearing (ATPJB). It provides the qualified reader with the tools to model an ATPJB, while staying clear of pitfalls. The model is based on well known techniques and allows for local stability analyses, harmonic stationary...... are performed for a tilting-pad journal bearing (TPJB) and an ATPJB under static conditions, followed by a generalisation to dynamic conditions (transient as well as stationary harmonic). These analyses will be of interest to experimentalists, since they permit experiments performed on scaled down test rigs...... the addition of a control system may just as well harm rotor-bearing performance as improve it....

  7. Fluid-film bearings: a finite element method of analysis

    International Nuclear Information System (INIS)

    Pururav, T.; Soni, R.S.; Kushwaha, H.S.; Mahajan, S.C.

    1995-01-01

    Finite element method (FEM) has become a very popular technique for the analysis of fluid-film bearings in the last few years. These bearings are extensively used in nuclear industry applications such as in moderator pumps and main coolant pumps. This report gives the methodology for the solution of Reynold's equation using FEM and its implementation in FE software LUBAN developed in house. It also deals with the mathematical basis and algorithm to account for the cavitation phenomena which makes these problems non-linear in nature. The dynamic coefficients of bearings are evaluated by one-step approach using variational principles. These coefficients are useful for the dynamic characterisation of fluid-film bearings. Several problems have been solved using this code including two real life problems, a circumferentially grooved journal bearing for which experimental results are available and the bearing of moderator pump of 500 MWe PHWR, have been solved. The results obtained for sample problems are in good agreement with the published literature. (author). 9 refs., 14 figs., 5 tabs., 2 ills

  8. Correction of compressor critical speed condition through fluid-film bearing optimization

    International Nuclear Information System (INIS)

    Spencer, J.W.; Obeid, V.E.

    1985-01-01

    A critical speed condition for an overhung centrifugal compressor was corrected through a relatively minor bearing modification. The resonant condition was evaluated analytically through rotor dynamic analyses (stability and forced response) which included fluid film bearing characterization and rotor model generation (experimentally evaluated by model analysis). The importance of adequate specification, inspection, and analytical characterization, of fluid film bearings are discussed. The effects of unbalance on the stability of plain journal bearings are also commented upon. 1 ref., 6 figs

  9. Effect of Viscosity Variation on the Micropolar Fluid Squeeze Film Lubrication of a Short Journal Bearing

    Directory of Open Access Journals (Sweden)

    N. B. Naduvinamani

    2013-01-01

    Full Text Available A theoretical study of the effect of the viscosity variation on the squeeze film performance of a short journal bearing operating with micropolar fluid is presented. The modified Reynolds equation accounting for the viscosity variation in micropolar fluid is mathematically derived. To obtain a closed form solution, the short bearing approximation under constant load is considered. The modified Reynolds equation is solved for the fluid film pressure and then the bearing characteristics, such as obtaining the load carrying capacity and the squeeze film time. According to the results evaluated, the micropolar fluid as a lubricant improves the squeeze film characteristics and results in a longer bearing life, whereas the viscosity variation factor decreases the load carrying capacity and squeezes film time. The result is compared with the corresponding Newtonian case.

  10. Dynamic Characteristics of Rotors on Passive and Active Thrust Fluid-film Bearings with Fixed Pads

    Directory of Open Access Journals (Sweden)

    Babin Alexander

    2018-01-01

    Full Text Available Application of fluid-film bearings in rotor machines in many cases could have no alternative due to obvious advantages when compared to roller element bearings. Integration of information technology in mechanical engineering resulting in emergence of a new field of research – mechatronic bearings which allowed tracking condition of the most important parts of a machine and adjusting operational parameters of the system. Application of servo valves to control the flow rate through a fluid-film bearing is the most universal and simple way of rotor’s position control due to relative simplicity of modelling and absence of need to radically change the design of conventional hydrodynamic bearings. In the present paper numerical simulations of passive (conventional as opposed to mechatronic and active hybrid thrust fluid-film bearings with a central feeding chamber are presented, that are parts of a mechatronic rotor-bearing node. Numerical model of an active thrust bearing is based on solution of equations of hydrodynamics, rotor dynamics and an additional model of a servo valve. Various types of control have been investigated: P, PI and PID control, and the dynamic behaviour of a system has been estimated under various loads, namely static, periodic and impulse. A design of a test rig has been proposed to study passive and active thrust fluid-film bearings aimed at, among other, validation of numerical results of active bearings simulation.

  11. Experimental determination of the distributed dynamic coefficients for a hydrodynamic fluid film bearing

    Science.gov (United States)

    Gyurko, John Harrison

    Most current rotor bearing analysis utilizes lumped parameter bearing coefficients to model the static and dynamic characteristics of fluid film bearings. By treating the stiffness and damping properties of the fluid film as acting upon the axial centerline of the rotor, these models are limited in their analysis to first order lateral rotor-bearing motion. The development of numerical methods that distribute the dynamic properties of the fluid film around the bearing circumference allow for higher order analysis of the motion between the bearing and rotor. Assessment of the accuracy of the numerical method used to calculate distributed dynamic fluid film bearing coefficients is performed by developing a novel hydrodynamic journal bearing test rig and experimental testing procedure capable of obtaining measured distributed dynamic coefficients over a range of bearing operating conditions. The instrumented bearing test rig is used to measure the dynamic bearing displacement and fluid film pressure responses from application of an externally applied excitation force. Least squares solution to a system of perturbated pressure equations, populated by measured displacement and pressure responses, is used to determine the hydrodynamic stiffness and damping properties for a finite region of the bearing surface. Incremental rotation of pressure sensors embedded in the body of the test bearing allow for measurement of the fluid film circumferential pressure distribution which is used to calculate a set of experimentally determined dynamic bearing coefficients. Distributed bearing coefficients derived from experimental measurements are compared to numerically calculated distributed coefficients as well as to lumped parameter coefficients generated from experimental and numerical methods found in the literature. Overall, the numerically calculated distributed coefficients successfully model both the circumferential distribution and the operating conditions of the experimental

  12. Analysis of oil lubricated, fluid film, thrust bearings with allowance for temperature dependent viscosity

    Science.gov (United States)

    Pan, C. H. T.; Malanoski, S. B.

    1972-01-01

    A preliminary design study was performed to seek a fluid-film thrust bearing design intended to be part of a high-speed, hybrid (rolling element/fluid film) bearing configuration. The base line used is a design previously tested. To improve the accuracy of theoretical predictions of load capacity, flow rate, and friction power loss, an analytical procedure was developed to include curvature effects inherent in thrust bearings and to allow for the temperature rise in the fluid due to viscous heating. Also, a narrow-groove approximation in the treatment of the temperature field was formulated to apply the procedure to the Whipple thrust bearing. A comparative trade-off study was carried out assuming isothermal films; its results showed the shrouded-step design to be superior to the Whipple design for the intended application. An extensive parametric study was performed, employing isoviscous calculations, to determine the optimized design, which was subsequently recalculated allowing for temperature effects.

  13. Curvilinear Squeeze Film Bearing with Porous Wall Lubricated by a Rabinowitsch Fluid

    Science.gov (United States)

    Walicka, A.; Walicki, E.; Jurczak, P.; Falicki, J.

    2017-05-01

    The present theoretical analysis is to investigate the effect of non-Newtonian lubricant modelled by a Rabinowitsch fluid on the performance of a curvilinear squeeze film bearing with one porous wall. The equations of motion of a Rabinowitsch fluid are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation the modified Reynolds equation is obtained. The analytical solution of this equation for the case of a squeeze film bearing is presented. As a result one obtains the formulae expressing pressure distribution and load-carrying capacity. Thrust radial bearing and spherical bearing with a squeeze film are considered as numerical examples.

  14. Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface....

  15. Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings, phase 2

    Science.gov (United States)

    Sanandres, Luis

    1994-01-01

    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.

  16. Pressure Distribution in a Porous Squeeze Film Bearing Lubricated with a Herschel-Bulkley Fluid

    Directory of Open Access Journals (Sweden)

    Walicka A.

    2016-12-01

    Full Text Available The influence of a wall porosity on the pressure distribution in a curvilinear squeeze film bearing lubricated with a lubricant being a viscoplastic fluid of a Herschel-Bulkley type is considered. After general considerations on the flow of the viscoplastic fluid (lubricant in a bearing clearance and in a porous layer the modified Reynolds equation for the curvilinear squeeze film bearing with a Herschel-Bulkley lubricant is given. The solution of this equation is obtained by a method of successive approximation. As a result one obtains a formula expressing the pressure distribution. The example of squeeze films in a step bearing (modeled by two parallel disks is discussed in detail.

  17. Hydrodynamic Fluid Film Bearings and Their Effect on the Stability of Rotating Machinery

    Science.gov (United States)

    2006-11-01

    Refer to [2] for details on the analytical solution of Eqn. (18). This is not the case for squeeze film dampers (SFDs), however, since the long...on Finite Length Sealed Squeeze Film Dampers , L. San Andrés & J.M. Vance, ASLE Transactions, 30, 3, pp. 384-393, 1987. [5] Turbomachinery...RTO-EN-AVT-143 10 - 1 Hydrodynamic Fluid Film Bearings and Their Effect on the Stability of Rotating Machinery Luis San Andrés Mast

  18. Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface.......The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...

  19. Hydrodynamic Analyses and Evaluation of New Fluid Film Bearing Concepts

    Science.gov (United States)

    Keith, Theo G., Jr.; Dimofte, Florin

    1998-01-01

    Over the past several years, numerical and experimental investigations have been performed on a waved journal bearing. The research work was undertaken by Dr. Florin Dimofte, a Senior Research Associate in the Mechanical Engineering Department at the University of Toledo. Dr. Theo Keith, Distinguished University Professor in the Mechanical Engineering Department was the Technical Coordinator of the project. The wave journal bearing is a bearing with a slight but precise variation in its circular profile such that a waved profile is circumscribed on the inner bearing diameter. The profile has a wave amplitude that is equal to a fraction of the bearing clearance. Prior to this period of research on the wave bearing, computer codes were written and an experimental facility was established. During this period of research considerable effort was directed towards the study of the bearing's stability. The previously developed computer codes and the experimental facility were of critical importance in performing this stability research. A collection of papers and reports were written to describe the results of this work. The attached captures that effort and represents the research output during the grant period.

  20. Mechatronics Applied to Fluid Film Bearings: Towards More Efficient Machinery

    DEFF Research Database (Denmark)

    Cerda Varela, Alejandro Javier

    ; and the successful experimental application of this controllable machine element as a calibrated shaker, for rotordynamics parameter identification purposes. The theoretical model of the studied controllable bearing proves to be adequate to predict the static and thermal behavior of the bearing. Furthermore......The current trends regarding turbomachinery design and operation demand for an expansion of the operational boundaries of these mechanical systems, regarding production rate, reliability and adaptability. In order to face the new requirements, it is necessary to migrate towards a new concept, where...... of modifying the static, thermal and dynamic properties of the bearing, depending on the operational requirements at hand. The research activities carried out during the project included both theoretical as well as experimental investigations, using a test rig consisting of a rigid rotor supported by a tilting...

  1. Unsteady analysis of the fluid film forces in a long-bearing squeeze film damper

    Science.gov (United States)

    Schallhorn, Paul Alan

    The squeeze film damper is a device used to suppress vibrations in turbomachinery. One of two one-dimensional flow assumptions is typically used in the analysis of a squeeze film damper. In the long damper assumption, the flow in the axial direction is considered negligible, and all of the flow is circumferential. To date, all long squeeze film damper analyses have used either steady state methods or perturbation techniques to predict the fluid film force for circular centered orbits. This dissertation describes the first fully unsteady numerical analysis of the long squeeze film damper and compares the predictions of the analysis to experimental data. The Generalized Fluid System Simulation Program (GFSSP) is used to model the fluid flow within the damper. The results provided show that predicted damping falls within the uncertainty of the experimental data, and is a significant improvement over previous steady-state analyses. Additionally, the first unsteady analysis for statically eccentric operation of a squeeze film damper is provided.

  2. Dynamic Stability Analysis and Critical Speed of Rotor supported by a Worn Fluid film Journal Bearings

    Directory of Open Access Journals (Sweden)

    Adnan naji jameel

    2016-03-01

    Full Text Available In this paper, the effect of wear in the fluid film journal bearings on the dynamic stability of rotor bearing system has been studied depending on the development of new analytical equations for motion, instability threshold speed and steady state harmonic response for rotor with offset disc supported by worn journal bearings. Finite element method had been used for modeling the rotor bearing system. The analytical model is verified by comparing its results with that obtained numerically for a rotor supported on the short bearings. The analytical and numerical results showed good agreement with about 8.5% percentage error in the value of critical speed and about 3.5% percentage error in the value of harmonic response. The results obtained show that the wear in journal bearing decrease the instability threshold speed by 2.5% for wear depth 0.02 mm and 12.5% for wear depth 0.04 mm as well as decrease critical speed by 4.2% and steady state harmonic response amplitude by 4.3% for wear depth 0.02 mm and decrease the critical speed by 7.1% and steady state harmonic response amplitude by 13.9% for wear depth 0.04 mm.

  3. Feasibility of Influencing the Dynamic Fluid Film Coefficients of a Multirecess Journal Bearing by means of Active Hybrid Lubrication

    DEFF Research Database (Denmark)

    Santos, Ilmar; Watanabe, F. Y.

    2003-01-01

    The main objective of this research project is the investigation of multirecess hydrostatic journal bearings with active hybrid (hydrostatic and hydrodynamic) lubrication. This paper gives a theoretical contribution to the modeling of this kind of bearing, combining computational fluid dynamics...... and control techniques. The feasibility of influencing the dynamic fluid film coefficients (stiffness and damping) by means of a controllable fluid injection into opposed bearing recesses is investigated. By controlling the pressure and flow injection using servo control systems, it is possible to obtain...

  4. Design review and analysis for a Pratt and Whitney fluid-film bearing and seal testing rig

    Science.gov (United States)

    Childs, Dara W.

    1994-01-01

    A design review has been completed for a Pratt and Whitney (P&W)-designed fluid-film bearing and annular-seal test rig to be manufactured and installed at George C. Marshall Space Flight Center (MSFC). Issues covered in this study include: (1) the capacity requirements of the drive unit; (2) the capacity and configuration of the static loading system; (3) the capacity and configuration of the dynamic excitation system; (4) the capacity, configuration, and rotordynamic stability of a test bearing, support bearings, and shaft; and (5) the characteristics and configuration of the measurement transducers and data channels.

  5. Non-Invasive Parameter Identification in Rotordynamics via Fluid Film Bearings: Linking Active Lubrication and Operational Modal Analysis

    DEFF Research Database (Denmark)

    Santos, Ilmar; Svendsen, Peter Kjær

    2017-01-01

    In recent years, theoretical and experimental efforts have transformed the conventional tilting-pad journal bearing (TPJB) into a smart mechatronic machine element. The application of electromechanical elements into rotating systems makes feasible the generation of controllable forces over...... forces, resulting from a strong coupling between hydrodynamic, hydrostatic and controllable lubrication regimes, can be used either to control or to excite rotor lateral vibrations. If non-invasive forces are generated via lubricant fluid film, in situ parameter identification can be carried out...

  6. Non-Invasive Parameter Identification in Rotordynamics via Fluid Film Bearings: Linking Active Lubrication and Operational Modal Analysis

    DEFF Research Database (Denmark)

    Santos, Ilmar; Svendsen, Peter Kjær

    2016-01-01

    In recent years, theoretical and experimental efforts have transformed the conventional tilting pad journal bearing (TPJB) into a smart mechatronic machine element. The application of electromechanical elements into rotating systems makes feasible the generation of controllable forces over...... forces, resulting from a strong coupling between hydrodynamic, hydrostatic and controllable lubrication regimes, can be used either to control or to excite rotor lateral vibrations. If non-invasive forces are generated via lubricant fluid film, in situ parameter identification can be carried out...

  7. Characterization and experimental validation of a squeeze film damper with MR fluid in a rotor-bearing system

    Science.gov (United States)

    Dominguez-Nuñez, L. A.; Silva-Navarro, G.

    2014-04-01

    The general study and applications of Magneto-Rhelogical (MR) dampers have been spread in the lasts years but only some studies have been focusing on the vibration control problems on rotor-bearings systems. Squeeze-Film Dampers (SFD) are now commonly used to passively control the vibration response on rotor-bearing systems because they can provide flexibility, damping and extend the so-called stability thresholds in rotating machinery. More recently, SFD are combined with MR or Electro-Rheological (ER) fluids to introduce a semiactive control mechanism to modify the rotordynamic coefficients and deal with the robust performance of the overall system response for higher operating speeds. There are, however, some theoretical and technological problems that complicate their extensive use, like the relationship between the centering spring flexibility and the rheological behavior of the smart fluid to produce the SFD forces. In this work it is considered a SFD with MR fluid and a set of circular section beams in a squirrel cage arrangement in combination with latex seals as centering springs. The mathematical model analysis includes the controllable viscoelastic properties associated to the MR fluid. The characterization of the SFD is made by the determination of some coefficients associated with a modified Choi-Lee-Park polynomial model. During the analysis is considered a rotor-bearing system modeled using finite element methods. The SFD with MR fluid is connected to an experimental platform to validate and experimentally evaluate the overall system. Finally, to improve the open-loop system performance, a methodology for the use of different control schemes is proposed.

  8. Feasibility of Influencing the Dynamic Fluid Film Coefficients of a Multirecess Journal Bearing by means of Active Hybrid Lubrication

    DEFF Research Database (Denmark)

    Santos, Ilmar; Watanabe, F. Y.

    2003-01-01

    The main objective of this research project is the investigation of multirecess hydrostatic journal bearings with active hybrid (hydrostatic and hydrodynamic) lubrication. This paper gives a theoretical contribution to the modeling of this kind of bearing, combining computational fluid dynamics...

  9. Hydrodynamic Fluid Film Bearings and Their Effect on the Stability of Rotating Machinery

    National Research Council Canada - National Science Library

    Andres, Luis S

    2006-01-01

    .... 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...

  10. Influence of technological factors on characteristics of hybrid fluid-film bearings

    Science.gov (United States)

    Koltsov, A.; Prosekova, A.; Rodichev, A.; Savin, L.

    2017-08-01

    The influence of the parameters of micro- and macrounevenness on the characteristics of a hybrid bearing with slotted throttling is considered in the present paper. The quantitative assumptions of calculation of pressure distribution, load capacity, lubricant flow rate and power loss due to friction in a radial hybrid bearing with slotted throttling are taken into account, considering the shape, dimensions and roughness of the support surfaces inaccuracies. Numerical simulation of processes in the lubricating layer is based on the finite-difference solution of the Reynolds equation using an uneven orthogonal computational grid with adaptive condensation. The results of computational and physical experiments are presented.

  11. Static, Dynamic, and Thermal Properties of Compressible Fluid Film Journal Bearings

    DEFF Research Database (Denmark)

    Paulsen, Bo Terp; Morosi, Stefano; Santos, Ilmar

    2011-01-01

    Modern turbo-machinery applications, high-speed machine tools, and laboratory equipment require ever-growing rotational speeds and high degree of precision and reliability. Gas journal bearings are often employed because they meet the demands of high-speed performance, in a clean environment, and...

  12. Chaos and bifurcation of a flexible rotor supported by porous squeeze couple stress fluid film journal bearings with non-linear suspension

    International Nuclear Information System (INIS)

    Chang-Jian, C.-W.; Chen, C.-K.

    2008-01-01

    This study presents a dynamic analysis of a flexible rotor supported by two porous squeeze couple stress fluid film journal bearings with non-linear suspension. The dynamics of the rotor center and bearing center are studied. The analysis of the rotor-bearing system is investigated under the assumptions of non-Newtonian fluid and a short bearing approximation. The spatial displacements in the horizontal and vertical directions are considered for various non-dimensional speed ratios. The dynamic equations are solved using the Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor center and bearing center, power spectra, Poincare maps and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The numerical results show that the stability of the system varies with the non-dimensional speed ratios, the non-dimensional parameter l* and the permeability. The modeling results thus obtained by using the method proposed in this paper can be employed to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided

  13. Effect of fluid compressibility on journal bearing performance

    Science.gov (United States)

    Dimofte, Florin

    1993-01-01

    An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system.

  14. Modifications to Marshall's Annular Seal Test (MAST) Rig and Facility for Improved Rotordynamic Coefficient Testing of Annular Seals and Fluid Film Bearings

    Science.gov (United States)

    Darden, J. M.; Earhart, E. M.

    2011-01-01

    The limits of rotordynamic stability continue to be pushed by the high power densities and rotational speeds of modern rocket engine turbomachinery. Destabilizing forces increase dramatically with rotor speed. Rotordynamic stability is lost when these destabilizing forces overwhelm the stabilizing forces. The vibration from the unstable rotor grows until it is limited by some nonlinearity. For example, a rolling element bearing with a stiffness characteristic that increases with deflection may limit the vibration amplitude. The loads and deflections resulting from this limit cycle vibration (LCV) can lead to bearing and seal damage which promotes ever increasing levels of subsynchronous vibration. Engineers combat LCV by introducing rotordynamic elements that generate increased stabilizing forces and reduced destabilizing forces. For example, replacing a labyrinth seal with a damping seal results in substantial increases in the damping and stiffness rotordynamic coefficients. Adding a swirl brake to the damping seal greatly reduces the destabilizing cross-coupled forces generated by the damping seal for even further increases in the stabilizing capacity. Marshall?s Annular Seal Test (MAST) rig is designed to experimentally measure the stabilizing capacity of new annular seal designs. The rig has been moved to a new facility and outfitted with a new slave bearing to allow increased test durations and to enable the testing of fluid film bearings. The purpose of this paper is to describe the new facility and the new bearing arrangement. Several novel seal and bearing designs will also be discussed.

  15. Thin film superconductor magnetic bearings

    Science.gov (United States)

    Weinberger, Bernard R.

    1995-12-26

    A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

  16. Compliant hydrodynamic fluid journal bearing

    Science.gov (United States)

    Warren, E. L. (Inventor)

    1985-01-01

    An air bearing structure is described that prevents destructive bending moments within the top foil. Welds are eliminated by mounting the top bearing foil in the bearing cartridge sleeve without using a space block. Tabs or pins at the end of the top bearing foil are restrained by slots or stops formed in the cartridge sleeve. These structural members are free to move in a direction normal to the shaft while being restrained from movement in the direction of shaft rotation.

  17. Self-lubricating fluid bearing assembly

    International Nuclear Information System (INIS)

    Kapich, D.D.

    1981-01-01

    A sealed self-lubricating fluid bearing assembly is described for circulating fluid in the form of a gas coolant in a nuclear reactor, the power for the circulator being provided by a shaft located within the primary containment vessel. In such a system the reactor coolant is isolated from the fluid region at the far end of the drive shaft. (U.K.)

  18. Studying fluid squeeze characteristics for aerostatic journal bearing

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Rahman, Gamal M. [Department of Mathematics, Faculty of Science, Benha University, Benha 13518 (Egypt)], E-mail: gamalm60@yahoo.com

    2008-07-01

    The Reynolds equation for studying fluid squeeze of aerostatic journal bearing is solved numerically by considering the quasi-steady behavior of the air film. The radial displacement can influence the air film thickness modifying the pressure distribution in the journal-bearing gap. Also, the variations in the seal characteristics with eccentricity, time, squeeze number, length-to-diameter and supply pressure are presented. The numerical results for the squeeze load-carrying capacity are given in a non-dimensional for000.

  19. Hydrodynamic squeeze-film bearings for gyroscopes

    Science.gov (United States)

    Chiang, T.; Smith, R. L.

    1970-01-01

    Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action.

  20. Trends in Controllable Oil Film Bearings

    DEFF Research Database (Denmark)

    Santos, Ilmar

    2011-01-01

    This work gives an overview about the theoretical and experimental achievements of mechatronics applied to oil film bearings, with the aim of: controlling the lateral vibration of flexible rotating shafts; modifying bearing dynamic characteristics, as stiffness and damping properties; increasing...... the rotational speed ranges by improving damping and eliminating instability problems, for example, by compensating cross-coupling destabilizing effects; reducing startup torque and energy dissipation in bearings; compensating thermal effects. It is shown that such controllable bearings can act as "smart......" components and be applied to rotating machines with the goal of avoiding unexpected stops of plants, performing rotordynamic tests and identifying model parameters "on site". Emphasis is given to the controllable lubrication (active lubrication) applied to different types of oil film bearings, i...

  1. Global Dynamics of Shaft Lines Rotating in Surrounding Fluids Application to Thin Fluid Films

    Directory of Open Access Journals (Sweden)

    David Lornage

    2004-01-01

    a disc and a thin-walled shaft mounted on a hydrodynamic bearing. The second is intended for studying a more realistic structure composed of a shaft and a wheel coupled with a fluid film between the wheel and a casing. These applications make it possible to identify trends related to fluid effects and couplings between the flexible structural parts.

  2. EXPERIMENTAL APPARATUS FOR EXAMINATION OF MAGNETIC FLUID LUBRICATED THURST BEARING

    Directory of Open Access Journals (Sweden)

    Józef SALWIŃSKI

    2014-06-01

    Full Text Available In recent years, there has been development of the structure of thrust bearing with magnetic fluids . The essence of this type of bearing is to maintain a liquid lubricant in a very narrow gap with magnetic fluid by a magnetic field. Such systems can act as the bearing lubrication and sealing. This paper presents description of the experimental apparatus for examination magnetic fluid lubricated thrust bearing. Description of the construction and characteristics of the measuring possibilities ware presented.

  3. Thrust Porous Bearing with Rough Surfaces Lubricated by a Rotem-Shinnar Fluid

    Directory of Open Access Journals (Sweden)

    Walicka Anna

    2016-03-01

    Full Text Available In the paper the influence of both bearing surfaces roughness and porosity of one bearing surface on the pressure distribution and load-carrying capacity of a thrust bearing surfaces is discussed. The equations of motion of a pseudo-plastic fluid of Rotem-Shinnar, are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation and Christensen theory of hydrodynamic lubrication the modified Reynolds equation is obtained. The analytical solutions of this equation for the cases of squeeze film bearing and externally pressurized bearing are presented. As a result one obtains the formulae expressing pressure distribution and load-carrying capacity. Thrust radial bearing with squeezed film is considered as a numerical example.

  4. Critical Pressures of the Thrust Bearing Using a Magnetic Fluid

    OpenAIRE

    長屋, 幸助; 武田, 定彦; 佐藤, 淳; 井開, 重男; 関口, 肇; 斉藤, 登

    1990-01-01

    This paper proposes a thrust bearing lubricated by a magnetic fluid under a magnetic field. The critical pressures of the bearing versus the magnitude of the magnetic flux densities have been investigated experimentally. It is clarified that the critical pressures of the proposed bearing are larger than those of the normal lubricant bearing under high speeds.

  5. An Unsteady Long Bearing Squeeze Film Damper Model. Part 1; Circular Centered Orbits

    Science.gov (United States)

    Schallhorn, P. A.; Elrod, D. A.; Goggin, D. G.; Majumdar, A. K.

    2000-01-01

    This paper, the first of a two-part series, presents results of an unsteady rotordynamic analysis of a long-bearing squeeze film damper executing circular centered orbits using a fluid circuit approach. A series of nodes and branches represent the geometry of the flow circuit. The mass and momentum conservation equations are solved to predict the pressure distribution in the squeeze film. The motion of the bearing is simulated by the variation of geometry within the flow path. The modeling methodology is benchmarked against published experimental long-bearing squeeze film damper test results. The model provides good agreement with the experimental damping coefficient.

  6. A Study Of Magnetic Fluid Based Squeeze Film Between Porous ...

    African Journals Online (AJOL)

    Efforts have been made to study and analyze the effect of surface roughness on the performance of magnetic fluid based squeeze film between porous elliptic plates. The transverse roughness of the bearing surface is characterized by a stochastic random variable with non-zero mean, variance and skewness.

  7. Non-Newtonian Effects of Second-Order Fluids on the Hydrodynamic Lubrication of Inclined Slider Bearings.

    Science.gov (United States)

    Apparao, Siddangouda; Biradar, Trimbak Vaijanath; Naduvinamani, Neminath Bhujappa

    2014-01-01

    Theoretical study of non-Newtonian effects of second-order fluids on the performance characteristics of inclined slider bearings is presented. An approximate method is used for the solution of the highly nonlinear momentum equations for the second-order fluids. The closed form expressions for the fluid film pressure, load carrying capacity, frictional force, coefficient of friction, and centre of pressure are obtained. The non-Newtonian second order fluid model increases the film pressure, load carrying capacity, and frictional force whereas the center of pressure slightly shifts towards exit region. Further, the frictional coefficient decreases with an increase in the bearing velocity as expected for an ideal fluid.

  8. Analysis of Nanoparticle Additive Couple Stress Fluids in Three-layered Journal Bearing

    Science.gov (United States)

    Rao, T. V. V. L. N.; Sufian, S.; Mohamed, N. M.

    2013-04-01

    The present theoretical study investigates the load capacity and friction coefficient in a three-layered journal bearing lubricated with nanoparticle additive couple stress fluids. The couple stresses effects are analyzed based on Stokes micro-continuum theory. The nondimensional pressure and shear stress expressions are derived using modified Reynolds equation. The nondimensional load capacity increases and the coefficient of friction decreases using nanoparticle additive lubricants with couple stress effects. The three-layered journal bearing performance characteristics are improved with increase in both (i) surface adsorbent fluid film layer thickness and (ii) dynamic viscosity ratio of surface to core layer.

  9. Analysis of Nanoparticle Additive Couple Stress Fluids in Three-layered Journal Bearing

    International Nuclear Information System (INIS)

    Rao, T V V L N; Sufian, S; Mohamed, N M

    2013-01-01

    The present theoretical study investigates the load capacity and friction coefficient in a three-layered journal bearing lubricated with nanoparticle additive couple stress fluids. The couple stresses effects are analyzed based on Stokes micro-continuum theory. The nondimensional pressure and shear stress expressions are derived using modified Reynolds equation. The nondimensional load capacity increases and the coefficient of friction decreases using nanoparticle additive lubricants with couple stress effects. The three-layered journal bearing performance characteristics are improved with increase in both (i) surface adsorbent fluid film layer thickness and (ii) dynamic viscosity ratio of surface to core layer.

  10. An Unsteady Long Bearing Squeeze Film Damper Model. Part 2; Statically Eccentric Operation

    Science.gov (United States)

    Schallhorn, P. A.; Elrod, D. A.; Goggin, D. G.; Majumdar, A. K.

    2000-01-01

    This paper, the second of a two-part series, presents results of an unsteady rotordynamic analysis of a long-bearing squeeze film damper executing orbits about an off center position using a fluid circuit approach. A series of nodes and branches represent the geometry of the flow circuit. The mass and momentum conservation equations are solved to predict the pressure distribution in the squeeze film. The motion of the bearing is simulated by the variation of geometry within the flow path. This effort represents the first modeling approach which allows for an arbitrary orbit size about an arbitrary position.

  11. Application of computational fluid dynamics and fluid structure interaction techniques for calculating the 3D transient flow of journal bearings coupled with rotor systems

    Science.gov (United States)

    Li, Qiang; Yu, Guichang; Liu, Shulian; Zheng, Shuiying

    2012-09-01

    Journal bearings are important parts to keep the high dynamic performance of rotor machinery. Some methods have already been proposed to analysis the flow field of journal bearings, and in most of these methods simplified physical model and classic Reynolds equation are always applied. While the application of the general computational fluid dynamics (CFD)-fluid structure interaction (FSI) techniques is more beneficial for analysis of the fluid field in a journal bearing when more detailed solutions are needed. This paper deals with the quasi-coupling calculation of transient fluid dynamics of oil film in journal bearings and rotor dynamics with CFD-FSI techniques. The fluid dynamics of oil film is calculated by applying the so-called "dynamic mesh" technique. A new mesh movement approach is presented while the dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. The proposed mesh movement approach is based on the structured mesh. When the journal moves, the movement distance of every grid in the flow field of bearing can be calculated, and then the update of the volume mesh can be handled automatically by user defined function (UDF). The journal displacement at each time step is obtained by solving the moving equations of the rotor-bearing system under the known oil film force condition. A case study is carried out to calculate the locus of the journal center and pressure distribution of the journal in order to prove the feasibility of this method. The calculating results indicate that the proposed method can predict the transient flow field of a journal bearing in a rotor-bearing system where more realistic models are involved. The presented calculation method provides a basis for studying the nonlinear dynamic behavior of a general rotor-bearing system.

  12. External Squeeze-Film Damper For Hydrostatic Bearing

    Science.gov (United States)

    Buckmann, Paul S.

    1992-01-01

    External squeeze-film damping device suppresses vibrations of rapidly turning shaft supported by pivoted-pad hydrostatic bearing in high-pressure/high-power-density turbomachine. Stacked disks provide damping and clearance for alignment.

  13. On the Performance of Pivoted Curved Slider Bearings: Rabinowitsch Fluid Model

    Directory of Open Access Journals (Sweden)

    U.P. Singh

    2012-09-01

    Full Text Available The present theoretical analysis is to investigate the effect of nonNewtonian Pseudoplastic & Dilatant lubricants (lubricant blended with viscosity index improver–Rabinowitsch fluid model on the dynamic stiffness and damping characteristics of pivoted curved slider bearings. The modified Reynolds equation has been obtained for steady and damping states of the bearing. To analyze the steady state characteristics and dynamic characteristics, small perturbation theory has been adopted. The results for the steady state bearing performance characteristics (steady state film pressure, load carrying capacity and centre of pressure as well as dynamic stiffness and damping characteristics have been calculated numerically for various values of viscosity index improver using Mathematical 7.0 and it is concluded that these characteristics vary significantly with the non-Newtonian behavior of the fluid consistent with the real nature of the problem.

  14. Effects of fluid inertia and bearing flexibility on the performance of finite length journal bearing

    Science.gov (United States)

    Javorova, Juliana; Alexandrov, Vassil

    2017-02-01

    The paper describes the theoretical study concerning the effect of lubricant inertia forces and deformability of the bearing elastic layer on the performance of a plane journal bearing. The problem is investigated for a Newtonian lubricant under isothermal and isoviscous conditions. The analysis considers the generalized Reynolds equation governing the flow of lubricant in the clearance space and the linear elasticity equation governing the displacement field in the bearing shell. An iterative numerical procedure with successive over relaxation is used to pressure distribution within the lubricated conjunction. Bearing performance characteristics have been presented for typically selected values of generalized Reynolds number Re* and elasticity parameters of the elastic liner. It has been observed that the combined effect of fluid inertia forces and bearing flexibility affects the performance characteristics of dynamically loaded journal bearing.

  15. Use of thin films in high-temperature superconducting bearings.

    Energy Technology Data Exchange (ETDEWEB)

    Hull, J. R.; Cansiz, A.

    1999-09-30

    In a PM/HTS bearing, locating a thin-film HTS above a bulk HTS was expected to maintain the large levitation force provided by the bulk with a lower rotational drag provided by the very high current density of the film. For low drag to be achieved, the thin film must shield the bulk from inhomogeneous magnetic fields. Measurement of rotational drag of a PM/HTS bearing that used a combination of bulk and film HTS showed that the thin film is not effective in reducing the rotational drag. Subsequent experiments, in which an AC coil was placed above the thin-film HTS and the magnetic field on the other side of the film was measured, showed that the thin film provides good shielding when the coil axis is perpendicular to the film surface but poor shielding when the coil axis is parallel to the surface. This is consistent with the lack of reduction in rotational drag being due to a horizontal magnetic moment of the permanent magnet. The poor shielding with the coil axis parallel to the film surface is attributed to the aspect ratio of the film and the three-dimensional nature of the current flow in the film for this coil orientation.

  16. Linking rigid multibody systems via controllable thin fluid films

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    compressor. The system of equations is numerically solved for the case when the system operates with conventional hydrodynamic lubrication and for several cases of the bearing operating under controlled hybrid lubrication conditions. The analysis of the results is carried out with focus on the behaviour......This work deals with the mathematical modelling of multibody systems interconnected via thin fluid films. The dynamics of the fluid films can be actively controlled by means of different types of actuators, allowing significant vibration reduction of the system components. In this framework......, this paper gives a theoretical contribution to the combined fields of fluid–structure interaction and vibration control. The methodology is applied to a reciprocating linear compressor, where the dynamics of the mechanical components are described with help of multibody dynamics. The crank is linked...

  17. Static Performance of Surface Textured Magnetorheological Fluid Journal Bearings

    Directory of Open Access Journals (Sweden)

    D.A. Bompos

    2015-09-01

    Full Text Available Previous studies of journal bearings with artificial texturing on the bearing surface show potential benefits in certain cases. These benefits are usually focused on a specific operating area of the bearing, whereas under certain operating conditions the performance of the bearing is deteriorating due to the surface texturing. Gaining control over the viscosity of the lubricant may become a useful tool in order to take advantage of the surface texturing in a wider range of loads and journal velocities. One way to achieve this control is the use of magnetorheological fluid journal bearings. Magnetorheological fluids are solutions of iron based paramagnetic particles in conventional lubricant. Under the influence of an external magnetic field, these particles form chains, they hinder the flow of the lubricant and they ultimately alter its apparent viscosity. In this work the two techniques are combined in order to optimize the behaviour of the journal bearing in as much a variety of operating conditions as possible. Different shapes applied on the surface texturing will be examined.

  18. Study on performance of squeeze film damper with oil-air two-phase fluid

    Science.gov (United States)

    Shen, Xinmin; Li, Qihan; Du, Lijie

    1992-10-01

    This paper presents an analytical method for the lubrication film performance of a squeeze film damper with oil-air two-phase fluid, on the basis of the testing results and numerical analysis of oil film cavitation. The calculational results for the pressure distribution of lubrication oil film are in good agreement with the experimental results. The damper performance data obtained from two-phase fluid analysis are also compared with the results calculated by pure oil film damper. It is proven that the data can be used for the engineering analyses. The analytical method can be extended for the other bearings with similar lubrication film of oil-air two-phase fluid.

  19. Film Thickness in Grease Lubricated Rolling Bearings

    NARCIS (Netherlands)

    Lugt, Piet M.; Van Zoelen, M. T.; Venner, C. H.; Lugt, Piet M.

    2012-01-01

    In this chapter the theory from Chapter 9 will be applied to rolling bearings. The thin layer flow equations are used to describe the tangential and normal flow due to centrifugal forces. The interaction between the various contacts on inner ring and outer ring will be described followed by the

  20. Plain bearing stresses due to forming and oil film pressure

    Energy Technology Data Exchange (ETDEWEB)

    Burke-Veliz, A; Reed, P A S; Syngellakis, S [University of Southampton, School of Engineering Sciences, Southampton SO17 1BJ (United Kingdom); Wang, D; Wahdy, N; Merritt, D, E-mail: allan.burke@itesm.m [MAHLE Engine Systems UK Ltd, 2 Central park Drive, Rugby CV23 0WE (United Kingdom)

    2009-08-01

    This paper describes a methodology for assessing critical stress ranges arising in automotive plain bearings during engine operations. An industry-produced and run simulation program provides information on oil film pressure and overall bearing deformation during accelerated performance tests. This code performs an elasto-hydrodynamic lubrication analysis accounting for the compliance of the housing and journal. Finite element analyses of a multilayer bearing are performed to assess the conditions responsible for possible fatigue damage over the bearing lining. The residual stresses arising from the forming and fitting process are first assessed. The stress analyses over the engine cycle show the intensity and distribution of cyclic tensile and compressive stresses in the bearing. The location of maximum stress range is found to be consistent with the damage observed in accelerated fatigue tests. Critical zones are identified in the lining for possible fatigue crack initiation and growth studies.

  1. Design of an oil squeeze film damper bearing for a multimass flexible-rotor bearing system

    Science.gov (United States)

    Cunningham, R. E.; Gunter, E. J., Jr.; Fleming, D. P.

    1975-01-01

    A single-mass flexible-rotor analysis was used to optimize the stiffness and damping of a flexible support for a symmetric five-mass rotor. The flexible, damped support attenuates the amplitudes of motions and forces transmitted to the support bearings when the rotor operates through and above its first bending critical speed. An oil squeeze film damper was designed based on short bearing lubrication theory. The damper design was verified by an unbalance response computer program. Rotor amplitudes were reduced by a factor of 16 and loads reduced by a factor of 36 compared with the same rotor with rigid bearing supports.

  2. Behavior of a squeeze film damper with an electrorheological fluid

    Science.gov (United States)

    Tichy, John A.

    1993-01-01

    The flow properties of electrorheological (ER) fluids change with the application of an electric field. These materials have been proposed as smart lubricants. Existing ER fluids are best described by the Bingham model. The Bingham material is described by two parameters, yield shear stress and viscosity. When the shear stress magnitude exceeds the yield shear stress, quasi-Newtonian flow results; otherwise, the material is rigid. For many ER fluids, the yield shear stress is proportional to the square of the applied electric field. In the present study, the Bingham model is applied to the one-dimensional squeeze film damper. A rigid core forms midway across the film, the core thickness being proportional to the yield shear stress. A modified Reynolds equation is obtained, from which the bearing behavior can be predicted. The damper forces are predicted as a function of the eccentricity ratio, and a dimensionless parameter which depends on the yield shear stress. Calculations are performed for a simple rotordynamic system, illustrating the optimization of eccentricity and transmissibility by varying the applied voltage.

  3. Evaluation of rotating, incompressibly lubricated, pressurized thrust bearings

    Science.gov (United States)

    Fleming, D. P.

    1971-01-01

    Program evaluates a series hybrid, fluid film ball bearing consisting of an orifice compensated pressurized thrust bearing in conjunction with a self-acting journal bearing. Oil viscosities corresponding to experimentally measured ball bearing outer-race temperatures were used.

  4. Analysis of HD Journal Bearings Considering Elastic Deformation and Non-Newtonian Rabinowitsch Fluid Model

    Directory of Open Access Journals (Sweden)

    J. Javorova

    2016-06-01

    Full Text Available The purpose of this paper is to study the performance of a finite length journal bearing, taking into account effects of non-Newtonian Rabinowitsch flow rheology and elastic deformations of the bearing liner. According to the Rabinowitsch fluid model, the cubic-stress constitutive equation is used to account for the non-Newtonian effects of pseudoplastic and dilatant lubricants. Integrating the continuity equation across the film, the nonlinear non-Newtonian Reynolds-type equation is derived. The elasticity part of the problem is solved on the base of Vlassov model of an elastic foundation. The numerical solution of the modified Reynolds equation is carried out by using FDM with over-relaxation technique. The results for steady state bearing performance characteristics have been calculated for various values of nonlinear factor and elasticity parameters. It was concluded that in comparison with the Newtonian lubricants, higher values of film pressure and load carrying capacity have been obtained for dilatant lubricants, while the case was reversed for pseudoplastic lubricants.

  5. Squeeze-film flow between a flat impermeable bearing and an anisotropic porous bed

    Science.gov (United States)

    Karmakar, Timir; Raja Sekhar, G. P.

    2018-04-01

    We consider a theoretical model of the squeeze film in the presence of a porous bed. The gap between the porous bed and the bearing is assumed to be filled with a Newtonian fluid. We use the Navier-Stokes equation in the fluid region and the Darcy equation in the fluid filled porous region. Lubrication approximation is used to derive the corresponding evolution equation for the film thickness. We use G. S. Beavers and D. D. Joseph ["Boundary conditions at a naturally permeable wall," J. Fluid. Mech. 30, 197-207 (1967)] and M. Le Bars and M. G. Worster ["Interfacial conditions between a pure fluid and a porous medium: Implications for binary alloy solidification," J. Fluid. Mech. 550, 149-173 (2006)] condition at the liquid porous interface and present a detailed analysis on the corresponding impact. We assume that the porous bed is anisotropic in nature with permeabilities K2 and K1 along the principal axes. Accordingly, the anisotropic angle ϕ is taken as the angle between the horizontal direction and principal axis with permeability K2. We show that the anisotropic permeability ratio and the anisotropic angle make a significant influence on the contact time, flux, velocity, etc. Contact time to meet the porous bed when a bearing approaches under a constant prescribed load is estimated. We present some important findings (relevant to the knee joint) based on the anisotropic properties of the human cartilage. For a prescribed constant load, we have estimated the time duration, during which a healthy human knee remains fluid lubricated.

  6. Effects of Viscosity Variation and Surface Roughness on the Couple stress Squeeze Film Characteristics of Short Journal Bearings

    Directory of Open Access Journals (Sweden)

    G.H. Ayyappa

    2015-03-01

    Full Text Available The theoretical analysis of the combined effects of surface roughness and viscosity variation on the couple stress squeeze film characteristics of short journal bearings is presented. The modified stochastic Reynold’s equation accounting for the viscosity variation of couple stresses fluid and randomized surface roughness structure on bearing surface is mathematically derived using the Christensen stochastic theory. It is observed that, the transverse roughness pattern improves the squeeze film characteristics whereas the bearing performance is affected due to the presence of one dimensional longitudinal surface roughness. Further, it is observed that, the effect of viscosity variation is to reduce the load carrying capacity and squeeze film time as compared to the case of constant viscosity.

  7. Numerical analysis of capillary compensated micropolar fluid lubricated hole-entry journal bearings

    Directory of Open Access Journals (Sweden)

    Nathi Ram

    2016-06-01

    Full Text Available The micropolar lubricated symmetric/asymmetric hole-entry bearings using capillary restrictor have been analyzed in the present work. Reynolds equation for micropolar lubricant has been derived and solved by FEM. The results have been computed using selected parameters of micropolar lubricant for hole-entry hydrostatic/hybrid journal bearings. A significant increase in damping and stiffness coefficients is observed for bearings having micropolar parameter N2=0.9, lm=10 than similar bearings under Newtonian lubricant. The threshold speed gets increased when symmetric bearing lubricated under micropolar fluid than Newtonian lubricant. The threshold speed gets increased when symmetric bearing lubricated under micropolar fluid than Newtonian lubricant.

  8. Parched elasto hydrodynamic lubrication film thickness measurement in an instrument ball bearing

    Science.gov (United States)

    Kingsbury, E.; Schritz, B.; Prahl, J.

    1988-01-01

    Parched Elasto Hydrodynamic Lubricant (PEHL) film thickness in a large instrument ball bearing is measured by electrical capacitance across its ball set. Correlation is shown between changes in film thickness and changes in Basic Speed Ratio (BSR) measured at the same time. BSR is confirmed as a sensitive, non-intrusive measure of transients in film thickness in a real bearing.

  9. Coupling analysis of frictional heat of fluid film and thermal deformation of mechanical seal end faces

    International Nuclear Information System (INIS)

    Zhou Jianfeng; Gu Boqin

    2007-01-01

    The heat transfer model of the rotating ring and the stationary ring of mechanical seal was built. The method to calculate the frictional heat that transferred by the rings was given. the coupling analysis of the frictional heat of fluid film and thermal deformation of end faces was carried out by using FEA and BP ANN, and the relationship among the rotational speed ω, the fluid film thickness h i on the inner diameter of sealing face and the radial separation angle β of deformed end faces was obtained. Corresponding to a given ω, h i and β can be obtained by the equilibrium condition between the closing force and the bearing force of fluid film. The relationship between the leakage rate and the closing force was analyzed, and the fundamental of controlling the leakage rate by regulating the closing force was also discussed. (authors)

  10. Investigation of the influence of volute design on journal bearing bias force using computational fluid dynamics.

    Science.gov (United States)

    Graefe, Roland; Timms, Daniel; Böhning, Fiete; Schmitz-Rode, Thomas; Steinseifer, Ulrich

    2010-09-01

    Hydrodynamic fluid film bearings represent an optimal possibility for rotary blood pump (RBP) miniaturization and wear-free operation. Size is a key parameter in the development of ventricular assist devices (VADs) as smaller patients and the pediatric population become eligible for the device. In order to maintain rotor suspension, radial journal bearings have been widely used in industrial applications as well as in some VADs. A main influence on the performance of such a bearing is the applied hydraulic bias force. This study combines numerical and analytical approaches to determine the bias force of different impeller-volute configurations and the resulting eccentricity for the hydraulic design point and also for off-design operation. Significant differences occur for different impeller-volute configurations, with the circular volute displaying the most beneficial properties for a stable impeller suspension. Moreover, an analytical prediction of eccentricity was found to be incorrect for the relatively small forces that occur in RBPs. © 2010, Copyright the Authors. Artificial Organs © 2010, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  11. Entropy generation in non-Newtonian fluid flow in a slider bearing

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Non-Newtonian effects on the static character- istics of one-dimensional slider bearings in the internal flow regime were investigated by ... and beating flexibility affected the performance characteristics of slot-entry journal bearing significantly. A slider bearing with second- and third-grade fluids as lubricant was analyzed.

  12. Bearing, gearing, and lubrication technology

    Science.gov (United States)

    Anderson, W. J.

    1978-01-01

    Results of selected NASA research programs on rolling-element and fluid-film bearings, gears, and elastohydrodynamic lubrication are reported. Advances in rolling-element bearing material technology, which have resulted in a significant improvement in fatigue life, and which make possible new applications for rolling bearings, are discussed. Research on whirl-resistant, fluid-film bearings, suitable for very high-speed applications, is discussed. An improved method for predicting gear pitting life is reported. An improved formula for calculating the thickness of elastohydrodynamic films (the existence of which help to define the operating regime of concentrated contact mechanisms such as bearings, gears, and cams) is described.

  13. Fluid Compressibility Effects on the Dynamic Response of Hydrostatic Journal Bearings

    Science.gov (United States)

    Sanandres, Luis A.

    1991-01-01

    A theoretical analysis for the dynamic performance characteristics of laminar flow, capillar/orifice compensated hydrostatic journal bearings is presented. The analysis considers in detail the effect of fluid compressibility in the bearing recesses. At high frequency excitations beyond a break frequency, the bearing hydrostatic stiffness increases sharply and it is accompanied by a rapid decrease in direct damping. Also, the potential of pneumatic hammer instability (negative damping) at low frequencies is likely to occur in hydrostatic bearing applications handling highly compressible fluids. Useful design criteria to avoid undesirable dynamic operating conditions at low and high frequencies are determined. The effect of fluid recess compressibility is brought into perspective, and found to be of utmost importance on the entire frequency spectrum response and stability characteristics of hydrostatic/hybrid journal bearings.

  14. Simulation of the fluid structure interaction for an aerostatic bearing and a flexible substrate

    NARCIS (Netherlands)

    Olieslagers, R.; Wild, M. de; Melick, S. van; Knaapen, R.

    2014-01-01

    The fluid structure interaction for an aerostatic bearing and a substrate is solved numerically by a semi-analytical model, programmed in the software package MATLAB. This semi-analytical model uses a fluidic network of resistances and capacities to solve the pressure field in the bearing channel.

  15. Laminar Motion of the Incompressible Fluids in Self-Acting Thrust Bearings with Spiral Grooves

    Directory of Open Access Journals (Sweden)

    Cornel Velescu

    2014-01-01

    Full Text Available We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the “pumping” direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc., for the laminar and permanent motion regime.

  16. Laminar motion of the incompressible fluids in self-acting thrust bearings with spiral grooves.

    Science.gov (United States)

    Velescu, Cornel; Popa, Nicolae Calin

    2014-01-01

    We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the "pumping" direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime.

  17. Magnetic fluid based squeeze film between porous annular curved ...

    Indian Academy of Sciences (India)

    lower plate, considering a magnetic fluid lubricant in the presence of an external magnetic field oblique to the plates. Expressions were obtained for ... Keywords. Magnetic fluid; lubrication; annular curved plates. PACS No. 81.40.Pq. 1. Introduction ... is backed by a solid wall. The film thickness h is taken as h =h0 exp(-Br2); ...

  18. On the interaction between structure and oil film of a guide shoe bearing

    DEFF Research Database (Denmark)

    Vølund, Anders

    2001-01-01

    A solution procedure for the determination of the oil film thickness of a guide shoe bearing for a large two stroke marine diesel engine is presented. Based on a previous study considering oil film thickness of a guide shoe bearing with rigid structural parts a model for the interaction between...... structure and oil film is implemented. The model takes into account the elastic deformation of the bearing parts. An iterative procedure for determining pressure, deformation and squeeze velocity is applied. The results are compared to a traditional calculation of rigid components. The model...

