Design and optimization of fluid lubricated bearings operated with extreme working performances——a comprehensive review

Fluid lubricated bearings have been widely adopted as support components for high-end equipment in metrology,semiconductor devices,aviation,strategic defense,ultraprecision manufacturing,medical treatment,and power generation.In all these applications,the equipment must deliver extreme working performances such as ultraprecise movement,ultrahigh rotation speed,ultraheavy bearing loads,ultrahigh environmental temperatures,strong radiation resistance,and high vacuum operation,which have challenged the design and optimization of reliable fluid lubricated bearings.Breakthrough of any related bottlenecks will promote the development course of high-end equipment.To promote the advancement of high-end equipment,this paper reviews the design and optimization of fluid lubricated bearings operated at typical extreme working performances,targeting the realization of extreme working performances,current challenges and solutions,underlying deficiencies,and promising developmental directions.This paper can guide the selection of suitable fluid lubricated bearings and optimize their structures to meet their required working performances.

Research on heat dissipation characteristics of magnetic fluid bearings under multiple field coupling effects

This paper analyzes the sources of heat losses in magnetic fluid bearings,proposes various cou-pling relationships of physical fields,divides the coupled heat transfer surfaces while ensuring the continuity of heat flux density,and analyzes the overall heat dissipation pathways of the bearings.By changing parameters such as input current,rotor speed,and inlet oil flow rate,the study applies a multi-physics field coupling method to investigate the influence of different parameters on the temper-ature field and heat dissipation patterns of the bearings,which is then validated through experi-ments.This research provides a theoretical basis for the optimal design of magnetic fluid bearing sys-tems.

Application of Computational Fluid Dynamics and Fluid Structure Interaction Techniques for Calculating the 3D Transient Flow of Journal Bearings Coupled with Rotor Systems

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 approacb 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 joumal 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.

Fluid-solid coupling model for studying wellbore instability in drilling of gas hydrate bearing sediments

As the oil or gas exploration and development activities in deep and ultra- deep waters become more and more, encountering gas hydrate bearing sediments （HBS） is almost inevitable. The variation in temperature and pressure can destabilize gas hydrate in nearby formation around the borehole, which may reduce the strength of the formation and result in wellbore instability. A non-isothermal, transient, two-phase, and fluid-solid coupling mathematical model is proposed to simulate the complex stability performance of a wellbore drilled in HBS. In the model, the phase transition of hydrate dissociation, the heat exchange between drilling fluid and formation, the change of mechanical and petrophysical properties, the gas-water two-phase seepage, and its interaction with rock deformation are considered. A finite element simulator is developed, and the impact of drilling mud on wellbore instability in HBS is simulated. Results indicate that the re- duction in pressure and the increase in temperature of the drilling fluid can accelerate hydrate decomposition and lead to mechanical properties getting worse tremendously. The cohesion decreases by 25% when the hydrate totally dissociates in HBS. This easily causes the wellbore instability accordingly. In the first two hours after the formation is drilled, the regions of hydrate dissociation and wellbore instability extend quickly. Then, with the soaking time of drilling fluid increasing, the regions enlarge little. Choosing the low temperature drilling fluid and increasing the drilling mud pressure appropriately can benefit the wellbore stability of HBS. The established model turns out to be an efficient tool in numerical studies of the hydrate dissociation behavior and wellbore stability of HBS.

FLUID FLOW SEPARATION CHARACTER ON NOVEL HYBRID JOURNAL BEARING

The influence of the structure and running parameters of a novel spiral oil wedge hybrid journal bearing on the fluid flow trace is investigated. The governing equation of the flow trace of lubricant is set up, and the simulation is carried out by using finite difference method. The results show that the lubricant flow status and end leakage quantity are greatly influenced by spiral angle,and that the rotating speed has little influence on the flow status. With advisable geometry design, the separation of lubricant between different oil wedges can be obtained, which can decrease the temperature rise effectively.

