Investigation of Friction Power Losses in Automotive Journal Bearings (original) (raw)
Related papers
Simulating Friction Power Losses in Automotive Journal Bearings
Procedia Engineering, 2013
Journal bearings are used in a large number of critical positions in automotive internal combustion engines (ICE) and contribute a major contribution to the total friction power losses in these engines. Due to the worldwide effort to reduce CO 2 emissions, automotive manufacturers investigate the remaining potential for friction reduction also in the journal bearings, which leads to severe operating conditions due to the lower viscosity lubricants. At the same time modern ICEs utilize higher combustion pressures for increased thermodynamical efficiency, which imposes further stress on the journal bearings. These reasons motivate in addition the accurate and reliable simulation of the operating conditions and friction power losses in journal bearings.Within this work, the lubrication of journal bearings is investigated in detail starting from an extensive thermo-elastohydrodynamic (TEHD) simulation, which yields important insights into the thermodynamical behavior of journal bearings. From these results a powerful isothermal elastohydrodynamic (EHD) simulation model using a simple approach to calculate equivalent temperature is derived. The capabilities of the presented simulation methods are compared to extensive experimental measurements performed on a journal bearings test-rig, which show excellent agreement.
Contact and wear thermo-elastohydrodynamic model validation for engine bearings
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2017
Tribological machine components such as engine crankshaft bearings operating at high load or rotational speeds often experience very thin oil films leading to asperity contact between the bearing and crankshaft. When the oil film thickness drops below the peak asperity height there is an increase in contact, wear and asperity power loss leading to worsening severity factors and seizure risk. Key factors influencing the bearing lubrication performance are the surface characteristics of the materials at the contact interface. SABRE-TEHL is a software simulation tool used for performing thermo-elastohydrodynamic analysis of bearing applications. In this current study, the development of a combined contact and wear model is demonstrated. This includes a hard contact model giving a direct surface contact pressure in areas of zero oil film thickness, a surface yield model with yield limits and plastic gradient from measured stress–strain data, an asperity wear model using measured surface...
Nonlinear Engineering
The paper presents, surface roughness effect for thermo-hydrodynamic analysis of journal bearings extended to couple stress lubricants with high polymer additives. A modified energy equation is simultaneously solved with heat transfer equation as well as modified Reynolds equation by using Multigrid method. The effects of couple stress and surface roughness on the performances of a finite journal bearing are presented in detail. Further, it is shown that lubricants with couple stress and surface roughness, not only increases the load capacity and decreases the friction coefficient, but also generates a lower bearing temperature field. Thus, the lubricant with couple stress improves the performance of journal bearings. The characteristics of bearing are compared with numerical results.
Article Analysis of the Journal Bearing Friction Losses in a Heavy-Duty Diesel Engine
2015
Internal combustion engines (ICE) for the use in heavy-duty trucks and buses have to fulfil demanding requirements for both vehicle efficiency as well as for emission of greenhouse gases. Beside the piston assembly the journal bearings are among the largest contributors to friction in the ICE. Through a combination of measurements and validated simulation methods the journal bearing friction losses of a state-of-the-art heavy-duty Diesel engine are investigated for a large range of real world operating conditions. To this task recently developed and extensively validated simulation methods are used together with realistic lubricant models that consider the Non-Newtonian behaviour as well as the piezoviscous effect. In addition, the potential for further friction reduction with the use of ultra-low viscosity lubricants is explored. The results reveal a potential of about 8% friction reduction in the journal bearings using a 0W20 ultra-low viscosity oil with an HTHS-viscosity (The HTHS-viscosity is defined as the dynamic viscosity of the lubricant measured at 150 • C and at a shear rate of 10 6 s −1) of 3.6 mPa s. For the investigated engine, HTHS-viscosity limitations are determined which indicate that the use of lubricants with further reduced HTHS-viscosity would require engine and/or journal bearing modifications to be able to maintain the high service life of the engine.
