Lubrication Characteristics Of Bearings Research Articles

The Discussion of the Influence of Eccentricity Ratio on Lubrication Characteristics of Fluid Lubricated Bearings

Abstract: The operating quality of bearings has also led to higher criteria with the growing status of the manufacturing industry in social production. The eccentricity ratio of the bearing system is particularly susceptible to change during operation as a result of the external load, which has a direct impact on the lubricating properties. On the one hand, a reasonable eccentricity ratio will improve the bearing's lubrication performance, increase stability, and better meet processing requirements; on the other hand, it will result in uncontrollable bearing behavior and may even cause the real world to deviate from the theoretical design model. The study aimed to analyze and discuss the current findings on the change in bearing eccentricity ratio. More than 100 related articles have been summarized, and bearing behavior research results, such as lubrication and load-bearing characteristics, are discussed. This paper discusses the progress of research on the eccentricity ratio problem of fluid-lubricated bearings, as well as the effect of eccentricity ratio change on bearing lubrication characteristics for bearings using different lubricating media. Active control measures to mitigate the negative impact of changing bearing eccentricity ratios are also presented. After analyzing and summarizing the relevant literature, it has been found that the eccentricity is one of the important factors affecting the lubrication characteristics of bearings.

Research on Lubrication Characteristics of Ship Stern Bearings Considering Bearing Installation Errors

The installation quality of a propulsion shaft system directly affects the lubrication statuses of the bearings. The quality of the shaft system installation not only affects the progress of ship construction, but also the safety, stability, and reliability of the shaft system. This article takes sliding bearings in ship shafting as the research object and establishes a hydrodynamic lubrication model of sliding bearings while considering installation errors to address the issue of installation errors of ship stern bearings. The finite difference method and super-relaxation iteration method are used to solve the problem, and the influences of bearing installation errors on bearing lubrication characteristic parameters are explored. An installation error of the stern bearing can lead to an increase in the film pressure at both ends of the stern bearing in the axial direction, leading to a decrease in the lubrication status of the bearing. Poor lubrication and wear faults of the stern bearing are prone to occur at both ends of the stern bearing. As the installation error of the stern bearing increases, the minimum film thickness of the stern bearing decreases and the maximum film pressure increases, and as the installation error increases, the sensitivity of the aft stern bearing to the vertical installation error is greater than that of the lateral installation error, and the sensitivity of the fore stern bearing to the lateral installation error is greater than that of the vertical installation error. The sensitivity of the lateral and vertical film forces at both ends of the aft stern bearing and the fore stern bearing is greater than that of the middle part; the installation error of bearings has a significant impact on the lubrication characteristics of bearings.

Fatigue life prediction of double-row tapered roller bearings considering thermal effect

Thermal effects on fatigue life were investigated by analyzing the thermomechanical behavior of double-row tapered roller bearings (DTRBs) and a fatigue life prediction model was developed. A bearing’s mechanical behavior was analyzed using a quasi-static model and its thermal behavior was analyzed using a thermal network method. Viscous drag and sliding friction at the contact area were considered as heat generation factors for DTRBs. The bearing lubrication characteristics and shape dimensions interacted with the temperature and the analysis was repeated until the entire DTRB system’s temperature converged. DTRB fatigue life was estimated using a fatigue life formula based on Gupta and Zaretsky’s statistical model. Results confirmed that the fatigue life decreased rapidly because of an interference fit that occurred at very high rotation speeds or at very low supply oil flow rates. This interference fit phenomenon is caused by thermal expansion of the bearing element. The interference fit can be prevented by designing with a large initial clearance value, but an initial clearance that is too large affects fatigue life negatively because of load distribution imbalance. Optimal design of the roller end sphere radius to minimize sliding friction for the flange part can provide additional help in preventing interference fit.

Calculation and Lubrication Characteristics of Cylindrical Roller Bearing Oil Film with Consideration of Thermal Effects

Aiming at the problem of how the thermal characteristics of cylindrical roller bearings affect the lubrication characteristics of bearings under actual working conditions, the influence of parameters such as speed and load on the lubrication characteristics of cylindrical roller bearings under thermal effects is analyzed. The numerical calculation method combining the quasi-static model of cylindrical roller bearing and the thermal elastohydrodynamic lubrication model is adopted. The effects of rotational speed, load and thermal effect on the lubrication performance of the bearing and the lubrication state under certain oil supply conditions were analyzed via numerical model calculation. The oil film thickness was measured via an immersion ultrasonic method to verify the correctness of the model. The results show that the larger the bearing speed, the larger the central film thickness and the minimum film thickness. At the same time, the thermal effect on the film thickness is more obvious; the greater the load, the greater the maximum oil film pressure. The film thickness gradient in the inlet region is greatly reduced, but the thermal effect has no obvious effect on the overall film thickness. In addition, there is a critical value of effective lubrication film thickness for each set of operating parameters. When the actual film thickness is equal to the critical value, the bearing lubrication state is at its best; the numerical simulation results are compared with the experimental values. Under the calculation conditions, the maximum error at the measuring point is within 10%, which meets the error requirements and provides a theoretical basis for revealing the bearing lubrication mechanism.