  19. Fluid inclusions in coesite-bearing eclogites and jadeite quartzite at Shuanghe, Dabie Shan (China).

    NARCIS (Netherlands)

    Fu, B.; Touret, J.L.R.; Zheng, Y.-F.

    2001-01-01

    Fluid inclusions in coesite-bearing eclogites and jadeite quartzite at Shuanghe in Dabie Shan, East-central China, have preserved remnants of early, prograde and/or peak metamorphic fluids, reset during post-UHP (ultrahigh-pressure) metamorphic uplift. Inclusions occur in several minerals (e.g.

  20. Application of computational fluid dynamics on cavitation in journal bearings

    Directory of Open Access Journals (Sweden)

    Riedel Marco

    2014-03-01

    Full Text Available Journal bearings are applied in internal combustion engines due to their favourable wearing quality and operating characteristics. Under certain operating conditions damage of the journal bearing can occur caused by cavitation. The cavitation reduces the load capacity and leads to material erosion. Experimental investigations of cavitating flows in dimension of real journal bearing are difficult to realize or almost impossible caused by the small gap and transient flow conditions. Therefore numerical simulation is a very helpful engineering tool to research the cavitation behaviour. The CFD-Code OpenFOAM is used to analyse the flow field inside the bearing. The numerical cavitation model based on a bubble dynamic approach and requires necessary initial parameter for the calculation, such as nuclei bubble diameter, the number of nuclei and two empirical constants. The first part of this paper shows the influence of these parameters on the solution. For the adjustment of the parameters an experiment of Jakobsson et.al. [1] was used to validate the numerical flow model. The parameters have been varied according to the method Design of Experiments (DoE. With a defined model equation the parameters determined, to identify the parameter for CFD-calculations in comparison to the experimental values. The second part of the paper presents investigations on different geometrical changes in the bearing geometry. The effect of these geometrical changes on cavitation was compared with experimental results from Wollfarth [2] and Garner et.al. [3].

  1. Application of computational fluid dynamics on cavitation in journal bearings

    Science.gov (United States)

    Riedel, Marco; Schmidt, Marcus; Reinke, Peter; Nobis, Matthias; Redlich, Marcel

    2014-03-01

    Journal bearings are applied in internal combustion engines due to their favourable wearing quality and operating characteristics. Under certain operating conditions damage of the journal bearing can occur caused by cavitation. The cavitation reduces the load capacity and leads to material erosion. Experimental investigations of cavitating flows in dimension of real journal bearing are difficult to realize or almost impossible caused by the small gap and transient flow conditions. Therefore numerical simulation is a very helpful engineering tool to research the cavitation behaviour. The CFD-Code OpenFOAM is used to analyse the flow field inside the bearing. The numerical cavitation model based on a bubble dynamic approach and requires necessary initial parameter for the calculation, such as nuclei bubble diameter, the number of nuclei and two empirical constants. The first part of this paper shows the influence of these parameters on the solution. For the adjustment of the parameters an experiment of Jakobsson et.al. [1] was used to validate the numerical flow model. The parameters have been varied according to the method Design of Experiments (DoE). With a defined model equation the parameters determined, to identify the parameter for CFD-calculations in comparison to the experimental values. The second part of the paper presents investigations on different geometrical changes in the bearing geometry. The effect of these geometrical changes on cavitation was compared with experimental results from Wollfarth [2] and Garner et.al. [3].

  2. EFFECT OF SLIP VELOCITY ON MAGNETIC FLUID LUBRICATION OF ROUGH POROUS RAYLEIGH STEP BEARING

    Directory of Open Access Journals (Sweden)

    Snehal Shukla

    2013-06-01

    Full Text Available This article aims to analyze the performance of a magnetic-fluid-based porous rough step bearing considering slip velocity. The Neuringer-Rosensweig model governs the fluid flow while the velocity slip is modeled by the method of Beavers and Joseph. The bearing surfaces are assumed transversely rough and the transverse surface roughness of the bearing surfaces is characterized by a stochastic random variable with non-zero mean, variance, and skewness. With the usual assumptions of hydrodynamic lubrication, the related stochastically averaged Reynolds’ equation for the fluid pressure is solved with appropriate boundary conditions, which is then used to calculate the load-carrying capacity. It is found that although the bearing suffers owing to transverse surface roughness, the performance of the bearing system can be improved to some extent by the positive effect of magnetization, considering the slip parameter at the minimum; at least in the case of negatively skewed roughness. A comparison of this paper with some established investigations indicates that here, the reduction of load-carrying capacity due to porosity and slip velocity is comparatively less, especially, when negative variance occurs. In augmenting the performance of the bearing system, the step ratio plays a central role, even if the slip parameter is at the minimum.

  3. Establishment of Approximate Analytical Model of Oil Film Force for Finite Length Tilting Pad Journal Bearings

    Directory of Open Access Journals (Sweden)

    Yongliang Wang

    2015-01-01

    Full Text Available Tilting pad bearings offer unique dynamic stability enabling successful deployment of high-speed rotating machinery. The model of dynamic stiffness, damping, and added mass coefficients is often used for rotordynamic analyses, and this method does not suffice to describe the dynamic behaviour due to the nonlinear effects of oil film force under larger shaft vibration or vertical rotor conditions. The objective of this paper is to present a nonlinear oil force model for finite length tilting pad journal bearings. An approximate analytic oil film force model was established by analysing the dynamic characteristic of oil film of a single pad journal bearing using variable separation method under the dynamic π oil film boundary condition. And an oil film force model of a four-tilting-pad journal bearing was established by using the pad assembly technique and considering pad tilting angle. The validity of the model established was proved by analyzing the distribution of oil film pressure and the locus of journal centre for tilting pad journal bearings and by comparing the model established in this paper with the model established using finite difference method.

  4. Investigation of the Fluid-Solid Thermal Coupling for Rolling Bearing under Oil-Air Lubrication

    Directory of Open Access Journals (Sweden)

    Baohong Tong

    2015-02-01

    Full Text Available An excellent oil-air lubrication system helps to improve rolling bearing's working conditions and thus extend its service life span. Flowing and heat dissipating characteristics of oil-air media inside bearing chamber are very complicated due to the fluid-solid thermal coupling. Effects of fluid-solid thermal coupling are neglected in all previous simulation efforts. A numerical model for simulating the flowing inside bearing chamber is developed here based on an analytical fluid-solid thermal coupling method under oil-air lubrication. The effects of the coupling of air-oil flowing and heat dissipating in bearing chamber are predicted. The simulation results indicate that the coupling is influential in the performances of the flowing in rolling bearing under oil-air lubrication. With consideration of the coupling, the turbulence intensity, the turbulent kinetic energy, and the temperature of the rollers are predicted to be lower because part of the heat is carried out by the flow due to the heat transfer. On the contrary, the turbulent dissipation rate gets higher when considering the coupling effects. It is also interesting that the coupling effects have little influence on the flow pressure and the velocity, which is manifested by a little higher predicted value when considering the coupling.

  5. Study of design parameters for squeeze film air journal bearing – excitation frequency and amplitude

    Directory of Open Access Journals (Sweden)

    C. Wang

    2011-07-01

    Full Text Available The paper presents a design of squeeze film air journal bearing based on the design rules derived from CFX and FEA simulation study of an air film in between two flat plates, one of which was driven in a sinusoidal manner. The rules are that the oscillation frequency should be at least 15 kHz and that the oscillation amplitude be as large as possible to ensure a greater film thickness and to allow the bearing to reach its stable equilibrium quickly. The proposed journal bearing is made from AL2024-T3, of 20.02 mm outer diameter, 600 mm length and 2 mm thickness. Three 20-mm long fins are on the outer surface of the bearing tube and are spaced 120° apart; three longitudinal flats are milled equi-spaced between the fins and two piezoelectric actuators are mounted lengthwise on each flat. Such a design produces a modal shape on the bearing tube which resembles a triangle. When excited in this mode at the frequency of 16.37 kHz, and a voltage of 75 V AC with 75 V DC offset acting on the piezoelectric actuators, the air gap underneath of the bearing tube behaves as a squeeze air film with a response amplitude of 3.22 μm. The three design rules were validated by experiments.

  6. Nonlinear Dynamic Response of an Unbalanced Flexible Rotor Supported by Elastic Bearings Lubricated with Piezo-Viscous Polar Fluids

    Directory of Open Access Journals (Sweden)

    Mustapha Lahmar

    2015-04-01

    Full Text Available On the basis of the V. K. Stokes micro-continuum theory, the effects of couple stresses on the nonlinear dynamic response of the unbalanced Jeffcott’s flexible rotor supported by layered hydrodynamic journal bearings is presented in this paper. A nonlinear transient modified Reynolds’ equation is derived and discretized by the finite element method to obtain the fluid-film pressure field as well as the film thickness by means of the implicit Euler method. The nonlinear orbits of the rotor center are determined by solving the nonlinear differential equations of motion with the explicit Euler’s scheme taking into account the flexibility of rotor. According to the obtained results, the combined effects of couple stresses due to the presence of polymer additives in lubricant and the pressure dependent viscosity on the nonlinear dynamic response of the rotor-bearing system are significant and cannot be ignored or overlooked. As expected, these effects are more noticeable for polymers characterized by higher length molecular chains.

  7. Nonlinear dynamics of a flexible rotor supported by turbulent journal bearings with couple stress fluid

    International Nuclear Information System (INIS)

    Lo, C.-Y.; Chang-Jian, C.-W.

    2008-01-01

    This study presents a dynamic analysis of a rotor supported by two turbulent flow model journal bearings and lubricated with couple stress fluid under nonlinear suspension. The dynamics of the rotor center and bearing center is studied. The dynamic equations are solved using the Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor center and bearing center, power spectra, Poincare maps and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The results show that the values of dimensionless parameters l* strongly influence dynamic motions of bearing and rotor centre. It is found that couple stress fluid improve the stability of the system when l* > 0.4 even if the flow of this system is turbulent. We also demonstrated that the dimensionless rotational speed ratios s and the dimensionless unbalance parameter β are also significant system parameters. The modeling results thus obtained by using the method proposed in this paper can be employed to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided

  8. Proteins at fluid interfaces: adsorption layers and thin liquid films.

    Science.gov (United States)

    Yampolskaya, Galina; Platikanov, Dimo

    2006-12-21

    A review in which many original published results of the authors as well as many other papers are discussed. The structure and some properties of the globular proteins are shortly presented, special accent being put on the alpha-chymotrypsin (alpha-ChT), lysozyme (LZ), human serum albumin (HSA), and bovine serum albumin (BSA) which have been used in the experiments with thin liquid films. The behaviour of protein adsorption layers (PAL) is extensively discussed. The dynamics of PAL formation, including the kinetics of adsorption as well as the time evolution of the surface tension of protein aqueous solutions, are considered. A considerable place is devoted to the surface tension and adsorption isotherms of the globular protein solutions, the simulation of PAL by interacting hard spheres, the experimental surface tension isotherms of the above mentioned proteins, and the interfacial tension isotherms for the protein aqueous solution/oil interface. The rheological properties of PAL at fluid interfaces are shortly reviewed. After a brief information about the experimental methods for investigation of protein thin liquid (foam or emulsion) films, the properties of the protein black foam films are extensively discussed: the conditions for their formation, the influence of the electrolytes and pH on the film type and stability, the thermodynamic properties of the black foam films, the contact angles film/bulk and their dynamic hysteresis. The next center of attention concerns some properties of the protein emulsion films: the conditions for formation of emulsion black films, the formation and development of a dimpling in microscopic, circular films. The protein-phospholipid mixed foam films are also briefly considered.

  9. Meniscal Tear Film Fluid Dynamics Near Marx’s Line

    KAUST Repository

    Zubkov, V. S.

    2013-07-03

    Extensive studies have explored the dynamics of the ocular surface fluid, though theoretical investigations are typically limited to the use of the lubrication approximation, which is not guaranteed to be uniformly valid a-priori throughout the tear meniscus. However, resolving tear film behaviour within the meniscus and especially its apices is required to characterise the flow dynamics where the tear film is especially thin, and thus most susceptible to evaporatively induced hyperosmolarity and subsequent epithelial damage. Hence, we have explored the accuracy of the standard lubrication approximation for the tear film by explicit comparisons with the 2D Navier-Stokes model, considering both stationary and moving eyelids. Our results demonstrate that the lubrication model is qualitatively accurate except in the vicinity of the eyelids. In particular, and in contrast to lubrication theory, the solution of the full Navier-Stokes equations predict a distinct absence of fluid flow, and thus convective mixing in the region adjacent to the tear film contact line. These observations not only support emergent hypotheses concerning the formation of Marx\\'s line, a region of epithelial cell staining adjacent to the contact line on the eyelid, but also enhance our understanding of the pathophysiological consequences of the flow profile near the tear film contact line. © 2013 Society for Mathematical Biology.

  10. Effect of Temperature and Electric Field on the Damping and Stiffness Characteristics of ER Fluid Short Squeeze Film Dampers

    Directory of Open Access Journals (Sweden)

    H. P. Jagadish

    2013-01-01

    Full Text Available Squeeze film dampers are novel rotor dynamic devices used to alleviate small amplitude, large force vibrations and are used in conjunction with antifriction bearings in aircraft jet engine bearings to provide external damping as these possess very little inherent damping. Electrorheological (ER fluids are controllable fluids in which the rheological properties of the fluid, particularly viscosity, can be controlled in accordance with the requirements of the rotor dynamic system by controlling the intensity of the applied electric field and this property can be utilized in squeeze film dampers, to provide variable stiffness and damping at a particular excitation frequency. The paper investigates the effect of temperature and electric field on the apparent viscosity and dynamic (stiffness and damping characteristics of ER fluid (suspension of diatomite in transformer oil using the available literature. These characteristics increase with the field as the viscosity increases with the field. However, these characteristics decrease with increase in temperature and shear strain rate as the viscosity of the fluid decreases with temperature and shear strain rate. The temperature is an important parameter as the aircraft jet engine rotors are located in a zone of high temperature gradients and the damper fluid is susceptible to large variations in temperature.

  11. A Comparative Study of Finite Journal Bearing in Laminar and Turbulent Regimes Using CFD (Computational Fluid Dynamic

    Directory of Open Access Journals (Sweden)

    Susilowati

    2016-01-01

    Full Text Available In this paper, an investigation of hydrodynamic performance for journal bearing lubricated by thin film is performed by three-dimensional CFD (computational fluid dynamic. Two regimes, i.e. laminar and turbulent regimes are of main interest. The sliding velocity was varied from 3000, 5000 and 10000. The numerical simulation shows that the velocity magnitude of the journal has a strong effect on the hydrodynamic pressure. In addition, it is found that an appropriate modelling of flow regime affects the predicted lubrication performance. From the overall analysis, both using laminar and turbulent regimes, the distribution of static hydrodynamic pressure shows a similar trend. It is also found that at the beginning of the contact, the static pressure is low, and then, it gradually increases to the highest point, and finally drops significantly.

  12. Squeeze-Film Air Damping of a Five-Axis Electrostatic Bearing for Rotary Micromotors.

    Science.gov (United States)

    Wang, Shunyue; Han, Fengtian; Sun, Boqian; Li, Haixia

    2017-05-13

    Air-film damping, which dominates over other losses, plays a significant role in the dynamic response of many micro-fabricated devices with a movable mass suspended by various bearing mechanisms. Modeling the damping characteristics accurately will be greatly helpful to the bearing design, control, and test in various micromotor devices. This paper presents the simulated and experimental squeeze-film air damping results of an electrostatic bearing for use in a rotary high-speed micromotor. It is shown that the boundary condition to solve the three-dimensional Reynolds equation, which governs the squeeze-film damping in the air gap between the rotor and its surrounding stator sealed in a three-layer evacuated cavity, behaves with strong cross-axis coupling characteristics. To accurately characterize the damping effect, a set of multiphysics finite-element simulations are performed by computing both the rotor velocity and the distribution of the viscous damping force acting on the rotor. The damping characteristics varying with several key structure parameters are simulated and discussed to optimize the device structure for desirable rotor dynamics. An electrical measurement method is also proposed and applied to validate the numerical results of the damping coefficients experimentally. Given that the frequency response of the electric bearing is critically dependent on the damping coefficients at atmospheric pressure, a solution to the air-film damping measurement problem is presented by taking approximate curve fitting of multi-axis experimental frequency responses. The measured squeeze-film damping coefficients for the five-axis electric bearing agrees well with the numerical solutions. This indicates that numerical multiphysics simulation is an effective method to accurately examine the air-film damping effect for complex device geometry and arbitrary boundary condition. The accurate damping coefficients obtained by FEM simulation will greatly simplify the design

  13. Studies on the dynamic characteristics of gas film bearings and dampers

    Science.gov (United States)

    Stiffler, A. K.

    1975-01-01

    The dynamic characteristics of inherently compensated gas film bearings have been investigated for small excursion ratios. Both circular and rectangular cases have been solved for the stiffness and damping as a function of supply pressure, restrictor coefficient, and squeeze number. The effect of disturbance amplitude has been studied for the inherently compensated strip. Analytical solutions for the simple gas film damper problem have established the effect of disturbance amplitude at low squeeze numbers. These results are applicable to pressurized bearings as limiting case of the restrictor coefficient.

  14. Modelling of Outer and Inner Film Oil Pressure for Floating Ring Bearing Clearance in Turbochargers

    International Nuclear Information System (INIS)

    Zhang Hao; Shi Zhanqun; Gu Fengshou; Ball, Andrew

    2011-01-01

    Floating ring bearing is widely used in turbochargers to undertake the extreme condition of high rotating speed and high operating temperature. It is also the most concerned by the designers and users alike due to its high failure rate and high maintenance cost. Any little clearance change may result in oil leakage, which in turn cause blue smoke or black smoke according to leakage types. However, there is no condition monitoring of this bearing because it is almost impossible to measure the clearance especially the inner clearance, in which the inner oil film directly bears the high speed rotation. In stead of measuring clearance directly, this paper has proposed a method that uses film pressure as a measure to monitor the bearing clearance and its variation. A non-linear mathematical model is developed by using Reynolds equations with non-linear oil film pressure. A full description of the outer and inner film is provided along both axial and radial directions. A numerical simulation is immediately carried out. Variable clearance changes are investigated using the mathematical model. Results show the relationship between clearance and film pressure.

  15. Supercritical fluid molecular spray thin films and fine powders

    Science.gov (United States)

    Smith, Richard D.

    1988-01-01

    Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. The solvent is vaporized and pumped away. Solution pressure is varied to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solution temperature is varied in relation to formation of a two-phase system during expansion to control porosity of the film or powder. A wide variety of film textures and powder shapes are produced of both organic and inorganic compounds. Films are produced with regular textural feature dimensions of 1.0-2.0 .mu.m down to a range of 0.01 to 0.1 .mu.m. Powders are formed in very narrow size distributions, with average sizes in the range of 0.02 to 5 .mu.m.

  16. Measurement of oil film thickness and friction force on a guide shoe bearing

    DEFF Research Database (Denmark)

    Vølund, Anders

    2002-01-01

    An experimental program was carried out in order to reveal oil film thickness, and friction force of the guide shoe bearing of a large two stroke marine diesel engine. The experiment was conducted on a full size engine located at the research facility at MAN B&W Diesel A/S. The experiment...... was conducted such that the influence from the experiment on the characteristics were as small as possible. The objective of the experiment was to determine the frictional loss of this bearing and to check whether a suggested numerical model was applicable or not. Some future aspects for this bearing...

  17. Bifurcation and Nonlinear Dynamic Analysis of Externally Pressurized Double Air Films Bearing System

    Directory of Open Access Journals (Sweden)

    Cheng-Chi Wang

    2014-01-01

    Full Text Available This paper studies the chaotic and nonlinear dynamic behaviors of a rigid rotor supported by externally pressurized double air films (EPDAF bearing system. A hybrid numerical method combining the differential transformation method and the finite difference method is used to calculate pressure distribution of EPDAF bearing system and bifurcation phenomenon of rotor center orbits. The results obtained for the orbits of the rotor center are in good agreement with those obtained using the traditional finite difference approach. The results presented summarize the changes which take place in the dynamic behavior of the EPDAF bearing system as the rotor mass and bearing number are increased and therefore provide a useful guideline for the bearing system.

  18. Steady-state and transient analysis of a squeeze film damper bearing for rotor stability

    Science.gov (United States)

    Barrett, L. E.; Gunter, E. J.

    1975-01-01

    A study of the steady-state and transient response of the squeeze film damper bearing is presented. Both the steady-state and transient equations for the hydrodynamic bearing forces are derived. The bearing equivalent stiffness and damping coefficients are determined by steady-state equations. These coefficients are used to find the bearing configuration which will provide the optimum support characteristics based on a stability analysis of the rotor-bearing system. The transient analysis of rotor-bearing systems is performed by coupling the bearing and journal equations and integrating forward in time. The effects of unbalance, cavitation, and retainer springs are included in the analysis. Methods of determining the stability of a rotor-bearing system under the influence of aerodynamic forces and internal shaft friction are discussed with emphasis on solving the system characteristic frequency equation and on producing stability maps. It is shown that for optimum stability and low force transmissability the squeeze bearing should operate at an eccentricity ratio epsilon 0.4.

  19. The Evaluation of Linear Complementarity Problem Method in Modeling the Fluid Cavitation for Squeeze Film Damper with Off-Centered Whirling Motion

    OpenAIRE

    Tieshu Fan; Kamran Behdinan

    2017-01-01

    For the application of squeeze film damper (SFD) in aero-engine, a cavitation model is evaluated by means of linear complementarity problem (LCP) method. Different from the conventional SFD study that employs circular-center orbits (CCOs), a realistic condition is explored where the shaft whirling center and bearing center are misaligned. Taking into account the fluid as incompressible and compressible, the governing equations, including film cavitation, are respectively solved by developing ...

  20. Nonlinear Vibration Analysis for a Jeffcott Rotor with Seal and Air-Film Bearing Excitations

    Directory of Open Access Journals (Sweden)

    Yuefang Wang

    2010-01-01

    Full Text Available The nonlinear coupling vibration and bifurcation of a high-speed centrifugal compressor with a labyrinth seal and two air-film journal bearings are presented in this paper. The rotary shaft and disk are modeled as a rigid Jeffcott rotor. Muszynska's model is used to express the seal force with multiple parameters. For air-film journal bearings, the model proposed by Zhang et al. is adopted to express unsteady bearing forces. The Runge-Kutta method is used to numerically determine the vibration responses of the disk center and the bearings. Bifurcation diagrams for transverse motion of the rotor are presented with parameters of rotation speed and pressure drop of the seal. Multiple subharmonic, periodic, and quasiperiodic motions are presented with two seal-pressure drops. The bifurcation characteristics show inherent interactions between forces of the air-film bearings and the seal, presenting more complicated rotor dynamics than the one with either of the forces alone. Bifurcation diagrams are obtained with parameters of pressure drop and seal length determined for the sake of operation safety.

  1. Evaluation of Oil Film Pressure and Temperature of an Elliptical Journal Bearing - An Experimental Study

    Directory of Open Access Journals (Sweden)

    A. Singla

    2016-03-01

    Full Text Available The present study is aimed at experimental evaluation of both oil film pressure and temperature at the central plane of finite elliptical journal bearing configuration. These parameters have been obtained by running the machine at various speeds under different applied loads ranging from 500 N to 2000 N using three different grades of oil (HYDROL 32, 68 and 150. The data has been obtained through a test rig which is capable of measuring both pressure and temperature at the same location on the elliptical bearing profile. An elliptical journal bearing with journal diameter=100 mm, L/D ratio=1.0, Ellipticity Ratio=1.0 and radial clearance=0.1 mm has been designed and tested to access the pressure and temperature rise of the oil film at the central plane of the bearing. Two different lobes of positive pressure have been obtained for elliptical bearing which results in smaller area for cavitation zone and accounts for better thermal stability. Also, with the increase in load both pressure and temperature of an oil film increases for all the three grades of oil. Experimentally, it has been established that the HYDROL 68 is suitable grade of lubricating oil which gives the optimum rise of pressure and temperate under all operating conditions among the lubricating oils under study.

  2. Particle-bearing currents in uniform density and two-layer fluids

    Science.gov (United States)

    Sutherland, Bruce R.; Gingras, Murray K.; Knudson, Calla; Steverango, Luke; Surma, Christopher

    2018-02-01

    Lock-release gravity current experiments are performed to examine the evolution of a particle bearing flow that propagates either in a uniform-density fluid or in a two-layer fluid. In all cases, the current is composed of fresh water plus micrometer-scale particles, the ambient fluid is saline, and the current advances initially either over the surface as a hypopycnal current or at the interface of the two-layer fluid as a mesopycnal current. In most cases the tank is tilted so that the ambient fluid becomes deeper with distance from the lock. For hypopycnal currents advancing in a uniform density fluid, the current typically slows as particles rain out of the current. While the loss of particles alone from the current should increase the current's buoyancy and speed, in practice the current's speed decreases because the particles carry with them interstitial fluid from the current. Meanwhile, rather than settling on the sloping bottom of the tank, the particles form a hyperpycnal (turbidity) current that advances until enough particles rain out that the relatively less dense interstitial fluid returns to the surface, carrying some particles back upward. When a hypopycnal current runs over the surface of a two-layer fluid, the particles that rain out temporarily halt their descent as they reach the interface, eventually passing through it and again forming a hyperpycnal current. Dramatically, a mesopycnal current in a two-layer fluid first advances along the interface and then reverses direction as particles rain out below and fresh interstitial fluid rises above.

  3. Thin layer flow and film decay modeling for grease lubricated rolling bearings

    NARCIS (Netherlands)

    Venner, Cornelis H.; van Zoelen, M.T.; Lugt, Pieter Martin

    2012-01-01

    A model is presented to predict lubricant supply layer changes on tracks in rolling bearings due to centrifugal forces and elastohydrodynamic contact pressure. Experimental validation is shown for centrifugal force driven free surface flow, and layer thickness (film thickness) decay in single

  4. Arthrosis of the ankle evaluated on films in weight-bearing position

    International Nuclear Information System (INIS)

    Bauer, M.; Bergstroem, B.; Hemborg, A.

    1979-01-01

    About 7 years after a malleolar fracture 113 patients were examined for development of arthrosis. The addition of films exposed in weight-bearing position with a.p. beam direction to views of the ankle joint exposed in supine position did not contribute to the diagnosis of arthrosis. (Auth.)

  5. EFFECT OF SLIP VELOCITY ON THE PERFORMANCE OF A SHORT BEARING LUBRICATED WITH A MAGNETIC FLUID

    Directory of Open Access Journals (Sweden)

    Rachana U. Patel

    2013-12-01

    Full Text Available This paper aims at analyzing the effect of velocity slip on the behavior of a magnetic fluid based infinitely short hydrodynamic slider bearing. Solving the Reynolds’ equation, the expression for pressure distribution is obtained. In turn, this leads to the calculation of the load carrying capacity. Further, the friction is also computed. It is observed that the magnetization paves the way for an overall improved performance of the bearing system. However the magnetic fluid lubricant fails to alter the friction. It is established that the slip parameter needs to be kept at minimum to achieve better performance of the bearing system, although the effect of the slip parameter on the load carrying capacity is in most situations, negligible. It is found that for large values of the aspect ratio, the effect of slip is increasingly significant. Of course, the aspect ratio plays a crucial role in this improved performance. Lastly, it is established that the bearing can support a load even in the absence of flow, which does not happen in the case of a conventional lubricant.

  6. Lubrication of sliding bearings for hydropower applications

    OpenAIRE

    McCarthy, Donald

    2005-01-01

    The term "sliding bearing" refers to types of bearing where two conformal surfaces (usually the stationary bearing and a moving shaft) slide relative to one another with load distributed directly across the interface. A suitable lubricant may be employed to reduce the friction between these two surfaces. In "fluid film" bearings, this lubricant builds up a layer of sufficient thickness such that the two surfaces are completely separated. Examples include journal and thrust bearings and shaft ...

  7. Vibration control of rotor-bearing system by controlled squeeze-film damper bearings

    Science.gov (United States)

    He, Erming; Gu, Jialiu

    1992-07-01

    A new vibration control scheme for rotor-bearing systems is presented which offers many advantages over the scheme proposed by Gu (1990). Due to the nonlinear state feedback, closed-loop control becomes possible. Thus control can be readily adjusted in accordance with transient state information. Optimal structure parameters are determined by the optimal control law. The control force is applied on line; by merely adjusting CSFDB structure parameters, control forces can be applied to the system. The feasibility of the present design is confirmed by simulation, which is performed for a flexible Jeffcott rotor elastically supported at both ends on identical CSFDBs.

  8. Reversible dewetting of a molecularly thin fluid water film in a soft graphene-mica slit pore.

    Science.gov (United States)

    Severin, Nikolai; Lange, Philipp; Sokolov, Igor M; Rabe, Jürgen P

    2012-02-08

    The behavior of water and other molecular liquids confined to the nanoscale is of fundamental importance, e.g., in biology, material science, nanofluidics, and tribology. Direct microscopic imaging of wetting dynamics in subnanometer pores is however challenging. We will show in the following that a molecularly thin water film confined between mica and graphene is fluid. Ambient humidity allows to control the wetting and dewetting of the film. We follow these processes in space and time using scanning force microscopy imaging of the graphene conforming to the film. At sufficiently high humidity a continuous molecularly thin water film wets the interface between the graphene and mica. At lower humidities the film dewets with fractal depressions exhibiting dimensions around 1.7 and depths comparable to the size of a water molecule. The soft graphene cover offers a previously unexplored semihydrophilic slit pore of self-adjustable size, which enables high-resolution imaging of confined molecularly thin fluid films, and bears the potential for the fabrication of novel nanofluidic devices. © 2012 American Chemical Society

  9. Analysis of single oil-bearing fluid inclusions in mid-Proterozoic sandstones (Roper Group, Australia)

    Science.gov (United States)

    Siljeström, Sandra; Volk, Herbert; George, Simon C.; Lausmaa, Jukka; Sjövall, Peter; Dutkiewicz, Adriana; Hode, Tomas

    2013-12-01

    Hydrocarbons and organic biomarkers extracted from black shales and other carbonaceous sedimentary rocks are valuable sources of information on the biodiversity and environment of early Earth. However, many Precambrian hydrocarbons including biomarkers are suspected of being younger contamination. An alternative approach is to study biomarkers trapped in oil-bearing fluid inclusions by bulk crushing samples and subsequently analysing the extracted hydrocarbons with gas chromatography-mass spectrometry. However, this method does not constrain the hydrocarbons to one particular oil inclusion, which means that if several different generations of oil inclusions are present in the sample, a mix of the content from these oil inclusions will be analysed. In addition, samples with few and/or small inclusions are often below the detection limit. Recently, we showed that it is possible to detect organic biomarkers in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the present study, single fluid inclusion analysis has been performed on Proterozoic samples for the first time. Four individual oil-bearing fluid inclusions, found in 1430 Ma sandstone from the Roper Superbasin in Northern Australia, were analysed with ToF-SIMS. The ToF-SIMS spectra of the oil in the different inclusions are very similar to each other and are consistent with the presence of n-alkanes/branched alkanes, monocyclic alkanes, bicyclic alkanes, aromatic hydrocarbons, and tetracyclic and pentacyclic hydrocarbons. These results are in agreement with those obtained from bulk crushing of inclusions trapped in the same samples. The capability to analyse the hydrocarbon and biomarker composition of single oil-bearing fluid inclusions is a major breakthrough, as it opens up a way of obtaining molecular compositional data on ancient oils without the ambiguity of the origin of these hydrocarbons. Additionally, this finding suggests that it will be possible

  10. Computational Fluid Dynamic Analysis of the Flow around the Pivot Bearing of the Centrifugal Ventricular Assist Device

    Science.gov (United States)

    Nishida, Masahiro; Yamane, Takashi; Maruyama, Osamu; Sankai, Yoshiyuki; Tsutsui, Tatsuo

    Flow mechanisms within a monopivot centrifugal pump were clarified in order to prevent stagnation around the pivot bearing, which may cause thrombogenesis. We focused on the geometric effects of the pump, which included the effects of the washout hole diameter, the pivot friction area and the back gap width of the impeller relative to the washout around the pivot bearing. Flow patterns were carefully examined around the pivot bearing, including the region inside the washout hole and the back gap of the impeller, by computational fluid dynamic analysis. Based on the results from the computational fluid dynamic analyses, we found that a balance relationship between the washout hole diameter and the back gap width of the impeller affected the secondary flow toward the pivot bearing that eliminated the stagnation around the pivot bearing. In addition, while increasing in the pivot friction area eliminated stagnation around the pivot bearing, it also increased hemolysis within the pump.

  11. The influence of the lubricant film on the stiffness and damping characteristics of a deep groove ball bearing

    Science.gov (United States)

    Jacobs, William; Boonen, Rene; Sas, Paul; Moens, David

    2014-01-01

    This paper experimentally investigates the formation of a lubricant film in a deep groove ball bearing and its effect on the bearing dynamics. A novel test rig is introduced, which allows testing different types and sizes of bearings in real-life conditions. The test rig dynamics are optimised such that the dynamic properties of the bearing are measured in a frequency range below the resonances of the flexible modes. Two properties of the bearing, both its stiffness and damping value in the direction of the static bearing load, are identified. The behaviour of the lubricant film between the rolling elements and raceways is measured based on the electrical resistance through the bearing. For this purpose, the bearing housing is electrically isolated from the surrounding structure. The electrical resistance, stiffness and damping of the test bearing are identified during a speed run-up. The influence of the bearing temperature is analysed as well. During a run-up at constant bearing temperature, the measurement of the electrical resistance describes the formation of the lubricant film. Due to the formation of the lubricant film, the bearing stiffness increases by 3.2% while the damping increases by 24%. During a warm-up of the bearing, the viscosity of the lubricant film decreases strongly. A resulting decrease in electrical resistance, stiffness and damping is measured. Finally, the electrical resistance, stiffness and damping are identified at different speeds, after the bearing has reached a stable temperature at each speed. A combined effect of both rotation and temperature is observed and discussed.

  12. Au-bearing magnetite mineralizaion in Kashmar (alteration, mineralization, geochemistry, geochemistry and fluid inclusions;

    Directory of Open Access Journals (Sweden)

    Alireza Almasi

    2017-02-01

    Full Text Available Introduction The study area is located in the central part of the Khaf- Kashmar- Bardaskan volcano-plotunic belt (briefly KKBB. Several IOCG deposits such as Tanourjeh Au-bearing magnetite deposit and Kuh-e-Zar Specularite-rich Au deposit have been explored in KKBB. Geology, alteration, mineralization, geochemistry and fluid inclusion results in Kashmar suggest the IOCG type Au-bearing magnetite mineralization. These IOCG deposits at KKBB form at an active continental arc related to SSZ-type Sabzevar oceanic subduction. Materials and methods Use of Landsat 7+, IRS and Aster satellites. Petrography and alteration Studies in 150 thin sections of volcanic and intrusive rocks. Sampling of ore-bearing quartz vein and mineralography. Preparation of 28 geochemistry samples by the chip composite method of ore-bearing quartz vein and analyzing them in the ACME laboratory by Aqua Regia 1DX1. Fluid inclusions studies of 14 samples of quartz and barite related to the ore minerals of ore-bearing quartz vein by THM600 stage of Linkam company. Results Magmatic events in Kashmar occur at Paleocene-Eocene and include: (1 old mafic - intermediate volcano-plutonic series; (2 felsic volcanic and granitoids; and (3 parallel swarm dykes which are youngest (Almasi et al., 2016. Geochemically, Kashmar rocks are metaluminous to highly peraluminous and Tholeitic to calc-alkaline and shoshonitic in composition (Almasi et al., 2016. The field characteristics, together with isotope and geochemical analyses show that all rock types are essentially co-magmatic and post-collisional I-type (Almasi et al., 2016. Alteration of Kashmar is described in two ways: (1 intense ellipsoidal-linear Argillic-Sillicification and low sericitic with Silica caps and with medium widespread and propylitic alterations in triple regions, next to Dorouneh fault; and (2 Medium Hematite-Carbonate-Chlorite-Silicification alterations in Kamarmard heights. In parts of near the Doruneh fault, sometimes

  13. Computational Fluid Dynamics Simulation of Dual Bell Nozzle Film Cooling

    Science.gov (United States)

    Braman, Kalen; Garcia, Christian; Ruf, Joseph; Bui, Trong

    2015-01-01

    Marshall Space Flight Center (MSFC) and Armstrong Flight Research Center (AFRC) are working together to advance the technology readiness level (TRL) of the dual bell nozzle concept. Dual bell nozzles are a form of altitude compensating nozzle that consists of two connecting bell contours. At low altitude the nozzle flows fully in the first, relatively lower area ratio, nozzle. The nozzle flow separates from the wall at the inflection point which joins the two bell contours. This relatively low expansion results in higher nozzle efficiency during the low altitude portion of the launch. As ambient pressure decreases with increasing altitude, the nozzle flow will expand to fill the relatively large area ratio second nozzle. The larger area ratio of the second bell enables higher Isp during the high altitude and vacuum portions of the launch. Despite a long history of theoretical consideration and promise towards improving rocket performance, dual bell nozzles have yet to be developed for practical use and have seen only limited testing. One barrier to use of dual bell nozzles is the lack of control over the nozzle flow transition from the first bell to the second bell during operation. A method that this team is pursuing to enhance the controllability of the nozzle flow transition is manipulation of the film coolant that is injected near the inflection between the two bell contours. Computational fluid dynamics (CFD) analysis is being run to assess the degree of control over nozzle flow transition generated via manipulation of the film injection. A cold flow dual bell nozzle, without film coolant, was tested over a range of simulated altitudes in 2004 in MSFC's nozzle test facility. Both NASA centers have performed a series of simulations of that dual bell to validate their computational models. Those CFD results are compared to the experimental results within this paper. MSFC then proceeded to add film injection to the CFD grid of the dual bell nozzle. A series of

  14. Non-linear performance of a three-bearing rotor incorporating a squeeze-film damper

    Science.gov (United States)

    Holmes, R.; Dede, M.

    1987-01-01

    This paper is concerned with the non-linear vibration performance of a rigid rotor supported on three bearings, one being surrounded by a squeeze-film damper. This damper relies on the pressure built up in the squeeze film to help counter-act external forces arising from unbalance and other effects. As a result a vibration orbit of a certain magnetude results. Such vibration orbits illustrate features found in other non-linear systems, in particular sub-harmonic resonances and jump phenomena. Comparisons between theoretical prediction and experimental observations of these phenomena are made.

  15. Supercritical fluid molecular spray film deposition and powder formation

    Science.gov (United States)

    Smith, Richard D.

    1986-01-01

    Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. Upon expansion and supersonic interaction with background gases in the low pressure region, any clusters of solvent are broken up and the solvent is vaporized and pumped away. Solute concentration in the solution is varied primarily by varying solution pressure to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solvent clustering and solute nucleation are controlled by manipulating the rate of expansion of the solution and the pressure of the lower pressure region. Solution and low pressure region temperatures are also controlled.

  16. Backward whirl in a simple rotor supported on hydrodynamic bearings

    Science.gov (United States)

    Subbiah, R.; Rhat, R. B.; Sankar, T. S.; Rao, J. S.

    1985-01-01

    The asymmetric nature of the fluid film stiffness and damping properties in rotors supported on fluid film bearings causes a forward or a backward whirl depending on the bearing parameters and the speed of the rotor. A rotor was designed to exhibit backward synchronous whirl. The rotor-bearing system exhibited split criticals, and a backward whirl was observed between the split criticals. The orbital diagrams show the whirl pattern.

  17. Magnetic Fluid-Based Squeeze Film Performance in Rotating Curved Porous Circular Plates: The Effect of Deformation and Surface Roughness

    Directory of Open Access Journals (Sweden)

    M.E. Shimpi

    2012-06-01

    Full Text Available This investigation aims at analyzing the behaviour of a magnetic fluid based squeeze film between two rotating transversely rough porous circular plates taking bearing deformation into consideration. The results presented in graphical form inform that the transverse surface roughness introduces an adverse effect on the performance characteristics while the magnetic fluid lubricant turn in an improved performance. It is found that the combined effect of rotation and deformation causes significantly reduced load carrying capacity. However, this investigation establishes that the adverse effect of porosity, deformation and standard deviation can be compensated up to some extent by the positive effect of magnetic fluid lubricant in the case of negatively skewed roughness by choosing curvature parameters. To compensate, the rotational inertia needs to have smaller values.

  18. A Rotational Gyroscope with a Water-Film Bearing Based on Magnetic Self-Restoring Effect

    Science.gov (United States)

    Chen, Dianzhong; Liu, Xiaowei; Li, Hai; Li, Ling; Rong, Wanting; Zhang, Zhongzhao

    2018-01-01

    Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG) and electrostatically suspended gyroscopes (ESG)) with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement on fabrication technology. In the proposed gyroscope, a ball-disk shaped rotor is supported by a water-film bearing, formed by centrifugal force to deionized water at the cavity of the lower supporting pillar. Water-film bearing provides stable mechanical support, without the need for complicated electronics and control system for rotor suspension. To decrease sliding friction between the rotor ball and the water-film bearing, a supherhydrophobic surface (SHS) with nano-structures is fabricated on the rotor ball, resulting in a rated spinning speed increase of 12.4% (under the same driving current). Rotor is actuated by the driving scheme of brushless direct current motor (BLDCM). Interaction between the magnetized rotor and the magnetic-conducted stator produces a sinusoidal rotor restoring torque, amplitude of which is proportional to the rotor deflection angle inherently. Utilization of this magnetic restoring effect avoids adding of a high amplitude voltage for electrostatic feedback, which may cause air breakdown. Two differential capacitance pairs are utilized to measure input angular speeds at perpendicular directions of the rotor plane. The bias stability of the fabricated gyroscope is as low as 0.5°/h. PMID:29385105

  19. A Rotational Gyroscope with a Water-Film Bearing Based on Magnetic Self-Restoring Effect

    Directory of Open Access Journals (Sweden)

    Dianzhong Chen

    2018-01-01

    Full Text Available Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG and electrostatically suspended gyroscopes (ESG with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement on fabrication technology. In the proposed gyroscope, a ball-disk shaped rotor is supported by a water-film bearing, formed by centrifugal force to deionized water at the cavity of the lower supporting pillar. Water-film bearing provides stable mechanical support, without the need for complicated electronics and control system for rotor suspension. To decrease sliding friction between the rotor ball and the water-film bearing, a supherhydrophobic surface (SHS with nano-structures is fabricated on the rotor ball, resulting in a rated spinning speed increase of 12.4% (under the same driving current. Rotor is actuated by the driving scheme of brushless direct current motor (BLDCM. Interaction between the magnetized rotor and the magnetic-conducted stator produces a sinusoidal rotor restoring torque, amplitude of which is proportional to the rotor deflection angle inherently. Utilization of this magnetic restoring effect avoids adding of a high amplitude voltage for electrostatic feedback, which may cause air breakdown. Two differential capacitance pairs are utilized to measure input angular speeds at perpendicular directions of the rotor plane. The bias stability of the fabricated gyroscope is as low as 0.5°/h.

  20. A Rotational Gyroscope with a Water-Film Bearing Based on Magnetic Self-Restoring Effect.

    Science.gov (United States)

    Chen, Dianzhong; Liu, Xiaowei; Zhang, Haifeng; Li, Hai; Weng, Rui; Li, Ling; Rong, Wanting; Zhang, Zhongzhao

    2018-01-31

    Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG) and electrostatically suspended gyroscopes (ESG)) with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement on fabrication technology. In the proposed gyroscope, a ball-disk shaped rotor is supported by a water-film bearing, formed by centrifugal force to deionized water at the cavity of the lower supporting pillar. Water-film bearing provides stable mechanical support, without the need for complicated electronics and control system for rotor suspension. To decrease sliding friction between the rotor ball and the water-film bearing, a supherhydrophobic surface (SHS) with nano-structures is fabricated on the rotor ball, resulting in a rated spinning speed increase of 12.4% (under the same driving current). Rotor is actuated by the driving scheme of brushless direct current motor (BLDCM). Interaction between the magnetized rotor and the magnetic-conducted stator produces a sinusoidal rotor restoring torque, amplitude of which is proportional to the rotor deflection angle inherently. Utilization of this magnetic restoring effect avoids adding of a high amplitude voltage for electrostatic feedback, which may cause air breakdown. Two differential capacitance pairs are utilized to measure input angular speeds at perpendicular directions of the rotor plane. The bias stability of the fabricated gyroscope is as low as 0.5°/h.

  1. Differences between blood and a Newtonian fluid on the performance of a hydrodynamic bearing for rotary blood pumps.

    Science.gov (United States)

    Amaral, Felipe; Egger, Christina; Steinseifer, Ulrich; Schmitz-Rode, Thomas

    2013-09-01

    Assuming that blood has a constant viscosity is a common practice when designing rotary blood pumps (RBPs), where shear stresses are generally higher than in the human body. This eases the design and allows numerical simulations and bench top experiments to be performed with Newtonian fluids. However, specific flow conditions may cause a change in cell distribution leading to an apparent lower blood viscosity. It has been observed that decreasing the vessel diameters and increasing flow velocities contribute to this effect. Because a hydrodynamic bearing operates under flow conditions following this pattern, it is important to verify whether this effect also takes place when this type of bearing is applied to a RBP. Because the operation of a hydrodynamic bearing depends directly on the fluid viscosity, a local change in cell distribution in the bearing gap can be reflected in changes in the bearing performance. In this work, a spiral groove hydrodynamic bearing was tested with porcine blood in a specially built test rig. The generated suspension force, cross flow, and bearing torque were recorded and compared with the reference response when using a solution of water and glycerol. Experiments with porcine blood yielded lower suspension forces, lower flows, and lower bearing torques than when using the glycerol solution. An explanation could be a lower apparent viscosity due to inhomogeneity of blood cell concentrations. Therefore, it is crucial to consider the effective blood viscosity when designing hydrodynamic bearings for RBPs and performing experiments. © 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.

  2. Radial oil injection applied to main engine bearings: evaluation of injection control rules

    DEFF Research Database (Denmark)

    Estupiñan, EA; Santos, Ilmar

    2012-01-01

    The performance of main bearings in a combustion engine affects key functions such as durability, noise and vibration. Thus, with the aim of reducing friction losses and vibrations between the crankshaft and the bearings, the work reported here evaluates different strategies for applying...... of the actively lubricated bearing is compared with the performance of the conventional lubricated bearing, giving some insights into the minimum fluid film thickness, maximum fluid film pressure, friction losses and maximum vibration levels....

  3. Design and modeling of semi-active squeeze film dampers using magneto-rheological fluids

    Science.gov (United States)

    Kim, Keun-Joo; Lee, Chong-Won; Koo, Jeong-Hoi

    2008-06-01

    Conventional squeeze film dampers (SFDs) have shown their effectiveness in suppressing unbalanced vibrations in rotor systems, particularly supported by rolling element bearings. Recently, there is an increasing demand for 'controllable' SFDs to meet the need of modern rotating machinery, characterized by high operating speed and high load capacity. Thus, this paper presents a controllable semi-active SFD using magneto-rheological (MR) fluids, focusing on its design and modeling. It offers a comprehensive design method and an innovative experimental identification and modeling technique for MR-SFDs. The primary goal of the MR-SFD design is set to maximize its dynamic control bandwidth, and the design method includes the material selection, magnetic circuit analysis and sealing element design. After constructing a prototype MR-SFD based on the final design, this work investigated how some of the critical design parameters affect the performance of the MR-SFD (i.e. its dynamic control bandwidth change). Furthermore, it characterized the damper's dynamic behavior experimentally using a novel excitation method that adopts active magnetic bearing (AMB) units. Unlike conventional methods, the AMB system was able to precisely control the amplitude and frequency of the input excitation, enabling us to obtain the nonlinear dynamic stiffness properties of the MR-SFD with varying input current. In modeling the dynamic behavior of the MR-SFD, this study employed the describing function method. The describing function analysis effectively captured the nonlinear dynamic behavior of the MR-SFD.

  4. Approximate solution of oil film load-carrying capacity of turbulent journal bearing with couple stress flow

    Science.gov (United States)

    Zhang, Yongfang; Wu, Peng; Guo, Bo; Lü, Yanjun; Liu, Fuxi; Yu, Yingtian

    2015-01-01

    The instability of the rotor dynamic system supported by oil journal bearing is encountered frequently, such as the half-speed whirl of the rotor, which is caused by oil film lubricant with nonlinearity. Currently, more attention is paid to the physical characteristics of oil film due to an oil-lubricated journal bearing being the important supporting component of the bearing-rotor systems and its nonlinear nature. In order to analyze the lubrication characteristics of journal bearings efficiently and save computational efforts, an approximate solution of nonlinear oil film forces of a finite length turbulent journal bearing with couple stress flow is proposed based on Sommerfeld and Ocvirk numbers. Reynolds equation in lubrication of a finite length turbulent journal bearing is solved based on multi-parametric principle. Load-carrying capacity of nonlinear oil film is obtained, and the results obtained by different methods are compared. The validation of the proposed method is verified, meanwhile, the relationships of load-carrying capacity versus eccentricity ratio and width-to-diameter ratio under turbulent and couple stress working conditions are analyzed. The numerical results show that both couple stress flow and eccentricity ratio have obvious influence on oil film pressure distribution, and the proposed method approximates the load-carrying capacity of turbulent journal bearings efficiently with various width-to-diameter ratios. This research proposes an approximate solution of oil film load-carrying capacity of turbulent journal bearings with different width-to-diameter ratios, which are suitable for high eccentricity ratios and heavy loads.

  5. Solubility of gold in oxidized, sulfur-bearing fluids at 500-850 °C and 200-230 MPa: A synthetic fluid inclusion study

    Science.gov (United States)

    Guo, Haihao; Audétat, Andreas; Dolejš, David

    2018-02-01

    Although Au solubility in magmatic-hydrothermal fluids has been investigated by numerous previous studies, there is a dearth of data on oxidized (log fO2 > FMQ+2.5; FMQ - fayalite-magnetite-quartz buffer), sulfur-bearing fluids such as those that formed porphyry Cu-Au (-Mo) deposits. We performed experiments to constrain the effects of fluid salinity, HCl content, sulfur content, fO2 and temperature on Au solubility in such oxidized, sulfur-bearing fluids. For this purpose, small aliquots of fluids equilibrated with Au metal were trapped at high pressure and temperature in the form of synthetic fluid inclusions in quartz and were subsequently analyzed by LA-ICP-MS. Additionally, Raman spectra were collected from quartz-hosted fluid inclusions at up to 600 °C to help to identify the nature of dissolved gold and sulfur species. Gold solubility was found to be affected most strongly by the HCl content of the fluid, followed by fO2, fluid salinity and temperature. Compared to these factors the sulfur content of the fluid has relatively little influence. At 600 °C and 100 MPa, fluids with geologically realistic HCl contents (∼1.1 wt%) and salinities (7-50 wt% NaClequiv) dissolve ∼1000-3000 ppm Au at oxygen fugacities controlled by the magnetite-hematite buffer. At even more oxidized conditions (three log units above the hematite-magnetite fO2 buffer), HCl-, NaCl- and H2SO4-rich fluids can dissolve up to 5 wt% Au at 800 °C and 200 MPa. The observed Au solubility trends are controlled by HCl0 species in the Na-H-Cl-SO4 fluid and are quantitatively reproduced by existing thermodynamic data for Au-Cl complexes. In all experiments, AuCl0 and AuCl2- species are predicted to occur in comparable although variable concentrations, and account for more than 95% of Au solutes. Natural, high-temperature (>500 °C) brine inclusions from porphyry Cu-Au (-Mo) deposits contain significantly less Au than gold-saturated brines that were synthesized experimentally, implying that the

  6. Fluid flow and thin-film evolution near the triple line during droplet evaporation of self-rewetting fluids.

    Science.gov (United States)

    Yang, Yang; Zhou, Leping; Du, Xiao-Ze; Yang, Yongping

    2018-03-07

    The microscopic region near the triple line plays an important role in the heat and mass transfer of droplets, while the mechanisms of evaporation and internal flow remain unclear. This paper describes an experimental study of fluid flow and thin-film evolution near the triple line in sessile droplets of self-rewetting fluids, aqueous solutions of alcohols with number of carbon atoms varies from 1 to 7, to analyze the influence of various factors on the mesoscale flows. The mechanism of internal flow for self-rewetting fluid droplets was different from that of conventional fluids, and hence a novel expression of in-plane average velocity was fitted for them. The temporal and spatial evolution of thin-film thickness near the triple line during droplet evaporation was obtained by using a proposed sub-region method, which was developed from an evanescent wave based multilayer nanoparticle image velocimetry technique. The self-rewetting fluids are conducive to increase the microscopic critical contact angle and the energy barrier of contact line, which reduces the rate of thin-film thickness variation. The inhibited impact of self-rewetting fluids on the evaporation increases gradually with increasing number of carbon atoms.

