The steady-state performance of an aerodynamic double thrust wave bearing was investigated. The investigation showed that a double thrust wave bearing with an inner diameter of 15 mm and an outer diameter of 45 mm can support axial loads of 200 N at 100,000 rpm for a minimum film thickness of 3 microns. The influence of the wave bearing parameters on the bearing performance was also analyzed. The theoretical analysis was validated by experimentally testing one side of the thrust bearing. A special test rig was built for this purpose. The experimental data were close to the numerical predictions, validating the computer codes.

Polycrystalline diamond (PCD) bearings are designed for use in extreme environments; this includes process-fluid-lubricated applications such as those in oil and gas drilling turbines and marine hydrokinetic (MHK) energy machines. Past uses of PCD bearings in oil and gas down-hole tool applications have proven them to be robust, long lived, and rugged [1]. To be effective in MHK machines, PCD bearings must demonstrate adequate bearing efficiency and life in a submerged marine environment not nearly as severe as an oil well bore or a gas well bore. This paper discusses the advantages PCD bearings could provide when used in underwater MHK energy machines. Laboratory test results are presented that can help predict the performance of PCD in these MHK applications. Results from three types of tests are presented including tests that measure bearing capacity, those that observe and qualify hydrodynamic properties during testing, and those that evaluate diamond wear rates through a test representing the life time of a bearing in a MHK energy application. Failure tests conducted to measure bearing capacity revealed the PCD bearing could well endure conditions found in MHK machines, and coefficient of friction (COF) tests demonstrated the PCD ability to move from a boundary lubrication regime, to mixed mode lubrication, and then become hydrodynamic. The PCD wear test was designed to simulate years in the life of a tidal stream power generator, an MHK energy machine, and showed the PCD life is more than adequate for the MHK application. Bearing capacity, COF, and wear observed during laboratory testing illustrate that PCD thrust bearings can provide a robust, long lasting, and low maintenance bearing in MHK applications.

An experimental study is presented with the main objective of understanding the hydrodynamic behavior of a taper land thrust bearing with fixed geometry. The experimental results were obtained on an original test rig designed at the Pprime Institute. An extensive instrumentation of the thrust bearing allows a precise evaluation of various elements such as the temperature, the film thickness or the friction torque. The results are in good agreement with other literature surveys. However, an important difference of the measured parameters was found between the pads. The authors consider that this is most probably caused by the imperfections of the active surface produced during machining.

In the paper, numerical TEHD results for one of the biggest water power plant Itaipu were compared to available measurement data. Numerical simulations were carried out with the use of bearing model for which the accuracy was previously confirmed with the measurements available for smaller bearings. Several cases were analyzed. The only differences between the cases are the applied boundary conditions. The influence of heat transfer coefficient assumed at bearing pad side walls and collar deformation on predicted bearing performance was determined. Some conclusions concerning large thrust bearing modeling were drawn on the basis of comparisons of the theoretical results to measurements for analyzed bearing system.

In this paper, an analytical model for calculating eddy current loss in magnetic thrust bearings (MTBs) is presented. The surface magnetic field intensity, considering the skin effect of eddy current, is varying with the frequency and can be calculated by effective reluctance method. The magnetic field distribution and eddy current loss can be obtained from it. Finally, the validity of the model is verified by the finite element method (FEM) simulation and experimental results.