A Simulation Analysis of Ball Bearing Lubrication Characteristics Considering the Cage Clearance

Abstract Lubrication characteristics can greatly affect the service performances of ball bearings. To further clarify the variation law of oil–air distribution in bearing cavity, a new simulation method combining the dynamic and computational fluid dynamics (CFD) models is presented. The relative motion between the ball and the cage caused by the cage clearance is obtained by the dynamic model. The coupling model uses the multi-reference frame (MRF) method and local remeshing approach (LRA) to describe the motion of each bearing component. The oil–air two-phase (OATP) flow is described through the volume of fluid (VOF) numerical model. Note that the lubricating oil content in the bearing cavity decreases significantly with the increment of rotation speed. There is a sudden change of pressure at the contact area between the ball and inner raceway. The relative motion of ball caused by the cage clearance has a certain effect on the local lubrication; however, it has little effect on the overall lubrication characteristics.

Experimental study on the distributed lubrication characteristics of full-size water-lubricated stern bearings under hull deformation

A full-size test rig of water-lubricated stern bearing (WSB) with an elevation adjustment device was built. High-precision wireless telemetry device obtained four film pressure signals. Six eddy current sensors were adopted to measure the axis orbit. The effect of bias load, rotational speed, and hull deformation on bearing lubrication characteristics are systematically studied. Experimental results showed the distribution lubrication characteristic of WSB at the axial direction. The WSB lubrication region can be divided into the three sub-regions in the middle and both ends of the bearing. Three lubrication sub-regions have different take-off speeds. Under the bias load, the negative pressure was found in the film pressure distribution. The hull deformation affects the position and area of each lubrication sub-region, changing the loads carried by the water film and asperity contact. Research results have a great contribution to WSB optimization structure design.

NURBS-based IGA of viscous fluid movement with special-shaped small gaps in hybrid bearing

This paper attempts to solve the Reynolds equation of the lubrication problem in hybrid bearing using high-order isogeometric analysis method. The analysis model consists of two parts: the static characteristic calculation part composed of oil film static pressure distribution, oil film thickness and oil film bearing capacity; the dynamic characteristic calculation part including damping coefficient and stiffness coefficient. A mapping strategy based on NURBS basis function is used to realize the application of imposed Dirichlet condition inside the analysis domain of hybrid bearing lubrication characteristics. The analysis of hybrid bearing in fast reactor with complex dynamic and static pressure oil cavity structure shows that: (1) In high-order isogeometric calculation framework, imposed boundary conditions are applied accurately, and dynamic and static characteristics calculation results are given; (2) Compared with the finite element method, when using high-order isogeometric analysis method to solve the viscous fluid motion, the solution requires fewer degrees of freedom to achieve grid independence, and the computational efficiency is also improved in terms of time.

A study on diesel engine crankshaft bearing failure analysis with consideration of bearing lubrication

PurposeThe edge of diesel engine crankshaft main bearing is more likely to fail in its real working condition. This paper aims to study the bearing failure mechanism by finding the relationship between bearing lubrication characteristics and its working condition.Design/methodology/approachThis work builds the mixed lubrication model of crankshaft bearing to analyze the cause of bearing abnormal wear, and the finite difference method was used to solving the average Reynolds equation. During the analysis, journal misaligned angle, external load and roughness are considered.FindingsThe result shows that the wear of the diesel engine crankshaft bearing happens in engine startup phase and the bottom of the bearing are more prone to be excessively worn. Under the influence of journal misalignment, bearing asperity contact load and speed range of mixed lubrication will increase markedly. The edge of the bearing will be excessively worn. The effect of misalignment on bearing lubrication performance varies under different shaft rotation speed.Originality/valueThe former research studies on crankshaft bearing either just focused on its lubrication characteristics or interested in its failure types (wear, adhere, cavitation). This paper studies the relationship between bearing failure mechanism and lubrication performance.

