Academic literature on the topic 'Hybrid fluid bearings'
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Journal articles on the topic "Hybrid fluid bearings"
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Polyakov, Roman, Leonid Savin, and Denis Shutin. "Reliability Improvement of Rotor Supports by Combining Rolling-Element Bearings and Fluid-Film Bearings." Applied Mechanics and Materials 630 (September 2014): 188–98. http://dx.doi.org/10.4028/www.scientific.net/amm.630.188.
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Reliability of rotating machinery is determined to a considerable degree by the bearing units. For several applications the requirements in rotation speed, bearing load and maximal vibration level are so extreme that neither rolling-element bearings nor fluid-film bearings could provide necessary performance characteristics during all regimes of operation. Hybrid bearings, which are a combination of rolling-element and fluid-film bearings, can improve performance characteristics and reliability of the rotor-bearing systems. The aim of this work is to analyze the advantages and disadvantages of the hybrid bearings. Known real applications of hybrid bearings are discussed. Analysis shows that depending on the application different hybrid bearing types could improve dynamic characteristics and life time of the bearing unit, increase load capacity and DN limit of the rolling-element bearing.
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Polyakov, Roman, Leonid Savin, and Alex Fetisov. "Analysis of the conditions for the occurrence of the effect of a minimum of friction in hybrid bearings based on the load separation principle." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, no. 2 (May 21, 2018): 271–80. http://dx.doi.org/10.1177/1350650118777143.
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Reliability of rotating machinery is determined to a considerable degree by the bearing units. For several applications the requirements in rotational speed, bearing load and maximal vibration level are so extreme that neither rolling-element bearings nor fluid-film bearings could provide necessary operating characteristics during all regimes of operation. Hybrid bearings, which are a combination of rolling-element and fluid-film bearings, can improve performance characteristics and reliability of the rotor-bearing systems. A hybrid bearing, where a rolling-element bearing and a fluid-film bearing are positioned parallel to the vector of external load (PLEX), has the following advantages compared to a single bearing, whether rolling-element or fluid-film one: increase of life expectancy, load capacity increase, friction reduction, thermal regime enhancement, increase of stiffness, and damping properties. The present paper presents the results of theoretical and numerical research of friction characteristics of PLEX in mixed sliding and rolling friction, i.e. combination of viscous and rolling contact friction, regime. The conditions of minimum friction effect occurrence have been substantiated, and rational relations between characteristics of hybrid rolling-element bearings and fluid-film bearings needed for provision of such effect have been experimentally proven. Finally, the paper presents recommendations regarding design of such hybrid bearings for heavily loaded bearing nodes of rolling mills.
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San Andre´s, Luis. "Turbulent Hybrid Bearings With Fluid Inertia Effects." Journal of Tribology 112, no. 4 (October 1, 1990): 699–707. http://dx.doi.org/10.1115/1.2920318.
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High speed hybrid bearings for cryogenic applications demand large levels of external pressurization to provide substantial load capacity. These conditions give rise to large film Reynolds numbers, and thus, cause the fluid flow within the bearing film to be turbulent and dominated by fluid inertia effects both at the recess edges and at the thin film lands. The analysis includes the effect of recess fluid compressibility and a model for the pressure rise within the recess region. Flow turbulence is simulated by friction factors dependent on the local Reynolds numbers and surface conditions. A perturbation method is used to calculate the zeroth and first flow fields and determine the bearing steady-state and dynamic force response. Comparison of results with existing experimental data shows the accuracy of the present full inertial-turbulent analysis. A roughened bearing surface is shown to improve considerably the stability characteristics of hybrid bearings operating at high speeds.
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Fedorynenko, Dmytro, Serhii Sapon, Sergiy Boyko, and Anastasiia Urlina. "Increasing of Energy Efficiency of Spindles with Fluid Bearings." Acta Mechanica et Automatica 11, no. 3 (September 1, 2017): 204–9. http://dx.doi.org/10.1515/ama-2017-0031.
