Showing papers on "Fluid bearing published in 2015"
TL;DR: In this paper, the authors investigated the thermal effect of texture presence or absence on the bearing surface and found that the simulation results were in good concordance with those issued from the literature.
117 citations
01 Apr 2015
TL;DR: Textured surfaces are the subject of a great deal of research work in tribology, which mainly involves numerical studies of lubricated contacts as discussed by the authors, and a variety of shapes and arrangements of textures can be found.
Abstract: Textured surfaces are the subject of a great deal of research work in tribology, which mainly involves numerical studies of lubricated contacts. A variety of shapes and arrangements of textures can...
75 citations
TL;DR: In this article, the authors compared the performance of a three-layer composite bearing material with a rubber bearing of similar geometry and found that the rubber bearing has better bearing elasticity, good vibration damping properties and insusceptibility to shaft axis misalignment.
75 citations
TL;DR: In this article, the authors present a numerical model that characterizes both the hydrodynamic bearing as well as the wear present in its wall, and then, analyze the influence of the wear on the dynamic response of the rotor-bearing system in frequency domain, taking into account the rising of the backward component due to the increase of the bearing anisotropy.
41 citations
TL;DR: In this paper, the authors present experimental research conducted on comparable sliding bearing with lubrication grooves along entire bush circumference, assessing them against a different, modern solution, and it was proved that classic bush geometry is not appropriate for hydrodynamic lubrication.
38 citations
08 Jan 2015
TL;DR: In this paper, the authors present a case study of the effects of normal and shear stress on the performance of gear components in the context of work, energy, and power.
Abstract: Section I Basics Introduction Scope of the Book Mechanical Engineering Design Design Process Design Analysis Problem Formulation and Computation Factor of Safety and Design Codes Units and Conversion Loading Classes and Equilibrium Free-Body Diagrams and Load Analysis Case Studies in Engineering Work, Energy, and Power Stress Components Normal and Shear Strains Problems Materials Introduction Material Property Definitions Static Strength Hooke's Law and Modulus of Elasticity Generalized Hooke's Law Thermal Stress-Strain Relations Temperature and Stress-Strain Properties Moduli of Resilience and Toughness Dynamic and Thermal Effects Hardness Processes to Improve Hardness and the Strength of Metals General Properties of Metals General Properties of Nonmetals Problems Stress and Strain Introduction Stresses in Axially Loaded Members Direct Shear Stress and Bearing Stress Thin-Walled Pressure Vessels Stress in Members in Torsion Shear and Moment in Beams Stresses in Beams Design of Beams Plane Stress Combined Stresses Plane Strain Measurement of Strain Strain Rosette Stress-Concentration Factors Importance of Stress-Concentration Factors in Design Three-Dimensional Stress Equations of Equilibrium for Stress Strain-Displacement Relations: Exact Solutions Problems Deflection and Impact Introduction Deflection of Axially Loaded Members Angle of Twist of Shafts Deflection of Beams by Integration Beam Deflections by Superposition Beam Deflection by the Moment-Area Method Impact Loading Longitudinal and Bending Impact Torsional Impact Bending of Thin Plates Deflection of Plates by Integration Problems Energy Methods and Stability Introduction Strain Energy Strain Energy in Common Members Work-Energy Method Castigliano's Theorem Statically Indeterminate Problems Virtual Work Principle Use of Trigonometric Series in Energy Methods Buckling of Columns Critical Stress in a Column Initially Curved Columns Eccentric Loads and the Secant Formula Design Formulas for Columns Beam-Columns Energy Methods Applied to Buckling Buckling of Rectangular Plates Problems Section II Failure Prevention Static Failure Criteria and Reliability Introduction Introduction to Fracture Mechanics Stress-Intensity Factors Fracture Toughness Yield and Fracture Criteria Maximum Shear Stress Theory Maximum Distortion Energy Theory Octahedral Shear Stress Theory Comparison of the Yielding Theories Maximum Principal Stress Theory Mohr's Theory Coulomb-Mohr Theory Reliability Normal Distributions Reliability Method and Margin of Safety Problems Fatigue Failure Criteria Introduction Nature of Fatigue Failures Fatigue Tests S-N Diagrams Estimating