Presence Of Lubricant Research Articles

Lubrication and wear characteristics of bionic composite texture on friction pair under seawater condition

Abstract To improve the lubrication bearing capacity of the slipper pair of axial piston pump under seawater lubrication, a bionic composite texture (ball pit-ball convex) was designed based on the non-smooth surface structure of dung beetle, and friction and wear experiments were carried out with CF/PEEK and 316L stainless steel. Thirteen groups of experiments with different parameters and structure sizes were designed and studied. The surface morphology of materials under different structural sizes and test parameters were observed, and the lubrication and wear characteristics were analyzed. The results show that the cavitation effect can increase the total compressive capacity of the bionic composite texture by 51.2% and reduce the friction coefficient by 53.3%, and the diameter and area ratio of the ball pit have the most obvious influence on the bearing performance. It is also found that the bionic composite texture has better anti-friction performance than the single texture because it has the function of storing wear chips.

Fluid-Structure Interaction Lubrication Analysis of Compliant Journal Bearing Lubricated with Non-Newtonian Plastic Fluid

Abstract High-viscosity plastic fluids and polymer liners are expected to improve the lubrication and load-carrying performance of low-speed and heavy-load journal bearings. The objective of this paper is to investigate the elastohydrodynamic lubrication performance of compliant journal bearings lubricated with non-Newtonian plastic fluids (following the Herschel-Bulkley model) using computational fluid dynamics (CFD) and fluid-structure interaction (FSI) methods. The following data are obtained: fluid film pressure, total bearing deformation, cavitation volume fraction, bearing capacity, and coefficient of friction. The simulation results are in close agreement with the data reported in the existing literature. A comparative analysis of the lubrication characteristics of journal bearings with Babbitt metal, PEEK, and PTFE liners at varying rotational speeds is presented. The effects of yield stress, power-law index, elastic modulus, and liner thickness on the lubrication characteristics are investigated. The results indicate that the power-law index of non-Newtonian plastic fluids has a greater influence on the bearing lubrication performance than the yield stress. Increasing the power-law index could improve the bearing capacity and reduce the coefficient of friction. The research provides a theoretical basis for the application of non-Newtonian plastic fluid-lubricated polymer journal bearings in low-speed and heavy-load equipment.

АЛГОРИТМ ИССЛЕДОВАНИЯ ДИНАМИЧЕСКИХ ПРОЦЕССОВ В ТЕХНОЛОГИЧЕСКОМ ОБОРУДОВАНИИ НА ГАЗОСТАТИЧЕСКИХ ПОДШИПНИКАХ

Study purpose is to develop a generalized algorithm for studying dynamic processes during the operation of spindles and other equipment with gasostatic bearings using machine-building CAD tools. The following tasks are solved: analyzing dynamic processes during the operation of equipment, selecting software for studying stiffness and bearing capacity, and then studying vibrations of an unbalanced rotor with gasostatic bearings, performing computer calculating experiments (CCE) in accordance with the developed methodology, presenting the results graphically and analyzing them. Research method include computer calculating experiments in CAE-programs of machine-building CAD. The novelty of the work is in the developed generalized algorithm for studying dynamic processes by conducting computer calculating experiments based on a three-dimensional computational model; in the obtained functional dependencies for the pressure of a gas lubricant and the amplitudes of temperature fluctuations on various parameters and conditions. There are study results of the pressure distribution of air lubrication in conical gasostatic bearings of a high-speed spindle under varying external loads, as well as the amplitude of transverse vibrations of an unbalanced rotor during accelerating and passing three critical rotational speeds at which the phenomenon of resonance occurs. Conclusions: the developed algorithm of computer calculating experiments based on a three-dimensional computational model allows studying accurately the dynamic processes that occur during the operation of spindles using machine-building CAD systems; the presented algorithm is universal, therefore, it can be used to study physical processes during the operation of equipment for various purposes; the use of this algorithm allows obtaining the results necessary to make new technical facilities without conducting numerous field tests, which significantly reduces the time and cost of research and development work.