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AbstractPromising ways of energy efficiency gain of spindles with fluid flow bearings are offered. New design of journal hybrid flow bearing which contains spherical bearing pockets and adjustable valves with relay control system is offered to improve energy efficiency of spindle units of machine tools. To reduce power losses of fluid bearings at high speed special lubrication based on water with integrated system of corrosion protection is offered. Results of theoretical research of energy consumption of grinding machine tool with a new design of spindle hybrid bearings are presented. Power losses of the spindle unit with both new design and base design of journal bearings are assessed. Effectiveness of new design of spindle hybrid bearings at high operating speeds is shown.
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Xiu, Shi Chao, Shi Qiang Gao, and Zhi Li Sun. "Study on Thermal Properties of Hybrid Journal Bearing for Super High Speed Grinding Machine." Advanced Materials Research 126-128 (August 2010): 808–13. http://dx.doi.org/10.4028/www.scientific.net/amr.126-128.808.
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As the high speed bearings, hybrid journal bearings are usually used in high and super high speed grinding machine spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of bearing is a key factor to lower the accuracy of the spindle system and limit the bearings working speed, so restrict the bearing applications. In this paper, the model of hybrid journal bearing is established to analyze the heat mechanism. In addition, the temperature field distribution for the certain hybrid journal bearing at high speed is studied by ANSYS considering the heat transfer characters between fluid and solid. The experiment of temperature for hybrid journal bearing system in super high speed grinding machine is also performed. The thermal properties and the measure for controlling temperature rise of such bearings are analyzed.
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San Andre´s, Luis. "Bulk-Flow Analysis of Hybrid Thrust Bearings for Process Fluid Applications." Journal of Tribology 122, no. 1 (June 10, 1999): 170–80. http://dx.doi.org/10.1115/1.555340.
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Advanced cryogenic fluid turbopumps are very compact, operate at extremely high shaft speeds, and require hybrid (hydrostatic/hydrodynamic) radial and thrust fluid film bearings for accurate rotor positioning. Sound design and reliable operation of fluid film thrust bearings also allows for unshrouded impellers with a significant increase in the turbopump mechanical efficiency. A bulk-flow analysis for prediction of the static load performance and dynamic force coefficients of high speed, angled injection orifice-compensated, hybrid (hydrostatic/hydrodynamic) thrust bearings is presented. The model accounts for the bulk-flow mass, momentum and thermal energy transport, and includes flow turbulence and fluid inertia (advection and centrifugal) effects on the bearing film lands and recesses. The performance of a refrigerant hybrid thrust bearing for an oil-free air conditioning equipment is evaluated at two operating speeds and pressure differentials. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The axial stiffness coefficient shows a maximum for a certain intermediate load while the damping coefficient steadily increases with load. The computed results show the significance of centrifugal fluid inertia at low recess pressures (i.e. low loads) and high rotational speeds, and which can lead to film starvation at the bearing inner radius and subambient pressures just downstream of the bearing recess edge. [S0742-4787(00)02201-3]
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Wang, Jian, Jing Feng Shen, and Ya Wen Fan. "Static characteristics analysis of spherical hybrid sliding bearings." Industrial Lubrication and Tribology 72, no. 1 (September 7, 2019): 93–100. http://dx.doi.org/10.1108/ilt-06-2019-0213.
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Purpose The spherical hybrid sliding bearings (SHSBs) can be used in ultra-precision and heavy-duty machine tools. However, there is little related research for these bearings. The purpose of this study is to investigate the static characteristics and effect factors affecting SHSBs by fluid lubrication. Design/methodology/approach Based on the theories of fluid lubrication, the Reynolds equation of general Newtonian fluid is derived to obtain the steady-state lubrication equation. The system is solved by the finite difference method and the relaxation iterative method on the staggered grid to obtain the thickness and the pressure distribution of the oil film. The radial and axial load capacities of SHSBs are determined by the pressure field integration over the spherical surface. Findings The results show that the parameters such as oil supply pressure, bearing clearance, eccentricity ratio, rotating speed and orifices’ number affecting the static characteristics of bearings are significant and the cross-coupling effect exists. Originality/value The lubrication model of SHSB is established to analyze the pressure distribution with a variety of oil film thickness. The laws of oil supply pressure, bearing clearance, eccentricity ratio, rotating speed and orifices’ number on the load capacities are researched.
