Lubricating Oil Film Research Articles

Nonlinear time heteronymous damping in nonlinear parametric planetary systems

The analysis of dynamics of time heteronymous weakly and strongly nonlinear planetary transmission systems with kinematic couplings–gears constitutes a study of complicated function of many parameters including the material of gears, damping properties and damping viscous properties of lubricating oil film in the gear mesh. The purpose of this theoretical preexperimental study is to educe the methodology that makes possible to analyse the influence of all parameter variants in the area of linear and nonlinear systems with constant and time variable damping on internal dynamics. More precise dynamic analysis of such systems leads to mathematical–physical models, whose motions are described by ordinary deterministic nonlinear time heteronymous differential equations at the application of mass discretization. Their solution leads to the method of transformation of the nonlinear boundary problem of differential equations into the equivalent problem of solving integro-differential systems of equations by the method of decomposition of solving kernels of Green’s type and by the method of successive approximations. The structures with lightening holes in cog wheel discs are characterized by time variable damping in gear meshes. In this paper, the examples of resonance bifurcation characteristics in the gear mesh give a comparison between two variants with lightening wheel discs and the variant with full wheel disc, i.e. two variants with time variable quadratic damping and the variant with the constant one.

The Research Status and Progress of Heavy/Large Hydrostatic Thrust Bearing

How to improve the rotation speed of heavy/large CNC vertical lathe, the machining efficiency, and machining precision is one of the key issues which need to be solved urgently. Hydrostatic thrust bearing is the key part to the heavy/large CNC vertical lathe; its performance directly affects the machining quality and operation efficiency. This paper analyses the latest research results from the perspective of the mechanical properties of hydrostatic thrust bearing, oil film lubrication, static pressure bearing thermal deformation, and the high efficiency refrigeration and evaluates the future scientific research direction in this area. Analysis shows that with the development of hydrostatic thrust bearing to the high speed, high precision, high efficiency, high stability, high multifunction, and high power, the study of hydrostatic thrust bearing will focus on the optimal design of the oil chamber to produce the least amount of heat, how to control the thermal deformation of hydrostatic thrust bearing, and the high efficiency refrigeration to ensure the machining accuracy of CNC equipment.

Swing Characteristic of Pads in Four-pad Tilting Pad Bearing

The swing characteristic of pads on four-pad tilting pad bearing is studied systematically with the guide bearing for helim circulator in fourth generation nuclear power units HTR as object. Theoretical derivation reveals that dimensionless pad pendulum angle depends on structural parameters, preload and eccentricity, but independent of viscosity of lubrication oil film, shaft rotating speed and clearance. Numerical analysis shows that: pad pendulum angle is determined by pad circumferential position relative to the load, preload and eccentricity. When the structural parameters of tilting pad bearing are constant, pendulum angle curve of pad facing the load was depend on preload, its pendulum angle increases first and then decreases with the eccentricity ratio increase while the preload less than 0.5, when the preload is greater than 0.5 its pendulum angle decreases gradually with the eccentricity ratio increase; pendulum angle curve of pad side of the load increases or decreases with the eccentricity ratio increase when the preload is smaller, and remains constant first and then decreases with the eccentricity ratio increase when the preload is greater. Pad pendulum angle has great influence on minimum oil film thickness; its value maybe negative thus leads to the minimum oil film thickness greater than fixed pad. The study results provides basis for safety operation analysis of the helim circulator.

Thermomechanical Fatigue Life Prediction for a Marine Diesel Engine Piston considering Ring Dynamics

A newly designed marine diesel engine piston was modeled using a precise finite element analysis (FEA). The high cycle fatigue (HCF) safety factor prediction procedure designed in this study incorporated lubrication, thermal, and structure analysis. The piston ring dynamics calculation determined the predicted thickness of lubrication oil film. The film thickness influenced the calculated magnitude of the heat transfer coefficient (HTC) used in the thermal loads analysis. Moreover, the gas pressure of ring lands and ring grooves used in mechanical analysis is predicted based on the piston ring dynamics model.

