Oil Film Pressure Distribution Research Articles

Numerical Investigation of Pressure Profile in Hydrodynamic Lubrication Thrust Bearing.

Reynolds equation is solved using finite difference method (FDM) on the surface of the tilting pad to find the pressure distribution in the lubricant oil film. Different pressure profiles with grid independence are described. The present work evaluates pressure at various locations after performing a thorough grid refinement. In recent similar works, this aspect has not been addressed. However, present study shows that it can have significant effect on the pressure profile. Results of a sector shaped pad are presented and it is shown that the maximum average value of pressure is 12% (approximately) greater than the previous results. Grid independence occurs after 24 × 24 grids. A parameter “ψ” has been proposed to provide convenient indicator of obtaining grid independent results. ψ = |(P refinedgrid − P Refrence-grid)/P refinedgrid|, ψ ≤ ε, where “ε” can be fixed to a convenient value and a constant minimum film thickness value of 75 μm is used in present study. This important parameter is highlighted in the present work; the location of the peak pressure zone in terms of (r, θ) coordinates is getting shifted by changing the grid size which will help the designer and experimentalist to conveniently determine the position of pressure measurement probe.

Numerical Analyses of Hydrodynamic Lubrication and Dynamics of the Rolling Piston and Crankshaft in a Rotary Compressor

In this article, numerical analyses of hydrodynamic lubrication and dynamics of the crank, rolling piston, and vane were carried out to study the tribological performance of a rotary compressor. Dimensionless Reynolds equations of journal and thrust bearings in dynamic load condition were derived and solved numerically. To deal with the lubrication of the rolling piston, the effect of the nonuniformity of tangential velocity over the bearing surface on the Reynolds equation was taken into account. In addition, combined with the analyses of dynamics and kinematics of the crank, piston, and vane, the angular velocities of the crank and piston as well as the motion mode between the piston and vane were studied. Analysis results illustrate characteristic oil film pressure distributions of the crank and piston bearings, which are different from that of common journal bearings. Under the influences of dynamic load and eccentricity of the cam, the wedge effect as well as the stretch and squeeze effect contribute greatly to hydrodynamic pressure. The relative motion mode between the piston and vane tip is not always pure sliding but accompanies rolling in some cases, which depends on the magnitude of the friction coefficient between the piston and vane tip. The analysis results are helpful for the improvement of rotary compressor design.

Dynamic Mesh Method for Calculating Bearing Capacity and Overturning Moment of Partial Loaded Hydrostatic Rotary Tables under Rotating Condition

The hydrostatic rotary table's upper and lower guides are prone to scratch each other when the partial loaded hydrostatic rotary table is rotating. In the former study of this phenomenon, it is hard to establish a practical mathematical model of carrying capacity and overturning moment of the hydrostatic rotary table based on traditional analytical calculating method, and the modeling and calculating of fluid domain with a changing geometrical boundary can not be conducted when utilizing the traditional CFD simulation method. To solve this problem, a new calculation method based on dynamic mesh model is proposed, which is used to calculate the bearing capacity and overturning moment of the partial loaded hydrostatic rotary table under rotating condition in engineering practice. The change of oil film form is controlled by using user definition function. Deformation of oil film mesh caused by the changing of rotary table's tilting direction is refreshed using spring smoothing theoretical model. The oil film's moving boundary caused by rotational movement is changed into static boundary for avoiding the grid distortion. This method can realize the simulation of oil film with different thickness and tilt displacement rate using the same model, which can avoid the repeatedly building of calculating model and improving the computational efficiency. The dynamic process of three dimensional pressure distribution of oil film is reappeared. The impact of rotary table's motion on flow field distribution can be reflected in the calculating result which is closer to engineering practice. The bearing capacity and overturning moment of a typical hydrostatic rotary table are calculated by using the proposed method and the experiment of hydrostatic rotary table bearing partial load is conducted. The experimental results are in reasonable agreement with calculation ones, which have verified the effectiveness of the proposed calculating method.