the Endurance Limit and Fatigue Strength Modified Endurance Limit Endurance Limit Reduction Factors Fluctuating Stresses Theories of Fatigue Failure Comparison of the Fatigue Criteria Design for Simple Fluctuating Loads Design for Combined Fluctuating Loads Prediction of Cumulative Fatigue Damage Fracture Mechanics Approach to Fatigue Problems Surface Failure Introduction Corrosion Friction Wear Wear Equation Contact-Stress Distributions Spherical and Cylindrical Surfaces in Contact Maximum Stress in General Contact Surface-Fatigue Failure Prevention of Surface Damage Problems Section III Applications Shafts and Associated Parts Introduction Materials Used for Shafting Design of Shafts in Steady Torsion Combined Static Loadings on Shafts Design of Shafts for Fluctuating and Shock Loads Interference Fits Critical Speed of Shafts Mounting Parts Stresses in Keys Splines Couplings Universal Joints Problems Bearings and Lubrication Introduction Part A: Lubrication and Journal Bearings Lubricants Types of Journal Bearings Forms of Lubrication Lubricant Viscosity Petroff's Bearing Equation Hydrodynamic Lubrication Theory Design of Journal Bearings Lubricant Supply to Journal Bearings Heat Balance of Journal Bearings Materials for Journal Bearings Part B: Rolling-Element Bearings Types and Dimensions of Rolling Bearings Rolling Bearing Life Equivalent Radial Load Selection of Rolling Bearings Materials and Lubricants of Rolling Bearings Mounting and Closure of Rolling Bearings Problems Spur Gears Introduction Geometry and Nomenclature Fundamentals Gear Tooth Action and Systems of Gearing Contact Ratio and Interference Gear Trains Transmitted Load Bending Strength of a Gear Tooth: The Lewis Formula Design for the Bending Strength of a Gear Tooth: The AGMA Method Wear Strength of a Gear Tooth: The Buckingham Formula Design for the Wear Strength of a Gear Tooth: The AGMA Method Materials for Gears Gear Manufacturing Problems Helical, Bevel, and Worm Gears Introduction Helical Gears Helical Gear Geometry Helical Gear Tooth Loads Helical Gear Tooth Bending and Wear Strengths Bevel Gears Tooth Loads of Straight Bevel Gears Bevel Gear Tooth Bending and Wear Strengths Worm Gearsets Worm Gear Bending and Wear Strengths Thermal Capacity of Worm Gearsets Problems Belts, Chains, Clutches, and Brakes Introduction Part A: Flexible Elements Belts Belt Drives Belt Tension Relationships Design of V-Belt Drives Chain Drives Common Chain Types Part B: High Friction Devices Materials for Brakes and Clutches Internal Expanding Drum Clutches and Brakes Disk Clutches and Brakes Cone Clutches and Brakes Band Brakes Short-Shoe Drum Brakes Long-Shoe Drum Brakes Energy Absorption and Cooling Problems Mechanical Springs Introduction Torsion Bars Helical Tension and Compression Springs Spring Materials Helical Compression Springs Buckling of Helical Compression Springs Fatigue of Springs Design of Helical Compression Springs for Fatigue Loading Helical Extension Springs Torsion Springs Leaf Springs Miscellaneous Springs Problems Power Screws, Fasteners, and Connections Introduction Standard Thread Forms Mechanics of Power Screws Overhauling and Efficiency of Power Screws Ball Screws Threaded Fastener Types Stresses in Screws Bolt Tightening and Preload Tension Joints under Static Loading Gasketed Joints Determining the Joint Stiffness Constants Tension Joints under Dynamic Loading Riveted and Bolted Joints Loaded in Shear Shear of Rivets or Bolts due to Eccentric Loading Welding Welded Joints Subjected to Eccentric Loading Brazing and Soldering Adhesive Bonding Problems Miscellaneous Mechanical Components Introduction Basic Relations Thick-Walled Cylinders under Pressure Compound Cylinders: Press or Shrink Fits Disk Flywheels Thermal Stresses in Cylinders Exact Stresses in Curved Beams Curved Beam Formula Circular Plates Thin Shells of Revolution Special Cases of Shells of Revolution Pressure Vessels and Piping Filament-Wound Pressure Vessels Buckling of Cylindrical and Spherical Shells Problems Finite Element Analysis in Design Introduction Bar Element Formulation of the Finite Element Method Beam and Frame Elements Two-Dimensional Elements Triangular Element Plane Stress Case Studies Axisymmetric Element Problems Case Studies in Machine Design Introduction Floor Crane with Electric Winch High-Speed Cutter Problems Appendices Answers to Selected Problems References Index
31 citations
TL;DR: In this article, the authors proposed a new bearing bush with a transition-arc structure, which is favorable for increasing hydrodynamic load-carrying capacity of a water-lubricated journal bearing.