Types,Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area,Northern Continental Slope of the South China Sea

The first marine gas hydrate expedition in China has been conducted by Guangzhou Marine Geological Survey in the Shenhu Area, northern continental slope of the South China Sea. Previous study has analyzed the P-T conditions, geophysical anomalies and saturation calculations of these gas hydrates, but has not documented in detail the migration of gas-bearing fluids in the study area. Based on the interpretations of 2D/3D seismic data, this work identified two types of migration pathways for gas-bearing fluids in the Shenhu area, i.e., vertical and lateral pathways. The vertical pathways（largescale faults, gas chimneys and mud diapirs） presented as steep seismic reflection anomalies, which could be traced downward to the Eocene source rocks and may penetrate into the Late Miocene strata. The deeper gases/fluids might be allowed migrating into the shallower strata through these vertical conduits. However, the distributions showed distinct differences between these pathways. Large-scale faults developed only in the north and northeast of the Shenhu area, while in the drilling area gas chimneys were the sole vertical migration pathways. Since the Pliocene, normal faults, detachment faults and favorable sediments have constituted the lateral pathways in the Shenhu gas hydrate drilling area. Although these lateral pathways were connected with gas chimneys, they exerted different effects on hydrate formation and accumulation. Gas-bearing fluids migrated upward along gas chimneys might further migrate laterally because of the normal faults, thereby enlarging the range of the chimneys. Linking gas chimneys with the seafloor, the detachment faults might act as conduits for escaping gases/fluids. Re-deposited sediments developed at the early stage of the Quaternary were located within the gas hydrate stability zone, so hydrates would be enriched in these favorable sediments. Compared with the migration pathways（large-scale faults and mud diapirs） in the LW3-1 deep-sea oil/gas field, the migration efficiency of the vertical pathways（composed of gas chimneys） in the gas hydrate drilling area might be relatively low. Description and qualitative discrimination of migration pathways in the Shenhu gas hydrate drilling area are helpful to further understand the relationship between good-quality deep source rocks and shallow, mainly biogenicallyproduced, hydrates. As the main source rocks of the Baiyun sag, lacustrine mudstones in the Wenchang and Enping Formations may provide thermogenic methane. Gas chimneys with relatively low migration efficiency created the vertical pathways. Caused by the Dongsha tectonic movement, the release of overpressured fluids might reduce the vertical migration rates of the thermogenic methane. The thick bathyal/abyssal fine-grained sediments since the Late Miocene provided migration media with low permeability. These preconditions may cause carbon isotopic fractionation ofthermogenic methane during long-distance vertical migrations. Therefore, although geochemical analyses indicate that the methane forming gas hydrate in the Shenhu area was mainly produced biogenically, or was mixed methane primarily of microbial origin, thermogenic methane still contribute significantly.

Identification Method of Dynamic Coefficients of Fluid Film Bearings for HDD Spindle Motors

Fluid film bearings are widely used as support elements of rotating shaft for HDD （hard disk drive） spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipments such as mobile PCs, car navigation systems. Hence, the rotating shaft has a possibility to come in contact with the bearing and it causes wear or seizure to the bearing surface. In order to avoid the problems, it is extremely important to enhance the dynamic characteristics of the fluid film bearings for spindles. However, verification from both theory and experiment of dynamic characteristics such as spring coefficients and damping coefficients is rare and few. In this paper, the bearing vibration characteristics when the HDD spindle is oscillated are investigated theoretically and experimentally. And then the identification method ofoil film coefficients of fluid film bearing spindles is described.

