Numerical Modeling of Piston Secondary Motion and Skirt Lubrication in Internal Combustion Engines PDF Download
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Author: Fiona McClure
Publisher:
ISBN:
Category :
Languages : en
Pages : 241
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Book Description
Internal combustion engines dominate transportation of people and goods, contributing significantly to air pollution, and requiring large amounts of fossil fuels. With increasing public concern about the environment and the reliability of oil supplies, automotive companies are pushed to improve engine design in order to reduce engine emissions and fuel consumption. This project aims to develop a numerical model of piston dynamics and lubrication in internal combustion engines, enabling prediction of friction generation at the piston -cylinder bore interface, and oil transport in the power cylinder system. It is currently estimated that the piston - cylinder bore friction accounts for up to 25% of the power loss in a typical engine, while oil transported to the combustion chamber by the piston and ring-pack contributes significantly to engine emissions. A dry piston model was first developed to allow fast calculation of approximate piston dynamics. An elastohydrodynamic lubrication model was then developed to allow direct numerical simulation of the effect of piston tooling marks, and comparison with results obtained using an Average Reynolds equation with flow factors. The lubrication model was incorporated into the piston dynamics model, enabling more accurate evaluation of friction and oil transport. Comparison between the dry and lubricated model results demonstrate the effect of oil film thickness on piston lateral motion, tilt, friction generation and oil transport.
Author: Fiona McClure
Publisher:
ISBN:
Category :
Languages : en
Pages : 241
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Book Description
Internal combustion engines dominate transportation of people and goods, contributing significantly to air pollution, and requiring large amounts of fossil fuels. With increasing public concern about the environment and the reliability of oil supplies, automotive companies are pushed to improve engine design in order to reduce engine emissions and fuel consumption. This project aims to develop a numerical model of piston dynamics and lubrication in internal combustion engines, enabling prediction of friction generation at the piston -cylinder bore interface, and oil transport in the power cylinder system. It is currently estimated that the piston - cylinder bore friction accounts for up to 25% of the power loss in a typical engine, while oil transported to the combustion chamber by the piston and ring-pack contributes significantly to engine emissions. A dry piston model was first developed to allow fast calculation of approximate piston dynamics. An elastohydrodynamic lubrication model was then developed to allow direct numerical simulation of the effect of piston tooling marks, and comparison with results obtained using an Average Reynolds equation with flow factors. The lubrication model was incorporated into the piston dynamics model, enabling more accurate evaluation of friction and oil transport. Comparison between the dry and lubricated model results demonstrate the effect of oil film thickness on piston lateral motion, tilt, friction generation and oil transport.
Author: Dongfang Bai (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 147
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Book Description
Ever-increasing demand for reduction of the undesirable emissions from the internal combustion engines propels broader effort in auto industry to design more fuel efficient engines. One of the major focuses is the reduction of engine mechanical losses, to which the friction of the piston skirt is one important contributor. Yet there lacks a sufficient understanding of the skirt lubrication behavior to effectively optimize the piston skirt system in practice. The ultimate goal of this work is to develop a comprehensive model to advance the predictability of the skirt friction while integrating all the dynamic behavior of the piston secondary motion and the structural deformation of the piston skirt and cylinder liner. Major contributions of this work are analysis of and development of a model for the oil transport and exchange of the piston skirt region and its surroundings. The new oil transport model is composed with two elements. First, the oil scraped into the chamfer region by the oil control ring during a down-stroke is tracked and its accumulation and release to the skirt region are modeled. Second, oil separation and re-attachment are allowed in the skirt region, breaking conventional full-attachment assumption in lubrication studies. The new oil transport model together with hydrodynamic and boundary lubrication model were coupled with piston secondary motion and structural deformation of the piston skirt and cylinder liner. For numerical efficiency and physics clarity, we used different discretization for the lubrication from the structural deformation. The final model is robust and efficient. The discussion of the model results is focused mainly on the oil transport. There exist a general pattern in available oil for skirt lubrication, namely, skirt tends to be starved when it travels at the upper portion of a stroke. Comparison with visualization experiment for oil accumulation patterns show consistency between model prediction and observation. This work represents a major step forward to realistically predicting skirt friction and the influence of all the relevant design and operational parameters. However, oil supply to the region below the piston skirt can largely influence the outcome of the friction prediction and its mechanism is system dependent. Additionally, simple treatment of the oil transport in the current model is merely a first step to modeling the complex fluid problems involved. Improvements of this model based on application and further analysis will make it a more powerful engineering tool to optimize the skirt system to minimize its undesirable outputs.