Running Behavior of a High-Speed Spindle Using a Micro-Mist Lubrication System

This work investigates the effect of lubrication parameter on the operation performance of a high-speed spindle using a micro-mist lubrication system. Experiments are conducted through a long-time spindle test under different combinations of oil-supply parameter and rotating speed for a micro-mist lubricated spindle. The correspondent relationships among temperature rise, vibration, oil-supply parameter and rotating speed are established through the experiments under moderate oil-supply. The results show that the better oil-supply parameter combinations exist under different spindle rotating speeds, which could ensure the sufficient and adequate lubricating oil film to be formed and a stable elasto-hydro-dynamic lubrication could be further created during the operation period. The minimization of the temperature rise in bearings may be attained. Increasing air pressure contributed to the reduction in bearing temperature, but saturation might be appeared after the pressure level reached to a certain extent. The dynamic response measurement shows that this prototype spindle has an overly large vibration and rotation unbalance on the radial plane, which highlights the unstable operation problem of the spindle. Therefore, it is necessary to improve the constructed procedures, such as design, manufacture, and assembly for further use, to enhance the operation performance of the spindle. The analysis, measurement and diagnosis procedures established in this study could be helpful to uplift the related techniques for precision machinery industry.

Modeling the stiction effect in automatic compressor valves

The stiction effect is a source of thermodynamic losses in compressor suction and discharge systems. Deformation of the lubricant film between the valve and the seat delays the valve opening, as larger pressure differences between the cylinder and the discharge or suction chambers are needed to overcome the stiction force. A model is presented for the dynamic behavior of a ring-shaped lubricant oil film between a discharge valve and the seat. The valve is allowed to move under the action of an external force due to the time-dependent pressure difference between the cylinder and the discharge chamber. The main contributions of the model are the consideration of a finite oil amount between the valve and the seat and relationships for calculating the film thickness initial condition. At typical conditions of discharge systems of domestic refrigeration compressors, viscous effects are the dominant component in the oil stiction force under dynamic conditions.

Research on Commercial Vehicle Clutch Release Bearing Fatigue Life Prediction Model

Commercial vehicle clutch release bearings working at high speed, strong vibration,high temperature, damp and easy pollution conditions. Fatigue life analysis is based on the release bearing rings or rolling body began to appear fatigue spalling, in which this kind of phenomenon is under cyclic stress. The contact stress distribution is not uniform, the contact stress is mainly concentrated near the surface; influenced by the geometry and physical properties and lubrication of the surface significantly. Contact between the two types of fatigue crack extension methods: fatigue crack surface under expansion and surface fatigue crack propagation. The surface crack growth mainly originated from two kinds of cases: crack caused by surface pre crack and contact between the two surface asperity each other. New life prediction model for the release bearing based on L-P theory and Tallian model ,in which influence factors of fatigue life is introduced on the smelting process, surface defect, surface roughness, residual stress, elastohydrodynamic lubrication oil film,environmental cleanliness, temperature, the effect of varying load characteristics and other factors of fatigue life. The results show that: the clutch release bearing life prediction model of new and more close to the real conditions of automobile clutch, provide the theory basis for the development of a new generation high-speed heavy-duty clutch release bearing of the commercial vehicle.

Modeling and Analysis of High-Speed Journal Bearing Based on Thermal Hydrodynamic Lubrication Theory

Journal bearing in high-speed working conditions will generate a lot of heat, which affects its working performance. Based on hydrodynamic lubrication theory, a model of the thermal hydrodynamic lubrication was built, and the distributions of temperatures and pressures of the oil film were obtained from the simultaneous solution of generalized Reynolds, energy and viscosity-temperature equations. The results show that the temperature will increase and the pressure decrease of the lubrication oil film with the rising of the rotating speed, which will make the the bearing capacity decrease. Compared with the traditional isothermal model, the thermal hydrodynamic lubrication model is more consistent with the engineering practice.

The Research of Lubricating and Colling System of the Low-Speed and Heavy-Load Sliding Bearing

This paper analyzes the influence of lubricating oil film of the low-speed and heavy-load sliding bearing on a variety of factors. It introduces the operation of Bearing for lubricating oil film in monitoring method, common fault causes and treatment measures. Finally, the bearing cooling system structure is discussed, providing reference for practical engineering application. There are many reasons to cause the failure of the bearing lubrication such as bearing assembly defects, the error of size and cooling system problems. By detecting and contrast parameters, this study analyze the determine data and correct the fault. Through the use of reasonable structure of the oil tank and cooling water channel, we can improve the lubrication performance, and extend the bearing life. This paper analyzes the factors restricting the low speed and high load sliding bearing lubricant film, and solves the actual bearing lubrication problem.