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San Andre´s, Luis. "Effects of Misalignment on Turbulent Flow Hybrid Thrust Bearings." Journal of Tribology 124, no. 1 (May 3, 2001): 212–19. http://dx.doi.org/10.1115/1.1400997.
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An extended computational bulk-flow analysis for prediction of performance in angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings is presented. The fluid motion within the thin film lands is governed by mass conservation and momentum transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. A perturbation analysis for small amplitude shaft axial motions and angulations leads to zeroth and first-order equations describing the equilibrium and perturbed fluid flows. The computational procedure predicts the bearing flow rate, thrust load and restoring moments, drag torque, and 27 force and moment coefficients. The effects of misalignment on the dynamic performance of a refrigerant fluid-hybrid thrust bearing are evaluated at an optimal operating condition. The axial force/displacement stiffness coefficient and the direct moment/angle stiffness coefficients show a maximum for a certain recess pressure ratio, while the damping coefficient steadily increases with the applied load. As the misalignment angle increases, both moment and force coefficients also increase. Most operating conditions show a whirl frequency ratio equal to 0.50. Thus, thrust hybrid bearings offer the same limited stability characteristics as hydrodynamic thrust bearings when undergoing self-excited shaft angular motions.
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Xiu, Shi Chao, Shi Qiang Gao, and Zhi Li Sun. "Analysis of Thermal Properties of Super-High Speed Hybrid Journal Bearing Based on ANSYS." Advanced Materials Research 118-120 (June 2010): 753–57. http://dx.doi.org/10.4028/www.scientific.net/amr.118-120.753.
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Hybrid journal bearings are used in the high and super high speed cases mainly, such as the super-high speed spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of the bearing is a major reason to lower the accuracy of the main shaft system and limit the bearings working speed higher, as a result, restrict the bearing applications. In this paper, the thermal properties and the heat mechanism of such bearings are analyzed. The mathematical model of hybrid journal bearing is established to analyze the mechanism of generating heat. In addition, the temperature field distribution for the certain hybrid journal bearing at speed of 10000 rpm is studied by means of software ANSYS considering the heat transfer characters between fluid and solid. An improved measure about temperature rise of hybrid journal bearing is presented.
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Laurant, Franck, and Dara W. Childs. "Rotordynamic Evaluation of a Near-Tangential-lnjection Hybrid Bearing." Journal of Tribology 121, no. 4 (October 1, 1999): 886–91. http://dx.doi.org/10.1115/1.2834151.
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Given the inherent DN and assembly limitations of rolling-element bearings, research is underway to develop hybrid bearings (combining hydrostatic and hydrodynamic effects) for their replacement. Hybrid bearings develop cross-coupled stiffness coefficients due to fluid rotation, leading to predictions of onset speeds of instability and potential limitations in their range of application. Injecting fluid into a bearing recess against rotation, versus the customary radial injection, can reduce the circumferential flow and the cross-coupled-stiffness coefficients, and increase the margin of stability. Test results are presented here for a hybrid bearing with against-rotation injection. The bearing has a 76.4 mm diameter with LID = 1, and CrIR = 0.001. Data are presented for 55°C water at three speeds out to 25000 rpm and three pressures out to 7.0 MPa. Compared to a radial-injection hybrid bearing, experiments show injection against rotation enhances stability, yielding reductions of cross-coupled stiffness coefficients and whirl frequency ratios. However, increased flow rate and a drop of effective stiffness with increasing speed adversely affect the bearing performance. The prediction code developed by San Andres (1995) includes angled-orifice injection. The code correctly predicts trends, but at low speed, measured cross-coupled stiffness coefficients are positive, versus a prediction of larger negative values.
Dissertations / Theses on the topic "Hybrid fluid bearings"
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Elliott, Tony William. "Highly loaded hybrid journal bearings." Thesis, Liverpool John Moores University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238639.
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Hassini, Mohamed Amine. "Contribution à l'analyse des paliers fluides et des joints d'étanchéité utilisés dans lesturbopompes spatiales." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2285/document.