This application study of a swash-plate type axial piston pump was concerned about the hydrostatic lubrication characteristics of cylinder barrel and valve plate which are main rotating body and its opposite moving part respectively. A computer simulation was implemented to assess thrust bearing and mechanical sealing functions of the fluid film between cylinder barrel and valve plate. A new algorithm was developed to facilitate simultaneous calculations of dynamic cylinder pressure, 3 degree-of-freedom barrel motions considering inertia effect, and fluid film pressure assuming full fluid film lubrication regime. Using the simulation tool, force and moment balancing of cylinder barrel which is a key issue of piston pump design was analyzed. Time dependent fluid film pressure and thickness distributions for several given balance ratios were calculated. This analysis helps to decide appropriate balance ratio in the valve and cylinder barrel. Oil leakage flow and friction torque in the fluid film between cylinder barrel and valve plate were calculated as well and discussed in the viewpoint of energy loss. The results show that film thickness in plain surface is not high enough to bear the barrel and reduce power loss and that surface waviness which exists in actual sliding surfaces can have a positive effect on it. This simulation tool could also predict time dependent barrel motions due to simultaneous calculation algorithm. It has been known that cylinder barrel rotates with oscillation. Therefore average clearance, tilt angle, and azimuth angle were calculated for each time step and the results were discussed.

In the manufacturing process of small size fluid film bearings, the machining errors of groove affect the bearing characteristics. This paper describes the optimum design of small size fluid film thrust bearings to reduce the characteristics variability caused by some productivity. Firstly, from the original result of the modified spiral bearing obtained by the geometrical optimization, critical bearing parameters related to sensitivity of dynamic stiffness was investigated. From the sensitivity analysis, it was clarified that the parameters of groove depth and groove ratio have high sensitivity towards bearing stiffness. In the optimum design with consideration of productivity, errors for groove depth and groove ratio were given using probability theory with restriction towards the dynamic stiffness variability. From the results, the reduction of dynamic stiffness variability was accomplished. Furthermore, even if the manufacturing errors exist, the optimized bearing is operated safely without contact because it is able to stay in the range of the allowable film thickness.

This paper studies the numerical development of flow patterns and pressure profiles inside a hybrid Rayleigh step thrust bearing (HRSB) where the working magnetohydrodynamic (MHD) fluid is subject to an imposed magnetic field. This hybrid type bearing stems from integrating two classical component: the modified Rayleigh step (variable depth) and the hydrostatic feed entering at the center of the circular thrust bearing. The parameters used in this study consist of one geometric parameter, the Rayleigh step aspect ratio (depth to length ratio) and two dimensionless operational parameters, (i) the Reynolds number based on the hydrostatic fluid jet velocity entering the restrictor (Re jet ) and the Reynolds number based on the smooth upper plate angular speed (Re plate ). The numerical results are obtained using the commercially available package ANSYS (CFX) [4], which utilizes the full three-dimensional Navier-Stokes equations for the steady-state incompressible MHD fluid with constant properties. Results to be presented will will contain both vector and pressure fields within the Rayleigh step profile and on the smooth lands.

Tilting pad thrust bearings are designed to transfer high axial loads from rotating shafts to the static support structure. In the present paper, formulation of Reynolds’ equation for the bearing is done in two dimensions (planar). A finite difference method is used to convert the terms of the Reynolds’ equation in to a set of simultaneous linear algebraic equations. A solution procedure for finding value of the pressure in the oil film is described. Numerical integration of the pressure values gives the load distribution. Subsequently, the study of angular stiffness of the film is done by varying the value of the oil film thickness and calculating torques at three different film shapes 1, 2 & 3 of the pad. The angular stiffness, differential displacement and load pertaining to the 3-2 pair are calculated for 0.5%–20% variation of h o . The results obtained show that the values of Kt* and K* converge asymptotically.

Air foil thrust bearings are the critical component available on high-efficiency turbomachinery which needs ability to endure the large axial force. Previous investigations about the static characteristics were obtained over the region of the thin air film using finite-difference method and the characteristics of the corrugated bump foil using finite-element method. Moreover, a recent study demonstrated that bearing performance is sensitive to tilting thrust pad condition. In this study, experimentally measured bearing static characteristics are compared with the numerical model of the foil thrust bearing considering tilting pad condition. Three geometrically different type foil bearings were tested to measure their load capacity under tilting conditions that have continuous angles from zero to 0.0002 rad. These data are presented for use i 1 n the development of more accurate foil thrust bearing numerical models.