The Comparison and Analysis on the Approaches of Lubricant Oil-Thickness Testing

This paper describes the comparison on the approaches of bearing lubricant oil-thickness testing .The comparison and analysis involves in the areas of classification of methodsbackground theoryapplied range and experiment between refined optical method and new ultrasonic method. The result of optical method modify the result of ultrasonic method, which has a guidance on the development of testing lubricant oil-film thickness. It describes an ultrasonic array , based on the traditional single-element transducer. In this way, the two dimensional oil-thickness distributions can be extracted by data processing. The development of ultrasonic approach benefits the goal of monitoring bearing lubrication condition online , which demonstrates the potential value of the ultrasonic approach. The implications for improved measurement methods are then discussed.

Research on Load-Carrying Performances of Magnetic-Fluid Lubrication for Mill Oil-Film Bearing

The FEM model of lubricating oil film was built with mill oil-film bearing as the research target, the analysis system of magnetic-fluid lubricating oil film for oil-film bearing was developed. APDL and CEL languages were applied to compile the inner analytical programs, and the combination of VB, ANSYS Mechanical with ANSYS CFX was perfectly realized. Through the numerical simulation of magnetic-fluid lubricating film, the load-carrying performances of oil-film bearing with magnetic-fluid lubrication were analyzed, and the relationship among magnetic field intensity with oil-film pressure and temperature was quantitatively calculated. The numerical results have shown that the magnetic-fluid lubrication has obvious influences on oil-film pressure when magnetic field was applied on oil-film bearing, the lubricating viscosity increases with the magnetic-fluid intensity, and the oil-film pressure and temperature also increase with magnetic-field intensity. However, the increasing increment of oil-film temperature is far lower than that of oil-film pressure. The above conclusions prove that magnetic fluid with proper magnetic field can effectively improve the load-carrying capacity of lubricating oil film and enhances the stability of oil-film pressure. Moreover, the adjustable intelligent oil-film pressure with magnetic field is deduced to be feasible.

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.

Experimental Analysis on Oil Film Properties of Plane Port Pair in Axial Piston Machine

To find some rules keeping good lubrication condition for plane port pair in high-performance axial piston pump or motor, especially in the very severe applications, a new test rig was built up to simulate the operational principle of port pair, and to form the lubricating oil film for representative parameter acquisition. This rig is principally characterized by supply pressure up to 30 MPa, accurate control of oil film thickness by separate oil circuit design and electrohydraulic feedback control. The tested oil film working properties was analyzed by comparison with theoretical or simulation references. Experiments show that film balance time and thickness are two key parameters for describing oil film properties, and that working condition factors such as supply pressure, lubricating fluid temperature also notably affects the film thickness and its configuration, but they don’t show equivalent action. Lubrication effects can be valued by the tested frictional torque change of port pair.

Numerical Investigation of the Flow in a Hydrodynamic Thrust Bearing With Floating Disk

In this paper we present a novel method for the numerical simulation of flow in a hydrodynamic thrust bearing with floating disk. Floating disks are commonly employed in turbochargers and are situated between the thrust collar, which is rotating at turbocharger speed, and the static casing. A floating disk reduces wear, improves the skew compensating capacity of the bearing, and is freely movable in the axial direction. The simulation model presented combines a commercial flow solver (ANSYS CFX) with a control unit. Based on physical principles and a predefined axial thrust, the control unit automatically sets the rotational speed of the floating disk, the mass flow of the oil supply, and the oil film thickness between the rotating disk and the casing wall and collar, respectively. The only additional inputs required are the temperature and the pressure of the oil at the oil feed and the turbocharger speed. The width of the computational grid of the thin lubricating oil film in the gaps is adjusted using a mesh-morphing approach. The temperature-dependent variation in viscosity is included in the model. The calculated solution of the flow field in the domain, the oil film thickness, and the resulting rotational velocity of the floating disk are validated against experimental data and demonstrate favorable agreement. The influence of uncertainties in the measurements and the behavior of the systems are thoroughly investigated in parametric studies that reveal the key influencing factors. These are the temperature-dependent viscosity of the oil, the axial thrust, and turbulence effects in the supply grooves and ducts of the floating disk. Using the model presented here, it is now possible to predict design variants for this type of bearing.

