Oil Film Temperature Research Articles

Effect of starting time on hydro-viscous drive speed regulating start

Purpose– The purpose of this paper is to reveal the effect of starting time on hydro-viscous drive speed regulating start.Design/methodology/approach– The modified transient Reynolds equation, thermal energy equation and temperature–viscosity equation were solved simultaneously by using finite element method. And then variations of the oil film load capacity, variations of temperature and variations of the torque generated by the oil film during the starting process were obtained.Findings– The results show that during the starting process, both the oil film load capacity and the temperature show an upward trend, the torque increases during the beginning period and then decreases during the latter part of the starting process. When the starting time is less than 60 s, variations of the oil film load capacity and temperature show fluctuations, which decrease with the starting time. For any output speed, the corresponding oil film load capacity, temperature and torque decrease with the starting time, and the decreasing amplitude also decreases with the starting time.Originality/value– This paper indicates that the starting time can be set to 60-90 s to obtain a perfect starting process. The simulation results are verified by the speed regulating start experiments. Research findings of this work provide theoretical basis for the design and practical application of the hydro-viscous drive equipments.

The effect of the lubricating oil on heat transfer in a hermetic reciprocating compressor

In some types of hermetic refrigeration reciprocating compressors, the oil circulation pattern inside the crankcase produces an oil falling film on the inner wall of the compressor shell. The conjugate heat transfer between the shell and the oil affects the heat dissipation from the internal components to the external environment and, consequently, the compressor thermal profile. A differential model is proposed to calculate the oil film and compressor shell temperature distributions. This model is incorporated into an existing compressor model based on integral forms of the energy balances for its components. The combined (integrated) model results are verified against experimental data for the temperature of the components and of the compressor shell. The model can be used to predict the compressor performance as a function of the suction and discharge pressures, the total oil flow rate and the fraction of this flow rate flowing as a film on the shell.

Research on the Static and Dynamic Characteristics of Misaligned Journal Bearing Considering the Turbulent and Thermohydrodynamic Effects

Journal misalignment usually exists in journal bearings that affect nearly all the bearings static and dynamic characteristics including minimum oil film thickness, maximum oil film pressure, maximum oil film temperature, oil film stiffness, and damping. The main point in this study is to provide a comprehensive analysis on the oil film pressure, oil film temperature, oil film thickness, load-carrying capacity, oil film stiffness, and damping of journal bearing with different misalignment ratios and appropriately considering the turbulent and thermo effects based on solving the generalized Reynolds equation and energy equation. The results indicate that the oil thermo effects have a significant effect on the lubrication of misaligned journal bearings under large eccentricity ratio. The turbulent will obviously affect the lubrication of misaligned journal bearings when the eccentricity or misalignment ratio is large. In the present design of the journal bearing, the load and speed become higher and higher, and the eccentricity and misalignment ratio are usually large in the operating conditions. Therefore, it is necessary to take the effects of journal misalignment, turbulent, and thermal effect into account in the design and analysis of journal bearings.

Fast thermo-elasto-hydrodynamic modeling approach for mixed lubricated journal bearings in internal combustion engines

Journal bearings are key components in internal combustion engines. Their reliability, durability, and economy are of highest importance. Especially, the accurate prediction of friction loss power and wear are essential for the development of an engine. For an appropriate representation of the hydrodynamic load-carrying capacity and also the friction behavior, both the dynamics of the contacting components, the shape of the contacting component surfaces, the amount of the available lubricant, and the properties of the lubricant itself are of importance. A Reynolds-averaged equation with laminar flow conditions in combination with an asperity contact model is a typical modeling approach for that purpose. The lubricant properties are in particular influenced by its thermal conditions on one hand. On the other hand, the thermal conditions are influenced by the mixed lubricated contact conditions as well. These interactions require a coupled modeling approach, which combines the component flexibility and its interaction with load-carrying capacity as well as the thermal behavior of the lubricant and the component surfaces. In this work, a thermo-elasto-hydrodynamic contact model is presented, which computes the oil film temperature using a 2D energy equation. The 2D equation is derived from the equivalent 3D energy equation by integration over the clearance gap height. Besides component material properties such as specific heat capacity, density, heat conductivity for lubricant and structures, also heat transfer through mixed lubricated regimes and partly filled clearance gaps, as implied in cavitation regions, are being considered. The presented method is applied for a typical engineering task of a sensitivity analysis for oils with different viscosity index (VI) improvers in a main bearing of a four-cylinder inline diesel engine. The influence of the oil film temperature on the oil film viscosity and therefore on the load-carrying capacity is shown. Furthermore, the simplified 2D approach is compared with a 3D approach both in terms of obtained result data and in terms of elapsed calculation times. The presented results show similar accuracy of the 2D approach with significantly reduced simulation time compared to the equivalent 3D case.