Abstract: Purpose – The purpose of this paper is to improve hydrodynamic load-carrying capacity of a water-lubricated journal bearing by a new bush structure. Water-lubricated bearing is becoming more and more popular since it is environmentally friendly and saves energy. However, contrary to oil and grease-lubricated bearings, water-lubricated bearing is limited in many situations due to its low hydrodynamic load-carrying capacity. Design/methodology/approach – The present article proposes a new bearing bush, with a transition-arc structure, which is favorable for increasing hydrodynamic load-carrying capacity. Hydrodynamic load-carrying capacity was calculated by means of three-dimensional computational fluid dynamics (3-D CFD) analysis. Several variants of a journal bearing with a transition-arc structure of different dimensions are analyzed, while the radial clearance of the bearing, eccentricity ratio and the velocity of the journal remain unchanged. Findings – The results show that obvious changes are found i...
30 citations
09 Mar 2015
TL;DR: In this paper, a single-groove journal bearing is assessed under steady-state loading and the set of governing equations including continuity, momentum, and energy within the journal bearing are analyzed.
Abstract: Thermohydrodynamic behaviors of single-groove journal bearing are assessed operating under steady-state loading. The set of governing equations including continuity, momentum, and energy within the...
25 citations
23 citations
01 Apr 2015
TL;DR: In this article, surface texturing is used to increase hydrodynamic pressure and reduce friction and wear between parallel sliding surfaces in a variety of applications, and the shape, geometry, and density of the patt...
Abstract: Surface texturing is used to increase hydrodynamic pressure and reduce friction and wear between parallel sliding surfaces in a variety of applications. The shape, geometry, and density of the patt...
19 citations
TL;DR: In this paper, a linear stability analysis of hydrodynamic journal bearings is presented, including the effects of elastic distortion of the liner and micropolar lubrication, and the results show that stability decreases with an increase in the value of the elasticity parameter of the bearing linings.
Abstract: A linear stability analysis of hydrodynamic journal bearings is presented, including the effects of elastic distortion of the liner and micropolar lubrication. Hydrodynamic equations of the lubricant and equations of motion of the journal are solved simultaneously with the deformation equations for the bearing surface to predict the fluid film pressure distributions theoretically. The components of stiffness and damping coefficients, critical mass parameter, and whirl ratio, which reflect the dynamic characteristic of the journal bearing, are calculated for varying eccentricity ratio taking into account the flexibility of the liner and the micropolar properties of the lubricant. The results presented show that stability decreases with an increase in the value of the elasticity parameter of the bearing liner and micropolar fluids exhibit better stability in comparison to Newtonian fluids.
TL;DR: In this article, a new rational formulation of the cavitation phenomenon occurring in porous journal bearings in the regime of fully hydrodynamic lubrication is presented, where the suitably extended form of the Reynolds equation is coupled with the semi-phenomenological Darcys law so as to yield a proper description of the combined flow through the lubrication gap and the porous (sintered) seat, respectively.