Origin of Gold-Bearing Fluid and Its Initiative Localization Mechanism in Xiadian Gold Deposit,Shandong Province

The composition of quartz inclusions and trace elements in ore indicate that gold\|bearing fluid in the Xiadian gold deposit, Shandong Province, stemmed from both mantle and magma, belonging to a composite origin. Based on theoretical analysis and high temperature and high pressure experimental studies, gold\|bearing fluid initiative localization mechanism and the forming environment of ore\|host rocks are discussed in the present paper. The composite fluid extracted gold from rocks because of its expanding and injecting forces and flew through ore\|conducive structures, leading to the breakup of rocks. The generation of ore\|host faults and the precipitation of gold\|bearing fluid occurred almost simultaneously. This study provides further information about the relationships between gold ore veins and basic\|ultrabasic vein rocks and intermediate vein rocks, the spatial distribution of gold ore veins and the rules governing the migration of ore fluids.

Fluid Inclusions in the Gold-Bearing Quartz Veins at Um Rus Area, Eastern Desert, Egypt

Fluid inclusions in the gold-bearing quartz veins at the Um Rus area are of three types: H\-2O, H\-2O-CO\-2 and CO\-2 inclusions. H\-2O inclusions are the most abundant, they include two phases which exhibit low and high homogenization temperatures ranging from 150 to 200℃ and 175 to 250℃, respectively. The salinity of aqueous inclusions, based on ice melting, varies between \{6.1\} and 8 equiv. wt% NaCl. On the other hand, H\-2O-CO\-2 fluid inclusions include three phases. Their total homogenization temperatures range from 270 to 325℃, and their salinity, based on clathrate melting, ranges between \{0.8\} and \{3.8\} equiv. wt% NaCl. CO\-2 fluid inclusions homogenize to a liquid phase and exhibit a low density range from \{0.52\} to \{0.66\} g/cm\+3. The partial mixing of H\-2O-CO\-2 and salt H\-2O-NaCl fluid inclusions is the main source of fluids from which the other types of inclusions were derived. The gold-bearing quartz veins are believed to be of medium temperature hydrothermal convective origin.

Releasing of Cupric Ion of Three types of Copper-bearing Intrauterine Contraceptive Device in Simulated UterineFluid

Objective To compare the cupric ion releasing in vitro o.f the three IUDs. Methods The stability o.f cupric ion releasing o.f IUDs including TCu 380.4 IUD （TCu 380A）, Multiload Cu375 IUD （MCu 375） and Yuangong 365 copper-bearing indomethacin-releasing IUD （Yuangong 365） by the determination of cupric ion releasing in simulated uterine fluid. The simulated uterine fluid was used for releasing media. Copper ion was determined by flame atomic absorption spectrometer. Results The cupric ion releasing of three IUDs were instable at the beginning and tend to be stable gradually. In the stable phase, the average level of cupric ion releasing of TCu380A, MCu375 and Yuangong 365 were 4.25±2.71-7.62±6.42 μg, 4.92±1.23 -8.62±3.08 μg and 2.19±0.40-4.68±1.66 μg, respectively. TCu380A had higher instable releasing level than those of Yuangong 365 （P〈0. 05）. Conclusion TCu 380.4 and MCu 375 showed a ＂burst release＂ during the first few days and the.former was of great significance（P〈0.05）. The initial cupric ion releasing of Yuangong 365 appeared to be the lowest, followed by MCu375 and TCu380A in a releasing order

NONLINEAR NUMERICAL ANALYSIS OF A FLEXIBLE ROTOR EQUIPPED WITH SQUEEZE COUPLE STRESS FLUID FILM JOURNAL BEARINGS

This study performs a dynamic analysis of a rotor supported by two squeeze couple stress fluid film journal bearings with nonlinear suspension. The numerical results show that the stability of the system varies with the non-dimensional speed ratios and the dimensionless parameter l＊. It is found that the system is more stable with higher dimensionless parameter l＊. Thus it can conclude that the rotor-bearing system lubricated with the couple stress fluid is more stable than that with the conventional Newtonian fluid. The modeling results thus obtained by using the method proposed in this paper can be used to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided.