Observation of Oil Spills through Landsat Thermal Infrared Imagery: A Case of Deepwater Horizon

In the accidental oil spills of Deepwater Horizon at the Gulf of Mexico in 2010, cold plume of initial oil cover with the apparent surface temperature lower than the surrounding sea surface temperature by 0.6K, was detected; and away from the initial leakage location, the apparent temperature of oil film was found higher than the surrounding sea surface water temperature with a maximum difference of 3.2K. Both the cold and hot oil patches had relatively thicker film, but the cold patches were due to the initial low temperature during the crude oil upwelling from deep water while the hot ones were caused by sun heating. This suggests that thermal infrared imagery has the potential in locating the leakage place of crude oil spill upwelling especially from deep water and identifying thick oil aggregations.

Analysis of Thermal Effect on Elastohydrodynamic Lubrication in Angular Contact Ball Bearing

Based on the theory of point contact thermal elastohydrodynamic lubrication (EHL),the mathematical models for the thermal EHL of high-speed angular contact ball bearing are established. Multi-grid method and multigrid integration method are respectively used to calculate out the film pressure and film thickness respectively,and the column-by-column scanning method is used to calculate temperature rise of isothermal EHL and thermal EHL. The calculation results show that, under the pure rolling condition, temperature rise of oil film temperature is mainly caused by the compression work and shear heat at inlet and the heat in contact zone mainly comes from the inlet and the heat conduction around; the temperature rise results in oil viscosity lower and the lubricating film thinner ,in this way it reduces the lubrication performance in contact pair.

K07100 エンジントライボロジーとレーザー計測

To keep a better lubricating condition, the precise and the detailed measurement of lubricating oil film and the management and the control of lubrication is becoming more important recently. To cope with this aim, many types of measurement and diagnostic methods are developed and utilized in the field on engine tribology. In this paper, some of the measurement method, including the optical measurement techniques using lasers as the light source proposed by the authors, are introduced briefly. The target of the measurement are the oil film thickness, the oil film temperature and the flow visualization of oil film. The measurement principals applied are the stimulated emission of radiation, the laser induced fluorescence and the photochromic reactions respectively.

Numerical Modeling of Unsteady Oil Film Motion Characteristics in Bearing Chambers

AbstractTo obtain motion characteristics of the lubricating oil film on the aero-engine bearing chamber wall, a complete mathematical model based on theoretical study to solve three-dimensional unsteady oil film motion was established. On the basis of verifying the rationality of the computational model, the variations of the oil film thickness, velocity and temperature with the rotation speed and lubricating oil flow were analyzed and studied. The numerical results show that the following: In the stable oil film flow state, the oil film thickness shows a decreasing trend with increase in rotation speed and an increasing trend with increase in the lubricating oil flow. Particularly, comparison with the experimental work shows that the proposed numerical model based on theoretical study to solve unsteady oil film motion is a valuable technical means for the study of oil film movement mechanism and the design of actual bearing chamber.

Thermal effects for conventional and water-cooled thrust bearing using finite difference method: comparative analysis

The present paper describes the thermal effect on a sector shaped pad extensively used in thrust bearings, which supports the heavy duty axial loads. Large hydrogenerator thrust bearings are susceptible to too much thermo-elastic deformation when oil film thickness is subjected to high pressure and temperature, which can even lead to the bearing failure. So as a remedy, this study is an effort towards reducing the oil film temperature by incorporating a suitable cooling treatment. The cooling circuit, in this study, essentially follows a path of hot spots observed by solving Reynolds equation, energy equation and generalised Fourier heat conduction equation. The numerical scheme followed during investigation is finite difference method (FDM). The water circuit developed is just beneath the Babbitt lining of the pads. It has been observed that the overall temperature has reduced significantly when compared with a traditional cooling systems.