  7. Effect of ion-plated films of germanium and silicon on friction, wear, and oxidation of 52100 bearing steel

    Science.gov (United States)

    Buckley, D. H.; Spalvins, T.

    1977-01-01

    Friction and wear experiments were conducted with ion plated films of germanium and silicon on the surface of 52100 bearing steel both dry and in the presence of mineral oil. Both silicon and germanium were found to reduce wear, with germanium being more effective than silicon. An optimum film thickness of germanium for minimum wear without surface crack formation was found to be approximately 400 nanometers (4000 A). The presence of silicon and germanium on the 52100 bearing steel surface improved resistance to oxidation.

  8. Scaling laws for radial foil bearings

    Science.gov (United States)

    Honavara Prasad, Srikanth

    The effects of fluid pressurization, structural deformation of the compliant members and heat generation in foil bearings make the design and analysis of foil bearings very complicated. The complex fluid-structural-thermal interactions in foil bearings also make modeling efforts challenging because these phenomena are governed by highly non-linear partial differential equations. Consequently, comparison of various bearing designs require detailed calculation of the flow fields (velocities, pressures), bump deflections (structural compliance) and heat transfer phenomena (viscous dissipation in the fluid, frictional heating, temperature profile etc.,) resulting in extensive computational effort (time/hardware). To obviate rigorous computations and aid in feasibility assessments of foil bearings of various sizes, NASA developed the "rule of thumb" design guidelines for estimation of journal bearing load capacity. The guidelines are based on extensive experimental data. The goal of the current work is the development of scaling laws for radial foil bearings to establish an analytical "rule of thumb" for bearing clearance and bump stiffness. The use of scale invariant Reynolds equation and experimentally observed NASA "rule of thumb" yield scale factors which can be deduced from first principles. Power-law relationships between: a. Bearing clearance and bearing radius, and b. bump stiffness and bearing radius, are obtained. The clearance and bump stiffness values obtained from scaling laws are used as inputs for Orbit simulation to study various cases. As the clearance of the bearing reaches the dimensions of the material surface roughness, asperity contact breaks the fluid film which results in wear. Similarly, as the rotor diameter increases (requiring larger bearing diameters), the load capacity of the fluid film should increase to prevent dry rubbing. This imposes limits on the size of the rotor diameter and consequently bearing diameter. Therefore, this thesis aims

  9. Synovial fluid lubrication of artificial joints: protein film formation and composition.

    Science.gov (United States)

    Fan, Jingyun; Myant, Connor; Underwood, Richard; Cann, Philippa

    2012-01-01

    Despite design improvements, wear of artificial implants remains a serious health issue particularly for Metal-on-Metal (MoM) hips where the formation of metallic wear debris has been linked to adverse tissue response. Clearly it is important to understand the fundamental lubrication mechanisms which control the wear process. It is usually assumed that MoM hips operate in the ElastoHydrodynamic Lubrication (EHL) regime where film formation is governed by the bulk fluid viscosity; however there is little experimental evidence of this. The current paper critically examines synovial fluid lubrication mechanisms and the effect of synovial fluid chemistry. Two composition parameters were chosen; protein content and pH, both of which are known to change in diseased or post-operative synovial fluid. Film thickness and wear tests were carried out for a series of model synovial fluid solutions. Two distinct film formation mechanisms were identified; an adsorbed surface film and a high-viscosity gel. The entrainment of this gel controls film formation particularly at low speeds. However wear of the femoral head still occurs and this is thought to be due primarily to a tribo-corrosion mechanisms. The implications of this new lubrication mechanism and the effect of different synovial fluid chemistries are examined. One important conclusion is that patient synovial fluid chemistry plays an important role in determining implant wear and the likelihood of failure.

  10. The effects of a CO2-bearing fluid on the rheology of quartz-bearing rocks in subduction zones

    Science.gov (United States)

    Ashley, K. T.; Behr, W. M.

    2017-12-01

    The weakening effect of water on quartz rheology has been a well-recognized phenomenon for several decades. In many tectonic environments, however, the fluid phase is not pure H2O, but commonly includes other species such as CO2, dissolved silicates, and/or salts. CO2 is especially prevalent in subduction zone fluids due to subduction of carbonates and/or graphitic sediments. Some deformation experiments as well as natural observations suggest that CO2 can affect rheology and development of anisotropy in quartz-rich rocks, but the precise effects of CO2 are poorly understood. Here we take a petrologic approach to assess the role of a mixed H2O-CO2 fluid phase for deforming quartzite in the viscous regime. For quartz dislocation creep, CO2 in the fluid acts as a non-wetting phase, resulting in the reduction of water fugacity. However, for most rocks, the activity-composition (a-X) relationship of a H2O-CO2 fluid phase requires very high CO2 mole fractions to have a significant effect on strain rate. For XCO2 = 0.5 at 500°C, with a differential stress of 10 MPa, the water fugacity is only reduced by 30% and resultant strain rates are slowed by less than a factor of 3 — much less than the inherent uncertainty of the flow law. In contrast, because silica does not form complexes with CO2, its solubility greatly decreases at high carbonic fractions and pressure solution is greatly slowed. For most diagenetic conditions, a 50:50 H2O-CO2 fluid phase compared to a pure-H2O fluid phase results in a strain rate that is an order of magnitude slower. Higher carbonic fractions has dramatic effects on the rate of pressure solution (decreased by >3 orders of magnitude at XCO2 = 0.8). The difference in the response of quartz deformation mechanisms to changes in the fluid composition suggests CO2-rich fluids could result in the suppression of pressure solution and the activation of dislocation creep (or brittle failure) at lower temperatures than expected for a pure H2O fluid.

  11. Journal and Wave Bearing Impedance Calculation Software

    Science.gov (United States)

    Hanford, Amanda; Campbell, Robert

    2012-01-01

    The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

  12. Experimental Performance Study of a High Speed Oil Lubricated Polymer Thrust Bearing

    Directory of Open Access Journals (Sweden)

    Jie Zhou

    2015-01-01

    Full Text Available With the demand for turbomachinery to operate at higher speeds, loads, and power, fluid film bearings that support turbomachinery must be capable of operating in these more demanding applications. Thrust bearings operating at high speeds and loads can experience high surface temperatures and thin fluid film thickness. Typically, babbitt (white metal is the bearing lining material for most turbomachinery bearings but is limited in operating temperature and allowable film thickness. Polymer based materials are alternative materials that can operate at high temperatures and with thin films and have been in use for many decades in high load applications, such as electric submersible pumps (ESP. Test results of polymer lined thrust bearings subjected to modern turbomachinery speeds and loads are presented and compared to babbitt lined bearings of the same design and under similar conditions. The test results show polymer lined thrust bearings can operate at higher bearing unit loads than babbitt.

  13. Studying effect of MHD on thin films of a micropolar fluid

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Rahman, Gamal M., E-mail: gamalm60@yahoo.co [Department of Mathematics, Faculty of Science, Benha University, 13518 Benha (Egypt)

    2009-11-15

    This paper deals with the study of the effect of MHD on thin films of a micropolar fluid. These thin films are considered for three different geometries, namely: (i) flow down an inclined plane, (ii) flow on a moving belt and (iii) flow down a vertical cylinder. The transformed boundary layer governing equations of a micropolar fluid and the resulting system of coupled non-linear ordinary differential equations are solved numerically by using shooting method. Numerical results were presented for velocity and micro-rotation profiles within the boundary layer for different parameters of the problem including micropolar fluid parameters, magnetic field parameter, etc., which are also discussed numerically and illustrated graphically.

  14. Faunal communities at sites of gas- and oil-bearing fluids in Lake Baikal

    Science.gov (United States)

    Zemskaya, Tamara I.; Sitnikova, Tatiana Y.; Kiyashko, Sergei I.; Kalmychkov, Gennady V.; Pogodaeva, Tatiana V.; Mekhanikova, Irina V.; Naumova, Tatiana V.; Shubenkova, Olga V.; Chernitsina, Svetlana M.; Kotsar, Oleg V.; Chernyaev, Evgeny S.; Khlystov, Oleg M.

    2012-12-01

    Macro- and meiofaunal communities were examined at four geomorphologically distinct sites with different gas- and oil-bearing fluid characteristics in the northern, central and southern basins of Lake Baikal. All sites had elevated concentrations of bicarbonate, nitrate, sulphate and chloride ions in pore fluids, with highest values at the Frolikha vent. Elevated levels of iron ions were found in pore waters of the St. Petersburg methane seep and the Gorevoy Utes oil seep. The chemical composition of pore waters at the Malenky mud volcano was similar to that reported in earlier work. Consistent with published data, the Frolikha vent (northern basin) and the St. Petersburg methane seep (central basin) were characterised by methane of mixed genesis (thermogenic + biogenic), whereas the methane source was mainly thermogenic at the Gorevoy Utes oil seep (central basin) and biogenic at the Malenky mud volcano (southern basin). In contrast to marine seep ecosystems, the macrofauna was dominated only by amphipods, giant planarians and oligochaetes, whereas bivalves were absent; the meiofauna was similar to its marine counterpart, being dominated by nematodes, cyclops, harpacticoids and ostracods. A statistically significant positive relationship was revealed between faunal abundance and the availability of bacterial mats on seep sediments. Moreover, ANOVA tests showed significant increases in both meiozoobenthic and macrozoobenthic densities at "hot spot" vent/seep sites relative to discharge-free reference sites. The isotopic composition of carbon and nitrogen at various trophic levels of these benthic vent/seep communities was found to differ markedly from that reported by earlier studies for the pelagic and other benthic food webs in Lake Baikal. As in marine seeps, the macrofauna had variable isotopic signatures. Light δ13C and δ15N values suggest the utilization of chemosynthetically fixed and/or methane-derived organic matter. By contrast, the heavy δ13C

  15. Novel nano bearings constructed by physical adsorption

    Science.gov (United States)

    Zhang, Yongbin

    2015-09-01

    The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.

  16. Annular Pressure Seals and Hydrostatic Bearings

    Science.gov (United States)

    2006-11-01

    scale). The equation below presents a close form expression for estimation of the added mass coefficient (MXX) in a seal or squeeze film damper [14...Arauz & L. San Andrés, “ASME Journal of Tribology, 120, pp. 221-233, 1998. [14] Squeeze Film Dampers : Operation, Models and Technical Issues, L. San...fluid film bearing technology with very low number of parts and no DN limit operation. Details on the bulk- flow analysis of turbulent flow

  17. Performance of non-recessed hole-entry hybrid journal bearing operating under turbulent regime

    Directory of Open Access Journals (Sweden)

    Nathi Ram

    2016-03-01

    Full Text Available The effect of turbulent flow on non-recessed hole-entry hybrid journal bearing system has been investigated numerically. For turbulent flow of lubricant in compensated hole-entry hybrid journal bearing by CFV, the Reynolds equation has been modified and solved using finite element method. The performance characteristics parameters of bearing have been presented for different values of Reynolds numbers. The bearing provides the higher values of minimum fluid film thickness and fluid film stiffness coefficients for constant restrictor design parameter when bearing operates under turbulent regime than laminar regime.

  18. Refrigerant falling film evaporation review: Description, fluid dynamics and heat transfer

    International Nuclear Information System (INIS)

    Fernández-Seara, José; Pardiñas, Ángel Á.

    2014-01-01

    Falling film horizontal tube evaporators for refrigeration equipment are an interesting alternative to pool boiling evaporators concerning operation costs, safety, thermodynamic efficiency, charge of refrigerant or size. Plenty of literature works studied falling film evaporation, but for its application in fields such as desalination and petrochemical industry or OTEC. This review focuses mainly on those works from the literature that analysed the main issues of falling film evaporation of refrigerants, to better understand heat transfer and fluid dynamics in such evaporators. First, falling film evaporation is described and compared to pool boiling, to define its main advantages and inconveniences. Then, the literature concerning film around the tubes and between them is analysed, as well as the phenomenon of film breakdown, which sharply deteriorates the heat transfer performance of falling film evaporators. After it, the results from those works that studied analytically and experimentally the heat transfer coefficients (HTCs) with different types of tubes and refrigerants are discussed. The review finishes with a brief summary of important parameters of falling film evaporation, which might be useful for the design of such equipment. - Highlights: •We defined falling film evaporation and compared it with pool boiling. •We reviewed works from the literature concerning refrigerant falling film evaporation. •We classified the ideas from the works attending to crucial aspects of the process. •We developed a summary of the main ideas which could be useful for design purpose

  19. Chemical Processing for Sol-Gel Derived Metal Oxide Thin Films using Supercritical Carbon Dioxide Fluid

    Energy Technology Data Exchange (ETDEWEB)

    Asai, Y; Narishige, S; Fujioka, K; Uchida, H; Koda, S, E-mail: uchidah@sophia.ac.jp [Sophia University, Department of Materials and Life Sciences, Tokyo 102-8554 (Japan)

    2011-10-29

    Chemical processing using supercritical carbon dioxide fluid (scCO{sub 2}) was demonstrated for lowering processing temperature of sol-gel-derived metal oxide thin films. The film processing was performed in a hot-wall closed vessel filled with scCO{sub 2} fluid. Precursor films of titanium dioxide (TiO{sub 2}) on soda-glass substrates prepared by sol-gel coating using Ti-alkoxide solution were converted to crystalline TiO{sub 2} (anatase) films successfully by the scCO{sub 2} treatment at a fluid pressure of 15 MPa and a substrate temperature of 300deg. C whereas no crystallization was occurred by conventional heat treatment at 400 deg. C. XPS analysis indicated that the interface reaction related to Si element was suppressed successfully by scCO{sub 2} treatment at 300 deg. C. These results suggest that the sol-gel synthesis using scCO{sub 2} fluid would be a cadidate for low-temperature processing of crystalline oxide films, which is more preferable than conventional techniques based on the heat treatment.

  20. Interface architecture for superthick carbon-based films toward low internal stress and ultrahigh load-bearing capacity.

    Science.gov (United States)

    Wang, Junjun; Pu, Jibin; Zhang, Guangan; Wang, Liping

    2013-06-12

    Superthick diamond-like carbon (DLC) films [(Six-DLC/Siy-DLC)n/DLC] were deposited on 304 stainless steel substrates by using a plane hollow cathode plasma-enhanced chemical vapor deposition method. The structure was investigated by scanning electron microscopy and transmission electron microscopy. Chemical bonding was examined by Raman, Auger electron, and X-ray photoelectron spectroscopy techniques. Mechanical and tribological properties were evaluated using nanoindentation, scratch, interferometry, and reciprocating-sliding friction testing. The results showed that implantation of a silicon ion into the substrate and the architecture of the tensile stress/compressive stress structure decreased the residual stress to almost 0, resulting in deposition of (Six-DLC/Siy-DLC)n/DLC films with a thickness of more than 50 μm. The hardness of the film ranged from 9 to 23 GPa, and the adhesion strength ranged from 4.6 to 57 N depending on the thickness of the film. Friction coefficients were determined in three tested environments, namely, air, water, and oil. Friction coefficients were typically below 0.24 and as low as 0.02 in a water environment. The as-prepared superthick films also showed an ultrahigh load-bearing capacity, and no failure was detected in the reciprocating wear test with contact pressure higher than 3.2 GPa. Reasons for the ultrahigh load-bearing capacity are proposed in combination with the finite-element method.

  1. Three-Wave Gas Journal Bearing Behavior With Shaft Runout

    Science.gov (United States)

    Dimofte, Florin; Hendricks, Robert C.

    1997-01-01

    Experimental orbits of a free-mounted, three-wave gas journal bearing housing were recorded and compared to transient predicted orbits. The shaft was mounted eccentric with a fixed runout. Experimental observations for both the absolute bearing housing center orbits and the relative bearing housing center to shaft center orbits are in good agreement with the predictions. The sub-synchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds. A three-wave journal bearing can run stably under dynamic loads with orbits well inside the bearing clearance. Moreover, the orbits are almost circular free of the influence of bearing wave shape.

  2. Basic Technology of Squeeze-Film Dampers for Rotor Dynamics Control.

    Science.gov (United States)

    1981-11-01

    Squeeze - Film Damper Fluid Film Bearings Ro or Dynamics 1’F in Rupture 21...in the squeeze - film damper . The short bearing analysis was general- ized to accommodate a consistent treatment of the rupture domain for a squeeze ...the stiffness of the centering spring. While the above-stated scaling law between a journal bearing and a squeeze - film damper is basically sound,

  3. Entropy generation in non-Newtonian fluid flow in a slider bearing

    Indian Academy of Sciences (India)

    In the present study, entropy production in flow fields due to slider bearings is formulated. The rate of entropy generation is computed for different fluid properties and geometric configurations of the slider bearing. In order to account for the non-Newtonian effect, a special type of third-grade fluid is considered. It is found that ...

  4. THE EFFECT OF GAS HYDRATES DISSOCIATION AND DRILLING FLUIDS INVASION UPON BOREHOLE STABILITY IN OCEANIC GAS HYDRATES-BEARING SEDIMENT

    Science.gov (United States)

    Ning, F.; Wu, N.; Jiang, G.; Zhang, L.

    2009-12-01

    Under the condition of over-pressure drilling, the solid-phase and liquid-phase in drilling fluids immediately penetrate into the oceanic gas hydrates-bearing sediment, which causes the water content surrounding the borehole to increase largely. At the same time, the hydrates surrounding borehole maybe quickly decompose into water and gas because of the rapid change of temperature and pressure. The drilling practices prove that this two factors may change the rock characteristics of wellbore, such as rock strength, pore pressure, resistivity, etc., and then affect the logging response and evaluation, wellbore stability and well safty. The invasion of filtrate can lower the angle of friction and weaken the cohesion of hydrates-bearing sediment,which is same to the effect of invading into conventional oil and gas formation on borehole mechnical properties. The difference is that temperature isn’t considered in the invasion process of conventional formations while in hydrates-bearing sediments, it is a factor that can not be ignored. Temperature changes can result in hydrates dissociating, which has a great effect on mechanical properties of borehole. With the application of numerical simulation method, we studied the changes of pore pressure and variation of water content in the gas hydrates-bearing sediment caused by drilling fluid invasion under pressure differential and gas hydrate dissociation under temperature differential and analyzed their influence on borehole stability.The result of simulation indicated that the temperature near borehole increased quickly and changed hardly any after 6 min later. About 1m away from the borehole, the temperature of formation wasn’t affected by the temperature change of borehole. At the place near borehole, as gas hydrate dissociated dramatically and drilling fluid invaded quickly, the pore pressure increased promptly. The degree of increase depends on the permeability and speed of temperature rise of formation around

  5. Mapping of polycrystalline films of biological fluids utilizing the Jones-matrix formalism

    Science.gov (United States)

    Ushenko, Vladimir A.; Dubolazov, Alexander V.; Pidkamin, Leonid Y.; Sakchnovsky, Michael Yu; Bodnar, Anna B.; Ushenko, Yuriy A.; Ushenko, Alexander G.; Bykov, Alexander; Meglinski, Igor

    2018-02-01

    Utilizing a polarized light approach, we reconstruct the spatial distribution of birefringence and optical activity in polycrystalline films of biological fluids. The Jones-matrix formalism is used for an accessible quantitative description of these types of optical anisotropy. We demonstrate that differentiation of polycrystalline films of biological fluids can be performed based on a statistical analysis of the distribution of rotation angles and phase shifts associated with the optical activity and birefringence, respectively. Finally, practical operational characteristics, such as sensitivity, specificity and accuracy of the Jones-matrix reconstruction of optical anisotropy, were identified with special emphasis on biomedical application, specifically for differentiation of bile films taken from healthy donors and from patients with cholelithiasis.

  6. A Magnetorheological Fluid Damper for Rotor Applications

    OpenAIRE

    Forte, P.; Paternò, M.; Rustighi, E.

    2004-01-01

    Even though we are still far from industrial applications, in the last decade there has been increasing attention directed toward the employment of electrorheological (ER) and magnetorheological (MR) fluids in active bearings and active squeeze film dampers in rotordynamics. MR fluids react to magnetic fields undergoing reversible changes in their mechanical characteristics, viscosity, and stiffness in particular. In previous literature, some applications of ER fluids in rotor squeeze film da...

  7. Preparation and Characterization of Silver Liquid Thin Films for Magnetic Fluid Deformable Mirror

    Directory of Open Access Journals (Sweden)

    Lianchao Zhang

    2015-01-01

    Full Text Available Silver liquid thin film, formed by silver nanoparticles stacking and spreading on the surface of the liquid, is one of the important parts of magnetic fluid deformable mirror. First, silver nanoparticles were prepared by liquid phase chemical reduction method using sodium citrate as reducing agent and stabilizer and silver nitrate as precursor. Characterization of silver nanoparticles was studied using X-ray diffractometer, UV-vis spectrophotometer, and transmission electron microscope (TEM. The results showed that silver nanoparticles are spherical and have a good monodispersity. Additionally, the effect of the reaction conditions on the particle size of silver is obvious. And then silver liquid thin films were prepared by oil-water two-phase interface technology using as-synthesized silver nanoparticles. Properties of the film were investigated using different technology. The results showed that the film has good reflectivity and the particle size has a great influence on the reflectivity of the films. SEM photos showed that the liquid film is composed of multilayer silver nanoparticles. In addition, stability of the film was studied. The results showed that after being stored for 8 days under natural conditions, the gloss and reflectivity of the film start to decrease.

  8. A journal bearing with variable geometry for the suppression of vibrations in rotating shafts: Simulation, design, construction and experiment

    Science.gov (United States)

    Chasalevris, Athanasios; Dohnal, Fadi

    2015-02-01

    The idea for a journal bearing with variable geometry was formerly developed and investigated on its principles of operation giving very optimistic theoretical results for the vibration quenching of simple and more complicated rotor bearing systems during the passage through the first critical speed. The journal bearing with variable geometry is presented in this paper in its final form with the detailed design procedure. The current journal bearing was constructed in order to be applied in a simple real rotor bearing system that already exists as an experimental facility. The current paper presents details on the manufactured prototype bearing as an experimental continuation of previous works that presented the simulation of the operating principle of this journal bearing. The design parameters are discussed thoroughly under the numerical simulation for the fluid film pressure in dependency of the variable fluid film thickness during the operation conditions. The implementation of the variable geometry bearing in an experimental rotor bearing system is outlined. Various measurements highlight the efficiency of the proposed bearing element in vibration quenching during the passage through resonance. The inspiration for the current idea is based on the fact that the alteration of the fluid film characteristics of stiffness and damping during the passage through resonance results in vibration quenching. This alteration of the bearing characteristics is achieved by the introduction of an additional fluid film thickness using the passive displacement of the lower half-bearing part. • The contribution of the current journal bearing in vibration quenching. • Experimental evidence for the VGJB contribution.

  9. Magnetic Fluid-Based Squeeze Film Behaviour in Curved Porous-Rotating Rough Annular Plates and Elastic Deformation Effect

    Directory of Open Access Journals (Sweden)

    M. E. Shimpi

    2012-01-01

    Full Text Available Efforts have been directed to study and analyze the squeeze film performance between rotating transversely rough curved porous annular plates in the presence of a magnetic fluid lubricant considering the effect of elastic deformation. A stochastic random variable with nonzero mean, variance, and skewness characterizes the random roughness of the bearing surfaces. With the aid of suitable boundary conditions, the associated stochastically averaged Reynolds' equation is solved to obtain the pressure distribution in turn, which results in the calculation of the load-carrying capacity. The graphical representations establish that the transverse roughness, in general, adversely affects the performance characteristics. However, the magnetization registers a relatively improved performance. It is found that the deformation causes reduced load-carrying capacity which gets further decreased by the porosity. This investigation tends to indicate that the adverse effect of porosity, standard deviation and deformation can be compensated to certain extent by the positive effect of the magnetic fluid lubricant in the case of negatively skewed roughness by choosing the rotational inertia and the aspect ratio, especially for suitable ratio of curvature parameters.

  10. Use of supercritical fluid solution expansion processes for drug delivery, particle synthesis, and thin film deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hybertson, B.M.

    1992-01-01

    Properties of the gases and aerosols resulting from the expansion of supercritical fluid solutions were studied. Film deposition, particle formation, and drug delivery processes using supercritical fluids were developed. Thin films of palladium, copper, aluminum, silver, and silicon dioxide were deposited by a method called supercritical fluid transport-chemical deposition (SFT-CD). In each case, a precursor compound was dissolved in a supercritical fluid and the solution was allowed to expand through a restrictor nozzle into a reaction chamber at subcritical pressure, resulting in the formation of aerosol particles of the precursor. A chemical reaction was induced to occur at the surface of a substrate, resulting in deposition of a thin film. Micron-sized particles of aluminum fluoride and copper oxide were synthesized by a method called supercritical fluid transport-chemical formation of particles (SFT-CFP). The process was similar to that in SFT-CD, but the chemical reactions were induced to occur in the gas phase instead of at a substrate surface, resulting in the formation of fine particles. A new method of pulmonary drug delivery called supercritical fluid drug delivery (SFDD) was conceived and demonstrated. In SFDD a drug compound is dissolved in a supercritical fluid, and the solution is allowed to expand through a restrictor nozzle. The resultant aerosol is directly inhaled by a human or animal subject and the fine drug particles are deposited in the lungs. Menthol, vanillin, camphor, cholesterol, Sudan III, and Oil Blue N were used as model drug compounds for SFDD. Delivery of [alpha]-tocopherol to rat lung tissue was demonstrated, with observed increases of 80-290% above background levels.

  11. Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material

    Science.gov (United States)

    Keith, Theo G., Jr.; Dimofte, Florin

    2001-01-01

    It has been estimated that the noise levels in aircraft engine transmissions can be reduced by as much as 10 dB through the use of journal bearings. The potential benefits of lower noise levels include reduced wear, longer gear life and enhanced comfort for passengers and crew. Based on this concept the journal-thrust wave bearing was analyzed and its performance was evaluated. Numerical codes, developed over the past 30 years by Dr. Dimofte, were used to predict the performance of the bearing. The wave bearing is a fluid film bearing and therefore was analyzed using the Reynolds pressure equation. The formulation includes turbulent flow concepts and possesses a viscosity-temperature correction. The centrifugal growth of the bearing diameter and the deformation of the bearing under gear loads were also incorporated into the code. An experimental rig was developed to test the journal-thrust wave bearing.

  12. Influence of Wall Porosity and Surfaces Roughness on the Steady Performance of an Externally Pressurized Hydrostatic Conical Bearing Lubricated by a Rabinowitsch Fluid

    Science.gov (United States)

    Walicka, A.; Walicki, E.; Jurczak, P.; Falicki, J.

    2017-08-01

    In the paper, the influence of both the bearing surfaces roughness as well as porosity of one bearing surface on the pressure distribution and load-carrying capacity of a curvilinear, externally pressurized, thrust bearing is discussed. The equations of motion of a pseudo-plastic Rabinowitsch fluid are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation and Christensen theory of hydrodynamic lubrication with rough bearing surfaces the modified Reynolds equation is obtained. The analytical solution is presented; as a result one obtains the formulae expressing the pressure distribution and load-carrying capacity. Thrust radial and conical bearings, externally pressurized, are considered as numerical examples.

  13. Influence of Wall Porosity and Surfaces Roughness on the Steady Performance of an Externally Pressurized Hydrostatic Conical Bearing Lubricated by a Rabinowitsch Fluid

    Directory of Open Access Journals (Sweden)

    Walicka A.

    2017-08-01

    Full Text Available In the paper, the influence of both the bearing surfaces roughness as well as porosity of one bearing surface on the pressure distribution and load-carrying capacity of a curvilinear, externally pressurized, thrust bearing is discussed. The equations of motion of a pseudo-plastic Rabinowitsch fluid are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation and Christensen theory of hydrodynamic lubrication with rough bearing surfaces the modified Reynolds equation is obtained. The analytical solution is presented; as a result one obtains the formulae expressing the pressure distribution and load-carrying capacity. Thrust radial and conical bearings, externally pressurized, are considered as numerical examples.

  14. The Evaluation of Linear Complementarity Problem Method in Modeling the Fluid Cavitation for Squeeze Film Damper with Off-Centered Whirling Motion

    Directory of Open Access Journals (Sweden)

    Tieshu Fan

    2017-11-01

    Full Text Available For the application of squeeze film damper (SFD in aero-engine, a cavitation model is evaluated by means of linear complementarity problem (LCP method. Different from the conventional SFD study that employs circular-center orbits (CCOs, a realistic condition is explored where the shaft whirling center and bearing center are misaligned. Taking into account the fluid as incompressible and compressible, the governing equations, including film cavitation, are respectively solved by developing an algorithm using the LCP method. The numerical results are compared with experimental data and the effectiveness of the model is verified. The proposed model can provide some references to investigate the competency of this cavitation method in SFDs.

  15. Surface Roughness and Elastic Deformation Effects on the Behaviour of the Magnetic Fluid Based Squeeze Film Between Rotating Porous Circular Plates with Concentric Circular Pockets

    Directory of Open Access Journals (Sweden)

    M. E. Shimpi

    2010-06-01

    Full Text Available An attempt has been made to study and analyze the performance of a magnetic fluid based squeeze film between rotating porous transversely rough circular plates with concentric circular pockets. The porous housing is considered to be elastically negligibly deformable with its contact surface transversely rough. The stochastic film thickness characterizing the random roughness is assumed to be asymmetric with non zero mean and variance. The pressure distribution is obtained by solving the associated stochastically averaged Reynolds equation with appropriate boundary conditions. This results in the calculation of the load carrying capacity. All the results in graphical form establish that the transverse roughness in conjunction with the deformation has a strong negative effect on the performance of the bearing system. The bearing suffers on account of transverse surface roughness in general which probably is due to the fact that the roughness of the bearing surfaces tends to retard the motion of the lubricant resulting in decreased load carrying capacity. However, this negative effect of roughness, porosity and deformation can be minimized by the positive effect of the magnetization parameter in the case of negatively skewed roughness by choosing a suitable combination of pocket radius and rotational inertia. Lastly, the effect of radii ratio is noted to be quite significant.

  16. Squeeze film lubrication for non-Newtonian fluids with application to manual medicine.

    Science.gov (United States)

    Chaudhry, Hans; Bukiet, Bruce; Roman, Max; Stecco, Antonio; Findley, Thomas

    2013-01-01

    In this paper, we computed fluid pressure and force on fascia sheets during manual therapy treatments using Squeeze Film Lubrication theory for non-Newtonian fluids. For this purpose, we developed a model valid for three dimensional fluid flow of a non-Newtonian liquid. Previous models considered only one-dimensional flows in two dimensions. We applied this model to compare the one-dimensional flow of HA, considered as a lubricating fluid, around or within the fascia during sliding, vibration, and back-and-forth sliding manipulation treatment techniques. The fluid pressure of HA increases dramatically as fascia is deformed during manual therapies. The fluid force increases more during vertical vibratory manipulation treatment than in constant sliding, and back and forth motion. The variation of fluid pressure/force causes HA to flow near the edges of the fascial area under manipulation in sliding and back and forth motion which may result in greater lubrication. The fluid pressure generated in manual therapy techniques may improve sliding and permit muscles to work more efficiently.

  17. Experimental validation of numerical simulations: a comparison of computational fluid dynamics and the oil film method.

    Science.gov (United States)

    Stoiber, M; Grasl, C; Pirker, S; Huber, L; Gittler, P; Schima, H

    2007-04-01

    Today Computational Fluid Dynamics (CFD) is used for simulating flow in many applications. The quality of the results, however, depends on various factors, like grid quality, boundary conditions and the computational model of the fluid. For this reason, it is important to validate the performed computation with experimental results. In this work, a comparison of numerical simulation with the oil film method was performed for two cardiovascular applications. The investigations were conducted at various geometries, such as a bended cannula tubing, an impeller of a magnetically levitated rotary blood pump and tips of inflow cannulas. The oil film for the experimental validation was composed of black oil color and varnish. In the numerical simulation, color abrasion was displayed with a special post-processing tool by means of wall-attached pathlines. With the proper choice of numerical parameters, the computer simulations and the oil film method demonstrated good correlation. Improper generation of the simulation grid did lead to divergent results between the numerical simulation and the experiment. For the pump impeller as well as for the inflow cannulas, the calculation and the experiment showed similar flow patterns with backflow and stall zones. The oil film method represents a fast and simple approach to help validate numerical simulations of fluid flow. The experimentally generated near wall flow patterns can be easily compared with the solution of the CFD analysis.

  18. Noise of oil lubricated journal bearings

    International Nuclear Information System (INIS)

    Rho, Byoung Hoo; Kim, Kyung Woong

    2002-01-01

    The purpose of the paper is to provide a procedure to calculate the noise of oil lubricated journal bearings. To do this, the nonlinear transient analysis of rotor-bearing system including rotor imbalance is performed. Acoustical properties of the bearing are investigated through frequency analysis of the pressure fluctuation of the fluid film calculated from the nonlinear analysis. Furthermore, a transmission theory of plane waves on a boundary of the outer surface of the bearing is used to obtain the sound pressure level of the bearing. Results show that the sound pressure level of the bearing can be increased with the rotational speed of the rotor although the whirl amplitude of the rotor is decreased at high speed. Noise estimating procedures presented in this paper could be an aid in the evaluation and understanding of acoustical properties of oil lubricated journal bearings

  19. Thermal analysis of externally pressurised step bearing including ...

    African Journals Online (AJOL)

    A numerical study has been done for externally pressurized circular step thrust bearing lubricated with incompressible fluid with finely dispersed air bubbles taking into consideration the variation in lubricant physical properties due to temperature and pressure variation in the fluid film. Effect of misalignment / tilt and coning ...

  20. Design and evaluation of a 3 million DN series-hybrid thrust bearing

    Science.gov (United States)

    Scibbe, H. W.; Winn, L. W.; Eusepi, M.

    1976-01-01

    The design and experimental evaluation of a series-hybrid thrust bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, is presented. Tests were conducted up to 16,000 rpm and at this speed an axial load of 15,600 N (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. A speed reduction of this magnitude would result in a tenfold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system produced a flawless return to the original mode of hybrid operation.

  1. Study the Dynamic Behavior of Rotor Supported on a Worn Journal Bearings

    Directory of Open Access Journals (Sweden)

    Adnan Naji Jamil

    2015-12-01

    Full Text Available In this paper, the effect of wear in the fluid film journal bearings on the dynamic behavior of rotor bearing system has been studied depending on the analytical driven of dynamic stiffness and damping coefficients of worn journal bearing. The finite element method was used to modeling rotor bearing system. The unbalance response, critical speed and natural frequency of rotor bearing system have been studied to determine the changes in these parameters due to wear. MATLAB software was used to find the analytical values of dynamic coefficients of journal bearing. The results of rotor mounted on fluid film journal bearings showed that the wear in journal bearing increases the amplitude of unbalance response and decrease critical speed, stability and the natural frequencies.

  2. Slip behaviour of carbonate-bearing faults subjected to fluid pressure stimulations

    Science.gov (United States)

    Collettini, Cristiano; Scuderi, Marco; Marone, Chris

    2017-04-01

    Earthquakes caused by fluid injection within reservoir have become an important topic of political and social discussion as new drilling and improved technologies enable the extraction of oil and gas from previously unproductive formations. During reservoir stimulation, the coupled interactions of frictional and fluid flow properties together with the stress state control both the onset of fault slip and fault slip behaviour. However, currently, there are no studies under controlled, laboratory conditions for which the effect of fluid pressure on fault slip behaviour can be deduced. To cover this gap, we have developed laboratory experiments where we monitor fault slip evolution at constant shear stress but with increasing fluid pressure, i.e. reducing the effective normal stress. Experiments have been conducted in the double direct shear configuration within a pressure vessel on carbonate fault gouge, characterized by a slightly velocity strengthening friction that is indicative of stable aseismic creep. In our experiments fault slip history can be divided in three main stages: 1) for high effective normal stress the fault is locked and undergoes compaction; 2) when the shear and effective normal stress reach the failure condition, accelerated creep is associated to fault dilation; 3) further pressurization leads to an exponential acceleration during fault compaction and slip localization. Our results indicate that fault weakening induced by fluid pressurization overcomes the velocity strengthening behaviour of calcite gouge, resulting in fast acceleration and earthquake slip. As applied to tectonic faults our results suggest that a larger number of crustal faults, including those slightly velocity strengthening, can experience earthquake slip due to fluid pressurization.

  3. Measurement and calculation of dynamic coefficients in hydrodynamic bearings of gas films; Medicion y calculo de coeficientes dinamicos en cojinetes hidrodinamicos de peliculas de gas

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Rafael O.; Di Liscia, Marcelo H.; Diaz, Sergio E. [Universidad Simon Bolivar, Sartendejas, Baruta (Venezuela)

    2007-11-15

    The identification of the dynamic coefficients in air bearings is fundamental for a suitable roto-dynamic analysis. The present paper shows the development of an algorithm that allows the direct obtaining of the dynamic coefficients in hydrodynamic air bearings as much of numerical form as experimental. The testing bench used consists of two magnetic bearings, which support the rotor in their ends and work as well as actuators allowing inducing controlled orbits in the rotor. The test bearing is located between the magnetic bearings. The dynamic forces generated in the air bearing are registered from three load cells. The algorithm was developed in a commercial code of graphical programming, through which the signals can be collected, controlled and processed. The nonlinear behavior of this type of bearings makes difficult the calculation of the dynamic coefficients, therefore the processing of the signals in frequencial space facilitates, in a certain way, its handling. On the other hand, the numerical model was compared with the experimental results obtaining acceptable approaches in magnitude as well as in behavior. The numerical dynamic coefficients calculation was realized solving the Reynolds differential equation for a compressible fluid in the thickness of the gas film, taking into consideration the fluid mass flow that is introduced, as well as the pressure loss suffered by the same in passing through the feeding orifices. The numerical methods utilized include the solution of the differential equation of Reynolds for finite differences, the calculation of the profile realizing successive iterations and the calculation of the hydrodynamics forces through the Simpson numerical integration. The numerical dynamic coefficients were found applying a minimum squared technique to the hydrodynamic stresses generated in simulating an orbit of the rotor at a determined frequency and velocity, allowing in this way the calculation of the synchronous and asynchronous

  4. Analysis of Direct Samples of Extraterrestrial, Organic-Bearing, Aqueous Fluids

    Science.gov (United States)

    Zolensky, Michael

    2016-01-01

    I will describe water we have found in 4.5 billion year old extraterrestrial salt, and the organics that are also present. We hypothesize that organics being carried through the parent body of the halite have been deposited adjacent to the fluid inclusions, where they have been preserved against any thermal metamorphism. We are making bulk compositional, carbon and hydrogen isotopic measurements of solid organic phases associated with the aqueous fluid inclusions in the meteorites. We will compare these organics with those found in chondrites and Wild-2 comet coma particles to determine whether these classes of organics had an origin within aqueous solutions.

  5. Oil film thickness measurement and analysis for an angular contact ball bearing operating in parched elastohydrodynamic lubrication. M.S. Thesis. Final Report

    Science.gov (United States)

    Hunter, Scott D.

    1986-01-01

    The capacitance method is used to estimate the oil film thickness in the Hertzian contact zone of an angular contact ball bearing operating in parched elastohydrodynamic lubrication. The parched elastohydrodynamic lubrication regime is characterized by a transient film thickness and basic speed ratio (ball spin rate over combined race speed) and the formation of a friction polymer. The experimental apparatus tests 40 mm 108 H ball bearings in the counter rotating race mode at loads of 200 and 300 lb, a film parameter of 1.6 and nominal inner and outer race speeds of 38 and 26 rps, respectively. Experimental results are presented for the capacitance, thickness, and conductance of the oil film as functions of elapsed time and for the basic speed ratios as a function of elapsed time, load, and amount of lubricant applied to the test bearing. Results indicate that a friction polymer formed from the initial lubricant has an effect on the capacitance and basic speed ratio measurements.

  6. Experimental measurement of the dynamic pressure distribution in a squeeze film bearing damper executing circular centered orbits

    Science.gov (United States)

    Sanandres, L. A.; Vance, J. M.

    1987-01-01

    A review of previous experimental measurements of squeeze film damper (SFD) forces is given. Measurements by the authors of SFD pressure fields and force coefficients, for circular centered orbits with epsilon = 0.5, are described and compared with computer predictions. For Reynolds numbers over the range 2-6, the effect of fluid inertia on the pressure fields and forces is found to be significant.

  7. Analysis of thin film flow over a vertical oscillating belt with a second grade fluid

    Directory of Open Access Journals (Sweden)

    Taza Gul

    2015-06-01

    Full Text Available An analysis is performed to study the unsteady thin film flow of a second grade fluid over a vertical oscillating belt. The governing equation for velocity field with appropriate boundary conditions is solved analytically using Adomian decomposition method (ADM. Expressions for velocity field have been obtained. Optimal asymptotic method (OHAM has also been used for comparison. The effects of Stocks number, frequency parameter and pressure gradient parameters have been sketched graphically and discussed.

  8. Thermodynamic and Structural Properties of C-bearing Supercritical Aqueous Fluids

    Science.gov (United States)

    Seclaman, A. C.; Cohen, R. E.

    2016-12-01

    Aqueous fluids are important agents of mass transport in the Earth's crust and upper mantle. Their role in the deep mantle is poorly understood due to a lack of thermodynamic data at relevant pressures (P) and temperatures (T). Speciation of volatiles also plays a key role in understanding the reactivity of fluids, and the formation of complex anionic C species in supercritical fluids has been linked to the precipitation of diamond during fluid-rock interaction.1 Models have predicted equilibria between all oxidation states of C in aqueous fluids above 3 GPa.2 First principles approaches can help expand the PT range of models, and give an atomic-level understanding of fluid behavior. We are using first principles molecular dynamics to study the H-C-O system up to pressures of 40 GPa and 2500K, spanning a wide range of C concentrations. Since van der Waals (vdW) interactions play important roles in water and organic complexes we take into account vdW by using the non-local vdW-DF2 functional.3 From this data, we obtained the PVTX equation of state and investigated the dependence of pressure, temperature, and concentration on the C speciation. Water dissociation and the PT stability field of aqueous cations and anions were also investigated. The results of this work contribute to a better understanding of the C mantle cycle. Our work can help significantly expand the data sets employed by models4,5 used in the study of complex rock-fluid interactions. This work is supported by the ERC Advanced grant ToMCaT. 1. Sverjensky, D. A. & Huang, F. Nat. Commun. 53, 1689-1699 (2015). 2. Sverjensky, D. a., Stagno, V. & Huang, F. Nat. Geosci. 7, 909-913 (2014). 3. Lee, K., Murray, É. D., Kong, L., Lundqvist, B. I. & Langreth, D. C. Phys. Rev. B - Condens. Matter Mater. Phys. 82, 3-6 (2010). 4. Sverjensky, D. A., Harrison, B. & Azzolini, D. Geochim. Cosmochim. Acta 129, 125-145 (2014). 5. Ghiorso, M. S. & Gualda, G. A. R. Contrib. to Mineral. Petrol. 169, 1-30 (2015).

  9. Nonlinear Dynamical Analysis for a Plain Bearing

    Directory of Open Access Journals (Sweden)

    Ali Belhamra

    2014-03-01

    Full Text Available This paper investigates the nonlinear dynamic behavior for a plain classic bearing (fluid bearing lubricated by a non-Newtonian fluid of a turbo machine rotating with high speed; this type of fluid contains additives viscosity (couple-stress fluid film. The solution of the nonlinear dynamic problem of this type of bearing is determined with a spatial discretisation of the modified Reynolds' equation written in dynamic mode by using the optimized short bearing theory and a temporal discretisation for equations of rotor motion by the help of Euler's explicit diagram. This study analyzes the dynamic behavior of a rotor supported by two couple-stress fluid film journal lubricant enhances the dynamic stability of the rotor-bearing system considerably compared to that obtained when using a traditional Newtonian lubricant. The analysis shows that the dynamic behavior of a shaft which turns with high velocities is strongly nonlinear even for poor eccentricities of unbalance; the presence of parameters of couple stress allows strongly attenuating the will synchrony (unbalance and asynchrony (whipping amplitudes of vibrations of the shaft which supports more severe conditions (large unbalances.

  10. The solubility of thorium and uranium from respirable monazite bearing dust in simulated lung and gut fluids

    International Nuclear Information System (INIS)

    Twining, J.; McGlinn, P.; Hart, K.

    1993-01-01

    The accurate assessment of the radiological dose to workers in the mineral sands industry requires information on the human bio-availability of thorium and uranium from monazite bearing respirable dust. The results of a short-term test to determine some of the solubility characteristics of these radionuclides are presented, together with a discussion on the optimum methods which may be applied to longer term studies. The solubility of thorium and uranium were found to be generally less than that of the parent monazite bearing dust in simulated lung and gut fluids over the one month extraction period. In particular, thorium was up to two orders of magnitude less soluble than its host mineral matrix. Assuming that the conservative nature of these radioactive constituents can be extrapolated to longer term exposures, these results imply that radiological dose estimates to the lung should be increased. Solubility of both elements was proportional to particle size. An exponential increase in solubility with decreasing diameter was observed, which implies a time variable solubility. There was also some indication of preferential solubility of radium progeny in both decay series. These factors may have to be accounted for in model estimates of committed dose. 16 refs., 4 tabs., 2 figs

  11. Finite element analysis of misaligned rotors on oil-film bearings

    Indian Academy of Sciences (India)

    degree of freedom rotor model to more general finite element model of shaft disc systems on multiple bearings. The present work first proposes a fairly general coupling misalignment model using Lagrange multipliers. For an integrated analysis of the ...

  12. Design and evaluation of a 3 million DN series-hybrid thrust bearing. [stability tests and fatigue tests

    Science.gov (United States)

    Scibbe, H. W.; Winn, L. W.; Eusepi, M.

    1976-01-01

    The bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, was fatigue tested. Test conditions were representative of a mainshaft ball bearing in a gas turbine engine operating at maximum thrust load to simulate aircraft takeoff conditions. Tests were conducted up to 16000 rpm and at this speed an axial load of 15568 newtons (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. It was concluded that a speed reduction of this magnitude results in a ten-fold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system resulted in a flawless return to the original mode of hybrid operation.

  13. Evaluation of a series hybrid thrust bearing at DN values to three million. 2: Fabrication and testing

    Science.gov (United States)

    Eusepi, M.; Winn, L. W.

    1975-01-01

    Results of tests made to determine the experimental performance of a series hybrid bearing are reported. The bearing consists of a 150 mm ball bearing and a centrifugally actuated, conical, fluid film bearing fitting an envelope with an outer radius of 86.4 mm (3.4 in.) and inner radius of 71 mm (2.8 in.). Tests were conducted up to 16,500 rpm, at which speed an axial load of 15,568 N (3500 lb) was safely supported by the hybrid bearing system. Through the employment of the series hybrid bearing principle, it was possible to reduce the effective ball bearing speed to approximately one-half of the shaft speed. A reduction of this magnitude should result in a tenfold increase in the ball bearing fatigue life. A successful simulation of fluid film bearing lubricant supply failure, performed repeatedly at an operating speed of 10,000 rpm, resulted in complete and smooth change over to full scale ball bearing operation when the oil supply to the fluid film bearing was discontinued. Reactivation of the fluid film supply system produced a flawless return to the original mode of hybrid operation.

  14. Thrust bearing

    Science.gov (United States)

    Anderson, W. J. (Inventor)

    1976-01-01

    A gas lubricated thrust bearing is described which employs relatively rigid inwardly cantilevered spokes carrying a relatively resilient annular member or annulus. This annulus acts as a beam on which are mounted bearing pads. The resilience of the beam mount causes the pads to accept the load and, with proper design, responds to a rotating thrust-transmitting collar by creating a gas film between the pads and the thrust collar. The bearing may be arranged for load equalization thereby avoiding the necessity of gimbal mounts or the like for the bearing. It may also be arranged to respond to rotation in one or both directions.

  15. Multiscale Computational Fluid Dynamics: Methodology and Application to PECVD of Thin Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Marquis Crose

    2017-02-01

    Full Text Available This work focuses on the development of a multiscale computational fluid dynamics (CFD simulation framework with application to plasma-enhanced chemical vapor deposition of thin film solar cells. A macroscopic, CFD model is proposed which is capable of accurately reproducing plasma chemistry and transport phenomena within a 2D axisymmetric reactor geometry. Additionally, the complex interactions that take place on the surface of a-Si:H thin films are coupled with the CFD simulation using a novel kinetic Monte Carlo scheme which describes the thin film growth, leading to a multiscale CFD model. Due to the significant computational challenges imposed by this multiscale CFD model, a parallel computation strategy is presented which allows for reduced processing time via the discretization of both the gas-phase mesh and microscopic thin film growth processes. Finally, the multiscale CFD model has been applied to the PECVD process at industrially relevant operating conditions revealing non-uniformities greater than 20% in the growth rate of amorphous silicon films across the radius of the wafer.

  16. The adsorption and lubrication behavior of synovial fluid proteins and glycoproteins on the bearing-surface materials of hip replacements.

    Science.gov (United States)

    Roba, Marcella; Naka, Marco; Gautier, Emanuel; Spencer, Nicholas D; Crockett, Rowena

    2009-04-01

    The selectivity of synovial fluid protein adsorption onto ultra-high molecular weight polyethylene (UHMWPE) and alumina (Al(2)O(3)), and in particular the ability of glycoproteins to adsorb in the presence of all the other synovial fluid proteins, was investigated by means of fluorescence microscopy and gel electrophoresis (SDS-PAGE). The non-specific nature of protein adsorption from synovial fluid indicated that the lubrication of artificial hip-joint materials may not be attributable to a single protein as has been frequently suggested. The friction behavior of polyethylene (PE) sliding against Al(2)O(3) in solutions of bovine serum albumin (BSA), alpha-1-acid glycoprotein (AGP) and alpha-1-antitrypsin (A1AT) was investigated by means of colloidal probe atomic force microscopy. BSA was shown to be a poorer boundary lubricant than the phosphate buffered saline used as a control. This was attributed to denaturation of the BSA upon adsorption, which provided a high-shear-strength layer at the interface, impairing the lubrication. Interestingly, both the glycoproteins AGP and A1AT, despite their low concentrations, improved lubrication. The lubricating properties of AGP and A1AT were attributed to adsorption via the hydrophobic backbone, allowing the hydrophilic carbohydrate moieties to be exposed to the aqueous solution, thus providing a low-shear-strength fluid film that lubricated the system. The amount of glycoprotein adsorbed on hydrophobic surfaces was determined by means of optical waveguide lightmode spectroscopy (OWLS), allowing conclusions to be drawn about the conformation of the glycan residues following adsorption.

  17. Evaluation of a series hybird thrust bearing at DN values to three million. 1: Analysis and design

    Science.gov (United States)

    Gu, A.; Eusepi, M.; Winn, L. W.

    1974-01-01

    The analysis and design are presented of a hybrid bearing consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid film bearing fitting an envelope with an outer radius of 86.4 mm (3.4 in.) and an inner radius of 71 mm (2.8 in.). The bearing analysis, combined with available torque data on ball bearings, indicates that an effective speed split between the ball and fluid-film bearings of 50 percent may be expected during operation at 20,000 rpm and under an axial load of 17,800 newtons (4000 lbs.). This speed split can result in a ten-fold increase in the life of the ball bearing when compared to a simple ball bearing system operating under similar conditions.

  18. Finite element analysis of misaligned rotors on oil-film bearings

    Indian Academy of Sciences (India)

    The static equilibrium position of the journal within the bearing is determined using an iterative nonlinear static finite element analysis. The present work proposes a method for computing the displacement-dependent stiffness terms from the experimental static loaddisplacement data. Finally, the orbit of the rotor around the ...