A Spectral Finite Difference Method for Analysis of a Fluid-Lubricated Herringbone Grooves Journal Bearing under a Special Case at Rectangle Groove

A spectral difference method is applied to get numerical solutions for a fluid-lubricated herringbone grooved journal bearing with trapezoidal grooves by previous work of the authors. However, an inexpedience in which Fourier series of the film profile does not converge at jump points of groove start or groove end in the case of rectangle groove was still remained. In the paper, an inexpedience of numerical analysis under a special case at rectangle groove is challenged to solve. As a result, for compensation of which Fourier series does not converge at jump points in a special case of rectangle groove, Fourier coefficient of fluid film thickness is proposed as taking the limit of which in a case trapezoidal groove at trapezoidal angle approaches 0.

Ultralight Oxygen in Corundum-Bearing Rocks of North Karelia, Russia, as a Result of Isotope Separation by Thermal Diffusion (Soret Effect) in Endogenous Fluid Flow

Helium and argon isotopes in fluid inclusions in minerals of corundum bearing rocks with anomalous light oxygen of the Khitoostrov (North Karelia, Russia) were studied. It was found that atmospheric noble gas component is missing. Therefore, all previously proposed models of participation in the fluid surface ice meltwater are not valid. Proposed and justified endogenous mechanism of isotope fractionation of oxygen and other chemical elements by the mechanism of thermal diffusion. Geologically justified existence of the cascading effect for a number of the separation thermodiffusion cells, which lead to significant isotope effects. Cascading is realized due to the “fluid pump”, in which role are acting amphibolized gabbro in the contact with corundum metasomatites. It is assumed that the mechanism is not specific for the case corundum metasomatic rocks, which are a special case of manifestation of such a scenario in processes involving endogenous fluid flows.

Approximate Solution of Oil Film Load-carrying Capacity of Turbulent Journal Bearing with Couple Stress Flow

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 c[~brts, 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, whicb are suitable for high eccentricity ratios and heavy loads.

Finite Element Method Applied to the Eigenvalue Analysis of Flexible Rotors Supported by Journal Bearings

This work deals with a finite element procedure developed to perform the eigenvalue analysis of damped gyroscopic systems, represented by flexible rotors supported on fluid film journal bearings. The rotor finite element model is based on the Timoshenko beam theory, accounting for the shaft rotary inertia and gyroscopic moments. The governing equations for the hydrodynamic journal bearing are obtained through the Galerkin weighted residual method applied to the classical Reynolds equation. A perturbation scheme on the fluid film governing equation permits to obtain the zero-th and first order lubrication equations for the bearings, which allow the computation of the dynamic force coefficients associated with the bearing stiffness and damping. The rotor-bearing system equation, which consists of a case of damped gyroscopic equation, is rewritten on state form to compute the complex eigenvalues. The natural frequencies at several operating conditions are obtained and compared to the technical literature data. The influence of the effective damping on the eigenvalue real part sign is analyzed for some examples of rotor-bearing systems, showing how the stability conditions can be predicted by the eigenvalue analysis. The procedure implemented in this work can provide useful guidelines and technical data about the selection of the more appropriate set of bearing parameters for rotating machines operating at stringent conditions.

LOADING CAPACITY ANALYSIS OF THE MISALIGNED CONICAL-CYLINDRICAL BEARING WITH NON NEWTONIAN LUBRICANTS

A novel numerical method to lubricate a conventional finite diameterconical-cylindrical bearing with a non-Newtonian lubricant, while adhering to the power-law model,is presented. The elastic deformation of bearing and varied viscosity of lubrication due to thepressure distribution of film thickness are also considered. Simulation results indicate that thenormal load carrying capacity is more pronounced for higher values of flow behavior index n, highereccentricity ratios and larger misalignment factors. It is found that the viscosity-pressure to theeffect of lubricant viscosity is significant.