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La conception des turbomachines à haute densité énergétique nécessite de plus en plus la maîtrise d'un plus grand nombre de paramètres fonctionnels. La moindre défaillance d'un composant conduit quasi immédiatement la machine à la rupture. C'est en particulier le cas pour le comportement des composants à films minces.L'appellation "film mince" correspond à tout espace de très faible épaisseur situé entre le rotor et le stator de la turbomachine. Leur but est soit de limiter les fuites de manière à optimiser les performances intrinsèques de la machine, soit alors à supporter et stabiliser le rotor. Ces derniers cas sont plus appelés communément "joints lisses ou annulaires" et "paliers fluides".Lorsqu'un fluide circule dans un espace de très faible épaisseur, typiquement quelques centièmes de millimètres sur une distance très longue, son champ de vitesses, donc de pression, dépend fortement des phénomènes visqueux aux parois dont l'une est mise en rotation et l'autre est immobile. Les efforts fluides sur ces parois peuvent être alors importants et doivent être pris en compte dans le dimensionnement de la machine.La connaissance précise de ces écoulements très complexes est indispensable pour déterminer les efforts statiques et dynamiques appliqués au rotor de manière à pouvoir dimensionner un fonctionnement calmeThe design of high performance aerospace turbo pumps requires more control of an increasing number of functional parameters. Any component failure led almost immediately to a machine failure. This is particularly the case for the behavior of thin film lubricated components.The term "thin film" means any thin space between the rotor and the stator of the engine. Their goal is either to limit leakage to maximize the machine intrinsic performance, or to support and stabilize the rotor. These cases are more commonly called "smooth or annular seals" and "fluid film bearings".When a fluid flows in a space of very small thickness, typically a few hundredths of a millimeter, the velocity field, hence the pressure, are highly dependent on the walls viscous forces. Fluid forces on the walls (which one is rotated and the other is stationary) can then be important and should be taken into account in the design of the machine.The precise knowledge of these complex flows is essential to determine the static and dynamic forces applied to the rotor to ensure a quite functioning of the turbo pump
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Lawrence, Tom Marquis. "Characterization and Measurement of Hybrid Gas Journal Bearings." 2012. http://hdl.handle.net/1805/2926.
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Indiana University-Purdue University Indianapolis (IUPUI)This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to “basics” to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner’s permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow “compensation” should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an “apples-to-apples” comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is developed to study in unprecedented detail the aerostatic component of the hybrid bearings. It is used to definitively compare the feedhole bearings to the porous liner bearings. The hydrostatic bearing efficiency (HBE) is defined and it is determined that the maximum achievable hydrostatic bearing efficiency (MAHBE) is determined solely by the bearing’s mass addition configuration. The MAHBE of the porous liner bearings is determined to be over 5 times that of the feedhole bearings. The method also presents a means to tune the Kmeas to the clearance to achieve the MAHBE as well as giving a complete mapping of the hitherto misunderstood complex shapes of aerostatic load versus radial deflection curves. This method also rediscovers the obscure phenomenon of static instability which is called in this thesis the “near surface effect” and appears to be the first work to present a practical method to predict the range of static instability and quantify its resultant stiffness fall-off. It determines that porous liner type bearings are not subject to the phenomenon which appears for feedhole type bearings when the clearance exceeds a critical value relative to its mass-addition compensation. The standing pressure waves of hydrostatic and hybrid bearings with the 2 configurations of external pressurization as well as a geometrically identical hydrodynamic bearing are studied in detail under the methodology of the “CFD microscope”. This method is used to characterize and identify the development, growth, and movement of the pressure wave extrema with increased hydrodynamic action (either increasing speed or increasing eccentricity). This method is also used to determine the “cause” of the “near surface effect”. A gedanken experiment is performed based on these results which indicates that a bearing with a “stronger aerostatic strength” component should be more stable than one with a low aerostatic strength component. Numerical instability “speed limits” are found that are also related to the hydrostatic strength of the bearing. The local conditions in the standing waves are characterized in terms of their local Mach number, Knudsen number, Reynolds number, and Taylor Number. It is concluded that low eccentricity bearing whirl can be attributed to the off load-line orientation of the bearing load force caused by the overlay of the hydrodynamic bearing standing wave onto the hydrostatic bearing wave of the hybrid bearing, whereas it is hypothesized that aperiodic and random self-excited vibration which occurs at high eccentricity, as reported in the literature, is probably due to shock waves, turbulence, near surface effect, and slip at local areas of the standing wave.