Conrod Bearings With an Optimized Narrow Circumferential Oil Groove: Simulated Durability Improvement for Heavy-Duty Applications

Under normal operating conditions, engine crankshaft bearings experience variations in oil film temperature due to shearing of the oil film. This can have a negative impact on the bearing operating life since the viscosity of the lubricant is temperature dependent. In the current study, a thermo-elastohydrodynamic lubrication (TEHL) analysis has been conducted using an in-house specialized simulation package called (software for analysis of bearings in reciprocating engines) SABRE-TEHL. This advanced simulation tool has been used to optimize a new bearing design feature leading to a significant temperature reduction, which in turn increases the robustness of the system.

Numerical Study of Thermohydrodynamic Characteristics of Oil Tilting-Pad Journal Bearings with a Self-Pumping Fluid Flow Circulation

A thermohydrodynamic numerical code is developed for analyzing the steadily loaded finite tilting-pad journal bearings for vertical hydropower plants. The Reynolds equation and the two-dimensional energy equation in fluid film lubrication are solved by the central difference technique with a successive overrelaxation scheme and the backward difference with an iterative technique, respectively. In the simulation, the lubricant viscosity is changed with the temperature variation (in both axial and sliding directions) and the pad deformation is brought up in calculations. Oil circulation is considered as a self-pumping fluid flow through pad side leakage via a circumferential groove. Self-lubricating approach is guaranteed the oil cooling procedure and bearing performance in hydropower plants. The effects of pad number, preload factor, pivot position, and shaft rotational speed on the bearing performance are illustrated. Power friction loss, maximum oil film temperature, circulated oil fluid flow, minimum oil film thickness, and pad tilting angle are the most important results.

Numerical analysis of spiral oil wedge sleeve bearing including cavitation and wall slip effects

AbstractThe modified Reynolds equation is established on the basis of critical shear stress model, in which the circumferential and axial wall slip of sleeve and journal surface is considered. Cavitation is treated using modified Elrod algorithm that simplifies the solution of modified Reynolds equation in the full‐film region. The modified Reynolds equations considering wall slip and cavitation effect for two‐dimensional sleeve bearing are established. The results show that wall slip decreases oil film pressure, carrying capacity, friction drag and temperature rise but increases end leakage and cavitation region. The obtained results using the mass‐conserving boundary condition are compared with the Reynolds boundary condition. Copyright © 2014 John Wiley & Sons, Ltd.

Viscosity monitoring and control on oil-film bearing lubrication with ferrofluids

Ferrofluid application in the oil-film bearing can improve the viscosity and the load-carrying capacity in a magnetic field. A solenoid was developed to provide magnetic field for ferrofluid, using which the distribution of magnetic induction intensity was calculated. The viscosity equation of ferrofluid was derived. The effects of oil-film temperature T, oil-film pressure P and magnetic intensity H on ferrofluid viscosity ηf was analyzed and tested by an unifactor experiment method. The control equations and transfer functions of each variable were given based on a large-scale oil-film bearing test rig. The variations of P, T, H and ηf were simulated and monitored by a reasonable control strategy. The results suggest that the viscosity increment by magnetic intensity could compensate the viscosity decrement by temperature rise.

Dynamic characteristics of polymer faced tilting pad journal bearings

Dynamic characteristics of polymer faced tilting pad journal bearings are presented. Investigations are conducted using a single pad, load on pad configuration over a range of shaft speeds and loads. Two polyether ether ketone (PEEK) faced pads, one polytetrafluoroethylene (PTFE) faced pad and two entirely PEEK pads are investigated to determine the effect of varying mean bearing pressure and pivot characteristics as well as different material properties of the polymer layer. Experimental results indicate increased damping and decreased stiffness and slightly increased oil film temperature for entirely PEEK pads compared to pads with a PEEK lining and steel backing. Similar effects were observed by using a softer (PTFE) pad liner with a steel backing.