  19. Finite element analysis of misaligned rotors on oil-film bearings

    Indian Academy of Sciences (India)

    Al-Hussain K M 2003 Dynamic stability of two rigid rotors connected by a flexible coupling with angular misalignment. J. Sound and Vibration 266: 217–234. Ding J, Krodkiewski J M 1990 Inclusion of static indetermination in the mathematical model for nonlinear dynamic analyses of multi-bearing rotor system. J. Sound and ...

  20. Finite element analysis of misaligned rotors on oil-film bearings

    Indian Academy of Sciences (India)

    The present work deals with a two-step nonlinear finite element analysis for misaligned multi-disk rotors on short oil-film bearings of various types (cylindrical, pocket, symmetrical three-lobed, unsymmetrical three-lobed). As a first step, the conventional parallel, angular and combined parallel and angular misalignments are ...

  1. Lubrication analysis of the thrust bearing in the main coolant pump of SMART

    International Nuclear Information System (INIS)

    Lee, J. S.; Park, J. S.; Kim, J. H.; Hur, H.; Kim, J. I.

    2001-01-01

    Thrust bearing and journal bearings are installed in the main coolant pump for SMART to support the rotating shaft with proper lubrication. The canned motor type main coolant pumps are arranged vertically on the reactor vessel and especially the MCP bearings are lubricated with water without external lubricating oil supply. Because axial load capacity of the thrust bearing can hardly meet requirement to acquire hydrodynamic or fluid film lubrication state, self-lubrication characteristics of silicon graphite meterials would be needed. Lubricational analysis method for thrust bearing for the main coolant pump of SMART is proposed, and lubricational characteristics of the bearing generated by solving the Reynolds equation are examined in this paper

  2. Unsteady thin film flow of a fourth grade fluid over a vertical moving and oscillating belt

    Directory of Open Access Journals (Sweden)

    Taza Gul

    2016-09-01

    Full Text Available This article studies the unsteady thin film flow of a fourth grade fluid over a moving and oscillating vertical belt. The problem is modeled in terms of non-nonlinear partial differential equations with some physical conditions. Both problems of lift and drainage are studied. Two different techniques namely the adomian decomposition method (ADM and the optimal homotopy asymptotic method (OHAM are used for finding the analytical solutions. These solutions are compared and found in excellent agreement. For the physical analysis of the problem, graphical results are provided and discussed for various embedded flow parameters.

  3. Aligned magnetic field effect on unsteady liquid film flow of Casson fluid over a stretching surface

    Science.gov (United States)

    Sailaja, M.; Hemadri Reddy, R.; Saravana, R.; Avinash, K.

    2017-11-01

    The heat and mass transfer in non-Newtonian fluids plays a major role in technology and in nature due to its stress relaxation, shear thinning and thickening properties. In this study, we investigated the heat and mass transfer in unsteady liquid film flow of Casson fluid in the presence of aligned magnetic field, thermophoresis and Brownian moment effects. The transformed governing boundary layer equations are solved numerically by employing shooting technique. Dual solutions are explored for Newtonian and non-Newtonian cases. The impact of pertinent parameters on the flow, thermal and concentration fields are discussed with the assistance of graphical illustrations. The reduced Nusselt number is reported and discussed through tabular results.

  4. Three Types of Active Lubrication Systems for the Main Bearings of Reciprocating Machines

    DEFF Research Database (Denmark)

    Santos, Ilmar; Pulido, E. E.

    2010-01-01

    pressures, through orifices circumferentially located around the bearing surface. The computed bearing fluid film forces are coupled to the set of nonlinear equations that describes the dynamics of the reciprocating engine, obtained with the help of multibody dynamics (rigid components) and finite elements...

  5. An on-line monitoring system for oil-film, pressure and temperature distributions in large-scale hydro-generator bearings

    Science.gov (United States)

    Höbel, M.; Haffner, K.

    1999-05-01

    Instrumentation that allows the behaviour of a hydro-generator thrust bearing to be monitored during operation is described. The measurement system was developed at the Asea Brown Boveri corporate research centre in Switzerland and was tested under realistic operating conditions at the Harbin Electric Machinery Company bearing-testing facility in the People's Republic of China. Newly developed fibre-optical proximity probes were used for the on-line monitoring of the thin oil film between the static and rotating parts of the bearing. These sensors are based on a back-reflection technique and can be used for various target materials such as Babbitt and Teflon. The monitoring system comprises about 120 temperature sensors, four pressure sensors and five optical oil-film thickness sensors. Temperature sensors are installed at specific static locations, whereas pressure and oil-film sensors are positioned in the runner and generate data during rotation. A special feature of the monitoring equipment is its on-line processing capability. Digital signal processors operating in parallel handle pressure and oil-film thickness data. Important measurement parameters such as the maximum pressure, maximum temperature and minimum oil-film thickness are displayed on-line. Detailed three-dimensional temperature information on one of the load segments can be obtained from subsequent off-line data analysis. The system also calculates two-dimensional plots of the oil-film thickness and pressure for most of the 12 load segments.

  6. A Dynamic Analysis of Hydrodynamic Wave Journal Bearings

    Science.gov (United States)

    Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G.

    2008-01-01

    The purpose of this paper is to study the dynamic behavior of a three-wave journal bearing using a transient approach. The transient analysis permits the determination of the rotor behavior after the fractional frequency whirl appears. The journal trajectory is determined by solving a set of nonlinear equations of motion using the Runge-Katta method. The fluid film forces are computed by integrating the transient Reynolds equation at each time step location of the shaft with respect to the bearing. Because of the large values of the rotational speeds, turbulent effects were included in the computations. The influence of the temperature on the viscosity was also considered. Numerical results were compared to experimenta1 results obtained at the NASA Glenn Research Center. Comparisons of the theoretical results with experimental data were found to be in good agreement. The numerical and experimental results showed that the fluid film of a three-wave journal bearing having a diameter of 30 mm, a length of 27 mm, and a wave amplitude ratio greater than 0.15 is stable even at rotational speeds of 60,000 RPM. For lower wave amplitude ratios, the threshold speed at which the fluid film becomes unstable depends on the wave amplitude and on the supply pocket pressure. Even if the fluid film is unstable, the wave bearing maintains the whirl orbit inside the bearing clearance.

  7. Stability Analysis of a Turbocharger Rotor System Supported on Floating Ring Bearings

    International Nuclear Information System (INIS)

    Zhang, H; Shi, Z Q; Zhen, D; Gu, F S; Ball, A D

    2012-01-01

    The stability of a turbocharger rotor is governed by the coupling of rotor dynamics and fluid dynamics because the high speed rotor system is supported on a pair of hydrodynamic floating ring bearings which comprise of inner and outer fluid films in series. In order to investigate the stability, this paper has developed a finite element model of the rotor system with consideration of such exciting forces as rotor imbalance, hydrodynamic fluid forces, lubricant feed pressure and dead weight. The dimensionless analytical expression of nonlinear oil film forces in floating ring bearings have been derived on the basis of short bearing theory. Based on numerical simulation, the effects of rotor imbalance, lubricant viscosity, lubricant feed pressure and bearing clearances on the stability of turbocharger rotor system have been studied. The disciplines of the stability of two films and dynamic performances of rotor system have been provided.

  8. On The Modelling Of Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2011-01-01

    modeling for hybrid lubrication of a compressible fluid film journal bearing. Additional forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...

  9. On The Modeling Of Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2010-01-01

    of a compressible fluid film journal bearing. Control forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving this equation, stiffness and damping......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...

  10. A Comparison Study on Co- and Counterrotating Dual-Rotor System with Squeeze Film Dampers and Intermediate Bearing

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-01-01

    Full Text Available Nonlinear dynamic model of a coaxial rotor system was established with a method combining the finite element method and the fixed interface modal synthesis method. Then an implicit time domain method was presented to solve the nonlinear equations of motion; thus dynamic characteristics of the rotor system can be obtained. With nonlinear forces of squeeze film damper and intermediate bearing considered, nonlinear dynamic response characteristics of the co- and counterrotating coaxial rotor system under multiple unbalance forces were studied and compared in this work. It was found that the critical speeds of the corotating system were equal to or slightly higher than those of the counterrotating case due to the gyroscopic moments. The results showed that the unbalance excitation frequencies are dominant in the responses of the rotor system. Besides, due to coupling effect of the intermediate bearing some combinations of the unbalance excitation frequencies were also observed in the spectrogram but the combinations were different for co- and counterrotating cases. Stability and periodicity of the rotor system were investigated with bifurcation diagram, Poincare map, and phase diagram. It was found that the rotor system executes four-period quasi-periodic motion around critical speeds.

  11. Ferrofluid lubrication of circular squeeze film bearings controlled by variable magnetic field with rotations of the discs, porosity and slip velocity

    Science.gov (United States)

    Shah, Rajesh C.; Shah, Rajiv B.

    2017-12-01

    Based on the Shliomis ferrofluid flow model (SFFM) and continuity equation for the film as well as porous region, modified Reynolds equation for lubrication of circular squeeze film bearings is derived by considering the effects of oblique radially variable magnetic field (VMF), slip velocity at the film-porous interface and rotations of both the discs. The squeeze film bearings are made up of circular porous upper disc of different shapes (exponential, secant, mirror image of secant and parallel) and circular impermeable flat lower disc. The validity of Darcy's Law is assumed in the porous region. The SFFM is important because it includes the effects of rotations of the carrier liquid as well as magnetic particles. The VMF is used because of its advantage of generating maximum field at the required active contact area of the bearing design system. Also, the effect of porosity is included because of its advantageous property of self-lubrication. Using Reynolds equation, general form of pressure equation is derived and expression for dimensionless load-carrying capacity is obtained. Using this expression, results for different bearing design systems (due to different shapes of the upper disc) are computed and compared for variation of different parameters.

  12. Mueller-matrix of laser-induced autofluorescence of polycrystalline films of dried peritoneal fluid in diagnostics of endometriosis

    Science.gov (United States)

    Ushenko, Yuriy A.; Koval, Galina D.; Ushenko, Alexander G.; Dubolazov, Olexander V.; Ushenko, Vladimir A.; Novakovskaia, Olga Yu.

    2016-07-01

    This research presents investigation results of the diagnostic efficiency of an azimuthally stable Mueller-matrix method of analysis of laser autofluorescence of polycrystalline films of dried uterine cavity peritoneal fluid. A model of the generalized optical anisotropy of films of dried peritoneal fluid is proposed in order to define the processes of laser autofluorescence. The influence of complex mechanisms of both phase (linear and circular birefringence) and amplitude (linear and circular dichroism) anisotropies is taken into consideration. The interconnections between the azimuthally stable Mueller-matrix elements characterizing laser autofluorescence and different mechanisms of optical anisotropy are determined. The statistical analysis of coordinate distributions of such Mueller-matrix rotation invariants is proposed. Thereupon the quantitative criteria (statistic moments of the first to the fourth order) of differentiation of polycrystalline films of dried peritoneal fluid, group 1 (healthy donors) and group 2 (uterus endometriosis patients), are determined.

  13. Mach-Zehnder interferometer by utilizing phase modulation of transmitted light through magnetic fluid films possessing tunable refractive index

    International Nuclear Information System (INIS)

    Hong, C.-Y.; Yang, S.Y.; Fang, K.L.; Horng, H.E.; Yang, H.C.

    2006-01-01

    Due to its diverse applications in photonics, bio-sensors, mechanics, etc., Mach-Zehnder interferometer becomes one of important devices. Hence, lots of efforts have been paid to develop advanced Mach-Zehnder interferometers. In this work, we explore new-model Mach-Zehnder interferometer, in which one of arm is consisted of magnetic fluid films. By utilizing the tunable refractive index of magnetic fluid films under external magnetic fields, the traveling phase of a propagating light through the magnetic fluid film is changed. This could lead to a variation in the interfered intensity of the Mach-Zehnder interferometer when an external magnetic field is applied. The modulation in the interfered intensity by the external magnetic field is demonstrated experimentally, and the relevant physical origin is also discussed

  14. Investigation of film flow of a conducting fluid in a transverse magnetic field, (1)

    International Nuclear Information System (INIS)

    Oshima, Shuzo; Yamane, Ryuichiro; Mochimaru, Yoshihiro; Sudo, Kouzo.

    1985-01-01

    Accompanying the development of large electromagnetic pumps transporting liquid metals used as the heat transfer media for nuclear power plants and the electromagnetic flow meters of large capacity, many researches have been carried out on the flow of liquid metals under the action of magnetic field. The utilization of electromagnetic force for continuous casting facilities seems very effective for the total processes from refining to solidification. Hereafter, it will be a technologically important problem to clarify the behavior of electro-conductive fluid with free surface under the action of magnetic field concerning the non-contact control of the interface form of molten metals as well as the cooling problem in nuclear fusion reactors. In this study, first the flow phenomena of MHD liquid film flow in a magnetic field with intensity gradient was analytically examined, and the effect of magnetic field gradient exerted on liquid film thickness and liquid surface form was clarified. Next, the experiment using mercury was carried out. For liquid film flow, magnetic field gradient acted as a kind of non-contact weir. (Kako, I.)

  15. Cavitation effects on the pressure distribution of a squeeze film damper bearing

    Science.gov (United States)

    Zeidan, Fouad Y.; Vance, John M.

    1989-01-01

    High speed motion pictures have revealed several operating regimes in a squeeze film damper. Pressure measurements corresponding to these distinct regimes were made to examine their effect on the performance of such dampers. Visual observation also revealed the means by which the pressure in the feed groove showed higher amplitudes than the theory predicts. Comparison between vapor and gaseous cavitation are made based on their characteristic pressure wave, and the effect this has on the total force and its phase.

  16. Structural controls, fluid focussing and age of gold bearing quartz-breccia zones in Archean metaturbidites of the Gordon Lake region, Slave Province, NWT, Canada

    International Nuclear Information System (INIS)

    Stokes, T.R.; Zentilli, M.; Culshaw, N.

    1991-01-01

    Detailed surface and underground geological mapping, lithochemistry, fluid inclusion, and 40 Ar - 39 Ar geochronological studies pose restrictions on possible ore deposit models to explain the concentration of gold bearing quartz-breccia zones at Gordon Lake near Yellowknife, Northwest Territories, Canada. Metamorphic fluids were focussed into a fractured zone in the hinge of a sub-vertically plunging, regional refold structure. Carbon-rich metasiltstones probably exerted and important structural and geochemical control on the localization of quartz-breccia zones and gold deposition respectively. (author)

  17. Feasibility of Applying Controllable Lubrication to Dynamically Loaded Journal Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    of the upper and lower bearings of the crankshaft, when the system operates under passive and active lubrication conditions. It is thought that the dynamics of the fluid films can be passively or actively controlled by means of different types of actuators, allowing significant reduction in the vibration...... levels, wear and power losses of the system components. From the point of view of actively controlled lubrication and specifically for the case of dynamically loaded journal bearings, the injection pressure should be controlled in time domain. However, taking into account that the gas pressure...... are analyzed. The behavior of the following parameters is investigated when the system operates with hybrid controllable lubrication conditions: a) maximum fluid film pressure, b) minimum fluid film thickness, c) maximum vibration levels and d) injection oil pressures....

  18. Schemes for applying active lubrication to main engine bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    -difference method. The computed bearing fluid film forces are coupled to the set of nonlinear equations that describes the dynamics of the reciprocating engine, obtained with the help of multibody dynamics (rigid components) and finite elements method (flexible components). The main equations that govern...

  19. Analysis of a Thrust Bearing with Flexible Pads and Flexible Supports

    DEFF Research Database (Denmark)

    Klit, Peder; Thomsen, Kim

    2007-01-01

    A theoretical analysis of a hydrodynamic thrust bearing is presented. The bearing investigated is used in an ndustrial product. The lubricant is water, but the results are valid also for other lubricants.At first the results from a 1-dimensional model for the fluid film forces and the associated...... deformation of the bearing geometry is presented. This model enlightens the influence of pad flexibility and support location and flexibility. Subsequently results from a 2-dimensional model of the bearing is presented. The model is used to carry out an optimization of the bearing design, and the obtained...

  20. Identification Methods and Test Results for Tilting Pad and Fixed Geometry Journal Bearing Dynamic Coefficients – A Review

    Directory of Open Access Journals (Sweden)

    T.W. Dimond

    2009-01-01

    Full Text Available Fluid film journal bearings (FFBs are used to support high-speed rotors in turbomachinery which often operate above the rotor first bending critical speed. The FFBs provide both lateral support and dynamic coefficients: stiffness, damping, and mass terms, related to machine vibrations. Detailed numerical values of the bearing dynamic characteristics are necessary for proper design and operation of rotating machinery.

  1. Method of making supercritical fluid molecular spray films, powder and fibers

    Science.gov (United States)

    Smith, Richard D.

    1988-01-01

    Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a heated nozzle having a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. In another embodiment, the temperature of the solution and nozzle is elevated above the melting point of the solute, which is preferably a polymer, and the solution is maintained at a pressure such that, during expansion, the solute precipitates out of solution within the nozzle in a liquid state. Alternatively, a secondary solvent mutually soluble with the solute and primary solvent and having a higher critical temperature than that of primary solvent is used in a low concentration (<20%) to maintain the solute in a transient liquid state. The solute is discharged in the form of long, thin fibers. The fibers are collected at sufficient distance from the orifice to allow them to solidify in the low pressure/temperature region.

  2. Measurement of fluid dynamic loading on staphylococci bacteria bio-film structures using μPIV

    Science.gov (United States)

    Sherman, Erica; Moormeier, Derek; Bayles, Kenneth; Davidson, John; Ryu, Sangjin; Wei, Timothy

    2013-11-01

    Staphylococci bacteria are recognized as the most frequent cause of biofilm-associated infections. Although humans are regularly exposed to these bacteria without consequence, a localized infection can enter the bloodstream and lead to serious infections such as endocarditis, pneumonia, or toxic shock syndrome. The mechanics of staphylococci biofilm formation and dispersion through the bloodstream are not well known. It has recently been observed that under certain flow conditions, bacteria organize in tower-like structures which break and are transported downstream by the flow. The fundamental questions of interest are i) whether or not fluid mechanics plays a role in differentiating between film or tower formation and ii) whether or not the faulty towers are a bio-film propagation mechanism. This talk focuses on the application of μPIV to study this problem. Staphylococcus aureus bacteria were cultured in the Bioflux Fluxion square microchannel of a 65 by 65 um cross section, and subjected to a steady shear rate of 0.5 dynes. μPIV measurements were made to map the flow over and around a biofilm tower structure which occluded approximately 66% of the channel width. Data were recorded around the structure at a series of two dimensional planes, which when stacked vertically show a two dimensional flow field as a function of tower height. Measurements and control volume analysis will be presented quantifying forces acting on these structures.

  3. Experimental Investigation of Biotite-Rich Schist Reacting with B-Bearing Fluids at Upper Crustal Conditions and Correlated Tourmaline Formation

    Directory of Open Access Journals (Sweden)

    Andrea Orlando

    2017-08-01

    Full Text Available Fluid–rock interaction experiments between a biotite-rich schist (from Mt. Calamita Formation, Elba Island, Italy and B-bearing aqueous fluids were carried out at 500–600 °C and 100–130 MPa. The experiments have been carried out in order to reproduce the reaction, which would have produced tourmalinisation of the biotite schist, supposedly by circulation of magmatic fluids issued from leucogranitic dykes. The reacting fluids were either NaCl-free or NaCl-bearing (20 wt % aqueous solutions, with variable concentration of H3BO3 (0.01–3.2 M. The experimental results show that tourmaline (belonging to the alkali group crystallise under high-temperature and upper crustal conditions (500–600 °C, 100–130 MPa when H3BO3 concentration in the system is greater than 1.6 M. The composition of tourmaline is either dravitic (Mg-rich or schorlitic (Fe-rich, depending if an NaCl-bearing or NaCl-free aqueous solution is used. In the first case, a significant amount of Fe released from biotite dissolution remains in the Cl-rich solution resulting from the experiment. By contrast, when pure water is used, Na/K exchange in feldspars makes Na available for tourmaline crystallisation. The high concentration of Fe in the residual fluid has an important metallogenic implication because it indicates that the interaction between the saline B-rich fluid of magmatic derivation and biotite-rich schists, besides producing tourmalinisation, is capable of mobilising significant amounts of Fe. This process could have produced, in part or totally, the Fe deposits located close to the quartz–tourmaline veins and metasomatic bodies of the Mt. Calamita Formation. Moreover, the super-hot reservoir that likely occurs in the deepest part of the Larderello–Travale geothermal field would also be the site of an extensive reaction between the B-rich fluid and biotite-bearing rocks producing tourmaline. Thus, tourmaline occurrence can be a useful guide during deep

  4. Heat transfer for falling film evaporation of industrially relevant fluids up to very high Prandtl numbers

    Science.gov (United States)

    Gourdon, Mathias; Karlsson, Erik; Innings, Fredrik; Jongsma, Alfred; Vamling, Lennart

    2016-02-01

    In many industrial applications, falling film evaporation is an attractive technique for solvent removal due to high heat transfer and low residence times. Examples are the powder production in the dairy industry and in kraft pulp production process to remove water from so called black liquor. Common for both applications is that the fluids exhibit high viscosities in industrial practice. In this paper, results from experimental studies on both black liquor and a dairy product are reported for Prandtl numbers up to 800. The results are compared with several existing correlation in literature, and the need for a modified correlation is recognized especially to cover higher Prandtl-numbers. The following correlation for the turbulent flow region with 3 < Pr < 800 was derived from the data: {Nu}t = 0.0085 \\cdot Re^{0.2} \\cdot {Pr^{0.65}} The correlation has been compared to literature data from one additional study on two other fluids (propylene glycol and cyclohexanol) with fairly high Prandtl-numbers, from 40 to 58 and from 45 to 155 respectively and the agreement was within ±40 %.

  5. Bearings: Technology and needs

    Science.gov (United States)

    Anderson, W. J.

    1982-01-01

    A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

  6. A study on synchronously whirling motion of hydrodynamic journal bearings

    International Nuclear Information System (INIS)

    Rho, Byoung Hoo; Kim, Kyung Woong

    2001-01-01

    In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing

  7. A study on synchronously whirling motion of hydrodynamic journal bearings

    Energy Technology Data Exchange (ETDEWEB)

    Rho, Byoung Hoo; Kim, Kyung Woong [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    2001-09-01

    In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing.

  8. The R and D D's bearing test benches

    International Nuclear Information System (INIS)

    Vialettes, J.M.

    1997-01-01

    In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author)

  9. Small-scale modelling of cementation by descending silica-bearing fluids: Explanation of the origin of arenitic caves in South American tepuis

    Science.gov (United States)

    Aubrecht, R.; Lánczos, T.; Schlögl, J.; Audy, M.

    2017-12-01

    Geoscientific research was performed on South American table mountains (tepuis) and in their sandstone cave systems. To explain speleogenesis in these poorly soluble rocks, two theories were introduced: a) arenization theory implying selective weathering of quartz along grain boundaries and releasing of sand grains, b) selective lithification theory implying cementation by descending silica-bearing fluid flow. The latter theory presumes that the descending fluid flow becomes unstable on the interface between two layers with different porosity and splits to separate flow channels (so-called ;finger flow;). The arenites outside these channels remain uncemented. To verify the latter theory, small-scale modelling was performed, using layered sands and sodium-silicate solution. Fine to medium sand was used (0.08-0.5 mm), along with a coarse sand fraction (0.5-1.5 mm). The sands were layered and compacted in a transparent plastic boxes. Three liters of sodium-silicate solution (so-called water glass) were left to drip for several hours to the top of the sediment. The fine-grained layers were perfectly laterally impregnated, whereas the descending fluid flows split to ;fingers; in the coarse-grained layers due their higher hydraulic conductivity. This small-scale laboratory simulation mimics the real diagenesis by descending silica-bearing fluids and matches the real phenomena observed on the tepuis. The resulting cemented constructions closely mimic many geomorphological features observed on tepuis and inside their caves, e.g. ;finger-flow; pillars, overhangs, imperfectly formed (aborted) pillars in forms of hummocks hanging from ceilings, locally also thicker central pillars that originated by merging of smaller fluid-flow channels. The modelling showed that selective lithification theory can explain most of the geomorphological aspects related to the speleogenesis in tepuis.

  10. Quartz-Amethyst Hosted Hydrocarbon-Bearing Fluid Inclusions from the Green Ridge Breccia in the Snoqualmie Granite, North Cascades, WA, USA

    Directory of Open Access Journals (Sweden)

    Martin Feely

    2017-09-01

    Full Text Available The Green Ridge Breccia cuts the composite Miocene Snoqualmie Batholith in King County, WA, USA. The granite was emplaced at ~5 km depth between ~17 and 20 Ma and the crosscutting NW trending breccia contains large angular blocks of the host granite (<1 m in longest dimension. The brecciated granite blocks are cemented by quartz-amethyst euhedra (<10 cm in longest dimension bearing vugs. A notable feature is the presence of centimetric scale amber coloured oil inclusions within the quartz-amethyst crystals. Fluid inclusion studies using Transmitted Light Petrography, UV Microscopy, Microthermometry, Laser Raman Microspectroscopy and Gas Chromatography-Mass Spectrometry record the presence and the fluid composition of three fluid inclusion types hosted by the euhedra: primary Type 1 (liquid rich two-phase (L + V aqueous inclusions and secondary Type 2 bituminous two-phase (S + L inclusions and Type 3 amber coloured oil bearing two-phase immiscible liquid inclusions. The Green Ridge Breccia was the locus for convective hydrothermal fluid flow that formed the quartz-amethyst vugs formed at T~390 °C assuming a trapping pressure of ~1.65 kb. Later, hydrocarbon fluids migrated downwards from the roof source rock (e.g., the Guye Sedimentary Member and were trapped in the euhedra. This was followed by unroofing of the batholith and exposure of the Green Ridge Breccia. This study highlights the potential for other oil migrations into the Snoqualmie Batholith in areas where it forms the basement capped by the Guye Sedimentary Member.

  11. Modal interaction and vibration suppression in industrial turbines using adjustable journal bearings

    Science.gov (United States)

    Chasalevris, Athanasios; Dohnal, Fadi

    2016-09-01

    The vibration suppression by deliberately introducing a parametric excitation in the fluid-film bearings is investigated for an industrial turbine rotor system. A journal bearing with variable adjustable geometry is operated in such a way that the effective stiffness and damping properties vary periodically in time. The proposed bearing is designed for having the ability of changing the bearing fluid film thickness in a semi-active manner. Such an adjustment of the journal bearing properties introduces in the system a time-periodic variation of the effective stiffness and damping properties of the fluid-film. If the time-periodicity is tuned properly to match a parametric anti-resonance, vibration suppression is achieved in the overall system. The paper presents the principle of operation of the recently developed bearings. The simulation of an industrial turbine rotor-bearing shaft line at induced parametric excitation motivates the further development and application of such bearings since the vibration amplitudes are considerably decreased in critical speeds.

  12. Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chao; Xu, Zhijie; Lai, Canhai; Sun, Xin

    2018-07-01

    The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO2) capture to predict the CO2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive and reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.

  13. A technique to measure rotordynamic coefficients in hydrostatic bearings

    Science.gov (United States)

    Capaldi, Russell J.

    1993-01-01

    An experimental technique is described for measuring the rotordynamic coefficients of fluid film journal bearings. The bearing tester incorporates a double-spool shaft assembly that permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular orbit. This configuration yields data that enables determination of the full linear anisotropic rotordynamic coefficient matrices. The dynamic force measurements were made simultaneously with two independent systems, one with piezoelectric load cells and the other with strain gage load cells. Some results are presented for a four-recess, oil-fed hydrostatic journal bearing.

  14. Steady state characteristics of an adjustable hybrid gas bearing – Computational fluid dynamics, modified Reynolds equation and experimental validation

    DEFF Research Database (Denmark)

    Pierart Vásquez, Fabián Gonzalo; Santos, Ilmar

    2015-01-01

    for compressible fluid against computational fluid dynamics (CFD) model is presented in terms of pressure and flow rate considering pressurization levels, journal eccentricities and angular velocities. Correction factors for the jet discharge coefficients are necessary and calculated added by CFD model...

  15. Development of a Mechatronic Syringe Pump to Control Fluid Flow in a Microfluidic Device Based on Polyimide Film

    Science.gov (United States)

    Sek Tee, Kian; Sharil Saripan, Muhammad; Yap, Hiung Yin; Fhong Soon, Chin

    2017-08-01

    With the advancement in microfluidic technology, fluid flow control for syringe pump is always essential. In this paper, a mechatronic syringe pump will be developed and customized to control the fluid flow in a poly-dimethylsiloxane (PDMS) microfluidic device based on a polyimide laminating film. The syringe pump is designed to drive fluid with flow rates of 100 and 1000 μl/min which intended to drive continuous fluid in a polyimide based microfluidic device. The electronic system consists of an Arduino microcontroller board and a uni-polar stepper motor. In the system, the uni-polar stepper motor was coupled to a linear slider attached to the plunger of a syringe pump. As the motor rotates, the plunger pumps the liquid out of the syringe. The accuracy of the fluid flow rate was determined by adjusting the number of micro-step/revolution to drive the stepper motor to infuse fluid into the microfluidic device. With the precise control of the electronic system, the syringe pump could accurately inject fluid volume at 100 and 1000 μl/min into a microfluidic device.

  16. Film Flow Dominated Simultaneous Flow of Two Viscous Incompressible Fluids Through a Porous Medium

    Directory of Open Access Journals (Sweden)

    Olav eAursjø

    2014-11-01

    Full Text Available We present an experimental study of two-phase flow in a quasi-two-dimensional porous medium. The two phases, a water-glycerol solution and a commercial food grade rapeseed/canola oil, having an oil to water-glycerol viscosity ratio of 1.3, are injected simultaneously into a Hele-Shaw cell with a mono-layer of randomly distributed glass beads. The two liquids are injected into the model from alternating point inlets. Initially, the porous model is filled with the water-glycerol solution. We observe that after an initial transient state, an overall static cluster configuration is obtained. While the oil is found to create a connected system spanning cluster, a large part of the water-glycerol clusters left behind the initial invasion front is observed to remain immobile throughout the rest of the experiment. This could suggest that the water-glycerol flow-dynamics is largely dominated by film flow. The flow pathways are thus given through the dynamics of the initial invasion. This behavior is quite different from that observed in systems with large viscosity differences between the two fluids, and where compressibility plays an important part of the process.

  17. Compliant Foil Journal Bearings - Investigation of Dynamic Properties

    DEFF Research Database (Denmark)

    Larsen, Jon Steffen; Santos, Ilmar

    and dynamic coefficients, of the compliant foil bearing together with an efficient solution method, which can be easily adopted and implemented by mechanical engineers. A theoretical model of a radial compliant foil bearing that incorporates compressibility of the lubricating gas and flexibility...... a Bubnow-Galerkin approach. This constitutes the main original contribution of this work, considering the fact that the finite difference method is commonly used and thouroughly investigated in the literature. The finite element method leads to a set of non-linear equations for the static fluid film...... on the compliant foil bearings, and the understanding of their dynamic behaviour is growing. However, practical design involving these bearings are still associated with a large degree of trial and error. This study aims at establishing an accurate mathematical model, to calculate the pressure, film height...

  18. Design of instantaneous liquid film thickness measurement system for conductive or non-conductive fluid with high viscosity

    Directory of Open Access Journals (Sweden)

    Yongxin Yu

    2017-06-01

    Full Text Available In the paper, a new capacitive sensor with a dielectric film coating was designed to measure the thickness of the liquid film on a flat surface. The measured medium can be conductive or non-conductive fluid with high viscosity such as silicone oil, syrup, CMC solution and melt. With the dielectric film coating, the defects caused by the humidity in a capacitor can be avoided completely. With a excitation frequency 0-20kHz, the static permittivity of capacitive sensor is obtained and stable when small thicknesses are monitored within the frequency of 0-3kHz. Based on the measurement principle, an experimental system was designed and verified including calibration and actual measurement for different liquid film thickness. Experimental results showed that the sensitivity, the resolution, repeatability and linear range of the capacitive sensor are satisfied to the liquid film thickness measurement. Finally, the capacitive measuring system was successfully applied to the water, silicone oil and syrup film thickness measurement.

  19. Numerical investigation of cavitation flow in journal bearing geometry

    Directory of Open Access Journals (Sweden)

    Stücke P.

    2013-04-01

    Full Text Available The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

  20. Numerical investigation of cavitation flow in journal bearing geometry

    Science.gov (United States)

    Riedel, M.; Schmidt, M.; Stücke, P.

    2013-04-01

    The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD) are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

  1. Stable blood lubricated hydrodynamic journal bearing with magnetic loading.

    Science.gov (United States)

    Malanoski, S B; Belawski, H; Horvath, D; Smith, W A; Golding, L R

    1998-01-01

    The Cleveland Clinic Foundation's Innovative Ventricular Assist System (IVAS) is distinguished by the use of a special hydrodynamic journal bearing to support the rotating assembly of the blood pump. In a permanently implanted blood pump, this bearing's characteristics of long life and high reliability are of paramount importance. In addition, this bearing's inherent self-pumping flow and the axial through flow caused by an imposed end-to-end pressure difference provides good washing, thus guarding against deposition. The basic computer analysis and preliminary testing results of this bearing were previously presented. This article reports the ongoing studies (both analytic and in vitro tests) on this innovative bearing as a component of the IVAS in general, with particular emphasis on its stable operating characteristics and reliability. The absence of vibration attributable to hydrodynamic instabilities related to the thick fluid film are both calculated and demonstrated during testing. A stable operating center of the rotor is shown to be inherent under magnetic side loads and resulting hydrodynamic bearing forces. A low shear as a result of large fluid-film thicknesses has been calculated, and low hemolysis has been shown by in vitro testing. Several unique design features of the bearing are believed to be responsible for this high level of performance.

  2. A waved journal bearing concept with improved steady-state and dynamic performance

    Science.gov (United States)

    Dimofte, Florin

    1994-01-01

    Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. A three wave, waved journal bearing geometry is used to show the geometry of this concept. The performance of generic waved bearings having either three, four, six, or eight waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of dynamic coefficients and fluid film stability. It was found that the bearing wave amplitude has an important influence on both steady-state and dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases. Also, the waved bearing becomes more stable as the wave amplitude increases. In addition, increasing the number of waves reduces the waved bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the waved bearing design for a specific application. It is concluded that the stiffness of an air bearing, due to the hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.

  3. Polymer films removed from solid surfaces by nanostructured fluids: microscopic mechanism and implications for the conservation of cultural heritage.

    Science.gov (United States)

    Raudino, Martina; Selvolini, Giulia; Montis, Costanza; Baglioni, Michele; Bonini, Massimo; Berti, Debora; Baglioni, Piero

    2015-03-25

    Complex fluids based on amphiphilic formulations are emerging, particularly in the field of conservation of works of art, as effective and safe liquid media for the removal of hydrophobic polymeric coatings. The comprehension of the cleaning mechanism is key to designing tailored fluids for this purpose. However, the interaction between nanostructured fluids and hydrophobic polymer films is still poorly understood. In this study, we show how the combination of confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) provides interesting and complementary insight into this process. We focused on the interaction between an ethyl methacrylate/methyl acrylate 70:30 copolymer film deposited onto a glass surface and a water/nonionic surfactant/2-butanone (MEK) ternary system, with MEK being a good solvent and water being a nonsolvent for the polymer. Our results indicate a synergy between the organic solvent and the surfactant assemblies: MEK rapidly swells the outer layers of the polymer film allowing for the subsequent diffusion of solvent molecules, while the amphiphile decreases the interfacial energy between the polymeric coating and the liquid phase, favoring dewetting and dispersion of swollen polymer droplets in the aqueous phase. The chemical nature of the surfactant and the microstructure of the assemblies determine both the kinetics and the overall efficiency of polymer removal, as assessed by comparing the behavior of similar formulations containing an anionic surfactant (sodium dodecyl sulfate, SDS).

  4. Travelling-wave similarity solutions for a steadily translating slender dry patch in a thin fluid film

    KAUST Repository

    Yatim, Y. M.

    2013-01-01

    A novel family of three-dimensional travelling-wave similarity solutions describing a steadily translating slender dry patch in an infinitely wide thin fluid film on an inclined planar substrate when surface-tension effects are negligible is obtained, the flow being driven by gravity and/or a prescribed constant shear stress on the free surface of the film. For both driving mechanisms, the dry patch has a parabolic shape (which may be concave up or concave down the substrate), and the film thickness increases monotonically away from the contact lines to its uniform far-field value. The two most practically important cases of purely gravity-driven flow and of purely surface-shear-stress-driven flow are analysed separately. © 2013 AIP Publishing LLC.

  5. Metal ion concentrations in body fluids after implantation of hip replacements with metal-on-metal bearing--systematic review of clinical and epidemiological studies.

    Directory of Open Access Journals (Sweden)

    Albrecht Hartmann

    Full Text Available INTRODUCTION: The use of metal-on-metal (MoM total hip arthroplasty (THA increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure. OBJECTIVE: To systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA. METHODS: Systematic review of clinical trials (RCTs and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor, patient characteristics as well as study quality characteristics (secondary explanatory factors. RESULTS: Overall, 104 studies (11 RCTs, 93 epidemiological studies totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L. Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty. DISCUSSION: Due to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed "time out" for stemmed large-head MoM-THA and recommend a restricted

  6. Metal Ion Concentrations in Body Fluids after Implantation of Hip Replacements with Metal-on-Metal Bearing – Systematic Review of Clinical and Epidemiological Studies

    Science.gov (United States)

    Hartmann, Albrecht; Hannemann, Franziska; Lützner, Jörg; Seidler, Andreas; Drexler, Hans; Günther, Klaus-Peter; Schmitt, Jochen

    2013-01-01

    Introduction The use of metal-on-metal (MoM) total hip arthroplasty (THA) increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds) in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure. Objective To systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA. Methods Systematic review of clinical trials (RCTs) and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum) in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor), patient characteristics as well as study quality characteristics (secondary explanatory factors). Results Overall, 104 studies (11 RCTs, 93 epidemiological studies) totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine) irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L). Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty. Discussion Due to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed „time out“ for stemmed large-head MoM-THA and recommend a restricted indication for hip

  7. Vibration Propagation of Gear Dynamics in a Gear-Bearing-Housing System Using Mathematical Modeling and Finite Element Analysis

    Science.gov (United States)

    Parker, Robert G.; Guo, Yi; Eritenel, Tugan; Ericson, Tristan M.

    2012-01-01

    Vibration and noise caused by gear dynamics at the meshing teeth propagate through power transmission components to the surrounding environment. This study is devoted to developing computational tools to investigate the vibro-acoustic propagation of gear dynamics through a gearbox using different bearings. Detailed finite element/contact mechanics and boundary element models of the gear/bearing/housing system are established to compute the system vibration and noise propagation. Both vibration and acoustic models are validated by experiments including the vibration modal testing and sound field measurements. The effectiveness of each bearing type to disrupt vibration propagation is speed-dependent. Housing plays an important role in noise radiation .It, however, has limited effects on gear dynamics. Bearings are critical components in drivetrains. Accurate modeling of rolling element bearings is essential to assess vibration and noise of drivetrain systems. This study also seeks to fully describe the vibro-acoustic propagation of gear dynamics through a power-transmission system using rolling element and fluid film wave bearings. Fluid film wave bearings, which have higher damping than rolling element bearings, could offer an energy dissipation mechanism that reduces the gearbox noise. The effectiveness of each bearing type to disrupt vibration propagation in explored using multi-body computational models. These models include gears, shafts, rolling element and fluid film wave bearings, and the housing. Radiated noise is mapped from the gearbox surface to surrounding environment. The effectiveness of rolling element and fluid film wave bearings in breaking the vibro-acoustic propagation path from the gear to the housing is investigated.

  8. Dynamic force response of spherical hydrostatic journal bearing for cryogenic applications

    Science.gov (United States)

    Sanandres, Luis

    1994-01-01

    Hydrostatic Journal Bearings (HJB's) are reliable and resilient fluid film rotor support elements ideal to replace roller bearings in cryogenic turbomachinery. HJB' will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, large direct stiffness, and damping force coefficients. An analysis for the performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings (HJB's) is presented. Spherical bearings allow tolerance for shaft misalignment without force performance degradation and have also the ability to support axial loads. The spherical HJB combines these advantages to provide a bearing design which could be used efficiently on high performance turbomachinery. The motion of a barotropic liquid on the thin film bearing lands is described by bulk-flow mass and momentum equations. These equations are solved numerically using an efficient CFD method. Numerical predictions of load capacity and force coefficients for a 6 recess, spherical HJB in a LO2 environment are presented. Fluid film axial forces and force coefficients of a magnitude about 20% of the radial load capacity are predicted for the case analyzed. Fluid inertia effects, advective and centrifugal, are found to affect greatly the static and dynamic force performance of the bearing studied.

  9. Formation of Pt-bearing Western Pana pluton on the Kola Peninsula: Fluid regime as deduced from helium and argon isotopic compositions

    Science.gov (United States)

    Nivin, V. A.; Rundqvist, T. V.

    2017-01-01

    The distribution of He and Ar isotopes has been studied in 41 rock samples and seven monomineralic fractions from ore-bearing layered units and poorly differentiated host gabbronorite of the Western Pana mafic-ultramafic pluton on the Kola Peninsula. The gases assigned for mass-spectrometric analysis were released by means of whole-rock sample melting and by comminution mainly from fluid microinclusions. The data show that the present-day isotopic composition of noble gases in rocks from the pluton is caused by many factors: the degree of melt degassing, various concentrations and retention of the trapped isotopes, the contents of radioactive elements, and the generation and loss of radiogenic gases. The hypabyssal conditions of pluton formation facilitate the loss of primary mantle-derived volatile components and the dilution of magmatic fluid with near-surface paleometeoric waters containing air dissolved therein. The correlation of noble gas isotopes and ore-forming chemical elements does not suggest derivation of the latter from crustal material and evidences their mantle origin. Variations in the geochemical indices of the gas corroborate previously established or proposed multistage formation of the pluton, mainly, the autometamorphic character of postmagmatic processes and the participation of fluids in ore formation.

  10. Squeeze-film Lubrication of the Human Ankle Joint with Synovial Fluid Filtrated by Articular Cartilage with the Superficial Zone Worn out

    Czech Academy of Sciences Publication Activity Database

    Hlaváček, Miroslav

    2000-01-01

    Roč. 33, č. 11 (2000), s. 1415-1422 ISSN 0021-9290 R&D Projects: GA ČR GA103/00/0008 Keywords : human ankle joint * squeeze-film lubrication * synovial fluid filtration * worn-out cartilage superficial zone Subject RIV: BK - Fluid Dynamics Impact factor: 1.474, year: 2000

  11. Development of porous squeeze film damper bearings for improving the blade loss dynamics of rotor-support systems

    Science.gov (United States)

    Zhang, Shiping; Yan, Litang; Li, Qihan

    1992-07-01

    An efficient oil-film damper known as porous squeeze-film damper (PSFD) is developed based on conventional squeeze-film damper (SFD) for more effective and reliable rotor-vibration control and for improving the blade-loss dynamics for rotor-support systems. The permeability of the outer race of PSFD could remarkably improve the squeeze-film damping properties. The transient response of a simple rigid rotor and flexible Jeffcott's rotor supported on PSFD and SFD subjected to sudden unbalance of blade loss are investigated. Time-transient simulation shows that PSFD could operate effectively under much greater unbalance as compared with SFD, especially under relative large impact loading of blade loss. The effective eccentricities of PSFD with small transmissibilities extend to a range of epsilon of less than 0.9, and optimum film stiffness and damping distribution within the whole film clearance could be achieved.

  12. Magmatic nature of Sn-bearing fluids from isotopic (H,O) data of tourmalines (Solnechnoye deposit, Far East of Russia)

    Science.gov (United States)

    Sushchevskaya, Tatiana; Ignatiev, Alexander; Velivetskaya, Tatiana

    2010-05-01

    It was shown, that the main factors, controlled Sn-W ore deposition in hydrothermal systems in connection with granites were: a) cooling, b) mixing of fluids of different composition and genesis, c) heterogenization (boiling) of mineral forming fluids (Heinrich, 1990; et al). The results of physical chemical modelling of water-rock interaction pointed to magmatic nature of tin-bearing fluids in the hydrothermal systems, connected with granites. Tin concentration in model magmatogeneous fluid was calculated to be three times higher than in the model exogenic fluid (Sushchevskaya, Ryzhenko, 1998). New data on the source of ore forming fluids, which had formed the large economic Solnechnoye Sn deposit (Far East of Russia), were obtained from hydrogen and oxygen isotopic composition of tourmalines from successive mineral associations. Hydrogen position in the tourmaline crystal structure allows to suppose, that postproductive processes did not change the initial δD values, in contrast to phyllosilicates, often used for this purpose. During mineral formation at the Solnechnoye deposit tourmaline was formed practically without interruption. Its composition was gradually changed from schorl to dravite, when temperature decreased. The ores of cassiterite-tourmaline type were formed in a vertically dipping fracture zones, extended in a metamorphosed sandstone-shale rocks. Hydrogene and oxygen isotopic composition of fluids were calculated from tourmaline data with the help of equations, proposed in (Kotzer et al., 1993). The temperature intervals for these calculations were accepted as: 1- 450-400o C for quartz-tourmaline preore stage, 2 - 400-350o C -for early productive quartz-cassiterite stage, 3 - 350-300o C - for late quartz- cassiterite stage. The obtained results corresponded to magmatic character of the fluids of productive stage of the Solnechnoye deposit, because their isotopic composition lied in the interval: δ18О (3.2-9.3)‰, δD -(31.7-76.6)‰. The

  13. Mixed Lubrication Simulation of Hydrostatic Spherical Bearings for Hydraulic Piston Pumps and Motors

    Science.gov (United States)

    Kazama, Toshiharu

    Mixed and fluid film lubrication characteristics of hydrostatic spherical bearings for swash-plate-type axial piston pumps and motors are studied theoretically under non-steady-state conditions. The basic equations incorporating interference and contact of surface roughness are derived fundamentally through combination of the GW and PC models. Furthermore, a programming code that is applicable to the caulked-socket-type and open-socket-type bearings is developed. Effects of caulking, operating conditions, and the bearing dimension on the motion of the sphere and tribological performance of the bearings are examined. Salient conclusions are the following: The sphere's eccentricity increases in the low supply pressure period. The time-lag of the load change engenders greater motion of the sphere. Caulking of the bearing socket suppresses the sphere's motion. The bearing stiffness increases and power loss decreases for smaller recess angles. Minimum power loss is given under the condition that the bearing socket radius nearly equals the equivalent load radius.

  14. Effects on the structure of monolayer and submonolayer fluid nitrogen films by the corrugation in the holding potential of nitrogen molecules

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing

    2001-01-01

    of interactions were indicated by the comparison of the calculated and measured isosteric heats of adsorption in fluid films of nitrogen molecules on graphite. The melting temperatures were lowered by 7K and a region of liquid-gas coexistence was observed for films on the smooth graphite surface indicating......The effects of corrugation in the holding potential of nitrogen molecules on the structure of fluid monolayer and submonolayer films of the molecules on a solid substrate was studied using molecular dynamics simulation. Including McLachlan mediation of the intermolecular potential in a model...

  15. Development, implementation and assessment of specific, two-fluid closure laws for inverted-annular film-boiling

    Energy Technology Data Exchange (ETDEWEB)

    Cachard, F. de [Laboratory for Thermal Hydraulics, Villigen (Switzerland)

    1995-09-01

    Inverted-Annular Film-Boiling (IAFB) is one of the post-burnout heat transfer modes taking place during the reflooding phase of the loss-of-coolant accident, when the liquid at the quench front is subcooled. Under IAFB conditions, a continuous, liquid core is separated from the wall by a superheated vapour film. the heat transfer rate in IAFB is influenced by the flooding rate, liquid subcooling, pressure, and the wall geometry and temperature. These influences can be accounted by a two-fluid model with physically sound closure laws for mass, momentum and heat transfers between the wall, the vapour film, the vapour-liquid interface, and the liquid core. Such closure laws have been developed and adjusted using IAFB-relevant experimental results, including heat flux, wall temperature and void fraction data. The model is extensively assessed against data from three independent sources. A total of 46 experiments have been analyzed. The overall predictions are good. The IAFB-specific closure laws proposed have also intrinsic value, and may be used in other two-fluid models. They should allow to improve the description of post-dryout, low quality heat transfer by the safety codes.

  16. Mixed Lubrication Simulation of Hydrostatic Spherical Bearings for Hydraulic Piston Pumps and Motors

    OpenAIRE

    KAZAMA, Toshiharu

    2008-01-01

    Mixed and fluid film lubrication characteristics of hydrostatic spherical bearings for swash-plate-type axial piston pumps and motors are studied theoretically under non-steady-state conditions. The basic equations incorporating interference and contact of surface roughness are derived fundamentally through combination of the GW and PC models. Furthermore, a programming code that is applicable to the caulked-socket-type and open-socket-type bearings is developed. Effects of caulking, operatin...

  17. Elasto-Hydrodynamic Lubrication Effect in Thrust-Slide Bearings of Scroll Compressors

    OpenAIRE

    Ishii, Noriaki; Tsuji, Takuma; Oku, Tatsuya; Anami, Keiko; Morimoto, Takashi

    2012-01-01

    This paper presents the concept of the Elasto-Hydrodynamic Lubrication (EHL) effect for the thrust slide-bearings in scroll compressors, which accounts for the superior lubrication characteristics of these bearings. The thrust plate undergoes elastic deformation due to axial loading, resulting in the formation of a fluid wedge between the orbiting and fixed thrust plates, a region with very high induced oil film pressure which, in turn, accounts for the remarkably good lubrication characteris...

  18. The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids.

    Science.gov (United States)

    Hu, Bin; Kieweg, Sarah L

    2012-07-15

    Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability.

  19. The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids

    Science.gov (United States)

    Hu, Bin; Kieweg, Sarah L.

    2012-01-01

    Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability. PMID:23687391

  20. A Waved Journal Bearing Concept-Evaluating Steady-State and Dynamic Performance with a Potential Active Control Alternative

    Science.gov (United States)

    Dimofte, Florin

    1993-01-01

    Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. The performance of generic waved bearings having either three or four waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of fluid film stability and dynamic coefficients. It was found that the bearing wave amplitude has an important influence on both the steady-state and the dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases.

  1. Supercritical-Carbon Dioxide Fluid Extract from Chrysanthemum indicum Enhances Anti-Tumor Effect and Reduces Toxicity of Bleomycin in Tumor-Bearing Mice

    Directory of Open Access Journals (Sweden)

    Hong-Mei Yang

    2017-02-01

    Full Text Available Bleomycin (BLM, a family of anti-tumor drugs, was reported to exhibit severe side effects limiting its usage in clinical treatment. Therefore, finding adjuvants that enhance the anti-tumor effect and reduce the detrimental effect of BLM is a prerequisite. Chrysanthemum indicum, an edible flower, possesses abundant bioactivities; the supercritical-carbon dioxide fluid extract from flowers and buds of C. indicum (CISCFE have strong anti-inflammatory, anti-oxidant, and lung protective effects. However, the role of CISCFE combined with BLM treatment on tumor-bearing mice remains unclear. The present study aimed to investigate the potential synergistic effect and the underlying mechanism of CISCFE combined with BLM in the treatment of hepatoma 22 (H22 tumor-bearing mice. The results suggested that the oral administration of CISCFE combined with BLM could markedly prolong the life span, attenuate the BLM-induced pulmonary fibrosis, suppress the production of pro-inflammatory cytokines (interleukin-6, tumor necrosis factor-α, activities of myeloperoxidase, and malondiadehyde. Moreover, CISCFE combined with BLM promoted the ascites cell apoptosis, the activities of caspases 3 and 8, and up-regulated the protein expression of p53 and down-regulated the transforming growth factor-β1 by activating the gene expression of miR-29b. Taken together, these results indicated that CISCFE could enhance the anti-cancer activity of BLM and reduce the BLM-induced pulmonary injury in H22 tumor-bearing mice, rendering it as a potential adjuvant drug with chemotherapy after further investigation in the future.