Books on the topic "Hybrid fluid bearings"
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P, Hannum Ned, Meyer Scott D, and United States. National Aeronautics and Space Administration., eds. Evaluation of a hybrid hydrostatic bearing for cryogenic turbopump application. [Washington, DC]: National Aeronautics and Space Administration, 1986.
Find full textBook chapters on the topic "Hybrid fluid bearings"
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San Andrés, Luis. "Cryogenic Hybrid Fluid Film Bearings." In Encyclopedia of Tribology, 630–41. Boston, MA: Springer US, 2013. http://dx.doi.org/10.1007/978-0-387-92897-5_55.
Full textConference papers on the topic "Hybrid fluid bearings"
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Litwin, Wojciech. "Water Lubricated Hybrid Propeller Shaft Bearings With Polymer Bearing Bush." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63072.
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The article deals with water lubricated hybrid marine propeller shaft bearing which was designed and built at the Faculty of Ocean Engineering and Ship Technology of the Gdansk (Poland) University of Technology. The article contains the following parts: • Description of the test stand, the simulated working conditions, and tested bearings’ specifications. • Results of the conducted measurements. The results of the experimental work include: graphs of friction coefficient, pressures in the water hydrodynamic film and shaft trajectory. • Comparison of hybrid bearing with two others bearings. Typical main shaft bearing with grooved bearing bush working in a semi fluid friction conditions and hydrodynamic bearing with cull bearing bush (without any grooves). The work’s essential conclusion is that fluid film lubrication is possible also in hybrid bearings with grooves. As it was proven under simulated working conditions hydrodynamic lubrication does not take place in typical bearing with grooved bearing bush.
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Heshmat, Hooshang, H. Ming Chen, and James F. Walton. "On the Performance of Hybrid Foil-Magnetic Bearings." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-376.
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Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each others weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both. To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed.
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Weaver, Brian K., Gen Fu, Andres F. Clarens, and Alexandrina Untaroiu. "Performance Analysis of Gas-Expanded Lubricants in a Hybrid Bearing Using Computational Fluid Dynamics." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53735.
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Gas-expanded lubricants (GELs), tunable mixtures of synthetic oil and dissolved carbon dioxide, have been previously shown to potentially increase bearing efficiency, rotordynamic control, and long-term reliability in flooded journal bearings by controlling the properties of the lubricant in real time. Previous experimental work has established the properties of these mixtures and multiple numerical studies have predicted that GELs stand to increase the performance of flooded bearings by reducing bearing power losses and operating temperatures while also providing control over bearing stiffness and damping properties. However, to date all previous analytical studies have utilized Reynolds equation-based approaches while assuming a single-phase mixture under high-ambient pressure conditions. The potential implications of multi-phase behavior could be significant to bearing performance, therefore a more detailed study of alternative operating conditions that may include multi-phase behavior is necessary to better understanding the full potential of GELs and their effects on bearing performance. In this work, the performance of GELs in a fixed geometry journal bearing were evaluated to examine the effects of these lubricants on the fluid and bearing dynamics of the system under varying operating conditions. The bearing considered for this study was a hybrid hydrodynamic-hydrostatic bearing to allow for the study of various lubricant supply and operating conditions. A computational fluid dynamics (CFD)-based approach allowed for a detailed evaluation of the lubricant injection pathway, the flow of fluid throughout the bearing geometry, thermal behavior, and the collection of the lubricant as it exits the bearing. This also allowed for the study of the effects of the lubricant behavior on overall bearing performance.
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Estupinan, Edgar A., and Ilmar F. Santos. "Controllable Radial Oil Injection Applied to Main Engine Bearings: Hybrid Bearing Configurations and Control Pressure Rules." In STLE/ASME 2010 International Joint Tribology Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ijtc2010-41170.
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In order to reduce friction losses and vibrations in main engine bearings, fluid film lubrication is combined to controllable radial oil injection. This work evaluates different geometric hybrid bearing configurations and control pressure rules for applying radial oil injection in main engine bearings of internal combustion engines. The conventional hydrodynamic lubrication (CHL) is combined with hydrostatic lubrication which is actively modified by radially injecting oil at controllable pressures, through orifices circumferentially located around the bearing surface. The behaviour of a main bearing of a medium size combustion engine, operating with radial oil injection and with four different control strategies is analyzed, giving some insights into the minimum fluid film thickness (OFT) and reduction of viscous friction losses. The behaviour of such parameters is compared to the case when the bearing operates with conventional hydrodynamic lubrication.