TL;DR: In this article, the textured bearing performance enhancement passes essentially by an improvement of a minimum film thickness, a maximum pressure and a friction torque through an appropriate surface texture geometry and appropriate texture distribution on the contact surface.
Abstract: The journal bearing is a complex system with high film convergence and with cavitation hydrodynamic phenomena. The surface texturation influence study on journal bearing performances requires unavoidably experimental investigations followed by a numerical modelling of the problem. This work consists in modellization and understanding of the journal bearing characteristics in both cases of presence or absence of textures onto the bearing surface. The finite difference method is used as numerical approach in the analysis. The textured bearing performance enhancement passes essentially by an improvement of a minimum film thickness, a maximum pressure and a friction torque through an appropriate surface texture geometry and appropriate texture distribution on the contact surface. It is found that the simulations results are in good concordance with litteratures. The texture area position on the bearing surface is the primary endpoint for journal bearing performance enhancement. The best design of textured area depends strongly on the geometrical parameters and the journal bearing operating conditions.
TL;DR: In this article, the tribological performances of journal bearings at different conditions through four numerical methods, which are based on the Boussinesq elastic half-space hypothesis or finite element theory, are analyzed and compared.
Abstract: Purpose – The purpose of this study is to analyze and compare the tribological performances of journal bearings at different conditions through four numerical methods, which are based on the Boussinesq elastic half-space hypothesis or finite element theory. Design/methodology/approach – An elasto-hydrodynamic lubrication (EHL) model of journal bearings is established, with the oil film pressure obtained by the finite difference method, and the deformation of bearing calculated by four different numerical methods, i.e. the direct finite element method (DFEM), influence coefficient method (ICM), fast-Fourier transform method (FFTM) and direct Boussinesq method (DBM). The tribological performances of the journal bearings obtained with the four methods along with the computation efficiency of the methods are discussed. Findings – Under different operation conditions, the tribological performances with the finite element method-based methods (DFEM and ICM) agree with each other, and so do those with the Boussi...
TL;DR: It was found that a significant load-carrying capacity of the bearing can be generated for lowubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.
Abstract: 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.
TL;DR: In this article, a concept of hybrid hydrodynamic-permanent magnetic bearing for the radial applied load has been developed, where the static load is taken by magnetic bearing and dynamic load by hydrodynamically bearing.
Abstract: Journal bearings are well known for their lowest wear rate and high damping coefficients under fully developed hydrodynamic lubrication mechanism. However, metal-metal contact at start/stop and low speed condition, causing bearing wear and excessive power loss, are major disadvantages of hydrodynamic bearing. Therefore, a concept of hybrid (hydrodynamic-permanent magnetic) bearing for the radial applied load has been developed. In such bearings the static load is taken by magnetic bearing and dynamic load by hydrodynamic bearing. However, due to the unstable nature of passive magnetic bearings and larger axial thrust compared to radial thrust emphasis for the requirement of extra subassembly and proper alignment compared to conventional bearings test setup. In the present work, using 3D Coulombian model, the radial and axial forces of a passive magnetic bearing for the given dimension having different arc length of the top stator magnet have been analyzed. To reduce the unstable force, the required axial offset was estimated. After obtaining the required configuration from the theoretical results, the hybrid bearing was developed. Experiments were performed on the preliminary developed experimental setup and the challenges faced for development of setup and problems faced after performing the experiment have been reported. A detailed investigation was carried out to overcome the problems and various solutions have been provided.
TL;DR: In this article, the authors compared polymer-lined thrust bearings with babbitt-lined ones under similar conditions and showed that polymer-based materials can operate at higher bearing unit loads than Babbitt.
Abstract: 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.
18 Mar 2015
TL;DR: In this article, a link-spring structural model was employed to calculate the equivalent vertical stiffness of the bump foil bearing, which exhaustively considered the effect of three factors: flexibility of bump foil, interactions between bumps and frictional forces at the contact s. In an analytical model used to predict the performance of gas foil thrust bearings, fluid structure interaction must be considered because of the coupling effects of hydrodynamic lubrication and the compliance of bearing surface.