Study on a New Type of Lubricating Oil for Miniature Bearing Operating at Ultra-low Temperature

The synthetic oil has been extensively used in the miniature bearing thanks to its good low-temperature fluidity. However, most of commercial synthetic oils cannot meet the requirements for operating at ultra-low temperature, demanding that the lubricating oil should flow below -60℃ with its ISO VG being greater than 10 mm^2/s. In this paper, the relationships between the structures of the ester, polyether, and silicone oils, and low temperature fluidity were investigated. The results showed that the low-temperature fluidity of oil having a shorter molecular chain length and a smaller molecular weight became better. Moreover, except the silicone oil, other synthetic oil cannot reach the requirements for working at ultra-low temperature. Silicone oil has good low-temperature properties, but it has poor lubricating properties in an environment where steel is sliding against steel. Then based on the analytical results, a new type of non-Newtonian oil was developed. The test results showed that the fluidity of the newly developed oil at below -60℃ is much better than that of the commercial 4123, 4129 ester type aviation lubricants. In addition, it has good lubricating performance, which is much better than that of the silicone oil. The non-Newtonian oil demonstrates a promising prospect for application in miniature bearings operating at low load and ultra-low temperature.

Numerical Analysis of Blast Furnace Performance Under Charging Iron-Bearing Burdens With High Reducibility

The reducibility of iron-bearing burdens was emphasized for improving the operation efficiency of blast furnace. The blast furnace operation of charging the burdens with high reducibility has been numerically evaluated using a multi-fluid blast furnace model. The effects of reaction rate constants and diffusion coefficients were investigated separately or simultaneously for clarifying the variations of furnace state. According to the model simulation results, in the upper zone, the indirect reduction of the burdens proceeds at a faster rate and the shaft efficiency is enhanced with the improvement under the conditions of interface reaction and intra-particle diffusion. In the lower zone, direct reduction in molten slag is restrained. As a consequence, CO utilization of top gas is enhanced and the ratio of direct reduction is decreased. It is possible to achieve higher energy efficiency of the blast furnace, and this is represented by the improvement in productivity and the decrease in consumption of reducing agent. The use of high-reducibility burdens contributes to a better performance of blast furnace. More efforts are necessary to develop and apply highreducibility sinter and carbon composite agglomerates for practical application at a blast furnace.

MHD Flow of a Non-Newtonian Power Law through a Conical Bearing in a Porous Medium

The problem of analytical study of the MHD effect through a porous medium of the non-isothermal flow of a non-Newtonian power law lubricant through the gap of conical bearing through a porous medium when an external magnetic field is applied. At first, the more general basic equations of motion, continuity and energy in curvilinear form in the width direction are derived. Then, as a special case, a conical bearing gap is considered. By integrating a modified form of Reynolds equation, the bearing characteristics for a non-Newtonian power law lubricant when an external magnetic field is applied through a porous medium are obtained. Numerical results were presented in each of these forms: pressure, temperature and capacity of the conical bearing. The effects of the parameters of the non-Newtonian power law, magnetic field and porous medium are shown and discussed.

Vibration Response Characteristics against the Radial and Axial Shocks on Small Size Hard Disk Drive Spindle Supported by Oil Film Bearings

This paper describes the experimental study on shock response of FDB （fluid dynamic bearing） spindle for HDDs （hard disk drives）. The FDBs are widely used as rotating shaft support elements for HDD spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipment such as mobile PCs （personal computers）, video cameras, car navigation systems and so on. Hence, the rotating shaft has a possibility to come in contact with the bearing by external shocks and it causes wear or seizure to the bearing surface. To avoid the problem, it is extremely important to know how the spindle moves against the large shock on HDDs experimentally. However, as far as the authors know, there are few experimental studies treating the shock response of HDD spindles. In this paper, firstly, we propose a new test rig and experimental method for shock response of FDB spindles. Then the shock tests against the radial and axial disturbance on FDB spindle for 2.5＂ HDD are conducted. Finally, the experimental results of shock response waveforms and maximum displacement of disk are shown.