The start-up friction coefficient is a parameter which is very useful for engineers who design hydrodynamic bearings. It is most often issued from an approximation. Several studies can be found in the literature on this topic but most of them are concerned with air bearings or are only numerical. Some studies are more general and deal with the transient thermal behaviour in journal bearings as well as in thrust bearings. Other studies deal with the friction coefficient during running, at a fixed rotational speed. The aim of this study is to provide experimental measurements of the bush torque during start-up of plain journal bearings, varying the specific pressure. Thus, the friction coefficient at start-up (deduced from measurements) is obtained for four different bearings varying feeding conditions, radial clearance and length.

Theoretical models of hydrodynamic thrust bearings do not usually consider thermoelastic deformations of the collar, while pad deformations are usually taken into account. In many cases the results of theoretical analysis differ much from experimental data despite of variety of effects being included in the TEHD models. In the authors’ research an attempt of including runner thermoelastic deformation in a bearing model was taken up. The results of calculations of a water turbine thrust bearing were compared for three cases — no runner deformation, elastic runner deformation and thermoelastic deformation. Including runner thermoelastic deformations resulted in improved agreement between theoretical results and available experimental data. However a detailed knowledge on runner design and boundary conditions is necessary for realistic evaluation of deformations, which is to a great extent individual design dependent and difficult to generalize.

Inlet temperature is one of the main inputs in all models for analysis of fluid film bearings performance. On the other hand inlet temperature distribution and also oil speed distribution at the inlet is the result of flow phenomena in the gap between bearing pads. These phenomena are complex and in many cases additionally affected by a special bearing design incorporating various arrangements of forced oil supply to the gap between pads. The reason for such arrangements is more efficient introducing of the lubricant cooled in an external cooling system to the oil film. Not much is known about flow phenomena in the gap between the pads and even less if the bearing is fitted with any kind of directed lubrication system. One of those special bearing arrangement is a leading edge groove (LEG) design described by Mikula [1] Experimental results showed that LEG lubricating system in comparison to flooded lubrication caused about 10–20°C drop in maximum temperature in high-speed bearings. But not much is known of potential benefits of using this lubrication method in large low-speed bearings applied in water turbines. There were no attempts of adaptation of this lubrication system to large size bearings. In this case modeling is necessary because of large cost of experiments. Contemporary computer codes of Computational Fluid Dynamics (CFD) enable one to study flow between bearing pads or in lubricating groove and even to build models of a whole hydrodynamic bearing within CFD systems. Some results of modeling lubricant flow in the gap in a bearing with a directed lubrication system are presented in the paper.

This paper describes a model for the analysis of elastohydrodynamic (EHD) lubrication of a multi-body common-pin connecting-rod (conrod) big end bearing system. Two conrod and three thrust bearings are fully coupled in order to simulate real behavior of the system. An extended Reynolds equation including mass conservation and oil film history is solved in the big end conrod bearings. The HD behavior of the thrust bearings is simulated by a cylindrical coordinate Reynolds equation. By comparisons with classical single rod analysis results show the pertinancy of simulating twin moving conrods.

In conventional liquid lubrication it is assumed that surfaces are fully wetted and no slip occurs between the fluid and the solid boundary. Under the “no slip” condition the maximum shear gradient occurs at the fluid-surface interface. When one or both surfaces are non-wetted by the fluid, boundary slip can occur due to weak bonding between the fluid and the solid surface, which reduces shear stresses in the fluid adjacent to the non-wetted surface. A thrust bearing tribometer was used to compare the performance of “no slip” hydrodynamic thrust bearings with bearings surfaces that were made to slip at the interface between the surface and fluid. Hydrophobic surfaces on both runner and bearing were achieved with the deposition of hydrogenated diamond like carbon (H-DLC) films, produced by plasma-enhanced CVD on titanium alloy surfaces. Hydrophilic surfaces were created through the surface modification of DLC. A mixtures of water and glycerol was used as the lubricant. The tests were conducted using different constant bearing gaps. The normal load and the torque or traction force between the rotating runner and hydrodynamic thrust bearing were measured with load cells. The experimental results confirmed that load support is still possible when surfaces are partially-wetted or non-wetted.