  2. Heuristic Explanation of Journal Bearing Instability

    Science.gov (United States)

    1982-05-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small...other simple explanations of journal - bearing instability. It is shown that for non-cavitating long bearings the hypothesis predicts instability onset

  3. Numerical study on modeling of liquid film flow under countercurrent flow limitation in volume of fluid method

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Taro, E-mail: watanabe_t@qe.see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita-shi, Osaka 565-7895 (Japan); Takata, Takashi, E-mail: takata.takashi@jaea.go.jp [Japan Atomic Energy Agency, 4002 Narita-chou, Oarai-machi, Higashi-Ibaraki-gun, Ibaraki 331-1393 (Japan); Yamaguchi, Akira, E-mail: yamaguchi@n.t.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki 319-1188 (Japan)

    2017-03-15

    Highlights: • Thin liquid film flow under CCFL was modeled and coupled with the VOF method. • The difference of the liquid flow rate in experiments of CCFL was evaluated. • The proposed VOF method can quantitatively predict CCFL with low computational cost. - Abstract: Countercurrent flow limitation (CCFL) in a heat transfer tube at a steam generator (SG) of pressurized water reactor (PWR) is one of the important issues on the core cooling under a loss of coolant accident (LOCA). In order to improve the prediction accuracy of the CCFL characteristics in numerical simulations using the volume of fluid (VOF) method with less computational cost, a thin liquid film flow in a countercurrent flow is modeled independently and is coupled with the VOF method. The CCFL characteristics is evaluated analytically in condition of a maximizing down-flow rate as a function of a void fraction or a liquid film thickness considering a critical thickness. Then, we have carried out numerical simulations of a countercurrent flow in a vertical tube so as to investigate the CCFL characteristics and compare them with the previous experimental results. As a result, it has been concluded that the effect of liquid film entrainment by upward gas flux will cause the difference in the experiments.

  4. Coupling Fluid and Solute Dynamics Within the Ocular Surface Tear Film: A Modelling Study of Black Line Osmolarity

    KAUST Repository

    Zubkov, V. S.

    2012-07-06

    We present a mathematical model describing the spatial distribution of tear film osmolarity across the ocular surface of a human eye during one blink cycle, incorporating detailed fluid and solute dynamics. Based on the lubrication approximation, our model comprises three coupled equations tracking the depth of the aqueous layer of the tear film, the concentration of the polar lipid, and the concentration of physiological salts contained in the aqueous layer. Diffusive boundary layers in the salt concentration occur at the thinnest regions of the tear film, the black lines. Thus, despite large Peclet numbers, diffusion ameliorates osmolarity around the black lines, but nonetheless is insufficient to eliminate the build-up of solute in these regions. More generally, a heterogeneous distribution of solute concentration is predicted across the ocular surface, indicating that measurements of lower meniscus osmolarity are not globally representative, especially in the presence of dry eye. Vertical saccadic eyelid motion can reduce osmolarity at the lower black line, raising the prospect that select eyeball motions more generally can assist in alleviating tear film hyperosmolarity. Finally, our results indicate that measured evaporative rates will induce excessive hyperosmolarity at the black lines, even for the healthy eye. This suggests that further evaporative retardation at the black lines, for instance due to the cellular glycocalyx at the ocular surface or increasing concentrations of mucus, will be important for controlling hyperosmolarity as the black line thins. © 2012 Society for Mathematical Biology.

  5. Sensitivity analysis of size effect on the performance of hydrostatic bearing

    Directory of Open Access Journals (Sweden)

    Dongju Chen

    2016-01-01

    Full Text Available For size effect on solid-liquid interface of hydrostatic bearing oil film gap flow in two-dimension, fluid dynamic method is applied to investigate the influence of size effect on bearing capacity, dynamic stiffness and other performances. With the consideration of size effect, Reynolds equation is modified by adopting velocity slip boundary condition into Reynolds equation. The sensitivity factors are used to make a quantitative and qualitative analysis. Numerical simulation results show that size effect will affect bearing performances to a certain degree and the effect curve of size effect on bearing performances are given. The four maximum oil film pressures reduce with the increase of slip length. The maximum sensitivity of bearing capacity is 81.94%.

  6. The Effect of Fluid Shear Stress on the In Vitro Release Kinetics of Sirolimus from PLGA Films

    Directory of Open Access Journals (Sweden)

    Quan Zheng

    2017-11-01

    Full Text Available Drug-carrying coatings of stents implanted in blood vessels are exposed to various blood flows. This study investigated the effect of fluid shear stress on the in vitro release kinetics of sirolimus from poly(lactic-co-glycolic acid (PLGA films. The homemade parallel plate flow chamber was used to exert quantitative shear stress on the sirolimus-carrying film. By adjusting the flow rate of the release media in the chamber, three levels of shear stress (3.6, 12.0, and 36.0 dyn/cm2 were respectively applied. For each level of shear stress employed, the release kinetics of sirolimus from the PLGA films exhibited a four-phase profile: an initial burst release phase (Phase I, a lag phase (Phase II, a second burst release phase (Phase III, and a terminal release phase (Phase IV. During Phases I and II, sirolimus was released slowly and in small amounts (<10%; however, during Phases III and IV, the drug release increased considerably. Comparisons of different shear stresses indicated that greater shear stress resulted in earlier and faster sirolimus release, with more cumulative drug release observed. PLGA film degradations (molecular weight reduction, mass loss, and surface topographical variations were also investigated to better explain the observed drug release behavior. Consequently, fluid shear stress was found to significantly accelerate the release of sirolimus from the PLGA matrices. Therefore, this study could provide a practical method for evaluating the in vitro drug release from polymer matrices under uniform shear stress, and might help improve the design of biodegradable coatings on drug-eluting stents.

  7. Minimization of Power Loss in Hydrodynamic Bearings Design Using the Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    H Saruhan

    2005-12-01

    Full Text Available The search of bearing geometry and performance which satisfies at best design objective along with design criteria is not so easy task. Design optimization of hydrodynamic bearings is very complex in nature. The complexity and time consuming nature of the design process of hydrodynamic bearings warranted the development of a new methodology. The purpose of this study is to use of the genetic algorithm in the optimal design of a three-lobe preloaded fluid film bearing in essence developing the bearing configurations that optimize power loss along with other design criteria namely fluid film thickness, stability parameter, film temperature, and film pressure. The results obtained and presented in this study are compared to results from numerical optimization methods such as gradient-based method, and show the potential of the genetic algorithm in optimization of three-lobe preloaded hydrodynamic bearings. This robust method has been designed to search for most feasible solutions to problems and has gained recognition in many fields.

  8. Engineering applications and analysis of vibratory motion fourth order fluid film over the time dependent heated flat plate

    Science.gov (United States)

    Mohmand, Muhammad Ismail; Mamat, Mustafa Bin; Shah, Qayyum

    2017-07-01

    This article deals with the time dependent analysis of thermally conducting and Magneto-hydrodynamic (MHD) liquid film flow of a fourth order fluid past a vertical and vibratory plate. In this article have been developed for higher order complex nature fluids. The governing-equations have been modeled in the terms of nonlinear partial differential equations with the help of physical boundary circumstances. Two different analytical approaches i.e. Adomian decomposition method (ADM) and the optimal homotopy asymptotic method (OHAM), have been used for discoveryof the series clarification of the problems. Solutions obtained via two diversemethods have been compared using the graphs, tables and found an excellent contract. Variants of the embedded flow parameters in the solution have been analysed through the graphical diagrams.

  9. Experimental contribution to the study of gas bearings

    International Nuclear Information System (INIS)

    Gobert, G.

    1962-01-01

    Developments for gas-lubricated bearings are discussed. The study of how the fluid film behaves compared to what one can expect is discussed. Various devices are described which have allowed us to go up to peripheral velocity greater than 400 m/s, leading to rotational speed of several thousand revolutions per second. This is obtained by using an automatic setting for the distance between fixed and rotating walls. (author) [fr

  10. Compensation of Cross-Coupling Stiffness and Increase of Direct Damping in Multirecess Journal Bearings using Active Hybrid Lubrication

    DEFF Research Database (Denmark)

    Santos, Ilmar; Watanabe, F.Y.

    2004-01-01

    Fluid film forces are generated in hydrostatic journal bearings by two types of lubrication mechanisms: the hydrostatic lubrication in the bearing recesses and hydrodynamic lubrication in the bearing lands, when operating in rotation. The combination of both lubrication mechanisms leads to hybrid...... journal bearings (HJB). When part of hydrostatic pressure is also dynamically modified by means of hydraulic control systems, one refers to the active lubrication. The main contribution of the present theoretical work is to show that it is possible to reduce cross-coupling stiffness and increase...

  11. A study of the gross compositions of oil-bearing fluid inclusions using high performance liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Pang, L.S.K.; George, S.C.; Quezada, R.A. [CSIRO Petroleum, North Ryde (Australia)

    1998-12-31

    A high performance liquid chromatography (HPLC) method for assessing the compositions of crude oils and fluid inclusion oils is described. The necessary increase in instrumentation sensitivity was accomplished using a narrow bore Waters Spherisorb column with 5 {mu}m particle diameter. This HPLC method has advantages over the Iatroscan TLC-FID technique previously described as the < C{sub 16} fraction is measured by the HPLC method. However, due to uncertainties in the calibration procedure the HPLC method is only semi-quantitative. Aliphatic hydrocarbons were calibrated taking into account the molecular weight distribution of a typical oil derived by gas chromatography. Aromatic hydrocarbons were calibrated using standards according to retention times, but the response factors span two orders of magnitude, dependent on ring size. Polar compound response factors are strongly standard dependent. The gross composition of a suite of 12 inclusion oils and 17 co-occurring crude oils from various basins in Australia and Papua New Guinea have been analysed. The inclusion oils at the Jabiru and Tirrawarra wells are enriched in polar compounds relative to the co-occurring crude oils from these wells. This is attributed to an adsorption effect during trapping. However, many inclusion oils do not appear to be polar enriched, which may relate to trapping of inclusion oils in sealed fractures as well as on overgrowths. Inclusion oils tend to be relatively depleted in aromatic hydrocarbons, which could reflect a trapping phenomenon, with preferentially less aromatic hydrocarbons and/or more waxy aliphatic hydrocarbons being trapped in fluid inclusions. Alternatively, this may be a characteristic of the different chemistry of oils that are preserved early in the charge history of a reservoir. (author)

  12. Self-propagating exothermic reaction analysis in Ti/Al reactive films using experiments and computational fluid dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Seema, E-mail: seema.sen@tu-ilmenau.de [Technical University of Ilmenau, Department of Materials for Electronics, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau (Germany); Niederrhein University of Applied Science, Department of Mechanical and Process Engineering, Reinarzstraße 49, 47805 Krefeld (Germany); Lake, Markus; Kroppen, Norman; Farber, Peter; Wilden, Johannes [Niederrhein University of Applied Science, Department of Mechanical and Process Engineering, Reinarzstraße 49, 47805 Krefeld (Germany); Schaaf, Peter [Technical University of Ilmenau, Department of Materials for Electronics, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau (Germany)

    2017-02-28

    Highlights: • Development of nanoscale Ti/Al multilayer films with 1:1, 1:2 and 1:3 molar ratios. • Characterization of exothermic reaction propagation by experiments and simulation. • The reaction velocity depends on the ignition potentials and molar ratios of the films. • Only 1Ti/3Al films exhibit the unsteady reaction propagation with ripple formation. • CFD simulation shows the time dependent atom mixing and temperature flow during exothermic reaction. - Abstract: This study describes the self-propagating exothermic reaction in Ti/Al reactive multilayer foils by using experiments and computational fluid dynamics simulation. The Ti/Al foils with different molar ratios of 1Ti/1Al, 1Ti/2Al and 1Ti/3Al were fabricated by magnetron sputtering method. Microstructural characteristics of the unreacted and reacted foils were analyzed by using electronic and atomic force microscopes. After an electrical ignition, the influence of ignition potentials on reaction propagation has been experimentally investigated. The reaction front propagates with a velocity of minimum 0.68 ± 0.4 m/s and maximum 2.57 ± 0.6 m/s depending on the input ignition potentials and the chemical compositions. Here, the 1Ti/3Al reactive foil exhibits both steady state and unsteady wavelike reaction propagation. Moreover, the numerical computational fluid dynamics (CFD) simulation shows the time dependent temperature flow and atomic mixing in a nanoscale reaction zone. The CFD simulation also indicates the potentiality for simulating exothermic reaction in the nanoscale Ti/Al foil.

  13. Electrodeposited semiconductors at room temperature: an X-ray Absorption Spectroscopy study of Cu-, Zn-, S-bearing thin films

    International Nuclear Information System (INIS)

    Di Benedetto, Francesco; Cinotti, Serena; D’Acapito, Francesco; Vizza, Francesco; Foresti, Maria Luisa; Guerri, Annalisa; Lavacchi, Alessandro; Montegrossi, Giordano; Romanelli, Maurizio; Cioffi, Nicola; Innocenti, Massimo

    2015-01-01

    A SEM, DRS and XAS study was carried out on ultra-thin films with chemical composition belonging to the Cu-Zn-S ternary system, related to the kesterite-type materials, in the light of their potential application to thin film photovoltaic technology. The films, realized through the layer-by-layer E-ALD electrochemical technique, reveal variable phase composition as a function of the applied E-ALD sequence. In particular, by increasing the Zn cycles per Cu cycle from 1:1 to 9:1, the number of detected phases changes from 3 to 2. In all samples, Cu mainly crystallize in a Cu 2 S type phase, whereas Zn occurs as ZnS. In the 1:1 sample, additional ZnO is detected. The variable phase composition parallels apparent changes in the sample morphology. In all samples, a sulphide thin film is covered by a net of elongated nanostructures, the length of which decreases with increasing the number of Zn cycles per Cu cycle. All these evidences are interpreted as due to the operating electrochemical route during the synthesis and confirm the lack of miscibility between Cu 2 S and ZnS, thermodynamically relevant after the E-ALD has stopped. The band gap values exhibited by the three films, modulated by changing the copper:zinc ratio, progressively approach a value useful for solar energy conversion, thus strongly proposing these new sulfide nanomaterials for photovoltaics and photochemical applications.

  14. On the stability analysis of flexible rotors supported by Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    of external pressurization. The present contribution presents a detailed mathematical modeling for hybrid lubrication of a compressible fluid film journal bearing. Piezo-actuated valves are used in order to inject pressurized air into the bearing gap through orifices located on the bearing walls. A modified...... form of the compressible Reynolds equation for active lubrication is derived. Particular attention is given to the injections terms and a comparison is carried on between fully nonlinear and linearized expressions. By solving this equation, stiffness and damping coefficients can be determined...

  15. Hydrodynamic film thickness measurements and CFD analysis identify the root causes of repetitive thrust bearing failures on a 45 MW hydro generating unit at Hydro-Québec

    Science.gov (United States)

    Gauvin, P.; Huard, P.

    2016-11-01

    High temperature level recorded on the thrust bearing of a 45 MW hydro generating unit was resulting in frequent production stoppage. In spite of improvements brought to the oil cooling system since the rehabilitation in 2008, the operator had to activate the bearing oil lift system to keep the temperature below acceptable limits. Primary root cause analysis first pointed to the design of the shoe that was centrally pivoted, not allowing the formation of a thick hydrodynamic film. The removal of a strip of the soft metal layer near the trailing edge of the shoe resulted in a significant surface temperature reduction (about 15 deg. C), as predicted by a CFD model of the oil film. The goal of this machining was to increase the pivoting angle by moving the centre of hydrodynamic pressure. Proximity sensors were installed at each corner of the redesigned shoe to measure the film thickness and the bearing attitude. Signal analysis revealed a step of a magnitude close to the oil film thickness between the two halves of the rotating thrust block. This was the cause of another failure few hours since restarting the unit. The lessons learnt through these measurements and analyses were carefully applied to the ultimate build. The unit now runs with a robust thrust bearing and even survived a significant cooling flow reduction event. This paper presents the CFD analysis results and the measurements acquired during these events.

  16. Establishment of a novel specific ELISA system for rat N- and C-ERC/mesothelin. Rat ERC/mesothelin in the body fluids of mice bearing mesothelioma.

    Science.gov (United States)

    Hagiwara, Yoshiaki; Hamada, Yukiko; Kuwahara, Maki; Maeda, Masahiro; Segawa, Tatsuya; Ishikawa, Kiyoshi; Hino, Okio

    2008-04-01

    Mesothelioma is a type of malignant tumor that most commonly arises from the pleural or peritoneal membrane and is usually associated with previous exposure to asbestos. In humans, ERC/mesothelin is expressed on the normal mesothelium and in some cancers such as mesothelioma or ovarian carcinoma. Recently, several enzyme-linked immunosorbent assay (ELISA) systems for ERC/mesothelin have been developed, the reported usefulness of which has been assessed and demonstrated as a diagnostic tool. However, the basic roles or physiological functions of, and relationship between, ERC/mesothelin and asbestos exposure-mediated carcinogenesis remain to be resolved. In order to elucidate the precise mechanism, animal models of mesothelioma are desperately needed. In this study, we consider the development of a novel specific ELISA system for not only rat N-ERC/mesothelin but also C-ERC/mesothelin, and the first data on the presence of rat ERC/mesothelin in the body fluids of rat malignant mesothelioma-bearing nude mice. The transplanted mice have revealed the higher concentrations of rat N-ERC/mesothelin in the blood and ascites than C-ERC/mesothelin. We hope these novel ELISA systems are useful in the rat model system to clarify the mechanism of asbestos-induced carcinogenesis and to develop new effective drugs for mesothelioma.

  17. Linear and non linear dynamic behaviour of bearings and seals; Comportement dynamique lineaire et non lineaire des paliers et des joints

    Energy Technology Data Exchange (ETDEWEB)

    Bonneau, O. [Poitiers Univ., 86 (France). Laboratoire de Mecanique des Solides

    1998-07-01

    High speed rotors set a lot of stability problems especially when the speed of rotation is going through a critical speed. The dynamical behavior of the fluid bearings has, in that case, an important effect. This study presents several models of dynamical behavior of bearing taking into account the flexibility of the shaft. The squeeze film damper (SFD) behavior is also described. This element gives a lot of damping but its behavior is totally non linear. An approach of active squeeze film Damper is presented: a variable clearance SFD or a variable viscosity SFD (fed with electro-rheological fluid) is used to control a flexible shaft. (author)

  18. Design and application of squeeze film dampers for turbomachinery stabilization

    Science.gov (United States)

    Gunter, E. J.; Barrett, L. E.; Allaire, P. E.

    1975-01-01

    The steady-state transient response of the squeeze film damper bearing was investigated. Both the steady-state and transient equations for the hydrodynamic bearing forces are derived; the steady-state equations were used to determine the damper equivalent stiffness and damping coefficients. These coefficients are used to find the damper configuration which will provide the optimum support characteristics based on a stability analysis of the rotor-bearing system. The effects of end seals and cavitated fluid film are included. The transient analysis of rotor-bearing systems was conducted by coupling the damping and rotor equations and integrating forward in time. The effects of unbalance, cavitation, and retainer springs are included. Methods of determining the stability of a rotor-bearing system under the influence of aerodynamic forces and internal shaft friction are discussed.

  19. Magnetohydrodynamic thin film and heat transfer of power law fluids over an unsteady stretching sheet with variable thermal conductivity

    Directory of Open Access Journals (Sweden)

    Lin Yanhai

    2016-01-01

    Full Text Available This paper presents an investigation on the MHD thin film flow and heat transfer of a power law fluid over an unsteady stretching sheet. The effects of power law viscosity on a temperature field are taken into account with a modified Fourier’s law Proposed by Zheng by assuming that the temperature field is similar to the velocity field. The governing equations are reduced to a system of nonlinear ordinary differential equations. The numerical solutions are obtained by using the shooting method coupled with the Runge-Kutta method. The influence of the Hartmann number, the power law exponent, the unsteadiness parameter, the thickness parameter and the generalized Prandtl number on the velocity and temperature fields are presented graphically and analyzed. Moreover, the critical formula for parameters are derived which indicated that the magnetic field has no effect on the critical value.

  20. Heat transfer analysis of MHD thin film flow of an unsteady second grade fluid past a vertical oscillating belt.

    Science.gov (United States)

    Gul, Taza; Islam, Saeed; Shah, Rehan Ali; Khan, Ilyas; Khalid, Asma; Shafie, Sharidan

    2014-01-01

    This article aims to study the thin film layer flowing on a vertical oscillating belt. The flow is considered to satisfy the constitutive equation of unsteady second grade fluid. The governing equation for velocity and temperature fields with subjected initial and boundary conditions are solved by two analytical techniques namely Adomian Decomposition Method (ADM) and Optimal Homotopy Asymptotic Method (OHAM). The comparisons of ADM and OHAM solutions for velocity and temperature fields are shown numerically and graphically for both the lift and drainage problems. It is found that both these solutions are identical. In order to understand the physical behavior of the embedded parameters such as Stock number, frequency parameter, magnetic parameter, Brinkman number and Prandtl number, the analytical results are plotted graphically and discussed.

  1. Heat transfer analysis of MHD thin film flow of an unsteady second grade fluid past a vertical oscillating belt.

    Directory of Open Access Journals (Sweden)

    Taza Gul

    Full Text Available This article aims to study the thin film layer flowing on a vertical oscillating belt. The flow is considered to satisfy the constitutive equation of unsteady second grade fluid. The governing equation for velocity and temperature fields with subjected initial and boundary conditions are solved by two analytical techniques namely Adomian Decomposition Method (ADM and Optimal Homotopy Asymptotic Method (OHAM. The comparisons of ADM and OHAM solutions for velocity and temperature fields are shown numerically and graphically for both the lift and drainage problems. It is found that both these solutions are identical. In order to understand the physical behavior of the embedded parameters such as Stock number, frequency parameter, magnetic parameter, Brinkman number and Prandtl number, the analytical results are plotted graphically and discussed.

  2. Heat Transfer Analysis of MHD Thin Film Flow of an Unsteady Second Grade Fluid Past a Vertical Oscillating Belt

    Science.gov (United States)

    Gul, Taza; Islam, Saeed; Shah, Rehan Ali; Khan, Ilyas; Khalid, Asma; Shafie, Sharidan

    2014-01-01

    This article aims to study the thin film layer flowing on a vertical oscillating belt. The flow is considered to satisfy the constitutive equation of unsteady second grade fluid. The governing equation for velocity and temperature fields with subjected initial and boundary conditions are solved by two analytical techniques namely Adomian Decomposition Method (ADM) and Optimal Homotopy Asymptotic Method (OHAM). The comparisons of ADM and OHAM solutions for velocity and temperature fields are shown numerically and graphically for both the lift and drainage problems. It is found that both these solutions are identical. In order to understand the physical behavior of the embedded parameters such as Stock number, frequency parameter, magnetic parameter, Brinkman number and Prandtl number, the analytical results are plotted graphically and discussed. PMID:25383797

  3. Actively lubricated bearings applied as calibrated shakers to aid parameter identification in rotordynamics

    DEFF Research Database (Denmark)

    Santos, Ilmar; Cerda Varela, Alejandro Javier

    2013-01-01

    between hydrodynamic, hydrostatic and controllable lubrication regimes, can be used either to control or to excite rotor lateral vibrations. An accurate characterization of the active oil film forces is of fundamental importance to elucidate the feasibility of applying the active lubrication as non......-invasive perturbation forces, or in other words, as a "calibrated shaker", to perform in-situ rotordynamic tests. The main original contributions of this paper are three: a) the experimental characterization of the active fluid film forces generated in an actively-lubricated tilting-pad journal bearing in the frequency...... systems; c) experimental indication of how small such active fluid film forces (perturbation forces) should be, in order to perturb the rotor-journal bearing system without significantly changing its dynamic characteristics. To validate the experimental procedure and results obtained via actively-lubricated...

  4. Steady State Thermo-Hydrodynamic Analysis of Two-Axial groove and Multilobe Hydrodynamic Bearings

    Directory of Open Access Journals (Sweden)

    C. Bhagat

    2014-12-01

    Full Text Available Steady state thermo-hydrodynamic analysis of two axial groove and multi lobe oil journal bearings is performed in this paper. To study the steady state thermo-hydrodynamic characteristics Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. The effect of groove geometry, cavitation in the fluid film, the recirculation of lubricant, shaft speed has also been taken into account. Film temperature in case of three-lobe bearing is found to be high as compared to other studied bearing configurations. The data obtained from this analysis can be used conveniently in the design of such bearings, which are presented in dimensionless form.

  5. Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing

    Science.gov (United States)

    Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

    1994-01-01

    A new fluid film bearing package has been tested in the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most importantly, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance during testing on the NASA Technology Test Bed (TTB) Engine located at MSFC. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at ten percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65% of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

  6. A fully coupled variable properties thermohydraulic model for a cryogenic hydrostatic journal bearing

    Science.gov (United States)

    Braun, M. J.; Wheeler, R. L., III; Hendricks, R. C.

    1986-01-01

    The goal set forth here is to continue the work started by Braun et al. (1984-1985) and present an integrated analysis of the behavior of the two row, 20 staggered pockets, hydrostatic cryogenic bearing used by the turbopumps of the Space Shuttle main engine. The variable properties Reynolds equation is fully coupled with the two-dimensional fluid film energy equation. The three-dimensional equations of the shaft and bushing model the boundary conditions of the fluid film energy equation. The effects of shaft eccentricity, angular velocity, and inertia pressure drops at pocket edge are incorporated in the model. Their effects on the bearing fluid properties, load carrying capacity, mass flow, pressure, velocity, and temperature form the ultimate object of this paper.

  7. Heuristic explanation of journal bearing instability

    Science.gov (United States)

    Crandall, S. H.

    1982-01-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small whirling motion of the journal generates a wave of thickness variation progressing around the channel. The hypothesis that the fluid flow drives the whirl whenever the mean of the pumped fluid velocity is greater than the peripheral speed of the thickness variation wave is discussed and compared with other simple explanations of journal bearing instability. It is shown that for non-cavitation long bearings the hypothesis predicts instability onset correctly for unloaded bearings but gradually overpredicts the onset speed as the load is increased.

  8. Bearing system

    Science.gov (United States)

    Kapich, Davorin D.

    1987-01-01

    A bearing system includes backup bearings for supporting a rotating shaft upon failure of primary bearings. In the preferred embodiment, the backup bearings are rolling element bearings having their rolling elements disposed out of contact with their associated respective inner races during normal functioning of the primary bearings. Displacement detection sensors are provided for detecting displacement of the shaft upon failure of the primary bearings. Upon detection of the failure of the primary bearings, the rolling elements and inner races of the backup bearings are brought into mutual contact by axial displacement of the shaft.

  9. Controllable Sliding Bearings and Controllable Lubrication Principles—An Overview

    Directory of Open Access Journals (Sweden)

    Ilmar F. Santos

    2018-02-01

    Full Text Available Hydrodynamic and aerodynamic lubrication regimes in their controllable forms have been intensively investigated over the last two decades. With the aim of reducing friction and improving thermal, static, and dynamic characteristics of radial sliding bearings, different types of electro-mechanical actuators have been coupled to such bearings. Depending on (i the actuator type; (ii the actuation principle, i.e., hydraulic, pneumatic, piezoelectric or magnetic among others; and (iii how such an actuator is coupled to the sliding bearings, different regulation and control actions of fluid film pressure and lubricant flow can be obtained. The most common actions are: (a the control of the injection pressure to modify the fluid film pressure statically as well as dynamically; (b the adjustment of the angle and direction of injection flow (mostly passive action; (c the control of the sliding bearing gap and its preload via moveable and compliant sliding surfaces; and (d the control of the lubricant viscosity. All four parameters, i.e., pressure, flow (velocity profiles, gap and viscosity, are explicit parameters in the modified form of Reynolds’ equations for active lubrication. In this framework, this paper gives one main original contribution to the state-of-the-art of radial sliding bearings and controllable lubrication: a comprehensive overview about the different types of controllable sliding bearings and principles used by several authors. The paper ends with some conclusive remarks about advantages and drawbacks of the different design solutions for controllable sliding bearings and the main challenges to be overcome towards industrial applications.

  10. Flow and heat transfer in water based liquid film fluids dispensed with graphene nanoparticles

    Science.gov (United States)

    Zuhra, Samina; Khan, Noor Saeed; Khan, Muhammad Altaf; Islam, Saeed; Khan, Waris; Bonyah, Ebenezer

    2018-03-01

    The unsteady flow and heat transfer characteristics of electrically conducting water based thin liquid film non-Newtonian (Casson and Williamson) nanofluids dispensed with graphene nanoparticles past a stretching sheet are considered in the presence of transverse magnetic field and non-uniform heat source/sink. Embedding the graphene nanoparticles effectively amplifies the thermal conductivity of Casson and Williamson nanofluids. Ordinary differential equations together with the boundary conditions are obtained through similarity variables from the governing equations of the problem, which are solved by the HAM (Homotopy Analysis Method). The solution is expressed through graphs and illustrated which show the influences of all the parameters. The convergence of the HAM solution for the linear operators is obtained. Favorable comparison with previously published research paper is performed to show the correlation for the present work. Skin friction coefficient and Nusselt number are presented through Tables and graphs which show the validation for the achieved results demonstrating that the thin liquid films results from this study are in close agreement with the results reported in the literature. Results achieved by HAM and residual errors are evaluated numerically, given in Tables and also depicted graphically which show the accuracy of the present work.

  11. Vibratory motion of fourth order fluid film over a unsteady heated flat

    Science.gov (United States)

    Mohmand, Muhammad Ismail; Mamat, Mustafa Bin; Shah, Qayyum; Gul, Taza

    2017-03-01

    Analysis of heat transfer is studied in magnetohydrodynamic (MHD) thin layer flow of an unsteady fourth grade fluid past a moving and oscillating vertical plate for lift and drainage problem. The governing equations are modelled in terms of nonlinear partial differential equations with some physical boundary conditions. Two different analytical methods, namely Adomian Decomposition Method (ADM) and the Optimal Homotopy Asymptotic Method (OHAM) are used for finding the series solution of the problem. The solutions obtained through two different techniques are compared using graphs and tables and found an excellent agreement. The variants of embedded flow parameters in the solution are analyzed through graphical illustrations.

  12. Fluorine lubricated bearing technology

    Science.gov (United States)

    Mallaire, F. R.

    1973-01-01

    An experimental program was conducted to evaluate and select materials for ball bearings intended for use in liquid fluorine and/or FLOX. The ability of three different ball-separator materials, each containing nickel, to form and transfer a nickel fluoride film to provide effective lubrication at the required areas of a ball bearing operating in liquid fluorine was evaluated. In addition, solid lubrication of a ball bearing operating in liquid fluorine by either a fused fluoride coating applied to all surfaces of the ball separator or by a fluoride impregnation of porous sintered material ball separators was evaluated. Less bearing wear occurred when tests were conducted in the less reactive FLOX. Bearings fabricated from any of the materials tested would have relatively short wear lives and would require frequent replacement in a reusable engine.

  13. Film Coating of Nifedipine Extended Release Pellets in a Fluid Bed Coater with a Wurster Insert

    Directory of Open Access Journals (Sweden)

    Luciane Franquelin Gomes de Souza

    2014-01-01

    Full Text Available The objective of this work was to study the coating process of nifedipine extended release pellets using Opadry and Opadry II, in a fluid bed coater with a Wurster insert. The coating process was studied using a complete experimental design of two factors at two levels for each polymer. The variables studied were the inlet air temperature and the coating suspension flow rate. The agglomerate fraction and coating efficiency were the analyzed response variables. The air temperature was the variable that most influenced the coating efficiency for both polymers. In addition, a study of the dissolution profiles of coated and uncoated pellets using 0.5% sodium lauryl sulfate in simulated gastric fluid without enzymes (pH 1.2 was conducted. The results showed a prolonged release profile for the coated and uncoated pellets that was very similar to the standards established by the U.S. Pharmacopoeia. The drug content and the release profiles were not significantly affected by storage at 40°C and 75% relative humidity. However, when exposed to direct sunlight and fluorescent light (light from fluorescent bulbs, the coated pellets lost only 5% of the drug content, while the uncoated ones lost more than 35%; furthermore, the dissolution profile of the uncoated pellets was faster.

  14. Film Coating of Nifedipine Extended Release Pellets in a Fluid Bed Coater with a Wurster Insert

    Science.gov (United States)

    de Souza, Luciane Franquelin Gomes; Nitz, Marcello; Taranto, Osvaldir Pereira

    2014-01-01

    The objective of this work was to study the coating process of nifedipine extended release pellets using Opadry and Opadry II, in a fluid bed coater with a Wurster insert. The coating process was studied using a complete experimental design of two factors at two levels for each polymer. The variables studied were the inlet air temperature and the coating suspension flow rate. The agglomerate fraction and coating efficiency were the analyzed response variables. The air temperature was the variable that most influenced the coating efficiency for both polymers. In addition, a study of the dissolution profiles of coated and uncoated pellets using 0.5% sodium lauryl sulfate in simulated gastric fluid without enzymes (pH 1.2) was conducted. The results showed a prolonged release profile for the coated and uncoated pellets that was very similar to the standards established by the U.S. Pharmacopoeia. The drug content and the release profiles were not significantly affected by storage at 40°C and 75% relative humidity. However, when exposed to direct sunlight and fluorescent light (light from fluorescent bulbs), the coated pellets lost only 5% of the drug content, while the uncoated ones lost more than 35%; furthermore, the dissolution profile of the uncoated pellets was faster. PMID:24772426

  15. Evaluation of datum unit for diagnostics of journal-bearing systems

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Byung Chul; Jung, Joon Ha; Youn, Byeng Doog [Dept. of Mechanical and Aerospace Engineering, Seoul National University, Seoul (Korea, Republic of); Kim, Yeon Whan; Bae, Yong Chae [Power Generation Laboratory, KEPCO Research Institute, Daejeon (Korea, Republic of)

    2015-08-15

    Journal bearings support rotors using fluid film between the rotor and the stator. Generally, journal bearings are used in large rotor systems such as turbines in a power plant, because even in high-speed and load conditions, journal bearing systems run in a stable condition. To enhance the reliability of journal-bearing systems, in this paper, we study health-diagnosis algorithms that are based on the supervised learning method. Specifically, this paper focused on defining the unit of features, while other previous papers have focused on defining various features of vibration signals. We evaluate the features of various lengths or units on the separable ability basis. From our results, we find that one cycle datum in the time-domain and 60 cycle datum in the frequency domain are the optimal datum units for real-time journal-bearing diagnosis systems.

  16. Evaluation of datum unit for diagnostics of journal-bearing systems

    International Nuclear Information System (INIS)

    Jeon, Byung Chul; Jung, Joon Ha; Youn, Byeng Doog; Kim, Yeon Whan; Bae, Yong Chae

    2015-01-01

    Journal bearings support rotors using fluid film between the rotor and the stator. Generally, journal bearings are used in large rotor systems such as turbines in a power plant, because even in high-speed and load conditions, journal bearing systems run in a stable condition. To enhance the reliability of journal-bearing systems, in this paper, we study health-diagnosis algorithms that are based on the supervised learning method. Specifically, this paper focused on defining the unit of features, while other previous papers have focused on defining various features of vibration signals. We evaluate the features of various lengths or units on the separable ability basis. From our results, we find that one cycle datum in the time-domain and 60 cycle datum in the frequency domain are the optimal datum units for real-time journal-bearing diagnosis systems

  17. The R and D D`s bearing test benches; Les bancs d`essais de paliers de la DER

    Energy Technology Data Exchange (ETDEWEB)

    Vialettes, J.M. [Service Ensembles de Production, Departement Machines, Direction des Etudes et Recherches, Electricite de France (EDF), 92 - Clamart (France)

    1997-01-01

    In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author) 14 figs.

  18. Film

    OpenAIRE

    Jones, Sarah

    2002-01-01

    This book looks at the movie industry and at the labour intensive but fascinating process of making a feature film. It examines each stage in the production of a film, from initial idea through to the final cut and screening, and highlights the main activities that take place along the way. The book not only looks at the work of prominent people in the film world, such as directors and actors, but also describes the equally important but less high profile contributions of the gaffer, best boy...

  19. Thermophoresis and thermal radiation with heat and mass transfer in a magnetohydrodynamic thin-film second-grade fluid of variable properties past a stretching sheet

    Science.gov (United States)

    Khan, Noor Saeed; Gul, Taza; Islam, Saeed; Khan, Waris

    2017-01-01

    The influences of thermophoresis and thermal radiation of a magnetohydrodynamic two-dimensional thin-film second-grade fluid with heat and mass transfer flow in the presence of viscous dissipation past a stretching sheet are analyzed. The main focus of the study is to discuss the significant roll of the fluid variable properties like thermal conductivity and viscosity under the variation of the thin film. The thermal conductivity varies directly as a linear function of temperature showing the property that expresses the ability of a material to transfer heat, and the viscosity is assumed to vary inversely as a linear function of temperature showing that viscous forces become weak at increasing temperature. Thermophoresis occurs to discuss the mass deposition at the surface of the stretching sheet while thermal radiation occurs, especially, at high temperature. The basic governing equations for the velocity, temperature and concentration of the fluid flow have been transformed to high nonlinear coupled differential equations with physical conditions by invoking suitable similarity transformations. The solution of the problem has been obtained by using HAM (Homotopy Analysis Method). The heat and mass transfer flow behaviors are affected significantly by the thin film. The physical influences of thin film parameter and all other parameters have been studied graphically and illustrated. The residual graphs and residual error table elucidate the authentication of the present work.

  20. Axisymmetric computational fluid dynamics analysis of a film/dump-cooled rocket nozzle plume

    Science.gov (United States)

    Tucker, P. K.; Warsi, S. A.

    1993-01-01

    Prediction of convective base heating rates for a new launch vehicle presents significant challenges to analysts concerned with base environments. The present effort seeks to augment classical base heating scaling techniques via a detailed investigation of the exhaust plume shear layer of a single H2/O2 Space Transportation Main Engine (STME). Use of fuel-rich turbine exhaust to cool the STME nozzle presented concerns regarding potential recirculation of these gases to the base region with attendant increase in the base heating rate. A pressure-based full Navier-Stokes computational fluid dynamics (CFD) code with finite rate chemistry is used to predict plumes for vehicle altitudes of 10 kft and 50 kft. Levels of combustible species within the plume shear layers are calculated in order to assess assumptions made in the base heating analysis.

  1. On the matter of synovial fluid lubrication: implications for Metal-on-Metal hip tribology.

    Science.gov (United States)

    Myant, Connor; Cann, Philippa

    2014-06-01

    Artificial articular joints present an interesting, and difficult, tribological problem. These bearing contacts undergo complex transient loading and multi axes kinematic cycles, over extremely long periods of time (>10 years). Despite extensive research, wear of the bearing surfaces, particularly metal-metal hips, remains a major problem. Comparatively little is known about the prevailing lubrication mechanism in artificial joints which is a serious gap in our knowledge as this determines film formation and hence wear. In this paper we review the accepted lubrication models for artificial hips and present a new concept to explain film formation with synovial fluid. This model, recently proposed by the authors, suggests that interfacial film formation is determined by rheological changes local to the contact and is driven by aggregation of synovial fluid proteins. The implications of this new mechanism for the tribological performance of new implant designs and the effect of patient synovial fluid properties are discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Film

    OpenAIRE

    Bould, M.

    2014-01-01

    A critical overview of critical-theoretical understandings of sf film, especially those promulgated by critics devoted to sf as a prose fiction form. It also considers adaptation, spectacle and special effects.

  3. Active Lubrication for Reducing Wear and Vibration: A combination of Fluid Power Control and Tribology

    DEFF Research Database (Denmark)

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through ori...

  4. The mobility of Nb in rutile-saturated NaCl- and NaF-bearing aqueous fluids from 1–6.5 GPa and 300–800 °C

    Energy Technology Data Exchange (ETDEWEB)

    Tanis, Elizabeth A.; Simon, Adam; Tschauner, Oliver; Chow, Paul; Xiao, Yuming; Burnley, Pamela; Cline II, Christopher J.; Hanchar, John M.; Pettke, Thomas; Shen, Guoyin; Zhao, Yusheng (MUN); (Michigan); (CIW); (UNLV); (Bern)

    2015-08-26

    Rutile (TiO₂) is an important host phase for high field strength elements (HFSE) such as Nb in metamorphic and subduction zone environments. The observed depletion of Nb in arc rocks is often explained by the hypothesis that rutile sequesters HFSE in the subducted slab and overlying sediment, and is chemically inert with respect to aqueous fluids evolved during prograde metamorphism in the forearc to subarc environment. However, field observations of exhumed terranes, and experimental studies, indicate that HFSE may be soluble in complex aqueous fluids at high pressure (i.e., >0.5 GPa) and moderate to high temperature (i.e., >300 °C). In this study, we investigated experimentally the mobility of Nb in NaCl- and NaF-bearing aqueous fluids in equilibrium with Nb-bearing rutile at pressure-temperature conditions applicable to fluid evolution in arc environments. Niobium concentrations in aqueous fluid at rutile saturation were measured directly by using a hydrothermal diamond-anvil cell (HDAC) and synchrotron X-ray fluorescence (SXRF) at 2.1 to 6.5 GPa and 300–500 °C, and indirectly by performing mass loss experiments in a piston-cylinder (PC) apparatus at ~1 GPa and 700–800 °C. The concentration of Nb in a 10 wt% NaCl aqueous fluid increases from 6 to 11 μg/g as temperature increases from 300 to 500 °C, over a pressure range from 2.1 to 2.8 GPa, consistent with a positive temperature dependence. The concentration of Nb in a 20 wt% NaCl aqueous fluid varies from 55 to 150 μg/g at 300 to 500 °C, over a pressure range from 1.8 to 6.4 GPa; however, there is no discernible temperature or pressure dependence. The Nb concentration in a 4 wt% NaF-bearing aqueous fluid increases from 180 to 910 μg/g as temperature increases from 300 to 500 °C over the pressure range 2.1 to 6.5 GPa. The data for the F-bearing fluid indicate that the Nb content of the fluid exhibits a dependence on temperature between 300 and 500 °C at ≥2 GPa, but there is no observed

  5. The effect of bone cement particles on the friction of polyethylene and polyurethane knee bearings

    International Nuclear Information System (INIS)

    Ash, H E; Scholes, S C; Unsworth, A; Jones, E

    2004-01-01

    Compliant layer knee joints have been considered for use in an attempt to increase the serviceable life of artificial joints. If designed correctly, these joints should operate within the full-fluid film lubrication regime. However, adverse tribological conditions, such as the presence of bone and bone cement particles, may breach the fluid film and cause surface wear. The frictional behaviour of both polyurethane (PU) and conventional polyethylene (PE) tibial components against a metallic femoral component was therefore assessed when bone cement particles were introduced into the lubricant. The bone cement particles caused a large increase in the frictional torque of both the PE and PU bearings; however, the friction produced by the PU bearings was still considerably lower than that produced by the PE bearings. The volume of bone cement particles between each of the bearings and the resultant frictional torque both decreased over time. This occurred more quickly with the PE bearings but greater damage was caused to the surface of the PE bearings than the PU components

  6. Bifurcation Analysis of a Non-linear On-Board Rotor-Bearing System

    OpenAIRE

    Dakel, M. Zaki; Baguet, Sébastien; Dufour, Régis

    2014-01-01

    International audience; The non-linear dynamic behavior of an on-board rotor mounted on hydrodynamic journal bearings and subject to rigid base excitations is investigated in this work. The proposed finite element rotor model takes into account the geometric asymmetry of shaft and/or rigid disk and considers six types of base deterministic motions (rotations and translations) and non-linear fluid film forces obtained from the Reynoldsequation. The equations of motion contain time-varying para...

  7. Bulk-Flow Analysis of Hybrid Thrust Bearings for Advanced Cryogenic Turbopumps

    Science.gov (United States)

    SanAndres, Luis

    1998-01-01

    A bulk-flow analysis and computer program for prediction of the static load performance and dynamic force coefficients of angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings have been completed. The product of the research is an efficient computational tool for the design of high-speed thrust bearings for cryogenic fluid turbopumps. The study addresses the needs of a growing technology that requires of reliable fluid film bearings to provide the maximum operating life with optimum controllable rotordynamic characteristics at the lowest cost. The motion of a cryogenic fluid on the thin film lands of a thrust bearing is governed by a set of bulk-flow mass and momentum conservation and energy transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. The bulk-flow model includes flow turbulence with fluid inertia advection, Coriolis and centrifugal acceleration effects on the bearing recesses and film lands. The cryogenic fluid properties are obtained from realistic thermophysical equations of state. Turbulent bulk-flow shear parameters are based on Hirs' model with Moody's friction factor equations allowing a simple simulation for machined bearing surface roughness. A perturbation analysis leads to zeroth-order nonlinear equations governing the fluid flow for the thrust bearing operating at a static equilibrium position, and first-order linear equations describing the perturbed fluid flow for small amplitude shaft motions in the axial direction. Numerical solution to the zeroth-order flow field equations renders the bearing flow rate, thrust load, drag torque and power dissipation. Solution to the first-order equations determines the axial stiffness, damping and inertia force coefficients. The computational method uses well established algorithms and generic subprograms available from prior developments. The Fortran9O computer program hydrothrust runs

  8. Passive Thermal Management of Foil Bearings

    Science.gov (United States)

    Bruckner, Robert J. (Inventor)

    2015-01-01

    Systems and methods for passive thermal management of foil bearing systems are disclosed herein. The flow of the hydrodynamic film across the surface of bearing compliant foils may be disrupted to provide passive cooling and to improve the performance and reliability of the foil bearing system.

  9. Magnetic Bearing

    OpenAIRE

    Anbuselvan. T; Vinothkumar. K; Sai Vikash. M

    2013-01-01

    The use of bearings is essential to all types of machines, especially in marine aspects they provide the function of supporting heavier component in a desired position. These bearings have contact with the rotating part and causes surface wear which can be controlled by lubrication. Researches have raised the standards of performance for rotating equipment by providing robust, cost effective, easy to implement magnetic bearing solutions. Use of magnetic bearings in ships can be more advantag...

  10. Improvement of journal bearing operation at heavy misalignment using bearing flexibility and compliant liners

    OpenAIRE

    Thomsen, Kim; Klit, Peder

    2012-01-01

    A flexure journal bearing design is proposed that will improve operational behaviour of a journal bearing at pronounced misalignment. Using a thermoelastohydrodynamic model, it is shown that the proposed flexure journal bearing has vastly increased the hydrodynamic performance compared to the stiff bearing when misaligned. The hydrodynamic performance is evaluated on lubricant film thickness, pressure and temperature. Furthermore, the influence of a compliant bearing liner is investigated and...

  11. Rotordynamics of Automotive Turbochargers Linear and Nonlinear Rotordynamics – Bearing Design – Rotor Balancing

    CERN Document Server

    Nguyen-Schäfer, Hung

    2012-01-01

    This book deals with rotordynamics of automotive turbochargers while encompassing the analysis of the dynamics of rotating machines at very high rotor speeds of 300,000 rpm and above. This interdisciplinary field involves 1. thermodynamics and turbo-matching knowledge to compute working conditions of turbochargers, 2. fluid and bearing dynamics to calculate various operating thrust loads and to design the rotating floating ring bearings (two-oil-film bearings), and 3. tribology to improve the rotor stability and to reduce the bearing friction. Mathematical background in modeling and simulation methods is necessary; however, the prerequisites have been kept to a minimum. The book addresses both practitioners working in the field of rotordynamics of automotive turbochargers and graduate students in mechanical engineering.

  12. Journal bearing

    Science.gov (United States)

    Menke, John R.; Boeker, Gilbert F.

    1976-05-11

    1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.

  13. Film

    OpenAIRE

    Balint, Ruth; Dolgopolov, Greg

    2008-01-01

    From the beginning of the twentieth century, Sydney defined cosmopolitanism and modernity in the national imagination, and central to this image was the cinema: its technology, its architecture, its stars, its marketing and the stories it circulated to its audiences about Australia and the world. Though it is difficult to define a genre of Sydney film, Sydney provided the backdrop for a host of ideas about the city, and later suburbia. Sydney came to be seen as a ‘tinsel town’ of cultural ban...

  14. Fluid flow and heat transfer on a falling liquid film with surfactant from a heated vertical surface

    International Nuclear Information System (INIS)

    Kang, B. H.; Kim, K. H.; Lee, D. Y.

    2007-01-01

    The addition of surface active agent to a falling liquid film affects the flow characteristics of the falling film. In this study, the flow and heat transfer characteristics for a falling liquid film have been investigated by addition of the surfactant. The falling liquid film was formed on a vertical flat plate. Contact angle of a liquid droplet above a plate surface can be substantially reduced with an increase in the surfactant concentration. The results obtained indicate that not only the wetted area of falling liquid film is increased but also the film thickness is decreased as the surfactant concentration is increased. It is also found that heat transfer rate is significantly increased while the heat transfer coefficient is almost constant value with an increase in the surfactant concentration at a given mass flow rate

  15. Evaluation of the qualitative and quantitative effectiveness of three media of centrifugation (Maxifreeze, Cushion Fluid Equine, and PureSperm 100) in preparation of fresh or frozen-thawed brown bear spermatozoa.

    Science.gov (United States)

    Nicolas, M; Alvarez, M; Borragán, S; Martinez-Pastor, F; Chamorro, C A; Alvarez-Rodriguez, M; de Paz, P; Anel, L

    2012-04-01

    Centrifugation is a crucial procedure in sperm cryopreservation protocols of brown bear (Ursus arctos), because the semen must be processed to increase sperm concentration and/or clean urine-contaminated samples. The efficacy of three media for centrifugation (Maxifreeze [IMV technologies, L'Aigle, France], Cushion Fluid Equine (Minitübe, Tiefenbach, Germany), and PureSperm [Nidacon, Gothenburg, Sweden]) on the quality of bear spermatozoa was evaluated. In experiment one, two cushioned media used for protecting against mechanical stress during centrifugation were analyzed. In experiment two, a density gradient based on PureSperm was assessed in relation to the maximum retrieval and the quality of fresh spermatozoa, and the freezability of the spermatozoa selected in this density gradient was studied in experiment three. Finally, the selection of frozen-thawed sperm using PureSperm was analyzed in experiment four. Our results indicate that the use of dense isotonic cushion solutions (Maxifreeze, Cushion Fluid Equine) in centrifugation did not improve the quality of recovered spermatozoa compared with standard centrifugation. However, a density gradient prepared with PureSperm improved the quality of spermatozoa in fresh semen and frozen-thawed semen, but the spermatozoa selected from the fresh sample with this density gradient did not show a better resistance to freezing with this density gradient in comparison with the control sample. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Neutron radiographic detection limits of fluids in metal pipes

    International Nuclear Information System (INIS)

    Winn, W.G.

    1976-01-01

    Routine maintenance of process pipes at the Savannah River Plant has indicated that undesirable fluids can build up in the various gas lines. Thermal neutron radiography has been used to image thin films of various fluids in thick-walled high-pressure process pipes. A 3.5 x 10 6 n/(cm 2 -sec) thermal neutron beam and standard transfer imaging techniques were used to provide radiographs of the fluid-bearing pipes. In addition, a computer graphics procedure was developed that simulated the neutron radiographs; this method permitted examination of some fluid-pipe configurations not studied experimentally. Actual pipe dimensions ranged in OD from 1 / 4 to 9 / 16 in. with OD/ID = 3. Many common industrial fluids such as H 2 O, oils, and CCl 4 may be detected in thick-walled process pipes, even when distributed in thin (3 to 10 mil) fluid films. By contrast, fluids with a low thermal neutron cross section (D 2 O and T 2 O) can be detected only for much thicker films

  17. Computational design of rolling bearings

    CERN Document Server

    Nguyen-Schäfer, Hung

    2016-01-01

    This book comprehensively presents the computational design of rolling bearings dealing with many interdisciplinary difficult working fields. They encompass elastohydrodynamics (EHD), Hertzian contact theory, oil-film thickness in elastohydrodynamic lubrication (EHL), bearing dynamics, tribology of surface textures, fatigue failure mechanisms, fatigue lifetimes of rolling bearings and lubricating greases, Weibull distribution, rotor balancing, and airborne noises (NVH) in the rolling bearings. Furthermore, the readers are provided with hands-on essential formulas based on the up-to-date DIN ISO norms and helpful examples for computational design of rolling bearings. The topics are intended for undergraduate and graduate students in mechanical and material engineering, research scientists, and practicing engineers who want to understand the interactions between these working fields and to know how to design the rolling bearings for automotive industry and many other industries.