The Influence of Micro-Texturing Dimple on the Bearing Capacity of the Elastohydrodynamic Lubrication Based on CFD-FSI Fluid-Solid Coupling

Based on the CFD-FSI fluid-solid coupled method, the equivalent elastohydrodynamic lubrication model of the micro-texturing dimple surface on the condition of the medium velocity and medium load, low velocity and heavy load, high velocity and heavy load, low velocity and light load and high velocity and light load is respectively solved by numerical method in this paper. And obtain the oil film pressure distribution curve and the oil the film thickness distribution curve on the conditions of steady state, and analyze the influence of micro-texturing dimples on the bearing capacity of the equivalent elastohydrodynamic lubrication model. Analysis results show that: compared with the corresponding minimum film thickness on the conditions of smooth surface, the minimum film thickness of micro-texturing dimple surface on the conditions of the medium velocity and medium load, low velocity and light load is increased, which indicates the bearing capacity of the equivalent elastohydrodynamic lubrication model of the micro-texturing dimple surface is increased; while the minimum film thickness of the rest conditions is decreased, which shows that the bearing capacity of the equivalent elastohydrodynamic lubrication model of the micro-texturing dimple surface is decreased. The study in this paper lays the foundation for the design and optimization of the micro-texturing dimple.

Stress Distribution Analysis on Alloy Layer of High Power Marine Diesel Engine Bearing Bush

According to the characteristics of large size, small clearance ratio, high oil film pressure and thin oil film thickness in the actual conditions of high power marine diesel engine bearing, this Paper analyzes oil film pressure distribution on inner surface of bearing bush based on the finite difference method, uses finite element method to establish the hierarchical model, and analyzes stress and strain distribution on bearing alloy. In addition, this Paper researches the changes of stress and strain distribution on bearing alloy layer when alloy layer thickness changes for the optimization design of high power marine diesel engine bearing bush.

Analysis of EHL Line Contact in Rapid Braking Motion

As is well known, almost all the machines need to start and brake. In this process, the lubrication state of their parts changes instantaneously. In this paper, an isothermal study for the line contact elastohydrodynamic lubrication (EHL), which is in rapid braking process and under a constant load, is carried out by using a simplified multigrid method. Numerical results indicate that the oil film thickness decreases and the oil film pressure increases with the decrease of the speed during the process of rapid braking. The oil film shrinks quickly and the oil entrapment occurs when the speed reduces to a certain range. Simultaneously, the distribution of oil film pressure tends to the central lubrication area. The size of the oil entrapment area and the changes of the oil film pressure are closely related to the braking time and the initial speed, which reflects the transient effects of the lubricating oil film.

Study on thermoelastohydrodynamic performance of bearing with surface roughness considering shaft deformation under load in shaft‐bearing system

PurposeCurrent lubrication analyses of misaligned journal bearings are generally performed under some given preconditions. The purpose of this paper is to calculate the lubrication characteristics of a journal bearing with journal misalignment caused by shaft deformation under load, considering the surface roughness, thermal effect and (thermal and elastic) deformation of bearing surface simultaneously.Design/methodology/approachThe lubrication of bearing was analyzed by average flow model based generalized Reynolds equation. The deformation of bearing surface under pressure or heat of oil film was calculated by compliance matrix method. The compliance matrix was established by finite element analysis. The temperature distributions of oil film and bearing were calculated by energy equation and heat conduction equation.FindingsWhen the thermal deformation of bearing and journal surface is considered, the radius clearance affects not only the value of the maximum oil film pressure and minimum oil film thickness, but also the distribution of oil film pressure and thickness of misaligned bearing. The effect of thermal deformation of bearing on the performance of misaligned bearing is larger than that of elastic deformation of bearing. Whether or not the surface roughness affects the performance of misaligned bearing and the affecting level depends greatly on the condition of deformation of bearing surface.Originality/valueThe surface roughness, thermal effect and (thermal and elastic) deformation of bearing surface were considered simultaneously in the thermoelastohydrodynamic lubrication analysis of bearing with journal misalignment caused by shaft deformation under load. The results of this paper are helpful to the design of the bearing.

Numerical Model of Journal Bearing Lubrication Considering a Bending Stiffness Effect

An analysis for operating characteristics of journal bearing lubrication system is performed based on the numerical model. Dynamic bearing lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by applying the bending stiffness effect of journal. And the oil film thickness variation by the bending stiffness effect is applied to the fluid governing equations to calculate the oil film pressure in the elastohydrodynamic lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Also, a numerical example for the journal bearing lubrication system is demonstrated and compared with the experimental results. The numerical results considering the bending stiffness effect show a good agreement with the experimental results.

The Analysis of the Deformation and Contact Lubrication Problem of HPD Diesel Engine Connecting Rod Bearings Based on the FFT Method and Flexibility Matrix Method

Based on the fast fourier transform (FFT) and flexibility matrix method, the effects of the FFT and flexibility matrix method on the distribution of oil film pressure, elastic deformation in the steady load and the journal center orbit of the connecting rod big-end bearings in the dynamic load are investigated. The results are shown that when the eccentricity ratio is more than 1, the maximum oil film pressure obtained by FFT method is bigger on both ends of the journal bearing and on its intermediate position is smaller. To the connecting rod big-end bearing, under the dynamic load condition, there is the same trend of the journal center orbit with two methods. However, with FFT method, the journal is largely deviated from bearing center.