Analysis of the Journal Bearing Friction Losses in a Heavy-Duty Diesel Engine
Internal combustion engines (ICE) for the use in heavy-duty trucks and buses have to fulfil demanding requirements for both vehicle efficiency as well as for emission of greenhouse gases. Beside the piston assembly the journal bearings are among the largest contributors to friction in the ICE. Through a combination of measurements and validated simulation methods the journal bearing friction losses of a state-of-the-art heavy-duty Diesel engine are investigated for a large range of real world operating conditions. To this task recently developed and extensively validated simulation methods are used together with realistic lubricant models that consider the Non-Newtonian behaviour as well as the piezoviscous effect. In addition, the potential for further friction reduction with the use of ultra-low viscosity lubricants is explored. The results reveal a potential of about 8% friction reduction in the journal bearings using a 0W20 ultra-low viscosity oil with an HTHS-viscosity (The HTHS-viscosity is defined as the dynamic viscosity of the lubricant measured at 150 • C and at a shear rate of 10 6 s −1 ) of 3.6 mPa s. For the investigated engine, HTHS-viscosity limitations are determined which indicate that the use of lubricants with further reduced HTHS-viscosity would require engine and/or journal bearing modifications to be able to maintain the high service life of the engine.
Energies, 2018
Considerable prime global energy is used in the transport sector. Significant energy is lost to overcome the internal friction of engines in transport vehicles. Journal bearings are crucial tribo-pairs and passive components that cause energy loss. Frictional losses increase extensively during the warm-up period of an engine due to high lubricant viscosity. Recent tribological developments have shown that surface textures can be a potential solution to reduce friction. A numerical investigation is performed to evaluate the effect of surface texture on the frictional and lubrication performance of a journal bearing at varying thermal operating conditions in an internal combustion engine. Temperature variations during engine warm-up are considered with oil rheology to observe texture-based improvements. Surface texture substantially reduces frictional energy loss during engine warm-up. Eight different monograde and multigrade engine oils are considered, and consistency is observed in ...
Lubricants, 2015
The environmental impact of many industrial and naval applications is becoming increasingly important. Journal bearings are crucial components related with the reliable, safe and environmentally friendly operation of rotating machinery in many applications, e.g., in hydroplants, ships, power generation stations. The maintenance activities in certain cases also have considerable environmental impact. Fortunately, it is relatively easy to reduce the impact by changing the way lubricants are being used. Selecting the proper lubricant is important to sharply reduce long-term costs. The best-fit product selection can mean longer lubricant life, reduced machine wear, reduced incipient power losses and improved safety. Suitable basestocks and additives reduce environmental impact. In this paper, three types of lubricants are used in order to examine their effects on the tribological behavior of journal bearings. A mineral oil, a synthetic oil and a bio-based lubricant are experimentally and analytically examined for several configurations of load and journal rotational velocity. The friction forces and the hydrodynamic friction coefficients are calculated and compared. This investigation can assist the correct choice of lubricant in journal bearings with minimized environmental footprint.
Journal Bearings Lubrication of Non-Newtonian Lubricants with Surface Roughness Effects
2016
The objective of the study is to investigate the combined effects of interaction of surface asperities and the non-Newtonian nature of lubricant on the HD performance of finite journal bearings bearings. The roughness takes the form of sinusoidal ridges and furrows aligned in the transverse direction of lubricant entrainment. The modified Reynolds equation for pseudo-plastic lubricant is solved numerically by successive over-relaxation technique on a finite difference grid. The presented results demonstrate the influences of non-linear factor of lubricant and characteristics of surface roughness on the pressure distribution and some basic bearing characteristics.
Friction torque in rolling bearings lubricated with axle gear oils
Tribology International, 2018
As a part of the main research project within the aim of increasing significantly drive axle efficiency, this work focuses on rolling bearing friction torque lubricated with five fully formulated axle gear oils with different viscosity and different formulations. The lubricant tribological behaviour in different rolling bearings was analyzed. A modified Four-Ball Machine was used to test the rolling bearings. The effect of speed, temperature and axial load on rolling bearing friction torque was assessed. Experimental results for the internal friction torque were validated with an SKF model. Direct comparisons in terms of friction torque between axle gear oils when they are lubricating different rolling bearing types are presented and discussed.