Optimization of the lubrication conditions for minimization of the operating temperature of the high-speed ball bearings

Bearing lubrication for high speed application (above 20,000 rpm) has significant influence on the bearing heat generation and consenquently bearing operating temperature. For application in aerospace industry the selection of lubricant type, its amount and lubrication method should be carefuly conducted in order to achieve desired life and minimal weight. In this paper, experimental research was carried out in order to check whether and to what extent an open loop system can achieve similar bearing thermal behaviour as in a closed loop system. Tests were conducted on high-speed bearings of a turbo shaft engine. The experimental results showed that the open loop system, with oil mist lubrication, can achieve similar bearing operating temperature as the closed loop system, which operates with oil circulation, with the advantage of having a significantly lower mass. Also, a variation of lubrication conditions for open loop method, air pressure and oil amount, was carried out in order to minimize the operating temperature of high speed angular ball bearings. It has been shown that there is a combination of these two parameters that gives the least heating of high-speed bearings.

Experimental Study on the Effects of Controllable Parameters on the Healthy Operation of SF-2A Material Water-Lubricated Stern Bearing in Multi-Point Ultra-Long Shaft Systems of Ships

Effective control of the health operating condition of multi-support, ultra-long shaft system water-lubricated stern bearings is crucial for supporting the intelligent maintenance and health management of ships. This study investigates the failure modes of water-lubricated stern bearings and focuses on the critical failure modes of abnormal wear and high-temperature meltdown to analyze the mechanisms and influencing factors of these failures. It discusses the conditions for healthy operation of water-lubricated stern bearings, as well as methods for controlling lubrication and temperature rise. Based on this, controllable parameters for the healthy operation of water-lubricated stern bearings were selected, an experimental rig was constructed, and experiments were conducted using SF-2A material water-lubricated bearings. The experimental results indicate that by controlling parameters such as shaft rotational speed, inlet lubrication water temperature, clear-water lubrication, sediment-laden-water lubrication, bearing specific pressure, and the surface morphology of the bearing liner, the velocity characteristics, lubrication characteristics, and temperature rise characteristics of the bearings can be effectively altered. The sensitivity of the lubrication and temperature rise characteristics of SF-2A material water-lubricated stern bearings to controllable parameters varies under different environmental conditions. The study finds that precise control of these parameters can improve the operating condition and reliability of water-lubricated bearings.

Experimental Study of the Effect of Thickener on the Film Thickness in the Contacts of a Grease-Lubricated Ball Bearing at Low Speed

The level of starvation in axially loaded grease lubricated ball bearings can be well described by the product of the base oil viscosity, the half contact width and the rotational speed (ηbu). This paper highlights the effect of the thickener as another parameter for estimating the film thickness in a ball bearing. Film thickness measurements were done with an optical simulator of the ball-on-disc configuration and a real ball bearing using the capacitance method. Three greases with the same base oil but different thickener types were selected for the experiments. Two greases followed the ηbu model but the grease with alicyclic di-urea thickener produced a higher thickness than the model prediction, which is most likely caused by the formation of residual layers on the contact surfaces. The layer formation occurs in the first few hours of operation reaching a thickness of about 500–550 nm. Other greases also form layers, but they are comparable to prior observations, and they follow the model. The evolution of the normalized film thickness versus ηbu in the case of alicyclic-di urea grease shows the same trend as the other grease types but with overall higher values.

The Spatial Elastic-Hydrodynamic Problem of Lubrication of Radial Sliding Bearings

The Spatial Elastic-Hydrodynamic Problem of Lubrication of Radial Sliding Bearings

A thermofluid temperature modeling, prediction of closed-loop cooling system of roll grinder based on circulation differential equations

Roll grinders are essential in high-precision roll manufacturing. However, lubricant temperature fluctuations decrease the precision of grinders. The complicated dynamic heat transfer within the closed-loop cooling systems of roll grinders poses significant challenges to accurately modeling their thermal states. This study proposed a novel model based on circulation differential equations for the thermofluid temperatures in roll grinders. Based on thermodynamic principles, differential equations of each component within the closed-loop cooling system were derived. To improve model accuracy, a thermal resistance approach was utilized, and the thermal interaction between lubricant and hydrodynamic bearings under different speeds and the heat convection between hydraulic hoses and air are considered. To validate the proposed model, a series of experiments across a range of spindle speeds were carried out. The results showed the model could achieve prediction accuracy less than 5.27%. Subsequently, the influence of system design parameters on cooling performance was analyzed. The proposed temperature model better comprehends the thermodynamic interaction within closed-loop cooling systems featuring hydrodynamic bearings. The limitations and potential application in other industrial areas were discussed.