Abstract: Gas foil bearings have bright application prospects in oil-free turbomachinery such as aircraft air cycle machines, compressors, and gas turbines. To extend the applicability of foil bearings to high-speed and heavy-load systems, the axial force produced primarily by the pressure difference between the turbine and compressor sides must be taken into consideration. The thrust disc of the rotor is typically used to sustain the axial force and maintain the attitude of the rotor in a rotor-bearing system. In an analytical model used to predict the performance of gas foil thrust bearings, fluid–structure interaction must be considered because of the coupling effects of hydrodynamic lubrication and the compliance of bearing surface. In this study, a link-spring structural model was employed to calculate the equivalent vertical stiffness of the bump foil. This model exhaustively considered the effect of three factors: flexibility of the bump foil, interactions between bumps and frictional forces at the contact s...
TL;DR: In this article, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method.
Abstract: Purpose – The purpose of this paper is to develop a good calculation model to accurately predict the lubrication characteristic of main bearings of diesel engine and improve the service life. Design/methodology/approach – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the Component Mode Synthesis (CMS) method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method. Findings – Obviously, the mixed lubrication of bearings is normal, while full hydrodynamic lubrication is transient. The results show that under the whole flexible block model, maximum oil film pressure, maximum asperity contact pressure and radial shell deformation decrease, while minimum oil film thickness increases. Oil flow over edge decreases...
01 Oct 2015
TL;DR: In this paper, a calculating model for roller-pocket rotation and mechanics analysis is established to investigate the hydrodynamic lubrication between rollers and straight-sided cage pockets in a cylindrical roller bearing.
Abstract: A calculating model for roller-pocket rotation and mechanics analysis is established to investigate the hydrodynamic lubrication between rollers and straight-sided cage pockets in a cylindrical roller bearing. An algorithm for calculating roller-pocket oil film pressure and film thickness is developed. Hydrodynamic lubrication simulation of the roller-pocket clearances is carried out. Effects of inner ring rotation speed, cage angular acceleration, roller profile and cage geometry on roller-pocket oil film performance are numerically studied. Some regular curves and conclusions are obtained and analyzed.
TL;DR: In this article, the curved beam model is adopted to build an elastohydrodynamic model considering the area contact between adjacent foils, which is solved iteratively coupling the Reynolds equation with the finite element method.
Abstract: For multileaf foil bearings, the interactions between adjacent foils, foils, and gas film are key to predicting the bearing performance. However, most of the analytical models were based on line contact rather than area contact between adjacent foils and the latter may occur and play an important role in load capacity. In this study, the curved beam model is adopted to build an elastohydrodynamic model considering the area contact between adjacent foils, which is solved iteratively coupling the Reynolds equation with the finite element method. An algorithm is developed to judge and determine the contact condition of adjacent foils. The simulation results show that the area contact between adjacent foils does occur and the contact area expands with increasing eccentricity ratios and rotational speeds, which make the film thickness distribution smooth and are beneficial to the increase in load capacity. The area contact occurs near the trailing end of the foils first and then gradually expands. The later fo...
TL;DR: In this paper, a strongly coupled fluid structure interaction (FSI) model is proposed to solve the transient soft elastohydrodynamic lubrication (EHL) problems in U-cup hydraulic reciprocating rod seals.
