Curved Beam Based Model for Piston-ring Designs in Internal Combustion Engines PDF Download
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Author: Mohamed Aziz Bhouri
Publisher:
ISBN:
Category :
Languages : en
Pages : 173
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Book Description
Characterizing the piston ring behavior is inherently associated with the oil consumption, friction, wear and blow-by in internal combustion engines. This behavior varies along the ring's circumference and determining these variations is of utmost importance for developing ring-packs achieving desired performances in terms of sealing and conformability. This study based on straight beam model was already developed but does not consider the lubrication sub-models, the tip gap effects and the characterization of the ring free shape based on any final closed shape. In this work, three numerical curved beam based models were developed to study the performance of the piston ring-pack. The conformability model was developed to characterize the behavior of the ring within the engine. In this model, the curved beam model is adopted with considering ring-bore and ring-groove interactions. This interactions include asperity and lubrication forces. Besides, gas forces are included to the model along with the inertia and initial ring tangential load. In this model we also allow for bore, groove upper and lower flanks thermal distortion. We also take into account the thermal expansion effect of the ring and the temperature gradient from inner diameter (ID) to outer diameter (OD) effects. The piston secondary motion and the variation of oil viscosity on the liner with its temperature in addition to the existence of fuel and the different hydrodynamic cases (Partially and fully flooded cases) are considered as well. This model revealed the ring position relative to the groove depending on the friction, inertia and gas pressures. It also characterizes the effect of non-uniform oil distribution on the liner and groove flanks. Finally, the ring gap position within a distorted bore also reveals the sealing performance of the ring. Using the curved beam model we also developed a module determining the twist calculation under fix ID or OD constraint. The static twist is an experimental characterization of the ring during which the user taps on the ring till there is a minimum clearance between the ring lowest point and the lower plate all over the ring's circumference but without any force contact. Our last model includes four sub-models that relate the ring free shape, its final shape when subjected to a constant radial pressure (this final shape is called ovality) and the force distribution in circular bore. Knowing one of these distribution, this model determines the other two. This tool is useful in the sense that the characterization of the ring is carried out by measuring its ovality which is more accurate than measuring its free shape or force distribution in circular bore. Thus, having a model that takes the ovality as an input is more convenient and useful based on the experiments carried out to characterize the ring.
Author: Mohamed Aziz Bhouri
Publisher:
ISBN:
Category :
Languages : en
Pages : 173
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Book Description
Characterizing the piston ring behavior is inherently associated with the oil consumption, friction, wear and blow-by in internal combustion engines. This behavior varies along the ring's circumference and determining these variations is of utmost importance for developing ring-packs achieving desired performances in terms of sealing and conformability. This study based on straight beam model was already developed but does not consider the lubrication sub-models, the tip gap effects and the characterization of the ring free shape based on any final closed shape. In this work, three numerical curved beam based models were developed to study the performance of the piston ring-pack. The conformability model was developed to characterize the behavior of the ring within the engine. In this model, the curved beam model is adopted with considering ring-bore and ring-groove interactions. This interactions include asperity and lubrication forces. Besides, gas forces are included to the model along with the inertia and initial ring tangential load. In this model we also allow for bore, groove upper and lower flanks thermal distortion. We also take into account the thermal expansion effect of the ring and the temperature gradient from inner diameter (ID) to outer diameter (OD) effects. The piston secondary motion and the variation of oil viscosity on the liner with its temperature in addition to the existence of fuel and the different hydrodynamic cases (Partially and fully flooded cases) are considered as well. This model revealed the ring position relative to the groove depending on the friction, inertia and gas pressures. It also characterizes the effect of non-uniform oil distribution on the liner and groove flanks. Finally, the ring gap position within a distorted bore also reveals the sealing performance of the ring. Using the curved beam model we also developed a module determining the twist calculation under fix ID or OD constraint. The static twist is an experimental characterization of the ring during which the user taps on the ring till there is a minimum clearance between the ring lowest point and the lower plate all over the ring's circumference but without any force contact. Our last model includes four sub-models that relate the ring free shape, its final shape when subjected to a constant radial pressure (this final shape is called ovality) and the force distribution in circular bore. Knowing one of these distribution, this model determines the other two. This tool is useful in the sense that the characterization of the ring is carried out by measuring its ovality which is more accurate than measuring its free shape or force distribution in circular bore. Thus, having a model that takes the ovality as an input is more convenient and useful based on the experiments carried out to characterize the ring.
Author: Camille Baelden
Publisher:
ISBN:
Category :
Languages : en
Pages : 218
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Book Description
Fuel consumption reduction of more than 20% can be achieved through engine friction reduction. Piston and piston rings contribute approximately half of the total engine friction and are therefore central to friction reduction efforts. The most common method to reduce mechanical losses from piston rings has been to lower ring tension, the normal force providing sealing between the piston ring and the cylinder liner. However tension reduction can result in additional lubricant consumption. The objective of this thesis is to understand and model the physical mechanisms resulting in flow of oil to the combustion chamber in order to achieve optimal designs of piston rings. The optimal design is a compromise between friction reduction and adequate gas and lubricant sealing performance. To do so a multi-scale curved beam finite element model of piston ring is developed. It is built to couple ring deformation, dynamics and contact with the piston and the cylinder. Oil flow at the interfaces between the ring and the cylinder liner and between the ring and the piston groove can thus be simulated. The piston ring model is used to study the sealing performance of the Oil Control Ring (OCR), whose function is to limit the amount of oil supplied to the ring pack. The contributions of the three main mechanisms previously identified, to oil flow past the OCR are quantified: - Deformation of the cylinder under operating conditions can lead to a loss of contact between the ring and the liner. - Tilting of the piston around its pin can force the OCR to twist and scrape oil from the liner. - Oil accumulating below the OCR can flow to the groove and leak on the top of the OCR The OCR is found to be flexible enough to limit the impact of cylinder deformation on oil consumption. Both ring scraping and flow through the OCR groove can contribute to oil consumption in the range of engine running conditions simulated. Reduction of scraping is possible by increasing the ability of both OCR lands to maintain contact with the liner regardless of piston groove tilt. The flow of oil through the OCR groove can be reduced by designing appropriate draining of oil in the groove and an adequate oil reservoir below the OCR. The piston ring oil transport model developed in this thesis will be a valuable tool to optimize ring pack designs to achieve further ring pack friction reduction without increasing oil consumption.