Evaluation of Operational Characteristics in a Large Thrust Bearing

In this paper the non dimensional load parameter, volumetric flow rate, energy flux, oil film temperature and power loss of a large thrust pad bearing are formulated. The objective of the paper is to determine the novel non dimensional thermal, volumetric and power loss parameters in addition to the known load and energy flux parameters of the bearing. The computation is done by formulating and numerically solving the oil film thickness, two dimensional Reynolds', Vogel-Cameron and energy equations at the different nodes of the pad oil film using a finite difference procedure. The lower the degree of the objective shape polynomial more is the accuracy of the slider bearing shape and pressure distribution. The developed derives the value of ‘a' for which the load is maximum. The variation of the dominant bearing centre of pressure with respect to the corresponding values of ‘a' is studied. From the equation of fluid film temperature the minimum rise in bearing temperature corresponding to the values of ‘a' are determined. The oil film temperature distribution results are found satisfactory in terms of computer time and convergence criteria. The accuracy of the results is thoroughly validated by the variation of the load and thermal contours. This data and analysis serves as an input for rotor dynamic studies and includes the scope to develop safe operation of the bearing at high speeds in vertical hydro-electric rotors.

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.

Temperature Field of Hydrostatic Supporting Disk in Different Viscosity and Rotational Speed

With heavy hydrostatic bearing as the research object, establish oil film viscosity-temperature equation. Adopt finite volume method, respectively calculates the oil film temperature field under different rotate velocity in Invariant viscosity and variable viscosity, revealing the oil film temperature arise influence rule of hydrostatic bearing on the viscosity and rotate velocity. The results show that the viscosity and rotate velocity have a great influence on the hydrostatic bearing oil film temperature rise, but the effect regularity varied. The calculated results that provide a theoretical basis for the hydrostatic bearing structure design and bearing deformation calculation, and have very important significance on improve the reliability and precision of the whole machine tools.

An Experimental Investigation of Oil Film Temperatures in Elliptical Profile Journal Bearing

Hydrodynamic journal bearings experience significant variation in oil film temperature. Reliable data of operating temperatures in these journal bearings are very useful and important for practical bearing designers and mathematical modellers. Here, an elliptical journal bearing has been tested to access the temperature rise at oil-bush interface with three grade oils at loads varying from 100 N to 600 N and speeds = 3000, 3500, 4000 rpm at constant oil supply pressure. The results show that with increase in load at constant speed and pressure, and with increase in speed at constant load and pressure, the oil film temperature increases in the central plane of both the lobes of the bearing for all grade oils under study. Further, it is observed that under the given operating conditions, oil 2 gives the coolest operation of the elliptical bearing under analysis.

Research on Hydrostatic Supporting Temperature-Rise of Heavy NC Machine Tool

With heavy NC machine tool is widely used in many oil pad round guide hydrostatic bearing as the research object, in the under condition of variable viscosity, establish oil film viscosity-temperature equation. Adopt finite volume method, simulation the hydrostatic bearing internal fluid temperature field under different flow rates on the speed of 6R / min. Numerical simulation hydrostatic thrust bearing oil film temperature field, can find a general high temperature region, and then take effective control temperature. It can achieve the hydrostatic thrust bearing oil film temperature field prediction for engineering practical oil chamber structure, offer the theoretical foundation for optimization design.

프로세스 대형 모터-발전기의 저어널 베어링 설계 개선 - Part II : 로터다이나믹스 해석

In the preceding Part I study, for improving the unbalance response vibration of a large PRT motor-generator rotor fundamentally by design, a series of design analyses were carried out for bearing improvement by retrofitting from original plain partial journal bearings, applied for operation at a rated speed of 1,800 rpm, to final tilting pad journal bearings. To satisfy evenly key basic lubrication performances such as the minimum lift-off speed and maximum oil-film temperature, a design solution of 5-pad tilting pad journal bearings and maximizing the direct stiffness by about two times has been achieved. In this Part II study, a detailed rotordynamic analysis of the large PRT motor-generator rotor-bearing system will be performed, applying both the original plain partial journal bearings and the retrofitted tilting pad journal bearings, to confirm the effect of rotordynamic vibration improvement after retrofitting. The results show that the rotor unbalance response vibrations with the tilting pad journal bearings are greatly reduced by as much as about one ninth of those with the plain partial journal bearings. In addition, for the tilting pad journal bearings there exist no critical speed up to the rated speed and just one instance of a concerned critical speed around the rated speed, whereas for the plain partial journal bearings there exist one instance of a critical speed up to the rated speed and two instances of concerned critical speeds around the rated speed.