Vibration properties of full ceramic bearing under elastohydrodynamic fluid lubrication based on the energy approach

As an important part of rotating machinery, heat generation due to friction is inevitable during the rotating process of bearings. A large amount of heat causes the temperature of lubricating oil to increase, viscosity of lubricating oil to decrease, and lubricating performance decreases. Addressing the issue of inadequate lubrication between the rolling element and raceway due to increased lubricating oil temperature, this study focuses on full-ceramic ball bearings. It examines the impact of temperature fluctuations on the bearing's lubrication condition and investigates the vibration characteristics of the full-ceramic bearing. The variation in the viscosity of lubricating oil with respect to temperature is measured via a rotary viscometer. A dynamic model of the silicon nitride full-ceramic ball bearing, which considers the effects of elastohydrodynamic lubrication, is established. The impacts of changes in lubricating oil viscosity due to different temperatures on oil film pressure, oil film thickness, and bearing vibration are analyzed and then compared with experimental data. It is observed that under conditions of constant load and speed, the film thickness of the lubricating oil decreases as the viscosity decreases. Additionally, the second peak value of oil film pressure is reduced with the declining viscosity of the lubricating oil. As the viscosity decreases, the vibration of the bearing increases. The amplitude discrepancy between the simulated vibration signal and experimental vibration signal of the full-ceramic bearing is found to be less than 10 %, verifying the validity of the dynamic model.

Thoughts on a standardized FE-8 Test for the assessment of the WEC-carrying capacity of lubricants in rolling bearings

Thoughts on a standardized FE-8 Test for the assessment of the WEC-carrying capacity of lubricants in rolling bearings

Modelling and theoretical research on transient lubrication and wear coupling behavior of main bearing during start-up of low-speed diesel engine

This study endeavors to establish a transient mixed lubrication model for time-varying wear of main bearings under dynamic loading conditions during the startup process. This model accounts for variations in oil film thickness attributable to deformation, wear profiles, and journal misalignment throughout the operational cycle. The evolution of main bearing lubrication characteristics during the startup process was analyzed, as well as the evolution of wear profiles and their effects on lubricating properties under different numbers of startups. The results indicate that as the number of startup cycles increases, the wear rate gradually levels off. With increasing startup times, there is a decrease in contact pressure and a slight reduction in oil film pressure, resulting in enhanced lubricating performance. Furthermore, the influence of startup duration on wear is significantly greater than that of radial clearance.

Scratch geometry effects on lubrication and performance of two-lobe journal bearings: A detailed study

Scratches on bearing surfaces can significantly affect the performance and lifespan of journal bearings. This study investigates the impact of scratches on two-lobe journal bearings through both theoretical and numerical analyses. The theoretical approach provides insights into how scratches influence lubrication, while the numerical simulations investigate how the three key scratch parameters, namely width, position, and depth, affect bearing performance. Key metrics analyzed include pressure, velocity distributions, temperature profiles, eccentricity, attitude angle, minimum film thickness, and maximum temperature. The findings offer valuable guidance for optimizing bearing design, maintenance, and condition monitoring, contributing to enhanced reliability and operational efficiency.

Functionality of Bearings in the Shafts of a Vertical-Axis Wind Turbine

The article contains a description of the design solutions proposed by the authors for a hybrid wind turbine bearing, in which the sliding part takes over the load to the turbine shaft after reaching the shaft rotation speed, ensuring hydrodynamic lubrication of the plain bearing and relieving the rolling bearing. This allows for low starting resistance of the power plant and ensures quiet operation during use. Two conceptual solutions of a hybrid bearing were presented, differing in the shape of the plain bearing journal. A mechanism for automatic switching of the load between a rolling and a plain bearing was developed. A solid simulation model of this mechanism was built in the Autodesk Inventor—Dynamic Simulation software Inventor Professional 2023 environment, and its operation was simulated. The results confirmed the usefulness of using this design in shaft-bearing systems of wind turbines with a vertical axis of rotation. Based on the simulation, the speed at which the thrust roller bearing will be released was determined. Technical parameters of a plain bearing with a spherical journal shape were calculated. The height of the lubrication gap and the shaft rotational speed at which the bearing load capacity index reaches a critical value were determined.