  18. Parametric studies on floating pad journal bearing for high speed cryogenic turboexpanders

    Science.gov (United States)

    Jain, A.; Jadhav, M. M.; Karimulla, S.; Chakravarty, A.

    2017-12-01

    Most modern medium and large capacity helium liquefaction/refrigeration plants employ high speed cryogenic turboexpanders in their refrigeration/liquefaction cycles as active cooling devices. The operating speed of these turboexpanders is in the range of 3000-5000 Hz and hence specialized types of bearings are required. Floating pad journal bearing, which is a special type of tilting pad journal bearing, where mechanical pivots are absent and pads are fully suspended in gas, can be a good solution for stable operation of these high speed compact rotors. The pads are separated from shaft as well as from housing by fluid film between them, and both these sides of pad are interconnected by a network of feed holes. The work presented in this article aims to characterize floating pad journal bearings through parametric studies. The steady state performance characteristics of the bearing are represented by load capacity, stiffness coefficients and heat generation rate of the bearing. The geometrical parameters such as bearing clearances, preload of pads, etc. are varied and performance characteristics of the floating pad journal bearing are studied and presented. The dependence of stiffness coefficients on rotational speed of shaft is also analyzed.

  19. Improvement of journal bearing operation at heavy misalignment using bearing flexibility and compliant liners

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder

    2012-01-01

    A flexure journal bearing design is proposed that will improve operational behaviour of a journal bearing at pronounced misalignment. Using a thermoelastohydrodynamic model, it is shown that the proposed flexure journal bearing has vastly increased the hydrodynamic performance compared to the stiff...... bearing when misaligned. The hydrodynamic performance is evaluated on lubricant film thickness, pressure and temperature. Furthermore, the influence of a compliant bearing liner is investigated and it is found that it increases the hydrodynamic performance when applied to a stiff bearing, whereas...... the liner has practically no influence on the flexure journal bearing's performance....

  20. GAS BEARING

    Science.gov (United States)

    Skarstrom, C.W.

    1960-09-01

    A gas lubricated bearing for a rotating shaft is described. The assembly comprises a stationary collar having an annular member resiliently supported thereon. The collar and annular member are provided with cooperating gas passages arranged for admission of pressurized gas which supports and lubricates a bearing block fixed to the rotatable shaft. The resilient means for the annular member support the latter against movement away from the bearing block when the assembly is in operation.

  1. Transient response of two lobe aerodynamic journal bearing

    Directory of Open Access Journals (Sweden)

    Saurabh Kumar Yadav

    2018-03-01

    Full Text Available The dynamic behavior of a rotor-dynamic system is greatly affected by the performance of aerodynamic bearing and the performance of bearing is characterized by the stiffness and damping coefficients. In the present work, stiffness and damping coefficients of bearing are computed and the performance of the bearing is greatly changed with the change in bearing air film profile. The effect of lobe offset factors on the transient performance of aerodynamic bearing is presented. Bifurcation and Poincare diagrams of two lobe journal bearing have been presented for different offset factors. A bearing designer can judge the bearing performance based on bifurcation diagrams.

  2. Synthesis and Characterization of Novel Dendrons Bearing Amino-Nitro-Substituted Azobenzene Units and Oligo(ethylene glycol Spacers: Thermal, Optical Properties, Langmuir Blodgett Films and Liquid-Crystalline Behaviour

    Directory of Open Access Journals (Sweden)

    Ernesto Rivera

    2013-01-01

    Full Text Available In this work, we report the synthesis and characterization of a novel series of first and second generation Fréchet type dendrons bearing amino-nitro substituted azobenzene units and tetra(ethylene glycol spacers. These compounds were fully characterized by FTIR, 1H and 13C-NMR spectroscopies, and their molecular weights were determined by MALDI-TOF-MS. The thermal properties of the obtained dendrons were studied by TGA and DSC and their optical properties by absorption spectroscopy in solution and cast film. Molecular calculations were performed in order to determine the optimized geometries of these molecules in different environments. Besides, Langmuir and Langmuir Blodgett films were prepared with the first generation dendrons that were shown to be amphiphilic. Finally, some of the dendrons showed a liquid crystalline behaviour, which was studied by light polarized microscopy as a function of the temperature in order to determine the transition temperatures and the structure of the mesophase.

  3. Hydrodynamic air lubricated compliant surface bearing for an automotive gas turbine engine. 1: Journal bearing performance

    Science.gov (United States)

    Ruscitto, D.; Mccormick, J.; Gray, S.

    1978-01-01

    A 38.1 mm (1.5 inch) diameter Hydresil Compliant Surface Air Lubricated Journal Bearing was designed and tested to obtain bearing performance characteristics at both room temperature and 315 C (600 F). Testing was performed at various speeds up to 60,000 rpm with varying loads. Rotating sensors provided an opportunity to examine the film characteristics of the compliant surface bearing. In addition to providing minimum film thickness values and profiles, many other insights into bearing operation were gained such as the influence of bearing fabrication accuracy and the influence of smooth foil deflection between the bumps.

  4. Analysis of hydrostatic journal bearings with end seals

    Science.gov (United States)

    San Andres, L. A.

    1992-10-01

    An approximate analysis for the pressure field and dynamic force coefficients in turbulent flow, centered hydrostatic journal bearings (HJBs) with fluid inertia and liquid compressibility effects is presented. Results from the analysis show that HJBs with end seals have increased damping, better dynamic stability characteristics, as well as lower flow rates, than conventional HJBs. However, hydrostatic (direct) stiffness may be lost if excessively tight end seals are used. End seals are shown to compensate for the effect of liquid compressibility within the recess volume, and prescribe a net reduction in the whirl frequency ratio for hybrid operation. Hydrostatic squeeze film dampers (HSFD) with end seals are shown to be a viable alternative in applications where a tight control of the bearing leakage is important such as in jet-engines. Furthermore, HSFDs with end seals could be used as an active device to control the available damping in a typical application.

  5. Polar Bears

    Science.gov (United States)

    Amstrup, Steven C.; Douglas, David C.; Reynolds, Patricia E.; Rhode, E.B.

    2002-01-01

    Polar bears (Ursus maritimus) are hunted throughout most of their range. In addition to hunting polar bears of the Beaufort Sea region are exposed to mineral and petroleum extraction and related human activities such as shipping road-building, and seismic testing (Stirling 1990).Little was known at the start of this project about how polar bears move about in their environment, and although it was understood that many bears travel across political borders, the boundaries of populations had not been delineated (Amstrup 1986, Amstrup et al. 1986, Amstrup and DeMaster 1988, Garner et al. 1994, Amstrup 1995, Amstrup et al. 1995, Amstrup 2000).As human populations increase and demands for polar bears and other arctic resources escalate, managers must know the sizes and distributions of the polar bear populations. Resource managers also need reliable estimates of breeding rates, reproductive intervals, litter sizes, and survival of young and adults.Our objectives for this research were 1) to determine the seasonal and annual movements of polar bears in the Beaufort Sea, 2) to define the boundaries of the population(s) using this region, 3) to determine the size and status of the Beaufort Sea polar bear population, and 4) to establish reproduction and survival rates (Amstrup 2000).

  6. Lateral dampers for thrust bearings

    Science.gov (United States)

    Hibner, D. H.; Szafir, D. R.

    1985-01-01

    The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

  7. Multiscale Simulation of Gas Film Lubrication During Liquid Droplet Collision

    Science.gov (United States)

    Chen, Xiaodong; Khare, Prashant; Ma, Dongjun; Yang, Vigor

    2012-02-01

    Droplet collision plays an elementary role in dense spray combustion process. When two droplets approach each other, a gas film forms in between. The pressure generated within the film prevents motion of approaching droplets. This fluid mechanics is fluid film lubrication that occurs when opposing bearing surfaces are completely separated by fluid film. The lubrication flow in gas film decides the collision outcome, coalescence or bouncing. Present study focuses on gas film drainage process over a wide range of Weber numbers during equal- and unequal-sized droplet collision. The formulation is based on complete set of conservation equations for both liquid and surrounding gas phases. An improved volume-of-fluid technique, augmented by an adaptive mesh refinement algorithm, is used to track liquid/gas interfaces. A unique thickness-based refinement algorithm based on topology of interfacial flow is developed and implemented to efficiently resolve the multiscale problem. The grid size on interface is up O(10-4) of droplet size with a max resolution of 0.015 μm. An advanced visualization technique using the Ray-tracing methodology is used to gain direct insights to detailed physics. Theories are established by analyzing the characteristics of shape changing and flow evolution.

  8. Zymographic analysis using gelatin-coated film of the effect of etanercept on the extracellular matrix-degrading activity in synovial fluids of rheumatoid arthritis patients.

    Science.gov (United States)

    Kamataki, Akihisa; Ishida, Mutsuko; Komagamine, Masataka; Yoshida, Masaaki; Ando, Takanobu; Sawai, Takashi

    2016-04-01

    Rheumatoid arthritis (RA) is a chronic inflammatory disease. Most RA patients develop cartilage and bone destruction, and various proteinases are involved in the destruction of extracellular matrix of cartilage and bone. The aim of this study is to evaluate the utility of our newly developed method to measure total gelatinolytic activity. We adopted this method for measurement in synovial fluid from RA patients treated by the anti-rheumatic drug etanercept (ETN), a recombinant human soluble tumor necrosis factor receptor fusion protein, and compared the findings with clinical and laboratory data. Enzymatic activity of synovial fluid was analyzed by zymography using gelatin-coated film, and compared with the index of Disease Activity Score of 28 joints - C-reactive protein (DAS28-CRP), CRP and matrix metalloproteinase (MMP)-3 level before and after ETN therapy. Synovial fluids of 19 patients were collected before and after administration of ETN therapy. In nine of 19 patients, who showed a decrease in gelatin-degrading activity in synovial fluid, the index of DAS28-CRP (4.85-2.85, ΔDAS = -2.00) and CRP (3.30-0.94 mg/dL, ΔCRP = -2.36) was alleviated after ETN therapy, while cases with no change or an increase in gelatin-degrading activity showed a modest improvement in clinical data: DAS28-CRP (4.23-3.38, ΔDAS = -0.85) and CRP (1.70-0.74 mg/dL, ΔCRP = -0.96). Our newly developed method for measurement of gelatin-degrading activity in synovial fluid from RA patients is highly practicable and useful for predicting the effect of ETN therapy. © 2013 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.

  9. Evaluation of knee-joint cartilage and menisci ten years after isolated and combined ruptures of the medial collateral ligament. Investigation by weight-bearing radiography, MR imaging and analysis of proteoglycan fragments in the joint fluid

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, M. [Univ. Hospital, Linkoeping (Sweden). Dept. of Orthopaedics and Sports Medicine (Sweden); Thuomas, K.Aa. [Univ. Hospital, Linkoeping (Sweden). Dept. of Diagnostic Radiology; Messner, K. [Univ. Hospital, Linkoeping (Sweden). Dept. of Orthopaedics and Sports Medicine (Sweden)

    1997-01-01

    Purpose: To compare radiography, MR imaging, and chemical analysis in posttraumatic knees. Material and Methods: Ten matched pairs with either isolated partial rupture of the medial collateral ligament or combined medial collateral ligament/anterior cruciate ligament rupture were compared with matched controls 10 years after trauma. Weight-bearing radiographys and MR examinations were compared with proteoglycan fragment concentrations in the joint fluid. Results: The chemical analyses were similar in both trauma groups. The radiographs showed mild signs of arthrosis in half the patients with combined injury. MR images showed almost all injuried knees to have degenerative changes of various degrees in the cartilage and menisci. More frequent and more advanced changes were found after combined injury than after isolated injury (p<0.01). There were no changes in the controls. Conclusion: MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis. (orig.).

  10. Evaluation of knee-joint cartilage and menisci ten years after isolated and combined ruptures of the medial collateral ligament. Investigation by weight-bearing radiography, MR imaging and analysis of proteoglycan fragments in the joint fluid

    International Nuclear Information System (INIS)

    Lundberg, M.; Thuomas, K.Aa.

    1997-01-01

    Purpose: To compare radiography, MR imaging, and chemical analysis in posttraumatic knees. Material and Methods: Ten matched pairs with either isolated partial rupture of the medial collateral ligament or combined medial collateral ligament/anterior cruciate ligament rupture were compared with matched controls 10 years after trauma. Weight-bearing radiographys and MR examinations were compared with proteoglycan fragment concentrations in the joint fluid. Results: The chemical analyses were similar in both trauma groups. The radiographs showed mild signs of arthrosis in half the patients with combined injury. MR images showed almost all injuried knees to have degenerative changes of various degrees in the cartilage and menisci. More frequent and more advanced changes were found after combined injury than after isolated injury (p<0.01). There were no changes in the controls. Conclusion: MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis. (orig.)

  11. Methane-bearing fluids in subduction zones: an experimental study of abiotic methanogenesis during serpentinization at 12 kbar and 300°C

    Science.gov (United States)

    Lazar, C.; Manning, C. E.

    2009-12-01

    Serpentinization within subduction zones may generate reduced fluids that contain higher concentrations of abiotic methane than near-surface ultramafic environments. We present preliminary experimental data suggesting that the kinetics of abiotic methanogenesis are enhanced at high pressures. Thermodynamic calculations of C-O-H fluid speciations at the low oxygen fugacities attained during early serpentinization suggest complete conversion of oxidized carbon to methane, yet previous field and experimental investigations have reported fluid compositions with CH4/CO2 far below equilibrium (McCollom and Seewald, 2007). Much experimental work, therefore, has focused on CH4 production rates and the kinetic effects of temperature and mineral catalysis (Horita and Berdt, 1999; Foustoukos and Seyfried, 2004). Methane has been shown experimentally to form at very high pressures (Scott et al, 2004), but the quantitative effect of pressure on methanogenesis kinetics is unknown. We present preliminary results of a comparison of methane production rates at 0.35 and 12 kbar, 300°C, using experiments performed in piston cylinder and cold seal hydrothermal apparatus. Carbon was introduced as a roughly 70 mmol solution of isotopically-labeled formic acid, H13COOH, known to decompose to 13CO2 and H2 at run conditions. Roughly 15 mL of this solution, along with 1.9 mg of natural awaruite (Ni3Fe), was loaded into a gold capsule and then sealed via DC spot welding. Awaruite, a known methane catalyst (Horita and Berndt, 1999), was added to increase the overall rates of all experiments in order to boost the concentration for analysis and as an fO2 buffer appropriate for serpentinization. The experiments were held at T and P for approximately 160 hours. After each run, the capsule was placed in a gas vial and punctured with a needle. The contents of the vial were extracted via gas syringe and injected into gas chromatograph mass spectrometer (GC-MS). CH4 concentration in the 12 kbar run

  12. The dual action gas thrust bearing - A new high load bearing concept

    Science.gov (United States)

    Etsion, I.

    1976-01-01

    The principle of utilizing hydrodynamic effects in diverging films for improving load capacity in gas thrust bearings is discussed. A new concept of dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and improve their efficiency.

  13. Numerical Analyses of the Non-Newtonian Flow Performance and Thermal Effect on a Bearing Coated with a High Tin Content

    Directory of Open Access Journals (Sweden)

    K. Mehala

    2016-12-01

    Full Text Available The hydrodynamic bearings are stressed by severe workings conditions, such as speed, load, and the oil will be increasingly solicit by pressure and shear. The Newtonian behavior is far from being awarded in this case, the most loaded bearings operating at very high speeds; the shear rate of the oil is of higher order. A numerical analysis of the behavior of non-Newtonian fluid for plain cylindrical journal bearing finite dimension coated with antifriction material with a high tin content, for to facilitate the accommodation of the surfaces and save the silk of the shaft in the case of a contact. this analyses is implemented using the code-ANSYS CFX, by solving the energy equation with the finite difference method, considering that laminar regime and the fluid is non Newtonian by using the power law Ostwald model, the coefficient n is equal to 1.25 and for different model such as Bingham, cross and Hereshek-Bulkley model. This study aims to better predict the non-Newtonian behavior of the oil film in bearings operating under more severe conditions. The purpose conducted during this study is to predict the effect of non-Newtonian behavior of the film; the journal bearing operating under severe conditions, the speed of rotation varies from 1000 to 9000 rpm and the bearing working under radial load 2 to 10 kN. Temperature and the pressure within the fluid film assumed non-Newtonian are high, with a coefficient n greater than 1 that is to say for viscoelastic fluids.

  14. Bearing assemblies, apparatuses, and motor assemblies using the same

    Science.gov (United States)

    Sexton, Timothy N.; Cooley, Craig H.; Knuteson, Cody W.

    2015-12-29

    Various embodiments of the invention relate to bearing assemblies, apparatuses and motor assemblies that include geometric features configured to impart a selected amount of heat transfer and/or hydrodynamic film formation. In an embodiment, a bearing assembly may include a plurality of superhard bearing pads distributed circumferentially about an axis. At least some of the plurality of superhard bearing pads may include a plurality of sub-superhard bearing elements defining a bearing surface. At least some of the plurality of sub-superhard bearing elements may be spaced from one another by one or more voids to impart a selected amount of heat transfer and hydrodynamic film formation thereon during operation. The bearing assembly may also include a support ring that carries the plurality of superhard bearing pads. In addition, at least a portion of the sub-superhard bearing elements may extend beyond the support ring.

  15. Analytic Modeling of the Hydrodynamic, Thermal, and Structural Behavior of Foil Thrust Bearings

    Science.gov (United States)

    Bruckner, Robert J.; DellaCorte, Christopher; Prahl, Joseph M.

    2005-01-01

    A simulation and modeling effort is conducted on gas foil thrust bearings. A foil bearing is a self acting hydrodynamic device capable of separating stationary and rotating components of rotating machinery by a film of air or other gaseous lubricant. Although simple in appearance these bearings have proven to be complicated devices in analysis. They are sensitive to fluid structure interaction, use a compressible gas as a lubricant, may not be in the fully continuum range of fluid mechanics, and operate in the range where viscous heat generation is significant. These factors provide a challenge to the simulation and modeling task. The Reynolds equation with the addition of Knudsen number effects due to thin film thicknesses is used to simulate the hydrodynamics. The energy equation is manipulated to simulate the temperature field of the lubricant film and combined with the ideal gas relationship, provides density field input to the Reynolds equation. Heat transfer between the lubricant and the surroundings is also modeled. The structural deformations of the bearing are modeled with a single partial differential equation. The equation models the top foil as a thin, bending dominated membrane whose deflections are governed by the biharmonic equation. A linear superposition of hydrodynamic load and compliant foundation reaction is included. The stiffness of the compliant foundation is modeled as a distributed stiffness that supports the top foil. The system of governing equations is solved numerically by a computer program written in the Mathematica computing environment. Representative calculations and comparisons with experimental results are included for a generation I gas foil thrust bearing.

  16. Controllable Lubrication for Main Engine Bearings Using Mechanical and Piezoelectric Actuators

    DEFF Research Database (Denmark)

    Estupinan, Edgar; Santos, Ilmar

    2012-01-01

    Although mechatronic systems are nowadays implemented in a large number of systems in vehicles, active lubrication systems are still incipient in industrial applications. This study is an attempt to extend the active lubrication concept to combustion engines and gives a theoretical contribution...... to this field. One refers to active lubrication when conventional hydrodynamic lubrication is combined with dynamically modified hydrostatic lubrication. In this study, two different schemes for the oil injection system in actively lubricated main engine bearings are presented. The use of active lubrication...... located around the bearing surface. The main equations that govern the dynamics of the injection for a piezo-actuated oil injector and a mechanical-actuated oil injector are presented. It is shown how the dynamics of the oil injection system is coupled to the dynamics of the bearing fluid film through...

  17. Superconducting Meissner Effect Bearings for Cryogenic Turbomachines. Phase 2

    Science.gov (United States)

    1994-02-01

    significant sources of damping being squeeze - film damping in the gap and any structural damping in the bearings . The first of these damping sources is dependent... bearing / damper , that the gas bearing could be stabilized at cryogenic temperatures. Figure 12 shows the hybrid gas/Meissner-effect bearing . The tilt-pad...Housing TurbomachineAssembly with T Meissner Dampers and Self-Acting Tilt-Pad Gas Bearings In-Une Heaters Manually Controlled Uquid Nitrogen -j T

  18. Deformation Analysis of Fixed Bearing Inclined Plane Thrust Bearing

    Directory of Open Access Journals (Sweden)

    LI Yong--hai

    2017-02-01

    Full Text Available According to the theory of lubrication,Numerical simulation of the deformation of the thrust bearing of the fixed inclined plane was carried out,by finite element numerical analysis method and using the ANSYS software. The mathematical model of the oil film shape control equations about of the deformation and bearing is established. Analytical result showed that the force caused the tile surface generating concave deformation,and convex deformation increased with the height and the size of the load and bearing;Tile surface temperature generated convex deformation and increased with the height and the size of the temperature of bearing bush;The actual deformation of the tile surface is the superposition of the force and the thermal deformation. This conclusion can provide reference for the design and the application of thrust bearing,to reduce the tile surface,which is not conducive to the carrying capacity of the concave deformation.

  19. Analysis of the fluid flow and heat transfer in a thin liquid film in the presence and absence of gravity

    Science.gov (United States)

    Rahman, M. M.; Hankey, W. L.; Faghri, A.

    1991-01-01

    The hydrodynamic and thermal behavior of a thin liquid film flowing over a solid horizontal surface is analyzed for both plane and radially spreading flows. The situations where the gravitational force is completely absent and where it is significant are analyzed separately and their practical relevance to a micro-gravity environment is discussed. In the presence of gravity, in addition to Reynolds number, the Froude number of the film is found to be an important parameter that determines the supercritical and subcritical flow regimes and any associated hydraulic jump. A closed-form solution is possible under some flow situations, whereas others require numerical integration of ordinary differential equations. The approximate analytical results are found to compare well with the available two-dimensional numerical solutions.

  20. Computational Fluid Dynamic (CFD) analysis of axisymmetric plume and base flow of film/dump cooled rocket nozzle

    Science.gov (United States)

    Tucker, P. K.; Warsi, S. A.

    1993-01-01

    Film/dump cooling a rocket nozzle with fuel rich gas, as in the National Launch System (NLS) Space Transportation Main Engine (STME), adds potential complexities for integrating the engine with the vehicle. The chief concern is that once the film coolant is exhausted from the nozzle, conditions may exist during flight for the fuel-rich film gases to be recirculated to the vehicle base region. The result could be significantly higher base temperatures than would be expected from a regeneratively cooled nozzle. CFD analyses were conduced to augment classical scaling techniques for vehicle base environments. The FDNS code with finite rate chemistry was used to simulate a single, axisymmetric STME plume and the NLS base area. Parallel calculations were made of the Saturn V S-1 C/F1 plume base area flows. The objective was to characterize the plume/freestream shear layer for both vehicles as inputs for scaling the S-C/F1 flight data to NLS/STME conditions. The code was validated on high speed flows with relevant physics. This paper contains the calculations for the NLS/STME plume for the baseline nozzle and a modified nozzle. The modified nozzle was intended to reduce the fuel available for recirculation to the vehicle base region. Plumes for both nozzles were calculated at 10kFT and 50kFT.

  1. Theoretical and experimental comparisons for damping coefficients of a short-length open-end squeeze film damper

    Energy Technology Data Exchange (ETDEWEB)

    San Andres, L.A. [Texas A and M Univ., College Station, TX (United States). Mechanical Engineering Dept.

    1996-10-01

    Squeeze film dampers (SFD) provide load isolation and attenuate rotor vibrations in high speed turbomachinery. Operating parameters such as whirl frequency, amplitude of journal motion, and value of external pressure supply determine the SFD dynamic force response and its dissipation of mechanical energy. Measurements of pressure fields and fluid film forces in a fully submerged open-end squeeze film damper are presented for tests with rotor speeds to 5,000 cpm and low supply pressures. The damper has a clearance of 381 {micro}m (0.015 in.) and the journal describes circular centered orbits of amplitudes ranging from 30 to 50% of the bearing clearance. Experimental film pressures depict a vapor cavitation (close to zero absolute pressure) zone increasing in extent as the whirl frequency increases. Estimated fluid film forces from the measured pressure profiles are found to be proportional to whirl speed and lubricant viscosity. Test cross-coupled damping coefficients (C{sub rt}) are smaller than predicted values based on the short-length bearing model with a {pi} film cavitation assumption. The direct damping coefficients (C{sub tt}) are larger than theoretical values, especially at low frequencies where the dynamic cavitation region has not grown to half the circumferential flow extent. The experiments demonstrate the viscous character of the fluid film forces in a SFD test apparats where fluid inertia effects are minimal (squeeze film Reynolds number less than one). On the other hand, the extent of the cavitation zone appears to be dominant on the generation of fluid film forces.

  2. Hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  3. Performance of two-lobe hole-entry hybrid journal bearing system under the combined influence of textured surface and couple stress lubricant

    Science.gov (United States)

    Khatri, Chandra B.; Sharma, Satish C.

    2018-02-01

    Textured surface in journal bearings is becoming an important area of investigation during the last few years. Surface textures have the shapes of micro-dimple with a small diameter and depth having order of magnitude of bearing clearance. This paper presents the influence of couple stress lubricant on the circular and non-circular hole-entry hybrid journal bearing system and reports the comparative study between the textured and non-textured circular/non-circular hybrid journal bearing system. The governing Reynolds equation has been modified for the couple stress lubricant flow in the clearance of bearing and journal. The FEM technique has been applied to solve the modified Reynolds equation together with restrictor flow equation. The numerically simulated results indicate that the influence of couple stress lubricant is significantly more in textured journal bearing than that of non-textured journal bearing. Further, it has been observed that the textured two-lobe (δ = 1.1) hybrid journal bearing lubricated with couple stress lubricant provides larger values of fluid film stiffness coefficients and stability threshold speed against other bearings studied in the present paper.

  4. Hydrodynamic Lubrication Analysis Of Slider Bearings Lubricated ...

    African Journals Online (AJOL)

    Hydrodynamic Lubrication Analysis Of Slider Bearings Lubricated With Micropolar Fluids. ... In this paper, a theoretical study of the effect of micropolar lubricants on the performance characteristics of wide inclined slider bearings is presented. The finite element method and Gauss Seidel iterative procedure have been used ...

  5. Protecting a Ball-Bearing-Deflection Monitor

    Science.gov (United States)

    Kuhr, George A.

    1987-01-01

    Deflectometer probe monitors deflection of ball-bearing race in liquid oxygen with aid of small window or diaphragm. Diaphragm or window isolates optical deflectometer from liquid oxygen or other fluid in ball bearing. At high pressures, diaphragm integral part of housing preferable to window, since there would be no leakage.

  6. Identification of bearing supports' force coefficients from rotor responses due to imbalances and impact loads

    Science.gov (United States)

    de Santiago Duran, Oscar Cesar

    Experimental identification of fluid film bearing parameters is vital to validate predictions from often restrictive computational fluid film bearing models and is also promising for condition monitoring and troubleshooting. This dissertation presents the analytical bases of two procedures for bearing supports parameter identification with potential for in-situ implementation. Bearing support coefficients are derived from measurements of rotor responses to impact loads and due to calibrated imbalances in characteristic planes. Subsequent implementation of the procedures to measurements performed in a rigid massive rotor traversing two critical speeds provides force coefficients for a novel bearing support comprising a tilting pad bearing (TPJB ) in series with an integral squeeze film damper (SFD). At a constant rotor speed, the first method requires impacts loads exerted along two lateral planes for identification of frequency-dependent force coefficients. Simulation numerical examples show the method is reliable with a reduced sensitivity to noise as the number of impacts increases (frequency averaging). In the experiments, an ad-hoc fixture delivers impacts to the rotor middle disk at speeds of 2,000 and 4,000 rpm. The experimentally identified force coefficients are in close agreement with predicted coefficients for the series support TPJB-SFD. In particular, damping coefficients are best identified around the system first natural frequency. Bearing stiffness are correctly identified in the low frequency range, but show a marked reduction at higher frequencies apparently due to inertial effects not accounted for in the model. Measurements of rotor response to calibrated imbalances allow identification of speed-dependent force coefficients. The procedure requires a minimum of two different imbalance distributions for identification of force coefficients from the two bearing supports. The rotor responses show minimal cross-coupling effects, as also predicted by

  7. Analysis of Hard Thin Film Coating

    Science.gov (United States)

    Shen, Dashen

    1998-01-01

    MSFC is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using electron cyclotron resonance chemical vapor deposition (ECRCVD) to deposit hard thin film an stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

  8. Identification of dynamic properties of radial air-foil bearings

    NARCIS (Netherlands)

    Arora, Vikas; Arora, V.; van der Hoogt, Peter; Aarts, Ronald G.K.M.; de Boer, Andries

    2010-01-01

    Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are

  9. Bearing structures

    International Nuclear Information System (INIS)

    Lee, A.S.; Preece, G.E.

    1988-01-01

    A hydrostatic bearing for the lower end of the vertical shaft of a sodium pump comprises a support shell encircling the shaft and a bush located between the shell and shaft. Liquid sodium is fed from the pump outlet to the bush/shaft and bush/shell interfaces to provide hydrostatic support. The bush outer surface and the shell inner surface are of complementary part-spherical shape and the bush floats relative to the shaft so that the bush can align itself with the shaft axis. Monitoring of the relative rotational speed of the bush with respect to the shaft (such rotation being induced by the viscous drag forces present) is also performed for the purposes of detecting abnormal operation of the bearing or partial seizure, at least one magnet is rotatable with the bush, and a magnetic sensor provides an output having a frequency related to the speed of the bush. (author)

  10. On the computation of electrical resistance of hydrodynamic journal bearing

    Directory of Open Access Journals (Sweden)

    Eleonora Pop

    2014-12-01

    Full Text Available The paper approaches the mathematical model of electrical resistance of hydrodynamic journal bearing under different parameters of operation so as to predict bearing performance and safe load carrying capacity. The currents circulating in the journal bearing of electrical machine causes reducing of lifespan by appearance of pitting on their surface and the degradation of the lubricant. In a hydrodynamic journal bearing, the zone of minimum film thickness, load-carrying oil film varies along the circumference of a bearing through its length. This has been found to form a capacitor of varying capacitance between the journal and the bearings dependent on permittivity of the lubricant used, the bearing length, the eccentricity ratio and the clearance ratio. Besides this, load-carrying on oil film offers resistance that depends on operating parameters and resistivity of the lubricant.

  11. Camshaft bearing arrangement

    Energy Technology Data Exchange (ETDEWEB)

    Aoi, K.; Ozawa, T.

    1986-06-10

    A bearing arrangement is described for the camshaft of an internal combustion engine or the like which camshaft is formed along its length in axial order with a first bearing surface, a first cam lobe, a second bearing surface, a second cam lobe, a third bearing surface, a third cam lobe and a fourth bearing surface, the improvement comprising first bearing means extending around substantially the full circumference of the first bearing surface and journaling the first bearing surface, second bearing means extending around substantially less than the circumference of the second bearing surface and journaling the second bearing surface, third bearing means extending around substantially less than the circumference of the third bearing surface and journaling the third bearing surface, and fourth bearing means extending around substantially the full circumference of the fourth bearing surface and journaling the first bearing surface.

  12. Field Tests on Hydrodynamic and Hybrid Operation of a Bidirectional Thrust Bearing of a Pump-Turbine

    Directory of Open Access Journals (Sweden)

    Michał Wasilczuk

    2017-12-01

    Full Text Available In vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Due to the bidirectional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The research into fluid film thrust bearings has been quite extensive over the years, comprising theoretical studies of bearing properties with the use of more and more sophisticated calculation codes. On the other hand, the availability of experimental field data on bearing operation is limited, for obvious reasons. In this paper the authors present part of the results of extensive field tests of a large bearing of a pump-turbine they have conducted in a pumped storage power plant. Hopefully this data will be of interest to other researchers to compare theoretical predictions to measurement data.

  13. Vibration Control in Turbomachinery Using Active Magnetic Journal Bearings

    Science.gov (United States)

    Knight, Josiah D.

    1996-01-01

    The effective use of active magnetic bearings for vibration control in turbomachinery depends on an understanding of the forces available from a magnetic bearing actuator. The purpose of this project was to characterize the forces as functions shaft position. Both numerical and experimental studies were done to determine the characteristics of the forces exerted on a stationary shaft by a magnetic bearing actuator. The numerical studies were based on finite element computations and included both linear and nonlinear magnetization functions. Measurements of the force versus position of a nonrotating shaft were made using two separate measurement rigs, one based on strain gage measurement of forces, the other based on deflections of a calibrated beam. The general trends of the measured principal forces agree with the predictions of the theory while the magnitudes of forces are somewhat smaller than those predicted. Other aspects of theory are not confirmed by the measurements. The measured forces in the normal direction are larger than those predicted by theory when the rotor has a normal eccentricity. Over the ranges of position examined, the data indicate an approximately linear relationship between the normal eccentricity of the shaft and the ratio of normal to principal force. The constant of proportionality seems to be larger at lower currents, but for all cases examined its value is between 0.14 and 0.17. The nonlinear theory predicts the existence of normal forces, but has not predicted such a large constant of proportionality for the ratio. The type of coupling illustrated by these measurements would not tend to cause whirl, because the coupling coefficients have the same sign, unlike the case of a fluid film bearing, where the normal stiffness coefficients often have opposite signs. They might, however, tend to cause other self-excited behavior. This possibility must be considered when designing magnetic bearings for flexible rotor applications, such as gas

  14. Nonlinear Analysis of Squeeze Film Dampers Applied to Gas Turbine Helicopter Engines.

    Science.gov (United States)

    1980-11-01

    squeeze film bearings have been designed for the Centritech rotor. These damper - bearings have... squeeze film damper bearings is presented. The method incorporates a finite-length correction factor which modifies the nonlinear forces obtained from...design and application of a squeeze film damper for a single mass flexible rotor in journal bearings including before application and after

  15. RESEARCH RIG FOR EXAMINATION OF PRESSURE IN HYRDODYNAMIC OIL FILM

    Directory of Open Access Journals (Sweden)

    Wojciech HORAK

    2014-06-01

    Full Text Available The paper presents a concept of a didactic research rig for investigation and visualization of pressure distribution in an oil film of a journal fluid friction slide bearing. The rig being presented may be used during classes on subjects associated machine design. The paper presents an idea of a specific design, using an asynchronic motor with a long shaft, on which the slide bearing assembly is fixed. The design is elastic and allows many modifications of the construction. The possible modifications are presented in the summary part of the paper. The paper also presents ideas for development of the design, either to enable measurements of additional physical values, or presentation of specific cases of slide bearings operation.

  16. Exploration of fluid dynamic indicators/causative factors in the formation of tower structures in staphylococci bacteria bio-films

    Science.gov (United States)

    Sherman, Erica; Derek, Moormeier; Bayles, Kenneth; Wei, Timothy

    2015-11-01

    Staphylococcus aureus bacteria form biofilms with distinct structures that facilitate their ability to tolerate treatment and to spread within the body. As such, staph infections represent one of the greatest threats to post-surgery patients. It has been found that flow conditions play a significant role in the developmental and dispersal activity of a biofilm. The coupling between the growing biofilm and surrounding flow, however, is not well understood. Indeed, little is know why bacteria form tower structures under certain conditions but not in a predictable way. μ-PTV measurements were made in a microchannel to try to identify fluid dynamic indicators for the formation of towers in biofilm growth. Preliminary experiments indicated changes in the near wall flow up to five hours before a tower formed. The reason for that is the target of this investigation. Staphylococcus aureus bacteria were cultured in the Bioflux Fluxion channel and subjected to a steady shear rate of 0.5 dynes. In addition to μ-PTV measurement, nuclease production and cell number density counts were observed prior to and during tower development. These were compared against measurements made under the same nominal flow conditions where a tower did not form.

  17. Dual-action gas thrust bearing for improving load capacity

    Science.gov (United States)

    Etsion, I.

    1976-01-01

    The principle of utilizing hydrodynamic effects in diverging films to improve the load carrying capacity in gas thrust bearings is discussed. A new concept of a dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and can improve their efficiency.

  18. Wave Journal Bearing. Part 2: Experimental Pressure Measurements and Fractional Frequency Whirl Threshold for Wave and Plain Journal Bearings

    Science.gov (United States)

    Walker, James F.; Dimofte, Florin; Addy, Harold E., Jr.

    1995-01-01

    A new hydrodynamic bearing concept, the wave journal bearing, is being developed because it has better stability characteristics than plain journal bearings while maintaining similar load capacity. An analysis code to predict the steady state and dynamic performance of the wave journal bearing is also part of the development. To verify numerical predictions and contrast the wave journal bearing's stability characteristics to a plain journal bearing, tests were conducted at NASA Lewis Research Center using an air bearing test rig. Bearing film pressures were measured at 16 ports located around the bearing circumference at the middle of the bearing length. The pressure measurements for both a plain journal bearing and a wave journal bearing compared favorably with numerical predictions. Both bearings were tested with no radial load to determine the speed threshold for self-excited fractional frequency whirl. The plain journal bearing started to whirl immediately upon shaft start-up. The wave journal did not incur self-excited whirl until 800 to 900 rpm as predicted by the analysis. Furthermore, the wave bearing's geometry limited the whirl orbit to less than the bearing's clearance. In contrast, the plain journal bearing did not limit the whirl orbit, causing it to rub.

  19. Measuring fluid pressure

    International Nuclear Information System (INIS)

    Lee, A.S.

    1978-01-01

    A method and apparatus are described for measuring the pressure of a fluid having characteristics that make it unsuitable for connection directly to a pressure gauge. The method is particularly suitable for the periodic measurement of the pressure of a supply of liquid Na to Na-lubricated bearings of pumps for pumping Na from a reservoir to the bearing via a filter, the reservoir being contained in a closed vessel containing an inert blanket gas, such as Ar, above the Na. (UK)

  20. Fundamentals of fluid lubrication

    Science.gov (United States)

    Hamrock, Bernard J.

    1991-01-01

    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.

  1. STUDIES OF BASIC BEARING DESIGNS FOR AN ADVANCED GYRO TEST TURNTABLE.

    Science.gov (United States)

    pair of opposing-thrust air bearings, an eight-pad oil journal bearing , and an eight-pad air journal bearing . In addition to solving for flow, film...thickness and stiffness, a detailed analysis of the load capabilities of the oil journal bearing is carried out, as well as an optimization of the

  2. Influences of Lubricant Viscosity Ratio on Static Characteristics of Hydrostatic Thrust Bearing

    Directory of Open Access Journals (Sweden)

    Liao Chuan-Chieh

    2017-01-01

    Full Text Available This paper uses numerical simulation to study the influences of viscosity ratio on the static characteristics of hydrostatic thrust bearing compensated by various restrictors. The design parameters of open type hydrostatic bearing include: effective area, supply pressure, restriction constants of restrictor and bearing pad, and specific value of average viscosity of the lubricant passing through restrictor and bearing pad film. The optimal design requirements of restrictors and hydrostatic bearing and the corresponding range of design parameters for excellent bearing characteristics can be obtained from the relationships between these design parameters together with their composed parameters and ratios, and the static load capacity and film stiffness and worktable displacement of hydrostatic bearing. Fixing the other design parameters and changing viscosity ratio, the simulation results depict that the lubricant viscosity during restrictor being greater than that in bearing pad film will make the load capacity decrease, but will improve the film static stiffness.

  3. Analysis of thermoelastohydrodynamic performance of journal misaligned engine main bearings

    Science.gov (United States)

    Bi, Fengrong; Shao, Kang; Liu, Changwen; Wang, Xia; Zhang, Jian

    2015-05-01

    To understand the engine main bearings' working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic(TEHD) reaction on engine main bearings is investigated. The calculated method of main bearing's thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic(EHD) and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.

  4. Operating characteristics of a cantilever-mounted resilient-pad gas-lubricated thrust bearing

    Science.gov (United States)

    Nemeth, Z. N.

    1979-01-01

    A resilient-pad gas thrust bearing consisting of pads mounted on cantilever beams was tested to determine its operating characteristic. The bearing was run at a thrust load of 74 newtons to a speed of 17000 rpm. The pad film thickness and bearing friction torque were measured and compared with theory. The measured film thickness was less than that predicted by theory. The bearing friction torque was greater than that predicted by theory.

  5. Operating characteristics of heavy loaded cylindrical journal bearing with variable axial profile

    Directory of Open Access Journals (Sweden)

    Stanislaw Strzelecki

    2005-12-01

    Full Text Available During the operation of turbounit its bearings displace as a result of heat elongation of bearings supports. It changes the static deflection line of rotor determined during assembly of the turbounit, causing an increase in the stresses on the bearing edges and a decrease in the dynamic state of the machine. One of possibilities to avoid the edge stresses is to apply the bearings with variable axial profile, e.g. hyperboloidal, convex profile in the axial cross-section of bearing. Application of journal bearings with hyperboloidal profile allows to extend the bearing operation range without the stress concentration on the edges of bush. These bearings successfully carry the extreme load in conditions of misaligned axis of journal and the bush eliminating the necessity of using self-aligning bearings. Operating characteristics of bearing include the resulting force, attitude angle, oil film pressure and temperature distributions, minimum oil film thickness, maximum oil film temperature. In literature there is a lack of data on the operating characteristics of heavy loaded hyperboloidal journal bearings operating at the conditions of adiabatic oil film and static equilibrium position of the journal. For the hyperboloidal bearing the operating characteristics have been obtained. Different values of length to diameter ratio, assumed shape and inclination ratio coefficients have been assumed. Iterative solution of the Reynolds', energy and viscosity equations was applied. Adiabatic oil film, laminar flow in the bearing gap as well as aligned and misaligned orientation of journal in the bush were considered.

  6. Selection and evaluation of blood- and tribologically compatible journal bearing materials.

    Science.gov (United States)

    Murray, S F; Calabrese, S J; Malanoski, S B; Golding, L R; Smith, W A; Hamby, M

    1997-01-01

    A critical issue in the Cleveland Clinic Foundation (CCF) Innovative Ventricular Assist System (IVAS) blood pump is the selection of materials for the blood-lubricated journal bearing. Under normal operating conditions, the journal bearing geometry creates a thick blood film that separates the rotating and stationary surfaces. However, since start-up and certain transients could cause temporary contact, the material pair selected for these surfaces must be both tribologically and blood compatible. Combinations of two biocompatible alloys were tested: a titanium-zirconium-niobium alloy (Ti-13Zr-13Nb) and a zirconium-niobium alloy (Zr-2.5Nb). A standard pin-on-disk tester was used, with the contact surfaces lubricated by glycerol/saline mixtures simulating the viscosity range of blood. One test series evaluated start-up conditions; the other modeled a high-speed rub that might occur if the fluid film broke down. Results showed that the preoxidized Zr-2.5Nb pin/Ti-13Zr-13Nb disk combination was superior at all sliding velocities; a self-mated Zr-2.5Nb pair also showed promise. The oxide film on a self-mated Ti-13Zr-13Nb pair, and a Ti-13Zr-13Nb pin and Zr-2.5Nb disk combination did not show adequate wear life. More work remains to explain distinct performance differences of certain combinations, with more data needed on mechanical properties of thin, hard coatings on softer metal substrates.

  7. An Air Bearing Balance with 1-DOF Spin Capability

    National Research Council Canada - National Science Library

    Magill, J. C; McManus, K. R; Malonson, M. R; Ziehler, J. A; Hinds, M. F

    1998-01-01

    .... Five load components are measured by sensing pressures in the air bearing film. The sixth component - rolling torque - is determined by sensing the current needed by the brushless spin motor to maintain a given rotation rate...

  8. The preliminary design of bearings for the control system of a high-temperature lithium-cooled nuclear reactor

    Science.gov (United States)

    Yacobucci, H. G.; Waldron, W. D.; Walowit, J. A.

    1973-01-01

    The design of bearings for the control system of a fast reactor concept is presented. The bearings are required to operate at temperatures up to 2200 F in one of two fluids, lithium or argon. Basic bearing types are the same regardless of the fluid. Crowned cylindrical journals were selected for radially loaded bearings and modified spherical bearings were selected for bearings under combined thrust and radial loads. Graphite and aluminum oxide are the materials selected for the argon atmosphere bearings while cermet compositions (carbides or nitrides bonded with refractory metals) were selected for the lithium lubricated bearings. Mounting of components is by shrink fit or by axial clamping utilizing differential thermal expansion.

  9. Film history in the making : Film historiography, digitised archives and digital research dispositifs

    NARCIS (Netherlands)

    Olesen, C.G.

    2017-01-01

    The dissertation investigates the implications which digitisation bears upon scholarly film historiography. It addresses a deficit in our critical understanding of knowledge production with digital methods and their representational practices in film historical research, attending in particular data

  10. Nonlinear dynamics of a support-excited flexible rotor with hydrodynamic journal bearings

    Science.gov (United States)

    Dakel, Mzaki; Baguet, Sébastien; Dufour, Régis

    2014-05-01

    The major purpose of this study is to predict the dynamic behavior of an on-board rotor mounted on hydrodynamic journal bearings in the presence of rigid support movements, the target application being turbochargers of vehicles or rotating machines subject to seismic excitation. The proposed on-board rotor model is based on Timoshenko beam finite elements. The dynamic modeling takes into account the geometric asymmetry of shaft and/or rigid disk as well as the six deterministic translations and rotations of the rotor rigid support. Depending on the type of analysis used for the bearing, the fluid film forces computed with the Reynolds equation are linear/nonlinear. Thus the application of Lagrange's equations yields the linear/nonlinear equations of motion of the rotating rotor in bending with respect to the moving rigid support which represents a non-inertial frame of reference. These equations are solved using the implicit Newmark time-step integration scheme. Due to the geometric asymmetry of the rotor and to the rotational motions of the support, the equations of motion include time-varying parametric terms which can lead to lateral dynamic instability. The influence of sinusoidal rotational or translational motions of the support, the accuracy of the linear 8-coefficient bearing model and the interest of the nonlinear model for a hydrodynamic journal bearing are examined and discussed by means of stability charts, orbits of the rotor, time history responses, fast Fourier transforms, bifurcation diagrams as well as Poincaré maps.

  11. Experimental and analytical performance evaluation of short circular hydrodynamic journal bearings used in rotary blood pumps.

    Science.gov (United States)

    Boehning, Fiete; Timms, Daniel; Hsu, Po-Lin; Schmitz-Rode, Thomas; Steinseifer, Ulrich

    2013-10-01

    Rotary blood pumps (RBPs) have demonstrated considerable promise while treating heart failure patients, such that they are being placed at an earlier stage of the disease. These devices may therefore be required to operate for prolonged durations which yields the need for RBPs exhibiting high durability, reliability, and blood compatibility. Noncontacting bearings, utilizing magnetic and/or hydrodynamic suspension techniques, appear to provide a suitable solution to these challenges. Hydrodynamic suspension has the advantage that it does not need feedback control systems. Among various hydrodynamic bearing types, the circular journal bearing has the particular benefit of easy manufacturing. This study presents methods to evaluate the performance of short (length to diameter ratio 0.02 can provide sufficient fluid film thicknesses and low shear rates. The measurements were further used to evaluate the bearings' stability. The estimation of the stability threshold drawn in relation to a modified stability index and the equilibrium eccentricity of the rotor allows the prediction of stability for short circular HJB designs under full Sommerfeld condition. © 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.

  12. HIGHER ORDER APPROXIMATIONS IN THE ASYMPTOTIC SOLUTION OF THE REYNOLDS EQUATION FOR SLIDER BEARINGS AT HIGH BEARING NUMBERS.

    Science.gov (United States)

    is 0 (1/lambda squared), and the procedure for obtaining higher order terms is discussed. Results are given for the case of a converging film thickness with a parabolic shape and for a partial arc journal bearing . (Author)

  13. Passive magnetic bearing configurations

    Science.gov (United States)

    Post, Richard F [Walnut Creek, CA

    2011-01-25

    A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

  14. Design optimization of deep groove ball bearings using crowding ...

    Indian Academy of Sciences (India)

    The considered objectives are maximizing dynamic and static load bearing capacities and minimizing elastohydrodynamic film thickness. The technique is applied to bearings used in transmission system of a tractor for the purpose of farming. Pareto optimal solutions are obtained using the proposed technique. The results ...

  15. The Thermohydrodynamic Analysis of Sliding Bearing High-Speed Motorized Spindle by Rotor Dynamic

    Directory of Open Access Journals (Sweden)

    Li Songsheng

    2017-01-01

    Full Text Available This is paper presents thermohydrodynamic characteristics of high speed motorized spindle sliding bearing rotor system. The dynamic characteristic of the oil film bearing is affected by temperature increment, thereby affecting the high-speed spindle rotor system dynamics. This study applied the hydrodynamic lubrication theory, the influence of temperature on the viscosity of lubricating oil, associated with the bearing stiffness, oil film damping and other performance parameters, is considered in generalized Reynolds equation of oil film bearing. The theoretical model of the sliding bearing rotor system is established by using the transfer matrix method to analyze the dynamic characteristic and verified by experiments. The results show the high temperature environment in the motorized spindle and the friction of the bearing lead to oil temperature rise and viscosity reduction, which influences the bearing capacity, stiffness and damping, hence impact on the critical speeds and modal shapes of the sliding bearing rotor system.

  16. Improved gas thrust bearings

    Science.gov (United States)

    Anderson, W. J.; Etsion, I.

    1979-01-01

    Two variations of gas-lubricated thrust bearings extend substantially load-carrying range over existing gas bearings. Dual-Action Gas Thrust Bearing's load-carrying capacity is more than ninety percent greater than that of single-action bearing over range of compressibility numbers. Advantages of Cantilever-mounted Thrust Bearing are greater tolerance to dirt ingestion, good initial lift-off characteristics, and operational capability over wide temperature range.

  17. Nonlinear effects caused by coupling misalignment in rotors equipped with journal bearings

    Science.gov (United States)

    Pennacchi, Paolo; Vania, Andrea; Chatterton, Steven

    2012-07-01

    Misalignment is one of the most common sources of trouble of rotating machinery when rigid couplings connect the shafts. Ideal alignment of the shafts is difficult to be obtained and rotors may present angular and/or parallel misalignment (defined also as radial misalignment or offset). During a complete shaft revolution, a periodical change of the bearings load occurs in hyperstatic shaft-lines, if coupling misalignment between the shafts is excessive. If the rotating machine is equipped with fluid-film journal bearings, the change of the loads on the bearing causes also the variation of their instantaneous dynamic characteristics, i.e. damping and stiffness, and the complete system cannot be considered any longer as linear. Despite misalignment is often observed in the practice, there are relatively few studies about this phenomenon in literature and their results are sometimes conflicting. The authors aim at modeling accurately this phenomenon, for the first time in this paper, and giving pertinent diagnostic information. The proposed method is suitable for every type of shaft-line supported by journal bearings. A finite element model is used for the hyperstatic shaft-line, while bearing characteristics are calculated by integrating Reynolds equation as a function of the instantaneous load acting on the bearings, caused also by the coupling misalignment. The results obtained by applying the proposed method are shown by means of the simulation, in the time domain, of the dynamical response of a hyperstatic shaft-line. Nonlinear effects are highlighted and the spectral components of the system response are analyzed, in order to give diagnostic information about the signature of this type of fault.

  18. Full Life Wind Turbine Gearbox Lubricating Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Lutz, Glenn A.; Jungk, Manfred; Bryant, Jonathan J.; Lauer, Rebecca S.; Chobot, Anthony; Mayer, Tyler; Palmer, Shane; Kauffman, Robert E.