Analysis of underwater explosion shock on ship shaft stern bearing lubrication characteristics under different bearing working conditions

Warship always face the threat of underwater explosion shock, which may affect the ship stern tube bearing lubrication performance when the propeller shaft is bending. This paper builds the coupling model of shaft longitudinal vibration and bearing lubrication with consideration of shaft axial shock and misalignment. The performance of stern bearing under the influence of explosion shock was analyzed by solving the generalized Reynolds equation, shaft longitudinal vibration equation and explosion shock equation. The result shows that: the effect of underwater explosion shock on bearing lubrication performance is transient, and the effect will be more obvious when the bearing works at close quarter, larger misaligned angle, eccentricity and rotation speed. Moreover, the edge effect which caused by shaft bending will increase with the decrease of explosion distance and the increase of eccentricity.

Study on Lubrication Efficiency and Friction Power Loss of Engine Based on a Hybrid Hydrodynamic Model

Friction loss is one of the main factors affecting engine power. Reducing friction power losses to improve the power of engines is a significant concern for designers. Especially, under the background of energy-saving and emission reduction, it is indispensable to carry out an in-depth investigation on engine bearing lubrication characteristics. Unlike the previous studies of separate modelling, a new modelling method of coupling the dynamic and lubrication model is proposed in this paper. The bearing capacity, friction force, friction coefficient and eccentricity ratio were taken as the evaluation criterion, and the influence of design parameters such as angular speed, bearing radius and width on the lubrication efficiency and friction power loss (LE-FPL) were studied. The results indicate that increasing the angular speed, bearing radius or width can effectively reduce the eccentricity ratio and raise the minimum oil film thickness, which is beneficial to improve the lubrication efficiency. However, the above methods to improve engine lubrication efficiency will lead to more power loss of engine to a certain extent. Therefore, studies on reducing the friction power loss for the engine and on improving the lubrication efficiency for the engine should be considered coordinately in the dynamic design and optimisation of the engine.

Effects of Bearing Steps on Probable Wear Damage of Main Bearings of an IC Engine

When two bearing shells are assembled in the bearing housing, it is possible that the edges of the two shells do not fit in the radial direction completely and have an offset relative to each other. This assembly error, which can have different causes, is called the bearing step in this paper. The bearing step can lead to wear damage in bearings. The effects of bearing step on the lubrication performance of main bearings and the probable wear damage have been investigated. To calculate the bearing lubrication characteristics such as maximum oil film pressure and minimum oil film thickness, elasto-hydrodynamic model, which includes the mass conservation algorithm, has been applied. The objective of this work is to investigate the effects of bearing steps on the lubrication performance of the main bearings and assess the probable wear damage of main bearings due to bearing step. The prediction of elasto-hydrodynamic model is very proximate to what really happened. The results show that for the under-study 12-cyl engine, main bearing No. 2 involved with medium wear damage. Wear damage in this main bearing No. 3 is not a concern, while main bearing No.4, 5 and 6 do not predict the probability of wear damage. For main bearing No.7, it is concluded that considering step and bore relief in simulation has high importance so that the solution without step and bore relief does not predict the wear, but with step and bore relief predicts medium wear damage.

Numerical Calculation of Composite Water Lubricated Bearing Considering Effect of Elastic Deformation

Traditional bearing design neglects the influence of elastic deformation of materials on bearing lubrication characteristics, based on a new type of polymer composite water-lubricated bearing materials, the influence of elastic deformation of bearing material is introduced into the simulation. The lubrication performance of the water-lubricated bearings is studied with respect to material parameters and structural parameters. The effects of the elastic deformation on the lubrication characteristics such as the maximum pressure value and the minimum film thickness were compared and analyzed under different bearing clearance structures of a certain type of stern bearings. The results show that, the maximum water film pressure of bearing increases with the clearance ratio, and the maximum water film pressure of elastic bearing is less than that of rigid bearing. With the increase of clearance ratio, the elastic deformation of bearing increases linearly. The increase of bearing elastic deformation results in the difference between minimum water film thickness and maximum water pressure between the elastic bearing and rigid bearing.

Thermohydrodynamic lubrication analysis of misaligned journal bearing considering the axial movement of journal

Abstract In the journal-bearing system, the journal inevitably moves along the bearing axis, and the axial movement of journal may affect the performance of misaligned journal bearing. In this article, a numerical model for the thermohydrodynamic lubrication of bearing considering the axial movement of journal is established, and based on which a comprehensive analysis on the performance of misaligned journal bearing is conducted by solving the generalized Reynolds equation, heat conduction equation and energy equation. The results show that axial movement of misaligned journal has more obvious influence on the bearing lubrication characteristics at the lower speed, larger inclination angle and eccentricity. The impact of axial movement on the bearing lubrication performance is greatly affected by the thermal effect and surface roughness.