Abstract: Soft elastohydrodynamic lubrication (EHL) problems widely exist in hydraulic reciprocating rod seals and pose great challenges because of high nonlinearity and strong coupling effects, especially when the EHL problems are of high dimensions. In this paper, a strongly coupled fluid structure interaction (FSI) model is proposed to solve the transient soft EHL problems in U-cup hydraulic reciprocating rod seals. The Navier–Stokes equations, rather than the Reynolds equation, are employed to govern the whole fluid field in the soft EHL problems, with the nonlinearity of the solid taken into consideration. The governing equations of the fluid and solid fields are combined into one equation system and solved monolithically. To determine the displacements of nodes of the fluid field, a new moving mesh method based on the combination of the Laplace equation and the leader–follower methods is put forward. At last, the proposed FSI model runs successfully with the moving mesh method, and the boundaries of the hydrodynamic lubrication zones and the hydrostatic zones are formed automatically and change dynamically during the coupling process. The results are as follows: The soft EHL problems show typical characteristics, like the constriction effects of the lubricating films, and the law of dynamic development of the lubricating films and the fluid pressures is revealed. The minimum stroke lengths needed to generate complete lubricating films vary with the rod speeds and movement directions, so the design of the rod seals should be paid close attention to, in particular the rod seals of short stroke lengths. Furthermore, along with the dynamic development processes of the fluid pressures during the instroke of U-cup seals, the lubricating film humps expand and locate between the fluid pressure abrupt points and the outlet zones. After the U-cup seals reach the steady-states, the fluid abrupt points disappear and no changes of the film humps are observed. Theoretically, the proposed method can be popularized to solve similar soft EHL problems.
02 Aug 2015
TL;DR: In this article, a Taylor series expansion of bearing reaction force was used to identify the second-order oil-film forces of hydrodynamic bearing, and the results showed that these three models are more stable compared to those of other two nonlinear models.
Abstract: Journal bearings have been widely used in high-speed rotating machinery. The dynamic coefficients of oil-film force affect the machine unbalance response and machine stability. The oil-film force of hydrodynamic bearing is often characterized by a set of linear stiffness and damping coefficients. However the linear oil-film coefficients with respect to an equilibrium position of the journal are inaccurate when the bearing system vibrates with large amplitudes due to a dynamic load. The study on nonlinear oil-film forces is still rare and most papers are confined to theoretical analyses. The purpose of this paper is to derive some new non-linear force models (28-co., 24-co. and 36-co. models) to identify these dynamic coefficients based on experimental data. The fundamental test model is obtained from a Taylor series expansion of bearing reaction force. Tests were performed with a nominal diameter of 100mm and a length–to–diameter ratio of 0.7 using a suitable test rig in which it is possible to apply the static load in any direction. The results show that these three models are feasible to identify the oil-film forces in which the second-order oil-film coefficients received from the 24-co. model are more stable compared to those of other two nonlinear models.Copyright © 2015 by ASME
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04 Nov 2015TL;DR: In this paper, numerical run-up simulations of an automotive turbocharger are carried out in order to investigate the influence of circumferential grooves on the non-linear vibration behavior.
Abstract: Numerical run-up simulations of an automotive turbocharger are carried out in order to investigate the influence of circumferential grooves on the non-linear vibration behavior. The turbocharger rotor is modeled as a flexible multibody system. The hydrodynamic bearing forces are calculated based on two different approaches. Firstly, a modified short bearing solution is derived. Secondly, a finite-element model is coupled to the rotor model by means of a co-simulation technique. The latter is used to validate the modified short bearing solution. The results with circumferential grooves are compared to the results obtained with plain cylindrical bearings.
01 Jan 2015-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this paper, the authors investigated the design and characterization of a miniature fluid dynamic bearing using novel multi-step elliptical grooves for small-form-factor data storage applications and miniature fan motors.
Abstract: This paper investigates the design and characterization of a miniature fluid dynamic bearing using novel multi-step elliptical grooves for small-form-factor data storage applications and miniature fan motors. In contrast to conventional herringbone-grooved cylindrical journal bearings (HGJBs), the proposed journal bearing contains a single set of multi-step elliptical grooves (EGJB). The performance of the proposed multi-step EGJB is characterized numerically using proprietary flow field analysis software. In addition, to reduce the number of optimal full-factorial experimental design tests (323), the Taguchi parameter design methodology is used to find out the optimal design parameters of the multi-step EGJB. Results show that compared to the conventional HGJB presented by the current group in a previous study, the proposed multi-step EGJB improves the load capacity. Consequently, the proposed motor represents another solution for both existing and emerging miniaturized spindle motor applications.
TL;DR: In this paper, the effect of viscosity on the cavitation characteristics of a high speed sleeve bearing is investigated theoretically and experimentally by using the transparent bearing and the high-speed camera.