A Comparative Study of the Methods for Calculation of Journal Bearing Elastohydrodynamic Lubrication

Based on the fast fourier transform（FFT） and flexibility matrix method, the study is presented for journal bearing elastohydrodynamic lubrication. The effects of FFT and flexibility matrix method on the distribution of oil film pressure and elastic deformation in the steady load are investigated. The results are shown that the difficulty of the EHL for journal bearings in the case of high eccentricity ratios or heave loads can be effectively solved by the FFT method. When the eccentricity ratio is smaller, the magnitude and distribution of the oil film pressure are basic agreement by FFT method and flexibility matrix method. When the eccentricity ratio enhances, the maximum oil film pressure obtained by FFT method is bigger on both ends of the journal bearing and on its intermediate is smaller.

Full Shafting-Based Elastohydrodynamic Lubrication Simulation for Main Bearings of Marine Diesel Engine

To predict and analyze accurately the lubrication characteristics and its influencing factors of main bearing for large low-speed two-stroke marine diesel engine, based on EHD lubrication model of dynamically loaded bearing, coupling simulation between EHD and MBD for main bearing of marine diesel engine was carried out. Systemic models were established separately considering the independent crankshaft of diesel engine and the full shafting of propulsion power plant. Main bearing load, peak oil film pressure, oil film pressure distribution, MOFT and orbital path in one working cycle under rated working conditions were investigated, and simulation results were compared based on both models. The results show that, if the impact of full shafting was considered, the lubrication characteristics of No.8 main bearing changed significantly, the lubrication characteristics of other main bearings were similar as the simulation results of the independent crankshaft model.

S114012 CADを利用したジャーナル軸受の弾性流体潤滑解析 : 第3報エンジン用コンロッドの応力解析

In this study, stress distributions in a con-rod of an engine are studied using a 3 Dimensional Computer Aided Design Software, 3D-CAD CATIA. A structural CAD model of a con-rod is made with the CATIA. A FEM structural analysis is performed in the CATIA for making a compliance matrix which expresses relation between bearing deformation and oil film pressure distribution and is used in an Elastohydrodynamic Lubrication, EHL, analysis. Pressure distributions and deformation on a con-rod bearing is calculated with the EHL analysis under a dynamic load of the engine. The pressure distributions are used for calculation of nodal forces on the bearing surface which are used in the structural analysis of the con-rod. Finally, stress distributions in the con-rod under the engine operation can be obtained.

J111023 EHL下における工具表面テクスチャの潤滑効果

Rotary cutting is recently focused because of its excellent machining performance by equalizing the distribution of wear and processing heat on the circle of cutting tools. Previous studies showed that nano-texturing manufactured on the cutting tool is one of promising ways to reduce friction coefficient between chip and tool. A lot of researches on the surface texturing to improve the tribological properties are found, but there is still room for investigation of the effectiveness of nano-texturing to improve the lubrication performance under elastohydrodynamic lubrication (EHL). This study investigated the effect of nano-texturing on oil film thickness and pressure distribution under EHL by using an experimental apparatus with optical interferometry. The experimental apparatus mainly consists of a steel ball and a sapphire glass disk, and they made point contacts during the test. Three kinds of spiral-grooved nano-texturings with various groove distance and depth were manufactured on the ball surface by using femtosecond laser. The load was 20 N and the rotational speed varied from 100 to 350 rpm. The experimental results showed that the oil film with nano-texturing became thicker 1.4-2.2 times than that without texturing, proving that spiral-grooved nano-texturing was also effective even under EHL condition.

Study of Transient Elastohydrodynamic Lubrication of Spur Gears under Impact Load

Spur gear contacts experience a number of time-varying contact parameters including the load, surface velocities, radii of curvature, and slide-to-roll ratio. It is very hard to obtain transient elastohydrodynamic lubrication (EHL) solution of spur gears. In this study, a transient EHL model of involute spur gear tooth contacts is proposed. A full transient EHL solution of involute spur gear under impact load is obtained by utilizing the multigrid technique. The influences of impact load on the EHL of spur gear are analyzed in the paper. The numerical results show that the approach impact load has strong transient influence on the oil film thickness and pressure distribution between contact zones. The impact load may lead to instantaneous lubrication film deterioration between contact teeth of involute spur gears.