    2012-02-28

    Industrial gear box lubricants typically are hydrocarbon based mineral oils with considerable amounts of additives to overcome the lack of base fluid properties like wear protection, oxidation stability, load carrying capacity, low temperature solidification and drop of viscosity at higher temperatures. For today's wind turbine gearboxes, the requirements are more severe and synthetic hydrocarbon oils are used to improve on this, but all such hydrocarbon based lubricants require significant amounts of Extreme Pressure (EP) additives to meet performance requirements. Perfluoropolyether (PFPE) fluids provide load carrying capacity as an inherent property. During the course of the project with the main tasks of 'Establish a Benchmark', 'Lubricant Evaluation', 'Full Scale Gearbox Trial' and 'Economic Evaluation', the PAO Reference oil exhibited significant changes after laboratory gear testing, in service operation in the field and full scale gearbox trial. Four hydrocarbon base oils were selected for comparison in the benchmarking exercise and showed variation with respect to meeting the requirements for the laboratory micro-pitting tests, while the PFPE fluid exceeded the requirements even with the material taken after the full scale gear box trial. This is remarkable for a lubricant without EP additives. Laboratory bearing tests performed on the PFPE fluids before and after the full scale gear box trial showed the results met requirements for the industry standard. The PFPE fluid successfully completed the full scale gear box test program which included baseline and progressive staged load testing. The evaluation of gears showed no micro-pitting or objectionable wear. By the final stage, lubricant film thickness had been reduced to just 21% of its original value, this was by design and resulted in a lambda ratio of well below 1. This test design scenario of a low lambda ratio is a very undesirable lubrication condition

  19. Development of hydrodynamic micro-bearings

    Science.gov (United States)

    Wang, P.; Zhang, J.; Spikes, H. A.; Reddyhoff, T.; Holmes, A. S.

    2016-11-01

    This paper describes the modelling and testing of mm-scale hydrodynamic bearings which are being developed to improve the efficiency of a cm-scale turbine energy harvester, whose efficiency was previously limited by poorly lubricated commercial jewel-bearings. The bearings were fabricated using DRIE and their performance was assessed using a custom built MEMS tribometer. Results demonstrate that acceptably low friction is achieved when low viscosity liquid lubricants are used in combination with an appropriate choice of friction modifier additive. Further reduction in friction is demonstrated when the step height of bearing is adjusted in accordance with hydrodynamic theory. In parallel with the experiments, hydrodynamic lubricant modelling has been carried out to predict and further optimize film thickness and friction performance. Modelling results are presented and validated against experimental friction data.

  20. Testing of bearing materials for large two-stroke marine diesel engines

    DEFF Research Database (Denmark)

    Vølund, Anders; Klit, Peder; Persson, Sebastian

    2017-01-01

    In large two-stroke marine diesel engines, bearings are designed to last the lifetime of the engine. The design has shown very good service experiences. The design parameters of the main bearings are, among others, based on the average maximum specific load which the bearing should operate under....... In general, the frictional loss is less than 1% of the nominal power of the engine but is still a target for optimization. Fatigue mechanisms of bearing lining material are not fully understood and the design limits with regards to minimum oil film thickness, max oil film pressure and oil film pressure...

  1. Experiments with needle bearings

    Science.gov (United States)

    Ferretti, Pericle

    1933-01-01

    Experiments and results are presented in testing needle bearings, especially in comparison with roller bearings. Reduction in coefficient of friction is discussed as well as experimental methods and recording devices.

  2. Hydrodynamic journal bearings: Capacity, wear, and lubrication. (Latest citations from Fluidex data base). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    1992-08-01

    The bibliography contains citations concerning the characteristics of hydrodynamic journal bearings. Bearing load, lubrication, thermal effects, tolerance to misalignment, cavitation, and design are discussed. Studies on the effect of temperature and heat transfer on hydrodynamic films are presented. The impact of surface roughness on hydrodynamic journal bearing performance is also examined. (Contains 250 citations and includes a subject term index and title list.)

  3. A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF A SPHERICAL GAS JOURNAL BEARING

    Science.gov (United States)

    An externally pressurized spherical gas journal bearing , which has multiple spherically surfaced pads, was designed and fabricated for use as a three...model bearing, which duplicates the lubricating film of a journal bearing pad, was constructed in order to obtain experimental data to verify the

  4. Modeling and Analysis of the Static Characteristics and Dynamic Responses of Herringbone-grooved Thrust Bearings

    Science.gov (United States)

    Yu, Yunluo; Pu, Guang; Jiang, Kyle

    2017-12-01

    This paper describes a theoretical investigation of static and dynamic characteristics of herringbone-grooved air thrust bearings. Firstly, Finite Difference Method (FDM) and Finite Volume Method (FVM) are used in combination to solve the non-linear Reynolds equation and to find the pressure distribution of the film and the total loading capacity of the bearing. The influence of design parameters on air film gap characteristics, including the air film thickness, depth of the groove and rotating speed, are analyzed based on the FDM model. The simulation results show that hydrostatic thrust bearings can achieve a better load capacity with less air consumption than herringbone grooved thrust bearings at low compressibility number; herringbone grooved thrust bearings can achieve a higher load capacity but with more air consumption than hydrostatic thrust bearing at high compressibility number; herringbone grooved thrust bearings would lose stability at high rotating speeds, and the stability increases with the depth of the grooves.

  5. Analysis of short squeeze film dampers with a central groove

    Science.gov (United States)

    San Andres, Luis A.

    1992-10-01

    A novel analysis for the dynamic force response of a squeeze film damper with a central feeding groove considers the dynamic flow interaction between the squeeze film lands and the feeding groove. For small amplitude centered motions and based on the short bearing model, corrected values for the damping and inertia force coefficients are determined. Correlations with existing experimental evidence is excellent. Analytical results show that the grooved-damper behaves at low frequencies as a single land damper. Dynamic force coefficients are determined to be frequency dependent. Analytical predictions show that the combined action of fluid inertia and groove volume-liquid compressibility affects the force coefficients for dynamic excitation at large frequencies.

  6. Design optimization and probabilistic analysis of a hydrodynamic journal bearing

    Science.gov (United States)

    Liniecki, Alexander G.

    1990-01-01

    A nonlinear constrained optimization of a hydrodynamic bearing was performed yielding three main variables: radial clearance, bearing length to diameter ratio, and lubricating oil viscosity. As an objective function a combined model of temperature rise and oil supply has been adopted. The optimized model of the bearing has been simulated for population of 1000 cases using Monte Carlo statistical method. It appeared that the so called 'optimal solution' generated more than 50 percent of failed bearings, because their minimum oil film thickness violated stipulated minimum constraint value. As a remedy change of oil viscosity is suggested after several sensitivities of variables have been investigated.

  7. Investigation of Shear-Thinning Behavior on Film Thickness and Friction Coefficient of Polyalphaolefin Base Fluids With Varying Olefin Copolymer Content

    Energy Technology Data Exchange (ETDEWEB)

    Zolper, Thomas J.; He, Yifeng; Delferro, Massimiliano; Shiller, Paul; Doll, Gary; LotfizadehDehkordi, Babak; Ren, Ning; Lockwood, Frances; Marks, Tobin J.; Chung, Yip-Wah; Greco, Aaron; Erdemir, Ali; Wang, Qian

    2016-08-11

    This study investigates the rheological properties, elastohydrodynamic (EHD) film-forming capability, and friction coefficients of low molecular mass poly-alpha-olefin (PAO) base stocks with varying contents of high molecular mass olefin copolymers (OCPs) to assess their shear stability and their potential for energy-efficient lubrication. Several PAO-OCP mixtures were blended in order to examine the relationship between their additive content and tribological performance. Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize the molecular masses and structures, respectively. Density, viscosity, EHD film thickness, and friction were measured at 303 K, 348 K, and 398 K. Film thickness and friction were studied at entrainment speeds relevant to the boundary, mixed, and full-film lubrication regimes. The PAO-OCP mixtures underwent temporary shear-thinning resulting in decreases in film thickness and hydrodynamic friction. These results demonstrate that the shear characteristics of PAO-OCP mixtures can be tuned with the OCP content and provide insight into the effects of additives on EHD characteristics.

  8. Teddy Bear Stories

    DEFF Research Database (Denmark)

    van Leeuwen, Theo; Caldas-Coulthardt, Carmen

    2014-01-01

    This paper presents a semiotic analysis of a key cultural artefact, the teddy bear. After introducing the iconography of the teddy bear, it analyses different kinds of stories to show how teddy bears are endowed with meaning in everyday life: stories from children's books, reminiscenses by adults...... about their childhood teddy bears, and children's accounts of what they do with teddy bears, both written for school and told 'out of school', The chapter sees teddy bears as artefacts that provide a cultural channeling for the child's need of a transitional object and argues that the meanings of teddy...... bears have traditionally centred on interpersonal relations within the nuclear family, but have recently been institutionalized and commercialized....

  9. Global dynamics of shaft lines of turbo-machineries coupled to surrounding fluids: application to the case of fluid sheets; Dynamique globale des lignes d'arbres de turbomachines couplees aux fluides environnants: application au cas des lames fluides

    Energy Technology Data Exchange (ETDEWEB)

    Lornage, D.

    2001-12-15

    Shaft lines of turbo-machineries have to stand increasing reliability, efficiency and safety requirements. A precise modeling of the rotating parts with all possible coupling has become necessary. In this context, this work aims to develop a global modeling of rotating wheel/shaft system inside a surrounding fluid in order to foresee its dynamical behaviour. The use and advantage of Eulerian, Lagrangian and mixed (arbitrary Lagrangian Eulerian - ALE) formulations is recalled first. A bibliographic synthesis of the classical techniques used in structure mechanics and of coupling techniques for rotating machines is presented. The coupling technique retained is presented. It uses fluid and structure models independently developed and validated. The structure domain is discretized by the finite-element method. The fluid domain is discretized by the finite-difference method taking into consideration the hypotheses linked with thin films. A modal base projection combined with a mesh at the fluid-structure interface allows an efficient, adaptable and evolutive coupling. Finally, the method is applied to 3 test-cases. The first two ones comprise a shaft/disc system coupled to a fluid sheet between the disc and the casing and to an hydrodynamic bearing. Both cases allow a first validation of the coupling method. The third case aims to study a structure closer to a real system made of a shaft and a wheel coupled to a fluid sheet between a flange and a casing. These three applications allow to show the trends linked with the fluid effects and the coupling between the flexible sub-parts of the structure. (J.S.)

  10. Omental torsion in a captive polar bear (Ursus maritimus).

    Science.gov (United States)

    Mendez-Angulo, Jose L; Funes, Francisco J; Trent, Ava M; Willette, Michelle; Woodhouse, Kerry; Renier, Anna C

    2014-03-01

    This is the first case report of an omental torsion in a polar bear (Ursus maritimus). A captive, 23-yr-old, 250-kg, intact female polar bear presented to the University of Minnesota Veterinary Medical Center with a 2-day history of lethargy, depression, and vomiting. Abdominal ultrasound identified large amounts of hyperechoic free peritoneal fluid. Ultrasound-guided abdominocentesis was performed and yielded thick serosanguinous fluid compatible with a hemoabdomen. An exploratory laparotomy revealed a large amount of malodorous, serosanguineous fluid and multiple necrotic blood clots associated with a torsion of the greater omentum and rupture of a branch of the omental artery. A partial omentectomy was performed to remove the necrotic tissue and the abdomen was copiously lavaged. The polar bear recovered successfully and is reported to be clinically well 6 mo later. This condition should be considered as a differential in bears with clinical signs of intestinal obstruction and hemoabdomen.

  11. A Study of Static Performance of Fixed Inclined Slider Bearings – A ...

    African Journals Online (AJOL)

    Michael Horsfall

    and friction. He compared numerical solutions for the bearing performance metrics with analytical solution using a range of bearing aspect ratios and power law indices. In this paper, we present the effect of power law fluids on the static performance characteristics of inclined slider bearings. Based on the power law model ...

  12. Rotordynamics and bearing design of turbochargers

    Science.gov (United States)

    Chen, Wen Jeng

    2012-05-01

    Turbochargers have gained significant attention in recent years. They are already widely used in automotive, locomotive, and marine applications with diesel engines. They are also applied in the aerospace application to increase the engine performance now. The turbochargers used in automotive and aerospace industry are very light-weight with operating speeds above 100,000 rpm. The turbochargers used in locomotive and marine applications are relatively heavy in size and power compared to the automotive and aerospace applications, and the maximum continuous operating speeds are around 30,000 rpm depending on the diesel engine power rating. Floating ring bushings, semi-floating dampers, ball bearings, and ball bearings with dampers are commonly used in automotive applications for small turbochargers. However, these bearings may not be appropriate for large turbochargers in locomotive and marine applications. Instead, multi-lobed bearings with and without squeeze film dampers are commonly used in these heavy-duty turbochargers. This paper deals with the rotordynamic characteristics of larger turbochargers in locomotive and marine applications. Various bearing designs are discussed. Bearing design parameters are studied and optimal values are suggested. Test results are also presented to support the analytical simulation.

  13. Journal bearings design for a novel revolving vane compressor

    Energy Technology Data Exchange (ETDEWEB)

    Tan, K.M.; Ooi, K.T. [Thermal and Fluids Division, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2011-01-15

    This paper presents the theoretical details of the journal bearing design for Revolving Vane (RV) rotary type compressor. The mathematical models, force analysis, and the theoretical design analysis for the dynamically loaded journal bearing of the compressor are presented. The variations of the minimum oil film thickness and the maximum film pressure developed are shown and the influences of design parameters, compressor configurations, and operating conditions on the journal bearing performance are described. For an air-conditioning compressor of 1.5 kW cooling capacity, the lowest minimum oil film thickness for lower and upper journal bearings is 6.6 {mu}m and 4.3 {mu}m respectively, when the cylinder is simply supported and the rotor is cantilever-supported. The lowest minimum oil film thickness for the journal bearing, which supports the cylinder, reduces to 4.0 {mu}m if the cantilever-type support is used. Besides that, a short-fat configuration of RV compressor is favorable in the interest of lowering bearing forces. (author)

  14. Self-Assembling Brush Polymers Bearing Multisaccharides.

    Science.gov (United States)

    Lee, Jongchan; Kim, Jin Chul; Lee, Hoyeol; Song, Sungjin; Kim, Heesoo; Ree, Moonhor

    2017-06-01

    Three different series of brush polymers bearing glucosyl, maltosyl, or maltotriosyl moiety at the bristle end are successfully prepared by using cationic ring-opening polymerization and two sequential postmodification reactions. All brush polymers, except for the polymer containing 100 mol% maltotriosyl moiety, demonstrate the formation of multibilayer structure in films, always providing saccharide-enriched surface. These self-assembling features are remarkable, regarding the bulkiness of saccharide moieties and the kink in the bristle due to the triazole linker. The saccharide-enriched film surfaces reveal exceptionally high specific binding affinity to concanavalin A but suppress nonspecific binding of plasma proteins severely. Overall, the brush polymers bearing saccharide moieties of various kinds in this study are highly suitable materials for biomedical applications including biosensors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Synchrotron x-ray spectroscopy of EuHN O3 aqueous solutions at high temperatures and pressures and Nb-bearing silicate melt phases coexisting with hydrothermal fluids using a modified hydrothermal diamond anvil cell and rail assembly

    Science.gov (United States)

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2007-01-01

    A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to ???900??C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly. ?? 2007 American Institute of Physics.

  16. Diamond growth in mantle fluids

    OpenAIRE

    Bureau, Hélène; Frost, Daniel J.; Bolfan-casanova, Nathalie; Leroy, Clémence; Esteve, Imène; Cordier, Patrick

    2016-01-01

    International audience; In the upper mantle, diamonds can potentially grow from various forms of media (solid, gas, fluid) with a range of compositions (e.g. graphite, C–O–H fluids, silicate or carbonate melts). Inclusions trapped in diamonds are one of the few diagnostic tools that can constrain diamond growth conditions in the Earth's mantle. In this study, inclusion-bearing diamonds have been synthesized to understand the growth conditions of natural diamonds in the upper mantle. Diamonds ...

  17. Polar bears, Ursus maritimus

    Science.gov (United States)

    Rode, Karyn D.; Stirling, Ian

    2017-01-01

    Polar bears are the largest of the eight species of bears found worldwide and are covered in a pigment-free fur giving them the appearance of being white. They are the most carnivorous of bear species consuming a high-fat diet, primarily of ice-associated seals and other marine mammals. They range throughout the circumpolar Arctic to the southernmost extent of seasonal pack ice.

  18. EcoBears

    DEFF Research Database (Denmark)

    Nielsen, Nick; Pedersen, Sandra Bleuenn; Sørensen, Jens Ager

    2015-01-01

    In this paper, we introduce the EcoBears concept that aims to augment household appliances with functional and aesthetic features to promote their "use'' and "longevity of use'' to prevent their disposal. The EcoBears also aim to support the communication of environmental issues in the home setting....... We present our initial design and implementation of the EcoBears that consist of two bear modules (a mother and her cub). We also present our preliminary concept validations and lessons learned to be considered for future directions....

  19. Performance of solid lubricated ball bearings at high-temperatures in a vacuum

    Science.gov (United States)

    Seki, Katsumi; Suzuki, Mineo; Nishimura, Makoto; Hasegawa, Masaji; Moriyama, Minoru

    1994-07-01

    Ball bearings which can operate at high temperatures in a vacuum will be required with advances in technology. Among the issues for the operation of ball bearings at high temperatures, solid lubricants and bearing materials are crucial. The aim of this study was to develop ball bearings for use at high temperatures in a vacuum. The tested bearings were 20-mm bore-sized angular contact ball bearings. Three combinations of bearing materials were tested: M-50 bearings, hybrid bearings with M-50 races and Si3N4 balls, and Si3N4 bearings. M-50 bearings were lubricated with a silver film. Hybrid and ceramic bearings were lubricated with a pre-coated sputtered MoS2 film and a self-lubricating hot-pressed composite retainer. Tests were carried out at temperatures up to 500 C and a rotational speed of 600 rpm under an axial load of 50 N in a vacuum. Excellent performance at 500 C in a vacuum was obtained for Si3N4 bearings. Frictional torque was low and stable for more than 5x10(exp 7) revolutions. After the tests, the bearings were in very good condition with a small amount of wear. Hybrid bearings also showed very good performance at 350 C in a vacuum. M-50 steel bearings were operated without failure at 350 C in a vacuum, although frictional torque was rather high and unstable. X-ray photoelectron spectroscopy (XPS) analysis and scanning electron microscopy (SEM) observation revealed the existence of a film on the ball surface transferred from the composite retainer for both hybrid and ceramic bearings.

  20. Fluid Shearing for Accelerated Chemical Reactions - Fluid Mechanics in the VFD

    Science.gov (United States)

    Leivadarou, Evgenia; Dalziel, Stuart; G. K. Batchelor Laboratory, Department of Applied Mathematics; Theoretical Physics Team

    2016-11-01

    The Vortex Fluidic Device (VFD) is a rapidly rotating tube that can operate under continuous flow with a jet feeding liquid reactants to the tube's hemispherical base. It is a new 'green' approach to the organic synthesis with many industrial applications in cosmetics, protein folding and pharmaceutical production. The rate of reaction in the VFD is enhanced when the collision rate is increased. The aim of the project is to explain the fluid mechanics and optimize the performance of the device. One contribution to the increased yield is believed to be the high levels of shear stress. We attempt to enhance the shear stress by achieving high velocity gradients in the boundary layers. Another factor is the uncontrolled vibrations due to imperfections in the bearings and therefore it is important to assess their influence in the initial spreading. The surface area of the film should be maximized with respect to the rotation rate, geometry and orientation of the tube, flow rate, wettability and contact line dynamics. Experiments are presented for a flat disk and a curved bowl, establishing the optimum height of release, rotation rate and tube orientation. Vibrations were imposed to investigate the changes in the film formation. We discuss the implications of our results in the VFD.

  1. Fast Fourier transform analysis of rotor-bearing systems

    Science.gov (United States)

    Choy, K. C.; Gunter, E. J.; Allaire, P. E.

    1978-01-01

    Nonlinear transient analysis of rotor-bearing systems is becoming increasingly important in the analysis of modern-day rotating machinery to model such phenomena as oil film whirl. This paper develops an analysis technique incorporating modal analysis and fast Fourier transform techniques to analyze rotors with residual shaft bow and realistic nonlinear bearings. The technique is demonstrated on single-mass and three-mass rotor examples. Comparisons of the theoretical results with experimental data give excellent agreement.

  2. Experimental Study on the Dynamic Performance of Water-Lubricated Rubber Bearings with Local Contact

    Directory of Open Access Journals (Sweden)

    Wu Ouyang

    2018-01-01

    Full Text Available Accurate dynamic characteristic coefficients of water-lubricated rubber bearings are necessary to research vibration of ship propulsion system. Due to mixed lubrication state of water-lubricated rubber bearings, normal test rig and identification method are not applicable. This paper establishes a test rig to simulate shaft misalignment and proposes an identification method for water-lubricated rubber bearings, which utilizes rotor unbalanced motion to produce self-excited force rather than artificial excitation. Dynamic performance tests under different conditions are operated. The results show that when rotational speed is less than 700 r/min, even if specific pressure is 0.05 MPa, it is difficult to form complete water film for the rubber bearing which was investigated, and contact friction and collision of the shaft and bearing are frequent. In the mixed lubrication, water film, rubber, and contact jointly determine dynamic characteristics of water-lubricated rubber bearings. The contact condition has a significant effect on the bearing stiffness, and water film friction damping has a significant effect on bearing damping. As for the particular investigated bearing, when rotational speed is in the range of 400~700 r/min and specific pressure is in the range of 0.03~0.07 MPa, bearing stiffness is in the range of 5.6~10.06 N/μm and bearing damping is in the range of 1.25~2.02 Ns/μm.

  3. Determining minimum lubrication film for machine parts

    Science.gov (United States)

    Hamrock, B. J.; Dowson, D.

    1978-01-01

    Formula predicts minimum film thickness required for fully-flooded ball bearings, gears, and cams. Formula is result of study to determine complete theoretical solution of isothermal elasto-hydrodynamic lubrication of fully-flooded elliptical contacts.

  4. Analysis of wear of antifriction bearing using radioisotope method

    International Nuclear Information System (INIS)

    Bejcek, V.

    1986-01-01

    The time course was studied of the wear of one type of antifriction bearing in dependence on the thickness of lubricating film for five types of lubricating oil. The theory is described of the development of lubricating film, the experiment and its evaluation, and a detailed list is given of numerical results and practical conclusions. Briefly mentioned is the principle of the radioisotope method which has been described elsewhere: prior to the experiment the balls of the bearing were activated with a neutron beam from a nuclear reactor and the wear was determined from the activity of the worn material carried away by the lubricant. (A.K.)

  5. Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 2: Partially Sealed Configuration

    Science.gov (United States)

    Jung, S. Y.; Sanandres, Luis A.; Vance, J. M.

    1991-01-01

    Experimental results from a partially sealed squeeze film damper (SFD) test rig, executing a circular centered orbit are presented and discussed. A serrated piston ring is installed at the damper exit. This device involves a new sealing concept which produces high damping values while allowing for oil flow to cool the damper. In the partially sealed damper, large cavitation regions are observed in the pressure fields at orbit radii epsilon equals 0.5 and epsilon equals 0.8. The cavitated pressure distributions and the corresponding force coefficients are compared with a cavitated bearing solution. The experimental results show the significance of fluid inertia and vapor cavitation in the operation of squeeze film dampers. Squeeze film Reynolds numbers tested reach up to Re equals 50, spanning the range of contemporary applications.

  6. Topological Fluid Mechanics with Applications to Free Surfaces and Axisymmetric Flows

    DEFF Research Database (Denmark)

    Brøns, Morten

    1996-01-01

    Topological fluid mechanics is the study of qualitative features of fluid patterns. We discuss applications to the flow beneath a stagnant surface film, and to patterns in axisymmetric flow.......Topological fluid mechanics is the study of qualitative features of fluid patterns. We discuss applications to the flow beneath a stagnant surface film, and to patterns in axisymmetric flow....

  7. Free convection film flows and heat transfer

    CERN Document Server

    Shang, Deyi

    2010-01-01

    Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.

  8. Modelling and Identification for Control of Gas Bearings

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik; Santos, Ilmar

    2015-01-01

    Gas bearings are popular for their high speed capabilities, low friction and clean operation, but suffer from poor damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved through active lubrication techniques using feedback control laws...... to industrial rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric actuators in a gas bearing are efficiently used to perturb the gas film for identification over relevant ranges of rotational speed and gas injection pressure. Parameter...

  9. Prediction of Gas Lubricated Foil Journal Bearing Performance

    Science.gov (United States)

    Carpino, Marc; Talmage, Gita

    2003-01-01

    This report summarizes the progress in the first eight months of the project. The objectives of this research project are to theoretically predict the steady operating conditions and the rotor dynamic coefficients of gas foil journal bearings. The project is currently on or ahead of schedule with the development of a finite element code that predicts steady bearing performance characteristics such as film thickness, pressure, load, and drag. Graphical results for a typical bearing are presented in the report. Project plans for the next year are discussed.

  10. Gas Foil Bearing Technology Advancements for Closed Brayton Cycle Turbines

    Science.gov (United States)

    Howard, Samuel A.; Bruckner, Robert J.; DellaCorte, Christopher; Radil, Kevin C.

    2007-01-01

    Closed Brayton Cycle (CBC) turbine systems are under consideration for future space electric power generation. CBC turbines convert thermal energy from a nuclear reactor, or other heat source, to electrical power using a closed-loop cycle. The operating fluid in the closed-loop is commonly a high pressure inert gas mixture that cannot tolerate contamination. One source of potential contamination in a system such as this is the lubricant used in the turbomachine bearings. Gas Foil Bearings (GFB) represent a bearing technology that eliminates the possibility of contamination by using the working fluid as the lubricant. Thus, foil bearings are well suited to application in space power CBC turbine systems. NASA Glenn Research Center is actively researching GFB technology for use in these CBC power turbines. A power loss model has been developed, and the effects of a very high ambient pressure, start-up torque, and misalignment, have been observed and are reported here.

  11. MEDULLOBLASTOMA IN A GRIZZLY BEAR (URSUS ARCTOS HORRIBLIS).

    Science.gov (United States)

    Mitchell, Jeffrey W; Thomovsky, Stephanie A; Chen, Annie V; Layton, Arthur W; Haldorson, Gary; Tucker, Russell L; Roberts, Gregory

    2015-09-01

    A 3-yr-old female spayed grizzly bear (Ursus arctos horribilis) was evaluated for seizure activity along with lethargy, inappetence, dull mentation, and aggressive behavior. Magnetic resonance (MR) examination of the brain revealed a contrast-enhanced right cerebellar mass with multifocal smaller nodules located in the left cerebellum, thalamus, hippocampus, and cerebrum with resultant obstructive hydrocephalus. Cerebrospinal fluid analysis revealed mild mononuclear pleocytosis, with differentials including inflammatory versus neoplastic processes. Blood and cerebrospinal fluid were also submitted for polymerase chain reaction and agar gel immunodiffusion to rule out infectious causes of meningitis/encephalitis. While awaiting these results, the bear was placed on steroid and antibiotic therapy. Over the next week, the bear deteriorated; she died 1 wk after MR. A complete postmortem examination, including immunohistochemisty, revealed the cerebellar mass to be a medulloblastoma. This is the only case report, to the authors' knowledge, describing a medulloblastoma in a grizzly bear.

  12. On the Design of Tilting-Pad Thrust Bearings

    DEFF Research Database (Denmark)

    Heinrichson, Niels

    2007-01-01

    Pockets are often machined in the surfaces of tilting-pad thrust bearings to allow for hydrostatic jacking in the start-up phase. Pockets and other recesses in the surfaces of bearing pads influence the pressure distribution and thereby the position of the pivot resulting in the most advantageous...... friction and a small pressure build-up. As in parallel-step bearings the recesses may also have a depth of the same order of magnitude as the oil film thickness. Such recesses are characterized by a strong pressure build-up caused by the reduction of the flow area at the end of the recess. Numerical models...... based on the Reynolds equation are used. They include the effects of variations of viscosity with temperature and the deformation of the bearing pads due to pressure and thermal gradients. The models are validated using measurements. Tilting-pad bearings of standard design are studied and the influences...

  13. Ultra-precision bearings

    CERN Document Server

    Wardle, F

    2015-01-01

    Ultra-precision bearings can achieve extreme accuracy of rotation, making them ideal for use in numerous applications across a variety of fields, including hard disk drives, roundness measuring machines and optical scanners. Ultraprecision Bearings provides a detailed review of the different types of bearing and their properties, as well as an analysis of the factors that influence motion error, stiffness and damping. Following an introduction to basic principles of motion error, each chapter of the book is then devoted to the basic principles and properties of a specific type of bearin

  14. Dynamic behavior of hybrid sodium bearings. Theoretical and experimental studies

    International Nuclear Information System (INIS)

    Guidez, J.; Juignet, N.; Queval, M.

    1981-08-01

    The primary sodium pump shaft lower section of a fast breeder reactor is guided by a hydrostatic sodium bearing. This recess type bearing is supplied via orifices restrictors. Sodium is sampled at hight pressure at the diffuser outlet and is then centrifuged towards the orifices restrictors. Bearing stiffness and damping data is essential for the study of rotor dynamic behavior. Two points in particular may then be studied: - calculation of rotor instability ranges and critical speeds, - dynamic behavior of the rotor in the event of an earthquake. As regards the bearing design, the problem is to obtain the pressure fields in the liquid film. The integration of these pressure fields will then give the stiffness coefficients. The damping coefficients can then be obtained by the same calculation after slight displacement. The Reynolds equation can be used to study the liquid film (under any conditions for the turbulent and inertia effects). Then the computer code DELPAL is explained that solves the modified Reynolds equation using a finite element method. The presentation of tests conducted in 1981 on the Super-Phenix 1 full scall bearing (diameter 850 mm) in water is made. In conclusion this paper describes a method for calculating the stiffness and damping matrices of a hydrostatic bearing using the DELPAL calculation code and shows the loop of behavior tests on a bearing with sinusoidal excitation. The results, obtained by calculation and by testing, are indispensable when calculating the dynamic behavior of the shaft line

  15. Flexible, Hybrid Piezoelectric Film (BaTi(1-x)Zr(x)O3)/PVDF Nanogenerator as a Self-Powered Fluid Velocity Sensor.

    Science.gov (United States)

    Alluri, Nagamalleswara Rao; Saravanakumar, Balasubramaniam; Kim, Sang-Jae

    2015-05-13

    We demonstrate a flexible piezoelectric nanogenerator (PNG) constructed using a hybrid (or composite) film composed of highly crystalline BaTi(1-x)Zr(x)O3 (x = 0, 0.05, 0.1, 0.15, and 0.2) nanocubes (abbreviated as BTZO) synthesized using a molten-salt process embedded into a poly(vinylidene fluoride) (PVDF) matrix solution via ultrasonication. The potential of a BTZO/PVDF hybrid film is realized in fabricating eco-friendly devices, active sensors, and flexible nanogenerators to interpret its functionality. Our strategy is based on the incorporation of various Zr(4+) doping ratios into the Ti(4+) site of BaTiO3 nanocubes to enhance the performance of the PNG. The flexible nanogenerator (BTZO/PVDF) exhibits a high electrical output up to ∼11.9 V and ∼1.35 μA compared to the nanogenerator (BTO/PVDF) output of 7.99 V and 1.01 μA upon the application of cyclic pushing-releasing frequencies with a constant load (11 N). We also demonstrate another exciting application of the PNG as a self-powered sensor to measure different water velocities at an outlet pipe. The average maximum peak power of the PNG varies from 0.2 to 15.8 nW for water velocities ranging from 31.43 to 125.7 m/s during the water ON condition. This study shows the compositional dependence approach, fabrication of nanostructures for energy harvesting, and self-powered devices in the field of monitoring for remote area applications.

  16. Investigation of Bearing Technology

    National Research Council Canada - National Science Library

    Maciag, Walter

    1998-01-01

    .... They eliminate roller needles and balls in bearings. Since the GC design does not require lubrication maintenance, there is no need for the u-joint cross to contain lubrication reservoirs and distribution channels and their input fitting...

  17. DW_BEAR

    Data.gov (United States)

    Department of Homeland Security — Subset of BEAR (Bi-Weekly Examination Analysis and Reporting) data used for financial audit remediation reporting within the Coast Guard Business Intelligence (CGBI)...

  18. Gear bearing drive

    Science.gov (United States)

    Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

    2011-01-01

    A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

  19. Rolling bearing analysis

    CERN Document Server

    Harris, Tedric A

    2001-01-01

    One of the most well-known experts in the field brings cutting-edge research to practitioners in the new edition of this important reference. Covers the improved mathematical calculations for rolling bearing endurance developed by the American Society of Mechanical Engineers and the Society of Lubrication and Tribology Engineers. Updated with new material on Condition-Based Maintenance, new testing methods, and new bearing materials.

  20. A parameter identification method for the rotordynamic coefficients of a high Reynolds number hydrostatic bearing

    Science.gov (United States)

    Rouvas, C.; Childs, D. W.

    1993-01-01

    In identifying the rotordynamic coefficients of a high-Reynolds-number hydrostatic bearing, fluid-flow induced forces present a unique problem, in that they provide an unmeasureable and uncontrollable excitation to the bearing. An analysis method is developed that effectively eliminates the effects of fluid-flow induced excitation on the estimation of the bearing rotordynamic coefficients, by using power spectral densities. In addition to the theoretical development, the method is verified experimentally by single-frequency testing, and repeatability tests. Results obtained for a bearing are the twelve rotordynamic coefficients (stiffness, damping, and inertia coefficients) as functions of eccentricity ratio, speed, and supply pressure.

  1. EHD Effects in Lubricated Journal Bearing

    Directory of Open Access Journals (Sweden)

    Pavel Pavlovich Usov

    2018-01-01

    Full Text Available This paper presents a numerical analysis of the influence of deformation of infinite parallel cylindrical solids in partial journal bearing on the oil film characteristics. The stationary elastohydrodynamic EHD problems for three design models of bearings are considered: (1 The bearing in which the basic contribution to the elastic displacement of the surface brings the thin elastic liner; (2 The elastic cylinder and the elastic bushing which is modeled by the elastic space with a cylindrical cut; (3 The elastic cylinder and the elastic bushing in the presence of the thin elastic liner with a small module of elasticity. It is shown that when the minimum film thickness is fixed and deformations of the elastic solids increase, then the load capacity increases, reaches a maximum, and then decreases. The deformation of solids can raise load capacity many times over. When the deformation of solids increases from zero, the pressure distribution changes from the distribution of pressure in the case of rigid bodies to the distribution of pressure which takes place with the dry contact of elastic bodies.

  2. Load responsive hydrodynamic bearing

    Science.gov (United States)

    Kalsi, Manmohan S.; Somogyi, Dezso; Dietle, Lannie L.

    2002-01-01

    A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

  3. Stabilization of aerodynamically excited turbomachinery with hydrodynamic journal bearings and supports

    Science.gov (United States)

    Barrett, L. E.; Gunter, E. J.

    1980-01-01

    A method of analyzing the first mode stability and unbalance response of multimass flexible rotors is presented whereby the multimass system is modeled as an equivalent single mass modal model including the effects of rotor flexibility, general linearized hydrodynamic journal bearings, squeeze film bearing supports and rotor aerodynamic cross coupling. Expressions for optimum bearing and support damping are presented for both stability and unbalance response. The method is intended to be used as a preliminary design tool to quickly ascertain the effects of bearing and support changes on rotor-bearing system performance.

  4. The application of dichotomy in equilibrium position of journal bearing

    Science.gov (United States)

    Wu, G. K.; Luo, X. Q.

    2016-05-01

    The fluid lubricant force in the journal bearing is an important factor for the stability and dynamic characteristics of rotating machine. In order to obtain the dynamic coefficients of journal bearing, the equilibrium position must be known for further calculation. In this paper, the Reynolds equation is solved by finite difference method and the dichotomy is applied to acquire the equilibrium position of journal bearing by means of double loop. The effects of length, radius and clearance of journal bearing on the equilibrium position are also researched. The calculated results show that the dichotomy is an effective method for the equilibrium position of journal bearing and the geometry parameters play an important effect on the equilibrium position.

  5. Fluid Mechanics.

    Science.gov (United States)

    Drazin, Philip

    1987-01-01

    Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)

  6. Fluid Interfaces

    DEFF Research Database (Denmark)

    Hansen, Klaus Marius

    2001-01-01

    Fluid interaction, interaction by the user with the system that causes few breakdowns, is essential to many user interfaces. We present two concrete software systems that try to support fluid interaction for different work practices. Furthermore, we present specificity, generality, and minimality...... as design goals for fluid interfaces....

  7. A study on compliant layers and its influence on dynamic response of a hydrodynamic journal bearing

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder

    2011-01-01

    For some hydrodynamic bearing applications polymer-lined bearings are chosen over traditional metal alloy bearings due to their better wear and friction properties when operating at very thin films, e.g. in the mixed lubrication region. The introduction of a compliant layer also affects the dynamic...... behavior of the bearing. The influence of the liner stiffness on the dynamic response of a highly dynamically loaded journal bearing is evaluated by varying the stiffness and comparing the response. The configurations with different liner stiffnesses are evaluated on the parameters that are traditionally...... used to evaluate hydrodynamic bearing designs: dynamic response, maximum pressure, minimum film thickness, wear, power loss and temperature response. The primary findings are that the maximum pressures are reduced significantly and this comes at the expense of slightly higher eccentricity ratios during...

  8. Watchable Wildlife: The Black Bear

    Science.gov (United States)

    Lynn L. Rogers

    1992-01-01

    Black bears are the bears people most often encounter. Black bears live in forests over much of North America, unlike grizzlies that live only in Alaska, northern and western Canada, and the northern Rocky Mountains. This brochure presents the latest information on black bear life and how this species responds to an ever-increasing number of campers, hikers, and...

  9. Climate Drives Polar Bear Origins

    Science.gov (United States)

    In their provocative analysis of northern bears (“Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage,” Reports, 20 April, p. 344), F. Hailer et al. use independent nuclear loci to show that polar bears originated during the middle Pleistocene, rather than during t...

  10. Survey of Damage Investigation of Babbitted Industrial Bearings

    Directory of Open Access Journals (Sweden)

    Lyle A. Branagan

    2015-04-01

    Full Text Available This survey collects the efforts to understand the sources and consequences of damage to babbitted industrial bearings, which operate by means of a hydrodynamic, or hydrostatic, film. Major individual damage types are discussed in the context of major damage categories.

  11. Fluid dynamics of dilatant fluid

    DEFF Research Database (Denmark)

    Nakanishi, Hiizu; Nagahiro, Shin-ichiro; Mitarai, Namiko

    2012-01-01

    A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation...

  12. On the simplifications for the thermal modeling of tilting-pad journal bearings under thermoelastohydrodynamic regime

    DEFF Research Database (Denmark)

    Cerda Varela, Alejandro Javier; Fillon, Michel; Santos, Ilmar

    2012-01-01

    The relevance of calculating accurately the oil film temperature build up when modeling tilting-pad journal bearings is well established within the literature on the subject. This work studies the feasibility of using a thermal model for the tilting-pad journal bearing which includes a simplified...

  13. Measurement of Pressure Fluctuations inside a Model Thrust Bearing Using PVDF Sensors.

    Science.gov (United States)

    Youssef, Andrew; Matthews, David; Guzzomi, Andrew; Pan, Jie

    2017-04-16

    Thrust bearings play a vital role in propulsion systems. They rely on a thin layer of oil being trapped between rotating surfaces to produce a low friction interface. The "quality" of this bearing affects many things from noise transmission to the ultimate catastrophic failure of the bearing itself. As a result, the direct measure of the forces and vibrations within the oil filled interface would be very desirable and would give an indication of the condition of the bearing in situ. The thickness of the oil film is, however, very small and conventional vibration sensors are too cumbersome to use in this confined space. This paper solves this problem by using a piezoelectric polymer film made from Polyvinylidine Fluoride (PVDF). These films are very thin (50 m) and flexible and easy to install in awkward spaces such as the inside of a thrust bearing. A model thrust bearing was constructed using a 3D printer and PVDF films inserted into the base of the bearing. In doing so, it was possible to directly measure the force fluctuations due to the rotating pads and investigate various properties of the thrust bearing itself.

  14. Identification of stiffness and damping characteristics of axial air-foil bearings

    NARCIS (Netherlands)

    Arora, Vikas; Arora, Vikas; van der Hoogt, Peter; Aarts, Ronald G.K.M.; de Boer, Andries

    2011-01-01

    Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. AFBs are currently used in

  15. Nonlinear Transient Modeling and Design of Turbocharger Rotor/Semi-Floating Bush Bearing System

    OpenAIRE

    Jianming Cao; Saeid Dousti; Paul Allaire; Tim Dimond

    2017-01-01

    This work presents the bearing design and analysis of radial semi-floating bush oil lubricated bearings for a typical industrial turbocharger configuration. Initially, the stability analysis for a linear rotor/bearing system is evaluated through eigenvalues and eigenvectors. The stiffness and damping coefficients of the inner oil film are obtained for the linear modeling process. The operating speed range of the turbocharger is high enough, at 21,000 to 24,000 rpm, to be unstable, indicating ...

  16. Experimental contribution to the study of gas bearings; Contribution experimentale a l'etude des paliers a gaz

    Energy Technology Data Exchange (ETDEWEB)

    Gobert, G

    1962-07-01

    Developments for gas-lubricated bearings are discussed. The study of how the fluid film behaves compared to what one can expect is discussed. Various devices are described which have allowed us to go up to peripheral velocity greater than 400 m/s, leading to rotational speed of several thousand revolutions per second. This is obtained by using an automatic setting for the distance between fixed and rotating walls. (author) [French] Le present travail debute par un apercu de l'etat actuel des connaissances sur le processus de la lubrification, notamment sur les paliers a lubrification par gaz. Apres une analyse effectuee au moyen des recentes theories de R. Comolet sur le film fluide entre disques paralleles, nous decrivons des machines dont les charges axiales et radiales specialement etudiees ont permis, au moyen d'un reglage automatique des jeux entre parois fixes et parois tournantes, d'atteindre des vitesses peripheriques superieures a 400 m/s correspondant a des vitesses de plusieurs milliers de tours par seconde. (auteur)

  17. The Development of Open Water-lubricated Polycrystalline Diamond (PCD) Thrust Bearings for Use in Marine Hydrokinetic (MHK) Energy Machines

    Energy Technology Data Exchange (ETDEWEB)

    Cooley, Craig, H.; Khonsari, Michael,, M; Lingwall, Brent

    2012-11-28

    Polycrstalline diamond (PCD) bearings were designed, fabricated and tested for marine-hydro-kinetic (MHK) application. Bearing efficiency and life were evaluated using the US Synthetic bearing test facility. Three iterations of design, build and test were conducted to arrive at the best bearing design. In addition life testing that simulated the starting and stopping and the loading of real MHK applications were performed. Results showed polycrystalline diamond bearings are well suited for MHK applications and that diamond bearing technology is TRL4 ready. Based on life tests results bearing life is estimated to be at least 11.5 years. A calculation method for evaluating the performance of diamond bearings of round geometry was also investigated and developed. Finally, as part of this effort test bearings were supplied free of charge to the University of Alaska for further evaluation. The University of Alaska test program will subject the diamond bearings to sediment laden lubricating fluid.

  18. Radial Halbach Magnetic Bearings

    Science.gov (United States)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2009-01-01

    Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while

  19. Fluids engineering

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    Fluids engineering has played an important role in many applications, from ancient flood control to the design of high-speed compact turbomachinery. New applications of fluids engineering, such as in high-technology materials processing, biotechnology, and advanced combustion systems, have kept up unwaining interest in the subject. More accurate and sophisticated computational and measurement techniques are also constantly being developed and refined. On a more fundamental level, nonlinear dynamics and chaotic behavior of fluid flow are no longer an intellectual curiosity and fluid engineers are increasingly interested in finding practical applications for these emerging sciences. Applications of fluid technology to new areas, as well as the need to improve the design and to enhance the flexibility and reliability of flow-related machines and devices will continue to spur interest in fluids engineering. The objectives of the present seminar were: to exchange current information on arts, science, and technology of fluids engineering; to promote scientific cooperation between the fluids engineering communities of both nations, and to provide an opportunity for the participants and their colleagues to explore possible joint research programs in topics of high priority and mutual interest to both countries. The Seminar provided an excellent forum for reviewing the current state and future needs of fluids engineering for the two nations. With the Seminar ear-marking the first formal scientific exchange between Korea and the United States in the area of fluids engineering, the scope was deliberately left broad and general

  20. Magnetic remanence of hematite-bearing murals

    Science.gov (United States)

    Lanza, R.; Zanella, E.; Saudino, S.

    2009-12-01

    We report on a series of experiments designed to test the ability of hematite-bearing colors to record the direction of the ambient magnetic field. Plasterboards accurately oriented with respect to the Earth's magnetic field were painted with red tempera colors prepared with hematite pigments. Magnetic measurements indicate that the color film retains a remanent magnetization and acquires a well developed magnetic fabric. The remanence direction is close to, yet slightly deviated from the Earth's magnetic field. The deviation is interpreted to result from preferential alignment of the pigment grains parallel to the plasterboard surface and depends on both its orientation with respect to magnetic north and the degree of magnetic anisotropy of the color film, which in turn varies according to the pigment used. Investigation of the magnetic remanence of murals may complement archaeomagnetic information derived from traditional materials such as baked and fired structures.

  1. Fluid machinery

    International Nuclear Information System (INIS)

    Ha, Jae Hyeon; Son, Byeong Jin

    2001-04-01

    This book tells of definition and classification of fluid machinery, energy equation of incompressible fluid, principle of momentum, classification and structure of pump, size, safety of centrifugal pump, theory and operation of contraction pump, reciprocating pump, rotary pump, special pump, using of water power, classification of water turbine, impulse water turbine, reaction water turbine, pump water turbine, liquid movement apparatus, fluid type control machinery and solid and gas type pneumatic machine.

  2. Static characteristic analysis and experimental research of aerostatic thrust bearing with annular elastic uniform pressure plate

    Directory of Open Access Journals (Sweden)

    Hao Dong

    2015-03-01

    Full Text Available In this article, an aerostatic thrust bearing with annular elastic uniform pressure plate structure was designed. In order to obtain a relationship between bearing capacity and stiffness of aerostatic thrust bearing designed in this article, first, the stress field mechanics model of the gas thrust bearing was established in the static. Second, deformation control equations of the elastic uniform pressure plate and gas lubrication Reynolds equation were established according to the flow continuity principle. Here, finite element mesh of gas flow field was woven using the technology of grid overlapping and grid stitching. Then, gas–solid coupling control equations were solved using the numerical method. Gas film pressure distribution and gas static bearing capacity of thrust bearing were analyzed. Function relationship between bearing capacity and the stiffness and the thickness of gas film was obtained. Finally, the results of theory analysis and experiment were compared. The results of the comparison can be listed as, under the effect of gas pressure, orifice area and the equilibrium pressure groove depth are changed due to elastic deformation of the elastic uniform pressure plate. The static stiffness of aerostatic thrust bearing with elastic equilibrium pressure groove increased by 30% than the static stiffness of aerostatic thrust bearing with rigid equilibrium pressure groove. The maximum carrying capacity occurred in the gas film thickness of 3.5 µm. The maximum static stiffness appeared in the gas film thickness of 5.5 µm. It can be seen from the comparison results of experiments and theoretical analysis that data results of gas film thickness and the bearing capacity are the same. The feasibility of the theoretical analysis method is validated.

  3. Fast, self-supplied, all-solid photoelectrochromic film

    Energy Technology Data Exchange (ETDEWEB)

    De Filpo, Giovanni; Mormile, Sabrina; Chidichimo, Giuseppe [Department of Chemistry, University of Calabria, 87036 Arcavacata di Rende (CS) (Italy); Nicoletta, Fiore P. [Department of Pharmaceutical Sciences, University of Calabria, 87036 Arcavacata di Rende (CS) (Italy)

    2010-07-01

    This paper describes the fabrication and the characterization of a new nanostructured and self-supplied photoelectrochromic device. The main properties of this film are its all-solid nature, its fast coloration time as well as its fast bleaching time. The photoelectrochromic film was manufactured by coating dye functionalized TiO{sub 2} nanoparticles (dye-TiO{sub 2}) on a layer of WO{sub 3} nanoparticles. In order to improve their electrical conductance, both the dye-TiO{sub 2} and WO{sub 3} layers were properly doped with single wall carbon nanotubes (SWNT) bearing COOH groups. A layer of PEDOT/PSS was cast between the dye-TiO{sub 2} layer and the ITO counter electrode, without the use of any fluid component. When exposed to the light, SWNT doped dye-TiO{sub 2} layer generates electrons that reduce the WO{sub 3} layer. As a consequence of this redox reaction, the film changes its color if the two external electrodes are not short-circuited. On the contrary, a fast bleaching of the device can be achieved by shortcircuiting the electrodes. (author)

  4. Film/NotFilm

    OpenAIRE

    Willems, Gertjan

    2016-01-01

    Although Samuel Beckett (1906-1989) showed a genuine interest in audio-visual media in his fascinating and innovative radio plays and television works, and in 1936 even wrote a letter to Sergei Eisenstein to be accepted to the famous Soviet film school VGIK, the 22-minute Film (1965) was his only venture into cinema. Beckett conceived the film, wrote the screenplay, supervised the production and, as one of the film’s crew members recalled and as the director Alan Schneider himself acknowledge...

  5. Advanced Control of Active Bearings - Modelling, Design and Experiments

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane

    , the enhancement of damping, the extension of operating range and the minimisation of critical vibrations in machine elements are of fundamental importance. The main component to tackle the energy-loss-related problems is the bearing. The area of design of active bearings, while very promising, is still in its...... control design. One example is the controllable radial gas bearing, where the lubricant air is injected through controllable injectors to levitate the rotor on an air film. Feedback control of the injection can improve upon the poor damping to reduce the disturbance sensitivity and vibrations near...... the critical speeds. The feedback control law is preferably designed from a simple model, which captures the dominant dynamics of the machine in the frequency range of interest. This thesis offers two main original contributions in the field of active bearings. First, an experimental technique is proposed...

  6. Hybrid superconductor magnet bearings

    Science.gov (United States)

    Chu, Wei-Kan

    1995-01-01

    Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.

  7. Steady State Performance Characteristics of Micropolar Lubricated Hydrodynamic Journal Bearings with Flexible Liner

    Science.gov (United States)

    Bansal, Pikesh; Chattopadhyay, Ajit Kumar; Agrawal, Vishnu Prakash

    2016-04-01

    The aim of the present study is to theoretically determine the steady state characteristics of hydrodynamic oil journal bearings considering the effect of deformation of liner and with micropolar lubrication. Modified Reynolds equation based on micropolar lubrication theory is solved using finite difference method to obtain steady state film pressures. Minimum film thickness is calculated taking into consideration the deformation of the liner. Parametric study has been conducted and steady state characteristics for journal bearing with elasticity of bearing liner are plotted for various values of eccentricity ratio, deformation factor, characteristic length and coupling number.

  8. Improved adaptability of polyaryl-ether-ether-ketone with texture pattern and graphite-like carbon film for bio-tribological applications

    Science.gov (United States)

    Ren, Siming; Huang, Jinxia; Cui, Mingjun; Pu, Jibin; Wang, Liping

    2017-04-01

    With the development of surface treatment technology, an increasing number of bearings, seals, dynamic friction drive or even biomedical devices involve a textured surface to improve lubrication and anti-wear. The present investigation has been conducted in order to evaluate the friction and wear behaviours of textured polyaryl-ether-ether-ketone (PEEK) coated with a graphite-like carbon (GLC) film sliding against stainless steel pin in biological medium. Compared with pure PEEK, the PEEK coated with GLC film shows excellent tribological performance with a low friction of 0.08 and long lifetime (wear volumes are about 3.78 × 10-4 mm3 for un-textured one and 2.60 × 10-4 mm3 for textured GLC film after 36,000 s of sliding) under physiological saline solution. In particular, the GLC film with appropriate dimple area density is effective to improve friction reduction and wear resistance properties of PEEK substrate under biological solution, which is attributed to the entrapment of wear debris in the dimples to inhibit the graphitization and the fluid dynamic pressure effect derived from the texture surface to increase the thickness in elastohydrodynamic lubrication (EHL) film during sliding motions. Moreover, the friction coefficient of GLC film under physiological saline solution decreases with the increase in the applied load. With the increasing applied load, the texture surface is responsible for accounting the improved wear resistance and a much lower graphitization of the GLC film during whole test.

  9. On the mixture flow problem in lubrication of hydrodynamic bearings - Small solid volume fraction

    Science.gov (United States)

    Khonsari, M. M.; Dai, Fuling

    1992-01-01

    The lubrication problem of infinitely long slider bearings with a mixture of fluid and particulate solid at small volume fraction level is studied. Closed-form analytical solutions for pressure and shear stress are obtained for a class of solid aggregates. The results reduce to those of pure fluid in the limiting case. A parametric study of the bearing performance with particulate solid is presented.