A study on the temperature rise characteristics of high-speed ball bearings under starvation lubrication

PurposeThis paper aims to study the problem of starvation lubrication of high-speed ball bearings due to temperature rise during operation and to avoid thermal failure of bearing lubrication.Design/methodology/approachUnder the quasi-statics model of grease lubrication, both the oil film dragging force and the rolling friction between the balls and raceways collectively counteract the gyroscopic torque. Initially, the static model for grease lubrication is solved, followed by calculating the generated heat using the local heat generation method and ultimately the multinodal thermal network model is solved, and the solved results of the quasi-statics are updated by the temperatures of the grease nodes based on the relationship of the grease temperature and viscosity, as well as the relationship of the viscosity and the film thickness.FindingsBy comparing the numerical calculation results of bearings under different working conditions, the influence of starvation lubrication on the oil film thickness, oil film drag force and rolling friction of bearings is discussed, and it is found that the numerical calculation results of the outer ring temperature of bearings under the starvation lubrication due to the consideration of temperature rise are closer to the experimental values.Originality/valueThis study reveals the dynamic characteristics of bearings under starvation lubrication, which is more practical and engineering guiding significance for the design of bearings, and introduces a new method and basis for the calculation of temperature rise of rolling bearings.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0208/

The Role of the Working Fluid and Non-Ideal Thermodynamic Effects on Performance of Gas Lubricated Bearings

Abstract Small-scale turbomachinery operating at high rotational speed is a key technology for increasing the power density of energy and propulsion systems. A notable example is the turbine of an organic Rankine cycle turbogenerator for thermal recuperation from prime engines and industrial processes. Such systems typically operate with organic compounds characterized by complex molecular structures, to allow the design of efficient fluid machinery and flexibility in matching the heat source and sink temperature profiles. Gas bearings are considered advantageous compared to traditional oil-lubricated rolling element bearings for supporting the turbine rotor, enabling greater machine compactness and reduced complexity, and to avoid contamination of the working fluid. In certain operating conditions, however, the lubricant of the bearing is in thermodynamic states near the saturated vapor line or in the vicinity of the fluid critical point whereby non-ideal effects are relevant and may affect bearing performance. This work investigates the physics of thin film flows in gas bearings operating with fluids made by complex molecules. The influence of non-ideal thermodynamic effects on gas bearing performance is discussed by analysis of the fluid bulk modulus. Reduced values of the non-dimensional bulk modulus near the critical point or saturated vapor line decrease bearing performance. The main parameter characterizing the influence of molecular complexity on bearing performance is shown to be the acentric factor. For complex fluids with large acentric factors, the impact of non-ideal thermodynamic effects on non-dimensional bearing load capacity and rotor-dynamic characteristics is less pronounced.

Research on magnetic fluid precise localized lubrication thrust cylindrical roller bearing with low-friction micro-vibration and high load-bearing capacity

Abstract As the magnetic field that is difficult to be distributed in the existing magnetic fluid thrust cylindrical roller bearing structure, it is more difficult for the magnetic fluid to be evenly distributed inside the bearing raceway with the axial localized lubrication, which seriously affects the engineering application of the magnetic fluid bearing. To solve the magnetic field control problem that the magnetic fluid is uneasy to be accurately localized and adsorbed, a new type of magnetic fluid thrust cylindrical roller bearing is designed in this study, which shows good characteristics of low-friction, micro-vibration and high load-bearing capacity. The seat-ring is set as an annular raceway that can be used for magnetic fluid storage and matching with the roller lubrication system, and an annular permanent magnet is designed as an external magnetic field source to be placed below the annular raceway to adsorb the magnetic fluid on the friction surface. The structure design of the axial magnetic fluid localized lubrication bearing is reasonable, which is especially suitable for precision instruments with strict operating-conditions and precision-lubrication.