Piston ring–cylinder liner lubrication analysis in a CO2 refrigeration reciprocating compressor

A simulation model is developed for the piston ring–cylinder liner lubrication problem in a CO2 refrigeration reciprocating compressor. Patir and Cheng’s modified Reynolds equation including pressure flow factors, shear flow factors, and shear stress factors is used to consider the effect of surface roughness on lubrication. The piston ring is assumed to be fully flooded at the leading edge, and both the cavitation case and fully flooded case are considered at the trailing edge. Modified Reynolds boundary condition is employed. The simulation results show that, the minimum oil film thickness has a maximum magnitude in the middle stroke region for downward stroke and upward stroke. In the vicinity of the dead centres, the magnitude of the friction force is much higher than that in the middle stroke region. The oil film pressure distribution along the piston ring thickness at different specified crank angles is indicated. The effects of ring thickness, crown height on minimum oil film thickness, and friction force are also investigated.

Problems of Analytical Determination of Journal Bearing Bush Fatigue Strength Estimates

Problems connected with determination of stress distribution in sliding layer of thin-walled bearing bushes, investigated in bearing fatigue test rigs, have been presented. Using an example of plain bearings tested in the fatigue machine SMOK (built at the Gdańsk University of Technology) problems with obtaining a convergence of iterative procedure for determining the fatigue strength estimators of bearing alloy surface layer are analyzed. Calculations consisting in successive iterations of pressure distribution in oil film and corresponding elastic deformation of the bearing bush and housing were based on finite-element method and utilized ANSYS program. The objective of calculation was the estimation of values of radial, tangential, axial and reduced stresses in surface layer of the bearing bush corresponding to experimentally determined load magnitudes leading to fatigue cracks initiation. The convergence of analytical procedure has been achieved by the use of a relaxation method.

Numerical Computation of Dynamic Character Coefficient of Journal Bearing

The purpose of this study is to determine the dynamic character coefficient of journal bearing with the consideration of bearing load direction and oil groove. Based on numerical differential method, the oil film pressure distribution on journal bearing is obtained with the point-by-point relaxation iteration method. Then, the dynamic characters are calculated by numerical integral algorithm.The calculation program is developed for the dynamic characteristics of journal bearing. The computation method provides a useful guide for the numerical simulation of rotary parts.

Numerical Method for Pressure Distribution Calculation on Spherical Distribution Pair of IHT

To calculate the pressure distribution of oil film on spherical port plate of Innas hydraulic transformer (IHT), finite difference method (FDM) based on boundary fitted coordinate (BFC) technique is presented. Spherical curvilinear grid system was obtained with a coincident boundary of irregular physical area. The flux conservation form of Reynolds’ equation was applied as control equation. By FDM, the thickness distribution and pressure distribution of distribution pair were calculated. It shows that BFC transformation method is advantaged to closely simulate the physical domain with complex geometrical boundaries.

Transient CFD Analysis of Multi-Lobe Bearings at 60000RPM for A Gas Turbine

Transient CFD Analysis of Multi-Lobe Bearings at 60000RPM for A Gas Turbine

Development of a Measurement Method of Contact Pressure between Gear Teeth Using a Thin-Film Sensor (Measurement of Pressure Distribution by Multi-Point Pressure Sensor with Shared Lead Films)

In order to investigate the durability of the sliding surface of machinery, it is important to know the force acting on such parts and to evaluate stress distribution. Contact stress occurring on the surface of gear teeth is an important factor in determining bending stress on the gear teeth as well as load capacity. However, since the contact area of each gear tooth surface is extremely small, a conventional pressure sensor cannot be attached. For this reason, the authors developed a thin-film pressure sensor with a thickness of approximately 6μm for gear tooth surfaces by applying the same type of sensors which have been developed to measure oil-film pressure distribution in engine sliding surfaces, such as plain bearing and piston-pin bosses. A sensor with multi pressure sensing points connected by shared-type lead films was developed for narrow areas such as gear teeth surfaces, and can measure pressure distribution on the gear flank line when gears mesh together. In the results, the measured pressure was higher than the Hertzian pressure of line contact, and distributed unevenly in the axial direction. On the other hand, when the measured pressure was compared with Hertzian pressure of point contact, the calculated pressure was higher than the measured value. These disagreements seem to be caused by inexact gear geometry, nonparallel or uneven meshing and form of gear flank. In this study, details of the shape of the multipoint thin-film sensor, as well as the measurement results of pressure distribution are described.