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San Andrés, Luis, Stephen Phillips, and Dara Childs. "A Water Lubricated Hybrid Thrust Bearing: Measurements and Predictions of Static Load Performance." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56349.
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Process fluid lubricated thrust bearings (TBs) in a turbomachine control rotor placement due to axial loads arising from pressure fields on the front shroud and back surface of impellers. To date, prediction of aerodynamic induced thrust loads is still largely empirical. Thus needs persist to design and operate proven thrust bearings and to validate predictions of performance derived from often too restrictive computational tools. This paper describes a test rig for measurement of the load performance of water lubricated hydrostatic/hydrodynamic thrust bearings operating under conditions typical of cryogenic turbo pumps. The test rig comprises of a rigid rotor composed of a thick shaft and two end collars. A pair of flexure-pivot hydrostatic journal bearings (38 mm in diameter) support the rotor and quill shaft connected to a drive motor. The test rig hosts two thrust bearings (8 pockets with inner diameter equal to 41 mm and outer diameter equal to 76 mm); one is a test bearing and the other is a slave bearing, both facing the outer side of the thrust collars on the rotor. The slave TB is affixed rigidly to a bearing support. A load system delivers an axial load to the test TB through a non-rotating shaft floating on two aerostatic radial bearings. The test TB displaces to impose a load on the rotor thrust collar and the slave TB reacts to the applied axial load. The paper presents measurements of the TB operating axial clearance, flow rate and pocket pressure for conditions of increasing static load (max. 3,600 N) and shaft speed to 17.5 krpm (tip speed 69.8 m/s) and for an increasing water supply pressure into the thrust bearings, max. 17.2 bar (250 psig). Predictions from a bulk flow model that accounts for both fluid inertia and turbulence flow effects agree well with recorded bearing flow rates (supply and exiting thru the inner diameter), pocket pressure and ensuing film clearance due to the imposed external load. The measurements and predictions show a film clearance decreasing exponentially as the applied load increases. The bearing flow rate also decreases, and at the highest rotor speed and lowest supply pressure, the bearing is starved of lubricant on its inner diameter side, as predicted. The measured bearing flow rate and pocket pressure aid to the empirical estimation of the orifice discharge coefficient for use in the predictive tool. The test data and validation of a predictive tool give confidence to the integration of fluid film thrust bearings in cryogenic turbo pumps as well as in other more conventional (commercial) machinery. The USAF Upper Stage Engine Technology (USET) program funded the work during the first decade of the 21st century.
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Ertas, Bugra H. "Compliant Hybrid Journal Bearings Using Integral Wire Mesh Dampers." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50984.
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The following work presents a new type of hybrid journal bearing developed for enabling oil-free operation of high performance turbomachinery. The new design integrates compliant hydrostatic-hydrodynamic partitioned bearing pads with two flexibly mounted integral wire mesh dampers (IWMD). The primary aim of the new bearing configuration was to maximize the load carrying capacity and effective damping levels while maintaining adequate compliance to misalignment and variations in rotor geometry. The concept of operation is discussed along with the description of the bearing design. Several experiments using room temperature air as the working fluid were performed that demonstrate proof of concept, which include lift-off tests, bearing load tests, and rotordynamic characterization tests. The experiments demonstrate stable operation to 40,000 rpm (2.8 million DN) of a 2.750 in (70 mm) diameter bearing. In addition to the experimental results, an analytical model is presented for the compliant bearing system. The aeroelastic theory couples the steady state numerical solution of the compressible Reynolds flow equation with a flexible structure possessing translational and rotational compliance. This was achieved by formulating a fluid-structure force balance for each partitioned bearing pad while maintaining a global mass flow balance through the hydrostatic restrictors and bearing lands. Example numerical results for pad pressure profile, film thickness, torque, and leakage are shown.