This paper proposes a method to calculate the stiffness and the damping coefficients of the coupled journal and thrust bearings considering tilting motion. The Reynolds equations and their perturbation equations are derived by linearization of bearing reaction with respect to the general five degrees of freedom, i.e. the tilting displacement and angular velocity as well as the translational displacement and velocity. Reynolds equations and their perturbation equations are transformed to the finite element equations by considering the continuity of pressure and flow at the interface between the journal and the thrust bearings. It also includes the Reynolds boundary condition in the numerical analysis to simulate the cavitation phenomena. The stiffness and the damping coefficients of the proposed method are compared with those of the numerical differentiation of the loads with respect to finite displacements and velocities of bearing center. It shows that the proposed method can calculate the dynamic coefficients of a coupled journal and thrust bearing more accurately and efficiently than the differentiation method.

Hydrodynamic gas film bearings are widely used for very high speed, lightly loaded rotating machinery. In the design of hydrodynamic gas film bearings, it is of cardinal importance to enhance the stiffness of gas films for minimizing the vibration due to external excitations. Among various types of hydrodynamic gas film thrust bearings, grooved bearings have an advantage of high stiffness and load carrying capacity, but the stiffness of the bearings strongly depends on groove geometry. Therefore, when the groove geometry is designed suitably, it is expected to improve considerably the stability characteristics of the bearings. However, the conventional bearing geometries are based on the fixed logarithmic spiral curve, and there is no literature treating how to change effectively the groove geometry to improve drastically the bearing characteristics. In this paper, the entirely new optimum design methodology, in which the groove geometry can be changed flexibly by using the spline function, is presented to maximize the stiffness of gas films for grooved thrust bearings, and the effectiveness of the methodology is verified experimentally.

This paper describes a numerical procedure for analyzing the dynamics of transient and steady state vibrations in a wavy thrust bearing. The major effects of the wavy geometry and the operating parameters on the dynamic characteristics of the bearing had been discussed in previous work. The present study thus concentrates on examining the relationships between the development of the transient and steady state vibrations when operating conditions including rotational speed and load magnitude are parametrically varied. Special attention is given to the development of steady state vibrations from initial transients with comparisons and consequences to the overall system stability. Numerical based vibration signature analysis procedures are then used to identify and quantify the transient vibrations. The conclusions provide general indicators for designing wavy thrust bearings that are less susceptible to transients induced by external perturbations.

Results of a combined theoretical and experimental investigation into the operation of thrust bearings with PTFE-faced pads are reported. Bearing performance is analysed in terms of temperature, power loss, oil film thickness and pressure. These parameters are first calculated using a THD model. The effect of PTFE facing on bearing thermal performance is then presented and discussed. A TEHD model is subsequently employed. Obtained TEHD results show that oil film thickness and temperature are strongly affected by the PTFE layer. Theoretical results are compared with measured temperature, oil film thickness and pressure.

This paper proposes a method to calculate the stiffness and the damping coefficients of the coupled journal and thrust bearings. Reynolds equations and their perturbation equations of journal and thrust bearings are transformed to the finite element equations by considering the continuity of pressure and flow at the interface between the journal and the thrust bearings. It also includes the Reynolds boundary condition in the numerical analysis to simulate the cavitation phenomenon. The stiffness and damping coefficients of the proposed mathematical method are compared with those of the numerical differentiation of the bearing force with respect to finite displacements and finite velocities of bearing center. It shows that the proposed method can calculate the dynamic coefficients of a coupled journal and thrust bearing more numerically stable and computationally efficient than the differentiation method. It also investigates the coupling effect of the coupled journal and thrust bearing and it shows that the proposed method makes it possible to calculate the cross-coupled dynamic coefficients in the radial-axial direction of the coupled journal and thrust bearing.