Analysis of Factors Affecting Lubrication Performance of Main Bearings of Service Diesel Engine Based on Orthogonal Design Method1

Based on the established numerical lubrication simulation model of a main bearing of a certain type of diesel engine, combined with the orthogonal design method, the effects of engine speed, cylinder pressure, oil supply pressure and clearance on bearing lubrication characteristics are studied. The results of lubrication characters show that cylinder pressure and clearance are first and secondary factor of influence degree, oil supply pressure has the least impact, and the most effective way to improve bearing lubrication is to reduce the explosion pressure appropriately.

Effect of the axial movement of misaligned journal on the performance of hydrodynamic lubrication journal bearing with rough surface

Generally, the movement of journal along the direction of bearing axis under the combined action of various factors is neglected in the lubrication study of bearing, which is quite different from the actual working condition of bearing in the shaft-bearing system. In this paper, with a comprehensive consideration of the axial movement of journal, the surface topography of journal and bearing and the misalignment of journal, a new model about the hydrodynamic lubrication of misaligned journal bearing is established based on the average Reynolds equation. Considering the effect of the axial movement of misaligned journal, the lubrication characteristics parameters of rough journal bearing is presented and mainly discussed. The results show that the axial movement of misaligned journal has a distinct effect on the bearing lubrication characteristics. The influence of the axial movement of misaligned journal on the bearing lubrication characteristics is slightly reduced when considering the surface roughness.

Measurement of gas pressure distribution in aerostatic thrust bearings using pressure-sensitive film

Abstract Pressure distribution in aerostatic thrust bearing clearance has received a lot of attention for its fundamental influence on bearing lubrication characteristics. Study of pressure distribution in the bearing clearance has commonly been conducted by numerical calculation and experimental measurement is very limited. In this paper, a new method is proposed to experimentally measure pressure distribution in the aerostatic thrust bearing clearance. In this method, the Fuji prescale pressure-sensitive film is used to record pressure distribution in the gas film, and calibration is performed before the digital image of the pressure-sensitive film is post-processed and transformed into pressure values. Applications of the proposed measurement method in circular aerostatic thrust bearings with recesses of different shapes demonstrate its feasibility and accuracy.

Method and experiment of Temperature Collaborative Monitoring based on Characteristic Points for tilting pad bearings

High power rotating machinery require bearings that can perform under extreme conditions. Tilting pad bearing temperatures exceeding their design limits may cause unit downtime or failure. Through the analysis of tilting pad bearing lubrication characteristics, including temperature distribution and oil film pressure distribution, supplemented by a minimum oil film thickness analysis, a method named Temperature Collaborative Monitoring based on Characteristic Points is proposed. Using factory unit test bench, the geometric characteristics and the operational characteristics of the tilting pad bearing unit are analyzed. A reasonable arrangement of the bearing temperature measurement points is presented. A large amount of temperature data for the main-pad and vice-pad are obtained. Experimental results verify the feasibility of the proposed measurement method.

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.

Numerical modeling of journal bearing considering both elastohydrodynamic lubrication and multi-flexible-body dynamics

This study uses an elastohydrodynamic lubrication model coupled with multi-flexible-body dynamics (MFBD) to analyze dynamic bearing lubrication characteristics, such as pressure distribution and oil film thickness. To solve the coupled fluid-structure interaction system, this study uses an MFBD solver and an elastohydrodynamics module. The elastohydrodynamics module passes its force and torque data to the MFBD solver, which can solve general dynamic systems that include rigid and flexible bodies, joints, forces, and contact elements. The MFBD solver analyzes the positions, velocities, and accelerations of the multi-flexible-body system while incorporating the pressure distribution results of the elastohydrodynamics module. The MFBD solver then passes the position and velocity information back to the elastohydrodynamics solver, which reanalyzes the force, torque, and pressure distribution. This iteration is continued throughout the analysis time period. Other functions, such as mesh grid control and oil hole and groove effects, are also implemented. Numerical examples for bearing lubrication systems are demonstrated.

Lubrication Analysis of a Connecting-Rod Bearing in a High-Speed Engine. Part II: Lubrication Performance Evaluation for Non-Circular Bearings

In this article a numerical investigation of a connecting rod bearing operating at 6,500 rpm is performed. This is a companion to an earlier article that took into account the effects of the inertial force and the variable bolt tension force, which are considered to be the principal factors that affect the connecting rod bearing lubrication characteristics of an engine running at high speed. It was found that a thinner minimum oil film and a larger peak hydrodynamic pressure are predicted in a deformed connecting rod bearing than in a rigid connecting rod bearing. Multi-peaked hydrodynamic pressure was found to appear as well because of two or more converging-diverging film regions.