Abstract: The effect of viscosity on the cavitation characteristics of a high speed sleeve bearing is investigated theoretically and experimentally. The cavitation characteristics, the cavitation shape and the cavitation location of a spiral oil wedge hydrodynamic bearing are investigated experimentally by using the transparent bearing and the high-speed camera. The generalized Reynolds equation is established with considerations of the cavitation mechanism based on the modified Elrod method in theory, and the cavitations of different viscosity sleeve bearings are analyzed and compared. It is shown that the cavitations are strip-shaped for both the high viscosity lubricant and the low viscosity lubricant, and in the rupture region of the oil film at a high speed, the oil vapour or bubbles are produced. With the decrease of the supply pressure and the increase of the rotating speed, the rupture area of the oil film increases distinctly. The cavitation area decreases distinctly and the quality of lubrication is better for the low viscosity lubricant than for the high viscosity lubricant. The experiment results in general are consistent with the theoretical results.
12 Aug 2015
TL;DR: In this article, a flexibly supported herringbone-grooved aerodynamic journal bearing using straight spring wires made of stainless steel is proposed to provide a simple and reliable support system for a bearing bush.
Abstract: In recent years, small-size aerodynamic bearings for turbomachines such as blowers and compressors have attracted considerable attention for increasing rotational speed. These kinds of bearings require excellent stability at high speeds and durability in a high-temperature environment. Foil bearings are one of the most suitable candidates that can satisfy these requirements but their structure is very complicated, and it is difficult to control their manufacturing accuracy. It is well known that flexibly supported herringbone-grooved aerodynamic journal bearings have excellent stability at high speeds and they are relatively easy to manufacture compared with foil bearings. Moreover, their dynamic characteristics can be easily solved numerically. In this paper, a flexibly supported herringbone-grooved aerodynamic journal bearing using straight spring wires made of stainless steel is proposed to provide a simple and reliable support system for a bearing bush. Six straight spring wires were assembled into a hexagonal shape into which the bearing bush was inserted. The threshold speed of instability of the proposed aerodynamic bearing was investigated numerically and experimentally. For this investigation, the nonlinear orbit method was adopted in numerical calculations. This investigation found that straight spring wires could steadily support the bearing bush and provide a simple and reliable support system for the bearing bush and that a 6-mm-diameter rigid rotor with a mass of 4.8 g supported by the proposed aerodynamic journal bearings could stably rotate at speeds of more than 0.7 million rpm.Copyright © 2015 by ASME
TL;DR: In this article, the authors investigated the effect of the couple-stresses due to the presence of improving viscosity index (VI) additives on the steady-state behavior of a journal bearing operating under isothermal conditions and laminar flow.
Abstract: The proposed work is concerned with the theoretical and numerical investigation of the lubricant rheology effects on the steady-state behavior of a plain finite compliant journal bearing operating under isothermal conditions. In the present investigation, the couple-stresses due to the presence of improving viscosity index (VI) additives, the viscosity-pressure (piezoviscosity effect) as well as the density-pressure (compressibility effect) variations are considered. The hydrodynamic lubrication theory is based on the V.K. Stokes micro-continuum mechanics which takes into account the size of macro-molecular chains added to the basic oil. The Barus and Dowson-Higginson laws were used to express the viscosity-pressure and density-pressure variations. Using the classical assumptions of lubrication, a modified Reynolds’ equation is derived and solved numerically by the finite difference method. The displacement field at the fluid film bearing liner interface due to pressure forces is determined using the elastic thin liner model. The proposed work is concerned with the theoretical and numerical investigation of the lubricant rheology effects on the steady-state behavior of a plain finite compliant (elastic liner) journal bearing operating under isothermal conditions and laminar flow. The obtained results show that the couple-stresses have significant effects on the hydrodynamic performance characteristics such as the pressure field, the carrying capacity, the attitude angle and friction number especially when the viscosity-pressure variation is considered. Moreover, it is also shown that the compressibility of lubricant doesn’t affect the hydrodynamic characteristics.