A novel design of journal bearings for stability under shock loads

Mechanical systems are expected to operate under various load conditions, and it is necessary to use a lubrication system to achieve reliability and stable performance. Journal bearings, which are used to achieve such stable lubrication, are representative of hydrodynamic lubrication bearings. In this study, groove-shaped structures and rubber were applied to the ends of the bearings to ensure stable lubrication performance under conditions where, for various reasons, shock loads are applied in addition to static loads under misaligned conditions. The groove structure and rubber contribute to stable lubrication performance by preventing contact between the shaft and bearing as well as absorbing shock loads through elastic deformation of the groove’s end due to oil film pressure. This novel design, which utilizes groove-type flexible structures and rubber, led to journal bearings that exhibited improved lubrication performance under various shock load conditions. When a shock load is applied to a mechanical system, the design proposed in this study contributes to improving the reliability of the mechanical system by enhancing its lubrication performance.

The patterns of changes in the degree of lubrication of the crankshaft bearings of car engines depending on the parameters of the load-speed modes of operation

The practice of operating machines and mechanisms indicates that bearing wear is one of the main reasons for limiting their durability. This especially applies to the sliding bearings of crankshafts of car engines, where the intensity of wear of their working surfaces significantly depends on the properties of the lubricant. An experimental study of the wear resistance of the sliding bearings of the crankshafts of car engines was carried out on the KI-5543 model break-in and braking stand. In experimental studies, BELZONA Super E-Metal insulating material was used to provide electrical isolation of the main and connecting rod bearings of the crankshaft from the cylinder block of the car engine. The experimental dependencies of the values of the criteria characterizing the degree of lubrication of the friction surfaces on the parameters of the load-speed modes (the moment of the applied force and the frequency of rotation of the crankshaft) were obtained. The ranges of values of the investigated parameters, in which the effective operation of the sliding bearings of the crankshaft of car engines is implemented, have been revealed.

Effect of meshing-induced deformation on lubrication for journal planet gear bearings

To increase the power density and reliability of wind turbine gearboxes (WTGs), journal planet gear bearings (JPGBs) are increasingly employed in their low-speed planet stages. Except for the pressure- and temperature-induced deformations, the JPGB is also structurally deformed by the gear pair meshing in this application, complicating the lubrication and deformation characteristics. Considering the above meshing-induced deformation, a thermo-elasto-hydrodynamic (TEHD) model is proposed for the JPGB, whose deformation is predicted using a self-programmed procedure based on the finite element method (FEM). Besides, this model is verified through a lubrication experiment of the JPGB in the WTG. It is found that the appropriate meshing-induced deformation, varying periodically in the meshing process, can improve the TEHD and misalignment behaviors of the JPGB due to the load-carrying region expansion or twice hydrodynamic action. This phenomenon becomes increasingly obvious with increasing the WTG's input power and the planet's inner radius.

Numerical Study on Characteristics of Lead-Bismuth Lubricated Hydrodynamic Bearing Considering Non-Condensable Gas

Lead-Bismuth Eutectic (LBE) is an interesting candidate as a coolant for Generation IV nuclear power plants. Lead-bismuth lubricated radial guide bearing is the key component of the mechanical pump in a lead-bismuth coolant system. In this paper, the transient calculation model of multiphase lubrication flow field of journal bearing is established by using Singhal full cavitation model and structured dynamic grid technique. Due to the saturated vapors of LBE being very low, the effects of different Non-Condensable Gas (NCG) contents on the characteristics of lead-bismuth lubricated journal bearing systems were analyzed. The results show that the NCG content has an obvious influence on the working state of the bearing. With the increase in NCG content, the bearing load capacity decreases. Under the same load, with the increase in NCG content, the eccentricity of the static equilibrium position will be larger, which will increase the risk of bearing contact with the bearing bush. Moreover, the increase of NCG content will lead to the increase of tangential oil film force work, which is helpful to improve rotor stability.