  10. Influence of the Radial Clearance of a Squeeze Film Damper on the Vibratory Behavior of a Single Spool Gas Turbine Designed for Unmanned Aerial Vehicle Applications

    OpenAIRE

    Creci, Geraldo; Balastrero, José Orlando; Domingues, Sidney; Torres, Luis Vanderlei; Menezes, João Carlos

    2017-01-01

    This study presents a numerical investigation using the finite element method on the vibratory behavior of a single spool gas turbine designed for unmanned aerial vehicle applications. The shaft of the rotor-bearing system is supported on a front bearing composed of a deep groove ball bearing with a vibration absorber element and a rear squeeze film damper bearing. Three radial clearances for the squeeze film damper were analyzed to determine the best geometric configuration for the rear bear...

  11. Gas Foil Bearing Misalignment and Unbalance Effects

    Science.gov (United States)

    Howard, Samuel A.

    2008-01-01

    The effects of misalignment and unbalance on gas foil bearings are presented. The future of U.S. space exploration includes plans to conduct science missions aboard space vehicles, return humans to the Moon, and place humans on Mars. All of these endeavors are of long duration, and require high amounts of electrical power for propulsion, life support, mission operations, etc. One potential source of electrical power of sufficient magnitude and duration is a nuclear-fission-based system. The system architecture would consist of a nuclear reactor heat source with the resulting thermal energy converted to electrical energy through a dynamic power conversion and heat rejection system. Various types of power conversion systems can be utilized, but the Closed Brayton Cycle (CBC) turboalternator is one of the leading candidates. In the CBC, an inert gas heated by the reactor drives a turboalternator, rejects excess heat to space through a heat exchanger, and returns to the reactor in a closed loop configuration. The use of the CBC for space power and propulsion is described in more detail in the literature (Mason, 2003). In the CBC system just described, the process fluid is a high pressure inert gas such as argon, krypton, or a helium-xenon mixture. Due to the closed loop nature of the system and the associated potential for damage to components in the system, contamination of the working fluid is intolerable. Since a potential source of contamination is the lubricant used in conventional turbomachinery bearings, Gas Foil Bearings (GFB) have high potential for the rotor support system. GFBs are compliant, hydrodynamic journal and thrust bearings that use a gas, such as the CBC working fluid, as their lubricant. Thus, GFBs eliminate the possibility of contamination due to lubricant leaks into the closed loop system. Gas foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Aircraft Air Cycle Machines (ACMs) and ground

  12. 60NiTi Intermetallic Material Evaluation for Lightweight and Corrosion Resistant Spherical Sliding Bearings for Aerospace Applications

    Science.gov (United States)

    DellaCorte, Christopher; Jefferson, Michael

    2015-01-01

    NASA Glenn Research Center and the Kamatics subsidiary of the Kaman Corporation conducted the experimental evaluation of spherical sliding bearings made with 60NiTi inner races. The goal of the project was to assess the feasibility of manufacturing lightweight, corrosion resistant bearings utilizing 60NiTi for aerospace and industrial applications. NASA produced the bearings in collaboration with Abbott Ball Corporation and Kamatics fabricated bearing assemblies utilizing their standard reinforced polymer liner material. The assembled bearings were tested in oscillatory motion at a load of 4.54kN (10,000 lb), according to the requirements of the plain bearing specification SAE AS81820. Several test bearings were exposed to hydraulic fluid or aircraft deicing fluid prior to and during testing. The results show that the 60NiTi bearings exhibit tribological performance comparable to conventional stainless steel (440C) bearings. Further, exposure of 60NiTi bearings to the contaminant fluids had no apparent performance effect. It is concluded that 60NiTi is a feasible bearing material for aerospace and industrial spherical bearing applications.

  13. Design, Fabrication and Performance of Open Source Generation I and II Compliant Hydrodynamic Gas Foil Bearings

    Science.gov (United States)

    DellaCorte, Christopher; Radil, Kevin C.; Bruckner, Robert J.; Howard, S. Adam

    2007-01-01

    Foil gas bearings are self-acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost top foil layer traps a gas pressure film that supports a load while a layer or layers underneath provide an elastic foundation. Foil bearings are used in many lightly loaded, high-speed turbo-machines such as compressors used for aircraft pressurization, and small micro-turbines. Foil gas bearings provide a means to eliminate the oil system leading to reduced weight and enhanced temperature capability. The general lack of familiarity of the foil bearing design and manufacturing process has hindered their widespread dissemination. This paper reviews the publicly available literature to demonstrate the design, fabrication and performance testing of both first and second generation bump style foil bearings. It is anticipated that this paper may serve as an effective starting point for new development activities employing foil bearing technology.

  14. Thin Films

    Directory of Open Access Journals (Sweden)

    M. Benmouss

    2003-01-01

    the optical absorption are consistent with the film color changes. Finally, the optical and electrochromic properties of the films prepared by this method are compared with those of our sputtered films already studied and with other works.

  15. Computer assistant test and consultive system for aircraft fluid element

    Science.gov (United States)

    Liu, Jin-Ru

    The fluid bearing elements of an aircraft's control system are discussed in the context of aviation maintenance engineering. This paper explores the development of an artificially intelligent assistant to aid in the maintenance of hydraulic control systems.

  16. Schroedinger fluid

    International Nuclear Information System (INIS)

    Kan, K.K.

    1983-01-01

    The relationship of nuclear internal flow and collective inertia, the difference of this flow from that of a classical fluid, and the approach of this flow to rigid flow in independent-particle model rotation are elucidated by reviewing the theory of Schroedinger fluid and its implications for collective vibration and rotation. (author)

  17. Fluid Dynamics

    DEFF Research Database (Denmark)

    Brorsen, Michael

    These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University.......These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University....

  18. Bouncy Fluid Jets

    Science.gov (United States)

    Wadhwa, Navish; Jung, Sunghwan; Vlachos, Pavlos

    2012-11-01

    Contrary to intuition, free fluid jets can sometimes ``bounce'' off each other upon collision, due to an entrained air film that keeps them separated. So far, there have only been a few descriptive studies of bouncing jets, since the first recorded observation by Rayleigh more than a century ago. We present a quantitative investigation of non-coalescence in jets of same fluid upon an oblique collision. Using a simple experimental set-up, we carried out a parametric study of the bouncing jets by varying the jet diameter, velocity, angle of inclination and fluid viscosity. Our results reveal a scaling law for the contact time of bouncing jets. We further investigate the transition of colliding jets from non-coalescence to coalescence, which seems to be caused by instability of the fluid interface. A dimensionless parameter, which is a function of the Normal Weber Number, Normal Reynolds Number and the angle of inclination of the jets, quantitatively dictates the transition. Presently at Department of Physics, Danish Technical University, Denmark.

  19. Magnetic bearing and motor

    Science.gov (United States)

    Studer, Philip A. (Inventor)

    1983-01-01

    A magnetic bearing assembly (10) has an intermediate rotatable section (33) having an outer cylindrical member (30) coaxially suspended by a torsion wire (72) around an axially polarized cylindrical magnet (32). Axial alignment between the pole faces (40-43) of the intermediate section (33) and end surfaces (50-53) of opposed end bells (20, 22) provides a path of least reluctance across intervening air gaps (60-63) for the magnetic flux emanating from magnet (32). Radial dislocation increases the reluctance and creates a radial restoring force. Substitution of radially polarized magnets 107 fixed to a magnetically permeable cylinder (32') and insertion of pairs of armature coil windings (109-112) between the cylinder pair (33') provides an integral magnetic bearing and torsion motor (100) able to provide arcuately limited rotational drive.

  20. Passive magnetic bearing system

    Science.gov (United States)

    Post, Richard F.

    2014-09-02

    An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.

  1. Government Risk-Bearing

    CERN Document Server

    1993-01-01

    The u.s. government bulks large in the nation's financial markets. The huge volume of government-issued and -sponsored debt affects the pricing and volume ofprivate debt and, consequently, resource allocation between competing alternatives. What is often not fully appreciated is the substantial influence the federal government wields overresource allocation through its provisionofcreditandrisk-bearing services to the private economy. Because peopleand firms generally seekto avoid risk, atsomeprice they are willing to pay another party to assume the risk they would otherwise face. Insurance companies are a class of private-sector firms one commonly thinks of as providing these services. As the federal government has expanded its presence in the U.S. economy during this century, it has increasingly developed programs aimed at bearing risks that the private sector either would not take on at any price, or would take on but atapricethoughtto besogreatthatmostpotentialbeneficiarieswouldnotpurchase the coverage. To...

  2. COMPOSITION OF BLACK BEAR MILK.

    Science.gov (United States)

    An analysis of black bear ( Ursus americanus Pallas) milk showed that the total solids, fat and protein were much higher and the lactose lower than...either cow or human milk. In comparison with polar bear (Thalarcotos maritimus ), the black bear milk was lower in fat, protein and total calories. (Author)

  3. Frictionless Bearing Uses Permanent Magnets

    Science.gov (United States)

    1965-01-01

    The purpose of this innovation was to develop a frictionless bearing for high speed, light load applications. The device involves the incorporation of permanent magnets in the bearing design. The repulsion of like magnetic poles provides concentric support of the inner member so that no metallic contact occurs between the bearing surfaces.

  4. Rotating plug bearing and seal

    International Nuclear Information System (INIS)

    Wade, E.E.

    1977-01-01

    Disclosed is a bearing and seal structure for nuclear reactors utilizing rotating plugs above the nuclear reactor vessel. The structure permits lubrication of bearings and seals of the rotating plugs without risk of the lubricant draining into the reactor vessel below. The structure permits lubrication by utilizing a rotating outer race bearing. 19 claims, 3 figures

  5. Radium bearing waste disposal

    International Nuclear Information System (INIS)

    Tope, W.G.; Nixon, D.A.; Smith, M.L.; Stone, T.J.; Vogel, R.A.; Schofield, W.D.

    1995-01-01

    Fernald radium bearing ore residue waste, stored within Silos 1 and 2 (K-65) and Silo 3, will be vitrified for disposal at the Nevada Test Site (NTS). A comprehensive, parametric evaluation of waste form, packaging, and transportation alternatives was completed to identify the most cost-effective approach. The impacts of waste loading, waste form, regulatory requirements, NTS waste acceptance criteria, as-low-as-reasonably-achievable principles, and material handling costs were factored into the recommended approach

  6. Testing of Bearing Materials for Large Two-stroke Marine Diesel Engines

    DEFF Research Database (Denmark)

    Klit, Peder; Persson, Sebastian; Vølund, Anders

    2013-01-01

    In large two-stroke marine diesel engines bearings are designed with the intention that these need not be replaced during the life of the engine. The design has shown very good service experiences. The design parameters of the main bearings are, among others, based on the average maximum specific...... load which the bearing should operate under. In general, the frictional loss is less than 1% of the nominal power of the engine but is still a target for optimization. Fatigue mechanisms of bearing lining material are not fully understood and the design limits with regards to minimum oil film thickness...

  7. Laminar flow in a recess of a hydrostatic bearing

    Science.gov (United States)

    San Andres, Luis A.; Velthuis, Johannes F. M.

    1992-01-01

    The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows.

  8. Bearing for liquid metal pump

    International Nuclear Information System (INIS)

    Dickinson, R.J.; Pennell, W.E.; Wasko, J.

    1984-01-01

    A liquid metal pump bearing support comprises a series of tangentially oriented spokes that connect the bearing cylinder to the pump internals structure. The spokes may be arranged in a plurality of planes extending from the bearing cylinder to the pump internals with the spokes in one plane being arranged alternately with those in the next plane. The bearing support structure provides the pump with sufficient lateral support for the bearing structure together with the capability of accommodating differential thermal expansion without adversely affecting pump performance

  9. Bearing construction for refrigeration compresssor

    Science.gov (United States)

    Middleton, Marc G.; Nelson, Richard T.

    1988-01-01

    A hermetic refrigeration compressor has a cylinder block and a crankshaft rotatable about a vertical axis to reciprocate a piston in a cylinder on the cylinder block. A separate bearing housing is secured to the central portion of the cylinder block and extends vertically along the crankshaft, where it carries a pair of roller bearings to journal the crankshaft. The crankshaft has a radially extending flange which is journaled by a thrust-type roller bearing above the bearing housing to absorb the vertical forces on the crankshaft so that all three of the roller bearings are between the crankshaft and the bearing housing to maintain and control the close tolerances required by such bearings.

  10. 77 FR 70423 - Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC...

    Science.gov (United States)

    2012-11-26

    ... Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of..., 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor) and Black Bear Development Holdings, LLC and Black Bear SO, LLC (transferees) filed an application for the partial the transfer of licenses...

  11. Introgressive hybridization: brown bears as vectors for polar bear alleles.

    Science.gov (United States)

    Hailer, Frank

    2015-03-01

    The dynamics and consequences of introgression can inform about numerous evolutionary processes. Biologists have therefore long been interested in hybridization. One challenge, however, lies in the identification of nonadmixed genotypes that can serve as a baseline for accurate quantification of admixture. In this issue of Molecular Ecology, Cahill et al. (2015) analyse a genomic data set of 28 polar bears, eight brown bears and one American black bear. Polar bear alleles are found to be introgressed into brown bears not only near a previously identified admixture zone on the Alaskan Admiralty, Baranof and Chichagof (ABC) Islands, but also far into the North American mainland. Elegantly contrasting admixture levels at autosomal and X chromosomal markers, Cahill and colleagues infer that male-biased dispersal has spread these introgressed alleles away from the Late Pleistocene contact zone. Compared to a previous study on the ABC Island population in which an Alaskan brown bear served as a putatively admixture-free reference, Cahill et al. (2015) utilize a newly sequenced Swedish brown bear as admixture baseline. This approach reveals that brown bears have been impacted by introgression from polar bears to a larger extent (up to 8.8% of their genome), than previously known, including the bear that had previously served as admixture baseline. No evidence for introgression of brown bear into polar bear is found, which the authors argue could be a consequence of selection. Besides adding new exciting pieces to the puzzle of polar/brown bear evolutionary history, the study by Cahill and colleagues highlights that wildlife genomics is moving from analysing single genomes towards a landscape genomics approach. © 2015 John Wiley & Sons Ltd.

  12. Enhancing damping of gas bearings using linear parameter-varying control

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik; Galeazzi, Roberto

    2017-01-01

    Journal bearings can be lubricated through controllable injectors using pressurised fluids, whose viscosity highly determines the dynamic responses of the rotating machine. The use of fluids with low viscosity is attracting a growing interest due to the reduced friction forces and consequent loss...

  13. Interaction Study of Clay bearing Amphibolite-Crude Oil-Saline Water

    Indian Academy of Sciences (India)

    26

    Low saline water flooding (LSWF) had proved to be an efficient method for enhanced oil recovery. 34 in clay bearing hydrocarbon reservoirs but the interaction mechanisms among in-situ rocks - fluids. 35 and injection fluids within the reservoir has not yet properly known. Understanding molecular. 36 level interaction ...

  14. An investigation of material properties and tribological performance of magnetron sputtered thin film coatings

    Science.gov (United States)

    Singh, Harpal

    This dissertation is divided into two categories based upon lubrication functionality and its application. The categories are: Dry film lubrication and Fluid film lubrication with thin film coatings. Thin film coatings examined in this work were deposited using closed field unbalanced magnetron sputtering and RF-DC coupled magnetron sputtering systems. In Dry/Solid film lubrication, the mechanical, structural and tribological properties of two Molybdenum disulphide (MoS2) based coatings are examined and evaluated. Among the two coatings, one coating is doped with Ti (Ti-MoS2) and the other is a combination of metal, lubricant and oxide (Sb2O3/Au - MoS2). These coatings are known to provide low friction in vacuum environments. The goal of this work was to evaluate friction and wear performance of MoS2 doped coatings in unidirectional and reciprocating sliding contact under different environmental conditions. Sliding contact results showed friction and wear dependence on temperature and humidity. The formation and removal of transfer films and the recrystallization and reorientation of basal layers on the steel counterface was observed as the mechanism for low friction. Structural analysis revealed a relationship between the microstructural properties and tribological performance. It was also observed that the addition of dopants (Ti, Au, Sb 2O3) improved the mechanical properties as compared to pure MoS2 coatings. Further, the rolling contact performance of the coatings was measured on a five ball on rod tribometer and a Thrust bearing tribometer under vacuum and air environments. The rolling contact experiments indicated that life of the rolling components depend on the amount of material present between the contacts. Fluid film lubrication with thin film coatings investigates the possibilities to improve the performance and durability of tribological components when oils and thin films are synergistically coupled. In this work, the ability of a Diamond Like Carbon

  15. ER fluid applications to vibration control devices and an adaptive neural-net controller

    Science.gov (United States)

    Morishita, Shin; Ura, Tamaki

    1993-07-01

    Four applications of electrorheological (ER) fluid to vibration control actuators and an adaptive neural-net control system suitable for the controller of ER actuators are described: a shock absorber system for automobiles, a squeeze film damper bearing for rotational machines, a dynamic damper for multidegree-of-freedom structures, and a vibration isolator. An adaptive neural-net control system composed of a forward model network for structural identification and a controller network is introduced for the control system of these ER actuators. As an example study of intelligent vibration control systems, an experiment was performed in which the ER dynamic damper was attached to a beam structure and controlled by the present neural-net controller so that the vibration in several modes of the beam was reduced with a single dynamic damper.

  16. Fluid systems for RICH detectors

    CERN Document Server

    Ullaland, O

    2005-01-01

    The optical properties of the radiator media are of prime importance in Ring Imaging Cherenkov detectors. The main requirements for the radiator fluid are a stable refractive index and a photon absorption as low as possible. We will in this note cover some of the cleaning procedures which are required together with distillation and similar separation procedures. Thin film membranes have been introduced during the last decade. They have proven particularly interesting in separating air from some Cherenkov fluids. We will also discuss the use of molecular sieves.

  17. The analysis, design, and testing of a blood lubricated hydrodynamic journal bearing.

    Science.gov (United States)

    Walowit, J A; Malanoski, S B; Horvath, D; Golding, L R; Smith, W A

    1997-01-01

    The Cleveland Clinic Foundation's Innovative Ventricular Assist System (IVAS) uses a hydrodynamic journal bearing to support the rotating assembly of the blood pump. Bearing dimensions are chosen so that a stable film of lubricant develops and separates stationary and rotating pump surfaces during operation. This bearing type provides several advantages for a permanently implanted device, including essentially no wear for very long life and very high reliability, as well as a self pumping action that generates circumferential wash flow and thus lowers the risk of bearing associated deposition. However, these advantages are accompanied by design issues not encountered with typical journal bearing, such as low shear stress, bearing ends that are not at atmospheric pressure, and low radial bearing loads. To address these issues, several concepts for a hydrodynamic blood bearing were designed and analyzed using a special computer code to perform parametric studies. This design analysis code was developed to define optimum bearing performance under selected load and speed ranges and within practical tolerances. Results showed the range of dimensions and conditions over which an effective, reliable, blood lubricated journal bearing can be designed. Subsequent bench testing has validated the theoretical conclusions and shown this bearing type to be very robust in a blood pump application.

  18. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

  19. Nonlinear Transient Modeling and Design of Turbocharger Rotor/Semi-Floating Bush Bearing System

    Directory of Open Access Journals (Sweden)

    Jianming Cao

    2017-06-01

    Full Text Available This work presents the bearing design and analysis of radial semi-floating bush oil lubricated bearings for a typical industrial turbocharger configuration. Initially, the stability analysis for a linear rotor/bearing system is evaluated through eigenvalues and eigenvectors. The stiffness and damping coefficients of the inner oil film are obtained for the linear modeling process. The operating speed range of the turbocharger is high enough, at 21,000 to 24,000 rpm, to be unstable, indicating that the analysis should be and is carried out with nonlinear transient modeling. The nonlinear transient analysis evaluates the rotor and bush limit cycle orbits, rotor dynamics, the forces acting on the rotor and semi-floating bush surfaces, the oil flow through the bearing, the oil temperatures, and the power loss of the two oil films. The optimum design of a set of semi-floating bush bearings for this application depends strongly upon the clearances of the bush and squeeze film damper, usually expressed as the non-dimensional clearance to radius ratio. A typical clearance is evaluated to determine the bearing performance in terms of orbit size, forces acting on the bush and squeeze damper surfaces, oil flow through the bearing, power loss, and thermal heating. The nonlinear transient orbit values are evaluated for frequency content using the FFT to determine which orbits show both the synchronous and sub-synchronous vibration components and the associated rotor modes excited. These results are compared to the linear analysis over the operating speed range. The oil flow through the bearing component is much larger than the squeeze film damper. The forces acting on the bush and squeeze damper surfaces are related to the fatigue life of the bearing.

  20. Roughness effect on squeeze film pressure

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    siderable interest to many investigators. There is extensive literature available on this sub- ject. Jackson (1962) gave a theoretical analysis of this problem and Kuzma et al (1964) advanced the case of squeeze film with an applied magnetic film. In both these papers the fluid inertia effect has been neglected. This theory was ...

  1. Pressure Distribution in Hydrodynamic Journal Bearing with Lubricants Additives

    Directory of Open Access Journals (Sweden)

    Omer M. A.

    2014-07-01

    Full Text Available In this paper, the effects of additives on the base lubricants has been investigated and reported, aiming for enhancement and the improvement of hydrodynamic journal bearing performance. A pair of additives volume fractions with a viscosity ratio were considered as blended with the base binder. A dimensionless pressure distribution with improved viscosity over the lubricant film has been identified. The results show an increase on the pressure distribution in response to increase in volume fraction of the additives.

  2. A numerical approach for the analysis of deformable journal bearings

    Directory of Open Access Journals (Sweden)

    D. Benasciutti

    2012-07-01

    Full Text Available This paper presents a numerical approach for the analysis of hydrodynamic radial journal bearings. The effect of shaft and housing elastic deformation on pressure distribution within oil film is investigated. An iterative algorithm that couples Reynolds equation with a plane finite elements structural model is solved. Temperature and pressure effects on viscosity are also included with the Vogel-Barus model. The deformed lubrication gap and the overall stress state were calculated. Numerical results are presented with reference to a typical journal bearing configuration at two different inlet oil temperatures. Obtained results show the great influence of elastic deformation of bearing components on oil pressure distribution, compared with results for ideally rigid components obtained by Raimondi and Boyd solution.

  3. Theoretical and experimental studies on dynamics of double-helical gear system supported by journal bearings

    Directory of Open Access Journals (Sweden)

    Minghu Yin

    2016-05-01

    Full Text Available The dynamic behaviour of a double-helical gear system supported by journal bearings is theoretically and experimentally investigated in this study. A bending–torsional–axial coupling model for dynamic analysis of double-helical gear system is developed. Influence of the time-varying mesh stiffness and damping is considered. Oil film stiffness and damping of the supporting journal bearing are supposed to be time-varying, and the time-varying oil film stiffness and damping are predicted by a back propagation neural network, which is optimized by genetic algorithm. A double-helical gear–rotor–journal bearing system test rig is also established to carry out the experimental investigations, such as the dynamic transmission errors of gear pairs. The comparisons between theoretical and experimental results show that the time-varying oil film dynamic coefficients of journal bearings are an important internal excitation. The theoretical model with time-varying oil film stiffness and damping can predict the gear dynamics more accurate than the model with time-invariant oil film stiffness and damping, and the neural network optimized by genetic algorithm can obtain the time-varying oil film stiffness and damping efficiently and accurately for the dynamic analysis of double-helical gear system.

  4. Grease lubrication in rolling bearings

    CERN Document Server

    Lugt, Piet M

    2012-01-01

    The definitive book on the science of grease lubrication for roller and needle bearings in industrial and vehicle engineering. Grease Lubrication in Rolling Bearings provides an overview of the existing knowledge on the various aspects of grease lubrication (including lubrication systems) and the state of the art models that exist today. The book reviews the physical and chemical aspects of grease lubrication, primarily directed towards lubrication of rolling bearings. The first part of the book covers grease composition, properties and rheology, including thermal

  5. Improvement of bearing support lubrication

    Directory of Open Access Journals (Sweden)

    Shehovtseva E. V.

    2016-12-01

    Full Text Available Gas turbine engine bearing supports is an important part in providing product efficiency of general and special-purpose engineering industry. Attempts are being made to increase efficiency of bearing support. Such attempts are caused by the modern tendency of the development of engineering striving for compact machines and units possessing increased reliability and durability. Researches on finding discrepancies in operation of support for this purpose have been executed. The reasons of occurrence the fatigue crumbling on external bearing races at different stages development of working surface damage have been investigated. The basic constructions of support of shaft for the aviation gas turbine engine and methods of their lubrication have been considered. Shortcomings of existing methods of lubrication of bearing supports have been marked. The upgraded construction of the module of gas turbine bearing shaft, which allows to improve conditions of lubrication and bearing cooling as a result of a uniform oil feed to the contact zones of outside bearing race and rolling elements and forced oil removal from contact zones of inside bearing race and rolling elements has been suggested. The task of improving conditions of lubrication supply to an internal holder of the bearing has been solved. The developed design allows applying unconventional methods of lubrication and cooling of a bearing support. Thus it is recommended to use process of regulation of a microrough on working surfaces bearing support during grinding-in. It will allow to improve a stage grinding-in and to increase reliability and durability of bearing support.

  6. Fluid Shifts

    Science.gov (United States)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; hide

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  7. Hydrostatic and hybrid bearing design

    CERN Document Server

    Rowe, W B

    1983-01-01

    Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des

  8. Evaluation of the Thermal Effects in Tilting Pad Bearing

    Directory of Open Access Journals (Sweden)

    G. B. Daniel

    2013-01-01

    Full Text Available The analysis of thermal effects is of expressive importance in the context of rotordynamics to evaluate the behavior of hydrodynamic bearings because these effects can influence their dynamic characteristics under specific operational conditions. For this reason, a thermohydrodynamic model is developed in this work, in which the pressure distribution in the oil film and the temperature distribution are calculated together. From the pressure distribution, the velocity distribution field is determined, as well as the viscous dissipation, and consequently, the temperature distribution. The finite volume method is applied to solve the Reynolds equation and the energy equation in the thermohydrodynamic model (THD. The results show that the temperature is higher as the rotational speed increases due to the shear rate of the oil film. The maximum temperature in the bearing occurs in the overloaded pad, near the outlet boundary. The experimental tests were performed in a tilting pad journal bearing operating in a steam turbine to validate the model. The comparison between the experimental and numerical results provides a good correlation. The thermohydrodynamic lubrication developed in this assignment is promising to consistently evaluate the behavior of the tilting pad journal bearing operating in relatively high rotational speeds.

  9. Performance of Simple Gas Foil Thrust Bearings in Air

    Science.gov (United States)

    Bruckner, Robert J.

    2012-01-01

    Foil bearings are self-acting hydrodynamics devices used to support high speed rotating machinery. The advantages that they offer to process fluid lubricated machines include: high rotational speed capability, no auxiliary lubrication system, non-contacting high speed operation, and improved damping as compared to rigid hydrodynamic bearings. NASA has had a sporadic research program in this technology for almost 6 decades. Advances in the technology and understanding of foil journal bearings have enabled several new commercial products in recent years. These products include oil-free turbochargers for both heavy trucks and automobiles, high speed electric motors, microturbines for distributed power generation, and turbojet engines. However, the foil thrust bearing has not received a complimentary level of research and therefore has become the weak link of oil-free turbomachinery. In an effort to both provide machine designers with basic performance parameters and to elucidate the underlying physics of foil thrust bearings, NASA Glenn Research Center has completed an effort to experimentally measure the performance of simple gas foil thrust bearing in air. The database includes simple bump foil supported thrust bearings with full geometry and manufacturing techniques available to the user. Test conditions consist of air at ambient pressure and temperatures up to 500 C and rotational speeds to 55,000 rpm. A complete set of axial load, frictional torque, and rotational speed is presented for two different compliant sub-structures and inter-pad gaps. Data obtained from commercially available foil thrust bearings both with and without active cooling is presented for comparison. A significant observation made possible by this data set is the speed-load capacity characteristic of foil thrust bearings. Whereas for the foil journal bearing the load capacity increases linearly with rotational speed, the foil thrust bearing operates in the hydrodynamic high speed limit. In

  10. Improvement of Dynamic Performance of Hybrid Gas Bearings via Adjustable Lubrication

    DEFF Research Database (Denmark)

    Pierart Vásquez, Fabián Gonzalo; Santos, Ilmar

    2013-01-01

    In modern turbo-machinery gas journal bearings have been increasingly adopted, because they can operate at higher speed than most bearing designs. The main disadvantage of gas bearings is their low dynamic stability range. One solution to improve this and their performance is to combine the aerod......In modern turbo-machinery gas journal bearings have been increasingly adopted, because they can operate at higher speed than most bearing designs. The main disadvantage of gas bearings is their low dynamic stability range. One solution to improve this and their performance is to combine...... form of Reynolds Equation. To include the effect of the injection, an extra term is added to the Reynolds Equation, considering the fully developed Hagen-Poeiseuille flow in the injection pipeline. In order to verify this assumption, a Computational Fluid Dynamics (CFD) model is developed...

  11. Autosizing Control Panel for Needle Bearing

    OpenAIRE

    Prof.A.R.Wadhekar,; Ms Jyoti R. Rajput

    2016-01-01

    A needle roller bearing is a bearing which uses small cylindrical rollers. Bearings are used to reduce friction of any rotating surface. Needle bearings have a large surface in contact with the bearing outer surfaces as compared to ball bearings. There is less added clearance(Diameter of the shaft and the diameter of the bearing are different) so they are much compact. The structure consists of a needle cage which contains the needle rollersthemselves and an outer race (The housin...

  12. Drag reduction and improvement of material transport in creeping films

    Energy Technology Data Exchange (ETDEWEB)

    Scholle, M.; Rund, A.; Aksel, N. [University of Bayreuth, Department of Applied Mechanics and Fluid Dynamics, Bayreuth (Germany)

    2006-01-01

    It is widely accepted that for bodies in turbulent flows a reduction of skin friction can be reached if the surface of the body is provided with small ridges aligned in the local flow direction. This surprising and counterintuitive phenomenon is called the shark-skin effect, motivated from the dermal surface morphology of sharks. In the present article we examine the possibility of resistance reduction due to a rippled surface topography in Stokes flow. We especially analyse the influence of wall riblets perpendicular to the flow direction on the mean transport velocity in gravity-driven creeping film flows following the idea that eddies generated in the valleys of the riblets act like fluid roller bearings and hence may reduce drag. Using a theoretical treatment of the Stokes equations with complex function theory, parameter studies with varying flow rate, bottom amplitude and bottom shape are presented. For the given bottom shapes the maximum enhancement of transport velocity is found by optimising the film thickness. (orig.)

  13. Fabrication of nanochannels on polyimide films using dynamic plowing lithography

    Science.gov (United States)

    Stoica, Iuliana; Barzic, Andreea Irina; Hulubei, Camelia

    2017-12-01

    Three distinct polyimide films were analyzed from the point of view of their morphology in order to determine if their surface features can be adapted for applications where surface anisotropy is mandatory. Channels of nanometric dimensions were created on surface of the specimens by using a less common atomic force microscopy (AFM) method, namely Dynamic Plowing Lithography (DPL). The changes generated by DPL procedure were monitored through the surface texture and other functional parameters, denoting the surface orientation degree and also bearing and fluid retention properties. The results revealed that in the same nanolithography conditions, the diamine and dianhydride moieties have affected the characteristics of the nanochannels. This was explained based on the aliphatic/aromatic nature of the monomers and the backbone flexibility. The reported data are of great importance in designing custom nanostructures with enhanced anisotropy on surface of polyimide films for liquid crystal orientation or guided cell growth purposes. At the end, to track the effect of the nanolithography process on the tip sharpness, degradation and contamination, the blind tip reconstruction was performed on AFM probe, before and after lithography experiments, using TGT1 test grating AFM image.

  14. Demonstration, Testing and Qualification of a High Temperature, High Speed Magnetic Thrust Bearing

    Science.gov (United States)

    DeWitt, Kenneth

    2005-01-01

    The gas turbine industry has a continued interest in improving engine performance and reducing net operating and maintenance costs. These goals are being realized because of advancements in aeroelasticity, materials, and computational tools such as CFD and engine simulations. These advancements aid in increasing engine thrust-to-weight ratios, specific fuel consumption, pressure ratios, and overall reliability through higher speed, higher temperature, and more efficient engine operation. Currently, rolling element bearing and squeeze film dampers are used to support rotors in gas turbine engines. Present ball bearing configurations are limited in speed (bearings require extensive preventative maintenance in order to assure their safe operation. Since these bearings are at their operational limits, new technologies must be found in order to take advantage of other advances. Magnetic bearings are well suited to operate at extreme temperatures and higher rotational speeds and are a promising solution to the problems that conventional rolling element bearings present. Magnetic bearing technology is being developed worldwide and is considered an enabling technology for new engine designs. Using magnetic bearings, turbine and compressor spools can be radically redesigned to be significantly larger and stiffer with better damping and higher rotational speeds. These advances, a direct result of magnetic bearing technology, will allow significant increases in engine power and efficiency. Also, magnetic bearings allow for real-time, in-situ health monitoring of the system, lower maintenance costs and down time.

  15. Method to Increase Performance of Foil Bearings Through Passive Thermal Management

    Science.gov (United States)

    Bruckner, Robert

    2013-01-01

    This invention is a new approach to designing foil bearings to increase their load capacity and improve their reliability through passive thermal management. In the present case, the bearing is designed in such a way as to prevent the carryover of lubricant from the exit of one sector to the inlet of the ensuing sector of the foil bearing. When such passive thermal management techniques are used, bearing load capacity is improved by multiples, and reliability is enhanced when compared to current foil bearings. This concept has recently been tested and validated, and shows that load capacity performance of foil bearings can be improved by a factor of two at relatively low speeds with potentially greater relative improvements at higher speeds. Such improvements in performance with respect to speed are typical of foil bearings. Additionally, operation of these newly conceived bearings shows much more reliability and repeatable performance. This trait can be exploited in machine design to enhance safety, reliability, and overall performance. Finally, lower frictional torque has been demonstrated when operating at lower (non-load capacity) loads, thus providing another improvement above the current state of the art. The objective of the invention is to incorporate features into a foil bearing that both enhance passive thermal management and temperature control, while at the same time improve the hydrodynamic (load capacity) performance of the foil bearing. Foil bearings are unique antifriction devices that can utilize the working fluid of a machine as a lubricant (typically air for turbines and motors, liquids for pumps), and as a coolant to remove excess energy due to frictional heating. The current state of the art of foil bearings utilizes forced cooling of the bearing and shaft, which represents poor efficiency and poor reliability. This invention embodies features that utilize the bearing geometry in such a manner as to both support load and provide an inherent and

  16. Squeeze Film Damping for Aircraft Gas Turbines

    OpenAIRE

    R. W. Shende; S. K. Sane

    1988-01-01

    Modern aircraft gas turbine engines depend heavily on squeeze film damper supports at the bearings for abatement of vibrations caused by a number of probable excitation sources. This design ultimately results in light-weight construction together with higher efficiency and reliability of engines. Many investigations have been reported during past two decades concerning the functioning of the squeeze film damper, which is simple in construction yet complex in behaviour with its non-linearity a...

  17. Nuclear films

    International Nuclear Information System (INIS)

    Malone, Peter.

    1985-01-01

    This booklet is a resource for the study of feature films that highlight the theme of nuclear war. It provides basic credits and brief indication of the theme, treatment, quality and particular notable aspects; and a series of questions raised by the film. Seventy feature films and thirty documentaries are examined

  18. Stability of Intershaft Squeeze Film Dampers

    Science.gov (United States)

    El-Shafei, A.

    1991-01-01

    Intershaft squeeze film dampers were investigated for damping of dual rotor aircraft jet engines. It was thought that the intershaft damper would enhance the stability of the rotor-bearing system. Unfortunately, it was determined that the intershaft squeeze film damper was unstable above the engine's first critical speed. Here, a stability analysis of rotors incorporating intershaft squeeze film dampers is discussed. A rotor model consisting of two Jeffcott rotors with two intershaft squeeze film dampers was investigated. Examining the system characteristic equation for the conditions at which the roots indicate an ever-growing unstable motion results in the stability conditions. The cause of the instability is identified as the rotation of the oil in the damper clearance. Several proposed configurations of intershaft squeeze film dampers are discussed, and it is shown that the intershaft dampers are stable supercritically only with a configuration in which the oil film does not rotate.

  19. Rotor drop and following thermal growth simulations using detailed auxiliary bearing and damper models

    Science.gov (United States)

    Sun, Guangyoung

    2006-01-01

    Catcher bearings (CBs) or auxiliary bearings provide mechanical backup protection in the events of magnetic bearing failure. This paper presents numerical analysis for a rotor drop on CBs and following thermal growths due to their mechanical rub using detailed CB and damper models. The detailed CB model is determined based on its material, geometry, speed and preload using the nonlinear Hertzian load-deflection formula, and the thermal growths of bearing components during the rotor drop are estimated using a 1D thermal model. A finite-element squeeze film damper provides the pressure profile of an annular oil film and the resulting viscous damping force. Numerical simulations of an energy storage flywheel with magnetic suspensions failed reveal that an optimal CB design using the detailed simulation models stabilizes the rotor drop dynamics and lowers the thermal growths while preventing the high-speed backward whirl. Furthermore, CB design guides based on the simulation results are presented.

  20. Nanorheology of strongly confined molecular fluids : a compter simulation study

    NARCIS (Netherlands)

    Manias, Evangelos D.

    1995-01-01

    The method of Molecular Dynamics (MD) computer simulations is employed to study ultra thin films of oligomer fluids, confined in spaces comparable to their molecular dimensions and subjected to (very) strong flows. ... Zie: Summary

  1. Effect of oil around the pin boss bearing on bearing friction force; Piston pin jikuukebu kinbo no junkatsuyu ga masatsuryoku ni oyobosu eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Takiguchi, M.; Suhara, T.; Ato, S.; Someya, T. [Musashi Institute of Technology, Tokyo (Japan)

    1997-10-01

    Piston pin bearings are engine parts placed under severe lubricating condition because of the high unit load and temperature and the low sliding speeds. Therefore, they are vulnerable to many lubrication problems such as abnormal wear, scuffs and seizures. In our recent study, the bearing friction were measured using a original measuring device and it was found out that the lubricating conditions of piston pin boss bearings are non-fluid lubrication due to the oil starvation. In this study, we have also measured the lubricating oil behavior around the pin boss bearing using a special cylinder with glass window, and analyzed the relationship between the friction force and the oil behavior at the pin boss bearings in a actual operating gasoline engine. 2 refs., 9 figs., 1 tab.

  2. Permanent-Magnet Meissner Bearing

    Science.gov (United States)

    Robertson, Glen A.

    1994-01-01

    Permanent-magnet meissner bearing features inherently stable, self-centering conical configuration. Bearing made stiffer or less stiff by selection of magnets, springs, and spring adjustments. Cylindrical permanent magnets with axial magnetization stacked coaxially on rotor with alternating polarity. Typically, rare-earth magnets used. Magnets machined and fitted together to form conical outer surface.

  3. Superconducting bearings for flywheel applications

    DEFF Research Database (Denmark)

    Abrahamsen, A.B.

    2001-01-01

    A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings...

  4. What about the Javan Bear?

    NARCIS (Netherlands)

    Jentink, F.A.

    1898-01-01

    The other day I read in a dutch popular periodical a paper dealing with the different species of Bears and their geographical distribution. To my great surprise the Malayan Bear was mentioned from Java: the locality Java being quite new to me I wrote to the author of that paper and asked him some

  5. 60NiTi Intermetallic Material Evaluation for Lightweight and Corrosion Resistant Spherical Sliding Bearings for Aerospace Applications, Report on NASA-Kamatics SAA3-1288

    Science.gov (United States)

    Dellacorte, Christopher; Jefferson, Michael

    2015-01-01

    Under NASA Space Act Agreement (SAA3-1288), NASA Glenn Research Center and the Kamatics subsidiary of the Kaman Corporation conducted the experimental evaluation of spherical sliding bearings made with 60NiTi inner races. The goal of the project was to assess the feasibility of manufacturing lightweight, corrosion resistant bearings utilizing 60NiTi for aerospace and industrial applications. NASA produced the bearings in collaboration with Abbott Ball Corporation and Kamatics fabricated bearing assemblies utilizing their standard reinforced polymer liner material. The assembled bearings were tested in oscillatory motion at a load of 4.54 kN (10,000 lb), according to the requirements of the plain bearing specification SAE AS81820. Several test bearings were exposed to hydraulic fluid or aircraft deicing fluid prior to and during testing. The results show that the 60NiTi bearings exhibit tribological performance comparable to conventional stainless steel (440C) bearings. Further, exposure of 60NiTi bearings to the contaminant fluids had no apparent performance effect. It is concluded that 60NiTi is a feasible bearing material for aerospace and industrial spherical bearing applications.

  6. Nonlinear control of magnetic bearings

    Science.gov (United States)

    Pradeep, A. K.; Gurumoorthy, R.

    1994-01-01

    In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular sliding mode controllers, time optimal controllers, winding algorithm based controllers, nested switching controllers, fractional controllers, and synchronous switching controllers for the magnetic bearing. We show existence of solutions to systems governed by discontinuous control laws, and prove stability and robustness of the chosen control laws in a rigorous setting. We design sliding mode observers for the magnetic bearing and prove the convergence of the state estimates to their true values. We present simulation results of the performance of the magnetic bearing subject to the aforementioned control laws, and conclude with comments on design.

  7. Flywheel Challenge: HTS Magnetic Bearing

    International Nuclear Information System (INIS)

    Werfel, F N; Floegel-Delor, U; Riedel, T; Rothfeld, R; Wippich, D; Goebel, B

    2006-01-01

    A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know

  8. Diffusive spreading and mixing of fluid monolayers

    International Nuclear Information System (INIS)

    Popescu, M N; Dietrich, S; Oshanin, G

    2005-01-01

    The use of ultra-thin, i.e. monolayer, films plays an important role in the emerging field of nano-fluidics. Since the dynamics of such films is governed by the interplay between substrate-fluid and fluid-fluid interactions, the transport of matter in nanoscale devices may eventually be efficiently controlled by substrate engineering. For such films, the dynamics is expected to be captured by two-dimensional lattice-gas models with interacting particles. Using a lattice-gas model and the non-linear diffusion equation derived from the microscopic dynamics in the continuum limit, we study two problems of relevance in the context of nano-fluidics. The first one is the case in which along the spreading direction of a monolayer a mesoscopic-sized obstacle is present, with a particular focus on the relaxation of the fluid density profile upon encountering and passing the obstacle. The second one is the mixing of two monolayers of different particle species which spread side by side following the merger of two chemical lanes, here defined as domains of high affinity for fluid adsorption surrounded by domains of low affinity for fluid adsorption

  9. Fluid Mechanics

    Science.gov (United States)

    Pnueli, David; Gutfinger, Chaim

    1997-01-01

    This text is intended for the study of fluid mechanics at an intermediate level. The presentation starts with basic concepts, in order to form a sound conceptual structure that can support engineering applications and encourage further learning. The presentation is exact, incorporating both the mathematics involved and the physics needed to understand the various phenomena in fluid mechanics. Where a didactical choice must be made between the two, the physics prevails. Throughout the book the authors have tried to reach a balance between exact presentation, intuitive grasp of new ideas, and creative applications of concepts. This approach is reflected in the examples presented in the text and in the exercises given at the end of each chapter. Subjects treated are hydrostatics, viscous flow, similitude and order of magnitude, creeping flow, potential flow, boundary layer flow, turbulent flow, compressible flow, and non-Newtonian flows. This book is ideal for advanced undergraduate students in mechanical, chemical, aerospace, and civil engineering. Solutions manual available.

  10. Solar advanced internal film receiver

    International Nuclear Information System (INIS)

    Torre Cabezas, M. de la

    1990-01-01

    In a Solar Central Internal Film Receiver, the heat absorbing fluid (a molten nitrate salt) flows in a thin film down over the non illuminated side of an absorber panel. Since the molten salt working fluid is not contained in complicated tube manifolds, the receiver design is simples than a conventional tube type-receiver resulting in a lower cost and a more reliable receiver. The Internal Film Receiver can be considered as an alternative to the Direct Absorption Receiver, in the event that the current problems of the last one can not be solved. It also describes here the test facility which will be used for its solar test, and the test plans foreseen. (Author) 17 refs

  11. Fluid dynamics

    CERN Document Server

    Ruban, Anatoly I

    This is the first book in a four-part series designed to give a comprehensive and coherent description of Fluid Dynamics, starting with chapters on classical theory suitable for an introductory undergraduate lecture course, and then progressing through more advanced material up to the level of modern research in the field. The present Part 1 consists of four chapters. Chapter 1 begins with a discussion of Continuum Hypothesis, which is followed by an introduction to macroscopic functions, the velocity vector, pressure, density, and enthalpy. We then analyse the forces acting inside a fluid, and deduce the Navier-Stokes equations for incompressible and compressible fluids in Cartesian and curvilinear coordinates. In Chapter 2 we study the properties of a number of flows that are presented by the so-called exact solutions of the Navier-Stokes equations, including the Couette flow between two parallel plates, Hagen-Poiseuille flow through a pipe, and Karman flow above an infinite rotating disk. Chapter 3 is d...

  12. Extended-gate field-effect transistor (EG-FET) with molecularly imprinted polymer (MIP) film for selective inosine determination.

    Science.gov (United States)

    Iskierko, Zofia; Sosnowska, Marta; Sharma, Piyush Sindhu; Benincori, Tiziana; D'Souza, Francis; Kaminska, Izabela; Fronc, Krzysztof; Noworyta, Krzysztof

    2015-12-15

    A novel recognition unit of chemical sensor for selective determination of the inosine, renal disfunction biomarker, was devised and prepared. For that purpose, inosine-templated molecularly imprinted polymer (MIP) film was deposited on an extended-gate field-effect transistor (EG-FET) signal transducing unit. The MIP film was prepared by electrochemical polymerization of bis(bithiophene) derivatives bearing cytosine and boronic acid substituents, in the presence of the inosine template and a thiophene cross-linker. After MIP film deposition, the template was removed, and was confirmed by UV-visible spectroscopy. Subsequently, the film composition was characterized by spectroscopic techniques, and its morphology and thickness were determined by AFM. The finally MIP film-coated extended-gate field-effect transistor (EG-FET) was used for signal transduction. This combination is not widely studied in the literature, despite the fact that it allows for facile integration of electrodeposited MIP film with FET transducer. The linear dynamic concentration range of the chemosensor was 0.5-50 μM with inosine detectability of 0.62 μM. The obtained detectability compares well to the levels of the inosine in body fluids which are in the range 0-2.9 µM for patients with diagnosed diabetic nephropathy, gout or hyperuricemia, and can reach 25 µM in certain cases. The imprinting factor for inosine, determined from piezomicrogravimetric experiments with use of the MIP film-coated quartz crystal resonator, was found to be 5.5. Higher selectivity for inosine with respect to common interferents was also achieved with the present molecularly engineered sensing element. The obtained analytical parameters of the devised chemosensor allow for its use for practical sample measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Biomimetic hydration lubrication with various polyelectrolyte layers on cross-linked polyethylene orthopedic bearing materials.

    Science.gov (United States)

    Kyomoto, Masayuki; Moro, Toru; Saiga, Kenichi; Hashimoto, Masami; Ito, Hideya; Kawaguchi, Hiroshi; Takatori, Yoshio; Ishihara, Kazuhiko

    2012-06-01

    Natural joints rely on fluid thin-film lubrication by the hydrated polyelectrolyte layer of cartilage. However, current artificial joints with polyethylene (PE) surfaces have considerably less efficient lubrication and thus much greater wear, leading to osteolysis and aseptic loosening. This is considered a common factor limiting prosthetic longevity in total hip arthroplasty (THA). However, such wear could be mitigated by surface modification to mimic the role of cartilage. Here we report the development of nanometer-scale hydrophilic layers with varying charge (nonionic, cationic, anionic, or zwitterionic) on cross-linked PE (CLPE) surfaces, which could fully mimic the hydrophilicity and lubricity of the natural joint surface. We present evidence to support two lubrication mechanisms: the primary mechanism is due to the high level of hydration in the grafted layer, where water molecules act as very efficient lubricants; and the secondary mechanism is repulsion of protein molecules and positively charged inorganic ions by the grafted polyelectrolyte layer. Thus, such nanometer-scaled hydrophilic polymers or polyelectrolyte layers on the CLPE surface of acetabular cup bearings could confer high durability to THA prosthetics. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. An accurate solution of the gas lubricated, flat sector thrust bearing

    Science.gov (United States)

    Etsion, I.; Fleming, D. P.

    1976-01-01

    A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

  15. Elastic ring deformation and pedestal contact status analysis of elastic ring squeeze film damper

    Science.gov (United States)

    Zhang, Wei; Ding, Qian

    2015-06-01

    This paper investigates the dynamic parametric characteristic of the elastic ring squeeze film damper (ERSFD). Firstly, the coupled oil film Reynolds equations and dynamic equations of an ERSFD supported rotor system are established. The finite differential method and numerical simulation are used to analyze the oil film pressure distribution, bearing capacity of ERSFD, oil film stiffness and damping characteristics during a vibration period. Then, based on the oil film pressure results, the deformation of elastic ring is revealed by the finite element method. Finally, pedestal contact status is analyzed according to the change of oil film thickness during a vibration period. The results reveal that the oil film pressure is sectionally continuous, the deformation of elastic ring is complex under the compression of inner and outer oil film, and different pedestal contacts occur in a vibration period. The level of nonlinearity of the bearing capacity, oil film stiffness and damping can be effectively lightened by application of the elastic ring.

  16. Dual clearance squeeze film damper for high load conditions

    Science.gov (United States)

    Fleming, D. P.

    1985-01-01

    Squeeze film dampers are widely used to control vibrations in aircraft turbine engines and other rotating machinery. However, if shaft unbalance rises appreciably above the design value (e.g., due to a turbine blade loss), a conventional squeeze film becomes overloaded, and is no longer effective in controlling vibration amplitudes and bearing forces. A damper concept characterized by two oil films is described. Under normal conditions, only one low-clearance film is active, allowing precise location of the shaft centerline. Under high unbalance conditions, both films are active, controlling shaft vibration in a near-optimum manner, and allowing continued operation until a safe shutdown can be made.

  17. DESIGN HANDBOOK ON GAS BEARINGS FOR GYROSCOPES.

    Science.gov (United States)

    consisting of a plain journal for supporting radial loads flanked by two spiral-grooved thrust bearings to support double-acting thrust loads; (3) the spiral-grooved journal bearing ; and (4) the spiral-grooved conical bearing.

  18. Hybrid Hydrostatic/Transient Roller Bearing Assembly

    Science.gov (United States)

    Justak, John F.

    1992-01-01

    Proposed bearing assembly for shaft of high-speed turbopump includes both hydrostatic and rolling-element bearings. Rolling-element bearing unloaded at high speed by centrifugal expansion of outer race and transient retainer.

  19. Two pad axially grooved hydrostatic bearing

    Science.gov (United States)

    San Andres, Luis A. (Inventor)

    1995-01-01

    A hydrostatic bearing having two axial grooves on opposite sides of the bearing for breaking the rotational symmetry in the dynamic force coefficients thus reducing the whirl frequency ratio and increasing the damping and stiffness of the hydrostatic bearing.

  20. Tilting-Pad Journal Bearings with Active Lubrication Applied as Calibrated Shakers: Theory and Experiment

    DEFF Research Database (Denmark)

    Cerda Varela, Alejandro Javier; Santos, Ilmar

    2014-01-01

    In recent years, a continuous research effort has transformed the conventional tilting-pad journal bearing into a mechatronic machine element. The addition of electromechanical elements provides the possibility of generating controllable forces over the rotor as a function of a suitable control...... directly into the bearing clearance. The injected flow is controlled by means of a servovalve. The theoretical model includes the dynamics of servovalves and pipelines using a lumped parameter approach, whereas the coupling between the hydraulic system and the bearing oil film is modeled using a modified...