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Childs, Dara W., and Paul Esser. "Measurements Versus Predictions for a Hybrid (Hydrostatic Plus Hydrodynamic) Thrust Bearing for a Range of Orifice Diameters." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56213.
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A fixed-geometry hybrid thrust bearing is investigated with three different supply-orifice diameters, (1.63, 1.80, and 1.93 mm). The test rig uses a face-to-face thrust bearing design, with the test bearing acting as the rotor loading mechanism. A hydraulic shaker applies the static axial load, which is reacted by a second (slave) thrust bearing. The rotor is supported radially by two water-lubricated fluid film journal bearings and is attached to a 30,600 rpm motor via a high speed coupling with very low axial stiffness. Thrust bearings are tested for a range of supply pressures (5.17, 10.34, 17.34 bars), fluid film thicknesses, and speeds (7.5, 12.5, and 17.5 krpm). The water-lubricated test bearings have eight pockets, with feed orifices located centrally in each pocket. Experimental results are comparted to predictions found using the bulk-flow model HYDROTHRUST®. Analysis of the data reveals generally good agreements between predictions and measurements. Thrust-bearing inlet supply and inner radius flow rates all decreased with decreasing orifice diameters and bearing axial clearances. In most cases, the bearings with larger orifice diameters exhibit higher recess pressure ratios, operating clearances, and flow rates. The 1.93 mm orifice diameter configuration does not display higher recess pressure ratios or operating clearances at high speeds for some supply pressures, but it does continue to require additional lubricant flow rate compared to the smaller orifice bearings. In these cases, the results are not reflected in predictions, which otherwise correlate very well with experimental measurements. Estimations of static loading axial stiffness are obtained using experimental results. An optimum hybrid thrust bearing orifice diameter will depend on the conditions of individual applications. Larger orifices generally provide larger operating clearances and higher stiffnesses, but also require higher flow rates. For most applications, a compromise of bearing performance parameters will be desired. The test results and comparisons presented will aid in sizing orifice diameters for future hybrid thrust bearing designs and in validating and improving models and predictions.
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Gary, Keith, Bugra Ertas, and Adolfo Delgado. "A General-Purpose Test Facility for Evaluating Gas Lubricated Thrust Bearings." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15520.
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Abstract The design, construction, operational capabilities, and proof of concept results are presented for a test rig used to evaluate gas-lubricated thrust bearings. The following work is motivated by a desire to utilize the working fluid of high-performance turbomachinery, such as gas turbines, for bearing lubricant. Auxiliary equipment required to cool, pump, and clean oil for a typical thrust bearing is eliminated by taking advantage of the turbomachinery’s working fluid as bearing lubricant. The benefit of removing such auxiliary equipment is obvious when considering cost and weight of turbomachines, yet the working fluid of gas turbines typically has very low viscosity compared to oil which introduces load capacity and stability challenges. It is therefore necessary to build a facility capable of testing gas-lubricated thrust bearings to advance the technology. The test rig design in this work allows for 7 to 15 inch (180–380 mm) diameter thrust bearings, static loads up to 30,000 lbf (135 kN), and speeds up to 20 krpm. The test facility also provides up to 500 psig (3.45 MPa) static air pressure to enable testing of hydrostatic and hybrid (hydrodynamic combined with hydrostatic) bearings. This paper describes the test rig operating principle, details experimental procedures to obtain measurements, and provides test results necessary to prove the test rig concept by means of a hybrid gas bearing.
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Bently, Donald E., John W. Grant, and Phillip C. Hanifan. "Active Controlled Hydrostatic Bearings for a New Generation of Machines." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0354.