Author: Conor Peter McNally
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Book Description
Author: Pasquale Pio Totaro
Publisher:
ISBN:
Category :
Languages : en
Pages : 100
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Book Description
The interest in reducing emission and improving engine efficiency has become a major push in industry, due to upcoming stricter regulations. A great deal of attention has been given to the frictional losses due to piston and liner interaction, as they represent a significant portion of the total mechanical losses. This thesis work focuses on further development and application of an existing model for the piston's secondary motion and skirt lubrication. Model development has been focused on introducing liner dynamic deformation, temperature and shear-thinning effect on viscosity, and arbitrary skirt's shape definition. The theory behind the inclusion of these components is discussed and the modifications to the existing model are explained. In regards to the model's applications, an important topic is the model validation, for which friction results from simulations are compared with experimental results obtained on a floating liner engine. The analysis covers the running condition of 1000 rpm, at partial and full load. This study is, however, not concluded and more cases need to be studied in order to complete the validation of the model. The second application focuses on the effects of geometrical patterns on the skirt on friction and secondary motion of the piston. First, some regular patterns were studied and found to have negative effects on friction due to their inability to build sufficient hydrodynamic pressure, compared to the baseline design. Then, a different sets of patterns were proposed to more effectively utilize available oil and to maximize the hydrodynamic pressure generation in the skirt region. The results show that new strategy can significantly reduce friction of the skirt without introducing negative impact on the secondary motion. This thesis work aims to make the model a more complete and powerful tool to understand piston's secondary motion and the applications are meant to show the capabilities of the model, as an instrument to approach piston's design and inspire new ways and ideas to reduce frictional losses.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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By Conor P. McNally.
Author: Victor W. Wong
Publisher:
ISBN:
Category : Internal combustion engines
Languages : en
Pages : 15
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Book Description
Author: Jianbin Luo
Publisher: Springer Science & Business Media
ISBN: 3642036538
Category : Technology & Engineering
Languages : en
Pages : 1040
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Book Description
"Advanced Tribology" is the proceedings of the 5th China International Symposium on Tribology (held every four years) and the 1st International Tribology Symposium of IFToMM, held in Beijing 24th-27th September 2008. It contains seven parts: lubrication; friction and wear; micro/nano-tribology; tribology of coatings, surface and interface; biotribology; tribo-chemistry; industry tribology. The book reflects the recent progress in the fields such as lubrication, friction and wear, coatings, and precision manufacture etc. in the world. The book is intended for researchers, engineers and graduate students in the field of tribology, lubrication, mechanical production and industrial design. The editors Jianbin Luo, Yonggang Meng, Tianmin Shao and Qian Zhao are all the professors at the State Key Lab of Tribology, Tsinghua University, Beijing.
Author: Ramsey Gohar
Publisher: World Scientific
ISBN: 1786345196
Category : Technology & Engineering
Languages : en
Pages : 519
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Book Description
Fundamentals of Tribology deals with the fundamentals of lubrication, friction and wear, as well as mechanics of contacting surfaces and their topography. It begins by introducing the reader to the importance of tribology in everyday life and offers a brief history of the subject. It then describes the nature of rough surfaces and the mechanics of contacting elastic solids and their deformation under load and friction in their relative motion. The book goes on to discuss the importance of lubricant rheology with respect to viscosity and density. Then, the principles of hydrodynamic lubrication are covered with derivations of the governing Reynolds and energy equations. Applications of hydrodynamic lubrication in various forms of bearings — journal bearings, thrust bearings and externally pressurised bearings — are outlined. The important and still evolving subject of elastohydrodynamic lubrication is treated in some detail, both at its fundamentals and its applications in thin shell or overlay bearings, cam-followers and internal combustion engine pistons.The fundamentals of biotribology are also covered, particularly its applications to endo-articular mammalian joints such as hip and knee joints and their arthroplasty. In addition, there is a treatment of the rapidly emerging knowledge of tribological phenomena in lightly loaded vanishing conjunctions (nanotribology), in natural systems and very small devices, such as MEMS and high density data storage media. There is also a new chapter on the rapidly emerging subject of surface texturing to promote retention of microreservoirs of lubricant, acting as microbearings and improving lubrication of otherwise poorly lubricated conjunctions.This book targets the undergraduate and postgraduate body as well as engineering professionals in industry, where often a quick solution or understanding of certain tribological fundamentals is sought. The book can also form an initial basis for those interested in research into certain aspects of tribology.
Author: Andreas Petrou Panayi
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 676
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Book Description
Author: Bilge Albayrak Ceper
Publisher: BoD – Books on Demand
ISBN: 953513891X
Category : Technology & Engineering
Languages : en
Pages : 190
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Book Description
Internal combustion engines have remained a challenge due to depending heavily on fossil fuels, which are already limited reserves, and a requirement for improvement in emission levels continuously. The number of advanced technologies such as hybrid systems and low-temperature combustion engines has been introduced, and a number of reports about the use of alternative fuels have been presented in recent years to overcome these challenges. The efforts have made the new concepts to be used in practical along with the new problems which are required advanced control systems. This book presents studies on internal combustion engines with alternative fuels and advanced combustion technologies to obtain efficiency and environment-friendly systems, measurement methodology of exhaust emissions and modelling of a hybrid engine system, and mechanical losses arising from ring-cylinder and ring-groove side contacts as well. The main theme here is to identify solutions for internal combustion engines in terms of fuel consumption, emissions, and performance.