Influence of Working Parameters on Dynamic Pressure Effect of Heavy Constant Flow Hydrostatic Center Rest

In order to increase the working performance of a heavy constant flow hydrostatic center rest, a theoretical study concerning the lubricating oil film dynamic pressure effect of the heavy constant flow hydrostatic center rest is described. The Computational Fluid Dynamics and the Finite Volume Method have been used to compute numerically the static pressure field and the total pressure field of the lubricating oil film. The influences of spindle rotating rate, lubricating oil dynamic viscosity and inlet flow rate on the lubricating oil film dynamic pressure effect of the heavy constant flow hydrostatic center rest were analyzed based on the computational fluid dynamics and lubrication theory, and the influencing laws were revealed. By means of this method, the reasonable data can be provided for reasonably controlling dynamic pressure and structure optimal design of the heavy constant flow hydrostatic center rest.

Thermal analysis on piston of marine diesel engine

In this paper, an inverse heat transfer method is employed to conduct thermal numerical analysis on a 4-ring articulated piston of marine diesel engine. The secondary motion of piston and piston ring, and the lubrication oil film has been considered in estimating the coefficient of heat transfer values. Specially manufactured metal plugs were installed in the head of an articulated piston and the piston skirt to measure the temperature distribution of them. A Series of thermal couples were used for cylinder temperature measurement. The boundary condition for numerical simulation is verified with experiment result and applied to predict the temperature distribution of a new piston design which had small change of piston head profile and one less ring scheme. Reasonable agreement was obtained between prediction and experiment for the new design. Experiment result showed increase of temperature in low-temperature area and decrease of maximum value in high-temperature area. The thermal load of the top ring for new piston was lower than old one. The new design had some potential of intensifying improvement from the view point of piston thermal load.

Analysis of Elastohydrodynamic Lubrication of Ball Screw with Rotating Nut

The isothermal elliptical contact elastohydrodynamic lubrication (EHL) problem in ball screw with rotating nut was studied.Numerical solution to the problem was obtained for various parameters with a multigrid solver.Based on work mentioned above,the influence of the working parameters such as the rotating speed of screw shaft and the contact force,on the lubricant oil film thickness and pressure is analyzed .The results showed that, with the increasing loads,the pressure became higher,the film thickness became smaller. On the other hand,when the angular velocity was higher,the film thickness was higher, while the pressure spike was closer to the center of the contact. Because of the spinning, the slide-roll ratio was not a constant.

Analysis on Influence of Oil Film Thickness on Temperature Field of Heavy Hydrostatic Bearing in Variable Viscosity Condition

According to the problem of the influence of oil film thickness on temperature rise for heavy hydrostatic thrust bearing during operation， build viscosity-temperature equation of lubricating oil film and mathematics model of oil film temperature rise of heavy hydrostatic bearing with multiple oil pads, simulate the temperature field of hydrostatic bearing with sector cavity under various oil film thickness using FVM(finite volume method), and reveal the influence law of oil film thickness of temperature rise for hydrostatic bearing. The results show that temperature distribution of hydrostatic bearing is much the same under various oil film thicknesses, but the influence of oil film thickness of temperature rise for hydrostatic bearing is greater. The results of numerical calculations actually response flow state inside hydrostatic bearing ，offer theoretical foundation for the design of hydrostatic bearing in engineering practice, and have important significance in improving operation stability of NC machine.

Coupling Analysis of Dynamics and Oil Film Lubrication on Rotor - Floating Bush Bearing System

A coupling calculation method using dynamics and lubrication for a rotor and floating bush bearing system has been developed to predict self-excited oscillations and unbalance oscillations using a flexible multibody dynamics technique with hydrodynamic lubrication theory. Based on experimental results using a floating bush bearing, an accurate and numerically efficient lubrication model is proposed to calculate the hydrodynamic force, the bush rotating speed and the temperature of the oil film. In the multibody dynamics analysis, the rotor was modeled using the finite element method to include bending elasticity and the gyroscopic effect. The bearing bush was modeled by a rigid body. The coupling analysis between the rotordynamics and the oil film force of the bearing was performed by an in-house flexible multibody dynamics solver. Subsequently, the detailed mechanism of the rotor oscillation and the influence of some design parameters were investigated by numerical simulations and experiments.

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