Full textAbstract:
This paper presents a revolutionary approach of using a fluid-lubricated bearing for both traditional functions (load support, damping, and heat removal) and to actively control the rotor dynamics of rotating machinery. We will discuss how its use in the design of next generation turbomachinery can yield dramatic benefits. This includes an increase in efficiency, operational life, fault diagnostic, and reductions in machine size, weight, and cost. With the use of hydrostatic instead of hydrodynamic lubrication, traditional lubricants can be replaced by fluids more friendly to the process and environment. In this paper a comparison between the new hydrostatic bearing (Bently ServoFluid™ Control Bearing) and active magnetic bearings (AMB) will be presented. The Bently ServoFluid™ Control Bearing is an active controlled externally pressurized (a hybrid hydrostatic) bearing using fluid restoring force to compensate for rotor-related forces. It has the positive features of rolling element, fluid film and magnetic bearings with fewer negative attributes. The fluid restoring forces provide static and dynamic motion control similar to magnetic bearings, but with significantly larger compensation forces and with higher stiffness control. This revolutionary approach enables machinery owners to identify, understand and compensate for rotor system forces, an improvement over simply using vibration (motion) information for machinery diagnostics. This allows more complete diagnostics and prognostics of machine health. The bearing can be used to apply known perturbation forces to the rotor. Perturbation forces enable the determination of rotor system stiffness, and subsequent changes, thus improving machinery diagnostics. It can also provide information, such as the mechanical parameters governing the motion, system linearity, and stability margins for more accurate modeling of machines. Test results will be included to show experimentally determined transfer functions of each of the control loop elements, and predicted rotor forces. A typical root locus plot will be shown demonstrating how the characteristics change with bearing stiffness. Prototype machines, with both low viscosity fluid (water) and typical viscous fluid (T-10 turbine oil), have been built, tested, and successfully operated.
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Childs, Dara W., and David Mertz. "Comparative Lift-Off Performance in Flexure Pivot Pad and Hybrid (Hydrostatic and Hydrodynamic) Bearings With Water as the Test Fluid." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56212.
Full textAbstract:
Three nominally-identical, 4-pad flexure-pivot-pad bearings (FPBs) were manufactured, varying only in their (dimensionless) pad preloads, namely, 0.264, 0.511, and 0.695. A hybrid hydrostatic bearing (HBB) was also manufactured with the same nominal length, diameter, and clearances. Water was used as the test fluid. The FPBs were tested at the following three constant supply pressures (Ps): 0.689, 2.76, and 5.52 bar. The HBB was tested with a supply pressure that increased linearly to these same three terminal pressures. A magnetic bearing was used to load all bearings with an applied unit-load profile that increased linearly with time to reach the following two peak values: 0.745 and 1.38 bar. The design speed ωd was the maximum planned speed for a test run, and it was varied over 3, 3.5, 4, and 4.5 krpm. The tests aimed to produce a linearly increasing speed profile, ω(t) = At, before reaching ωd. For the HBB, bearing Ps also nominally increased linearly with ω. At lift-off, the shaft leaves the bearing surface during the shaft’s angular acceleration and remains separated and supported over a finite time and speed range. In some circumstances, FPB bearings lifted off and were then forced back into contact with the shaft due to the linearly increasing applied load. Once lifted off, the HBB always remained separated from the bearing surface. The peak load capacity was the maximum load supported by a bearing once lifted off (even if it was subsequently forced back into contact). FPBs have been used successfully in commercial turbomachinery handling low viscosity fluids. The results reported here indicate that preloads of m = 0.264 and 0.695 have comparable lift-off and peak load-capacity performance, substantially better than the m = 0.511 bearing. The FPB data also show a surprising steady drop in lift-off speeds and peak-load capacity with increasing Ps values, presumably because of end seals that were provided. From these results, an FPB should be used with end seals and preloads of m = 0.264 or 0.695. The HBB lift-off ω values also dropped with increasing terminal Ps values. For example, at ωd = 4.5 krpm, an increase in terminal Ps from 0.689 bar to 2.76 bar dropped lift-off ω from ∼3 krpm to ∼ 300 rpm. The supply pressure provided to the HBB increased linearly with time and, consequently, also increased linearly with ω. In reality, a centrifugal pump Ps would be proportional to ω2. To the extent that HBB lift-off ω performance depends on the supply pressure at lift off, lift-off ω and load-capacity performance of the present HBB would be worse with Ps ∼ ω2, since the same required lift-off supply pressure would occur only at a higher ω. Except at ωd = 3.5 krpm, the FPBs had better (lower) liftoff speeds than the HBB. The HBB tested maintained a consistently better peak-load capacity than the FPB. In some cases, the shaft lifted off the FPB and then returned to contact. In all cases, the HBB remained in a lifted-off condition. As a final conclusion, the present data provide no clear basis for choosing between the FPBs and the HBB.