Author: Yang Liu (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 217
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Book Description
Improving fuel economy of internal combustion engines is one of the major focuses in automotive industry. The piston ring friction contributes as much as 25% of total mechanical loss in internal combustion engines [1] and is an area of great interests to the automotive industry in their overall effort to improve engine efficiency. However, typical methods to reduce friction loss from piston ring pack, such as ring tension reduction, may cause additional oil consumption. A compromise between reduction of friction loss and control of gas leakage and oil consumption needs to be made, which requires a deep understanding of oil transport mechanism. This compromise gives rise to the interest in modeling work. Both experimental results and previous experience showed that oil film distribution on the piston varies significantly along the circumference and the oil leakage occurs locally. Therefore to predict oil transfer across different ring pack regions, one needs to integrate both global and local processes. This work is aimed at establishing an enduring framework for all the cycle-based processes at different length scales. As a first step, a multi-scale multi-physics piston ring pack model was developed by coupling the structural dynamics of the piston rings with gas flows and local interactions at ring-groove and ring-liner interfaces. A curved beam finite element method was adopted to calculate the ring structural response to interaction between the ring and the liner as well as the ring and the groove. Compared to a traditional straight beam finite element method, the curved beam separates the structural mesh and contact grid by utilizing the shape functions. In this work, a multi-length-scale ring pack model was, for the first time, successfully assembled. This model bears its fundamental values to truly reflect the integral results of all the relevant mechanisms. The significance of the current work is that it demonstrated such an integration of all the length scales is possible for a cycle model with a reasonable computation cost. With the current model, one can realistically investigate the effects of all kinds of piston and liner distortion, piston secondary motion, bridging, and lube-oil dilution on gas sealing, oil transport and lubrication. As a result, optimization of the ring designs and the part of block design contributing to bore distortion can be coordinated to reduce development costs.
Author: Dian Xu
Publisher:
ISBN:
Category :
Languages : en
Pages : 72
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Book Description
In the process of designing internal combustion engine, piston ring plays an important role in fulfilling the requirements of camber gas sealing, friction reduction and lubrication oil consumption. The goal of this thesis is to have a better understanding of the ring behaviors under different working conditions in a structural level. This thesis is an extension of existing ring design tool. A model is built up to simulate the processes of changing ring states from one to another such as free or fit the ring. It revealed the sensitive characters of the piston ring tip; it expanded the field of application of the existing piston ring design tool; it also investigated the ring bore interaction in more conditions. This work removed the symmetric assumption in the existing tool. A new method that calculates ring free shape and ring bore contact force from ring ovality data is introduced for the first time. The analysis of ring bore interaction is widened. The model was applied to an industry ring design case. In this case it shows the free and fit procedure in this model is physically and mathematically reversible. It shows these procedures are direction independent. The contact force distribution changes when the ring is moving within the distorted bore. It also changes when the wetting or roughness situation is different. This model can calculate the ring free shape from asymmetric measured ovality data. It can also retrieve the desired contact force from it. The piston ring design tool is updated and implemented with these highly appreciable new features. This complete package has high efficiency and a wider practical field.
Author: Tian Tian
Publisher:
ISBN:
Category :
Languages : en
Pages : 388
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Author: Grant Smedley
Publisher:
ISBN:
Category :
Languages : en
Pages : 131
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(Cont.) Experimental results conducted on a full-scale natural gas power generation engine supported the model predictions for the low-tension oil control ring design. The predicted reduction in piston ring friction would translate to a 0.5-1% increase in brake thermal efficiency, which would result in a significant improvement in fuel economy and a substantial reduction in emissions over the life of the engine.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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By Tian Tian.
Author: Qing Zhao (S.M.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 88
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Book Description
When decreasing of fossil fuel supplies and air pollution are two major society problems in the 21st century, rapid growth of internal combustion (IC) engines serves as a main producer of these two problems. In order to increase fuel efficiency, mechanical loss should be controlled in internal combustion engines. Interaction between piston ring pack and cylinder liner finish accounts for nearly 20 percent of the mechanical losses within an internal combustion engine, and is an important factor that affects the lubricant oil consumption. Among the total friction between piston ring pack and cylinder liner, boundary friction occurs when piston is at low speed and there is direct contact between rings and liners. This work focuses on prediction of contact between piston ring and liner finish based on 3D measured surface and different methods are compared. In previous twin-land oil control ring (TLOCR) deterministic model, Greenwood-Tripp correlation function was used to determine contact. The practical challenge for this single equation is that real plateau roughness makes it unreliable. As a result, micro geometry of liner surface needs to be obtained through white light interferometry device or confocal equipment to conduct contact model. Based on real geometry of liner finish and the assumption that ring surface is ideally smooth, contact can be predicted by three different models which were developed by using statistical Greenwood-Williamson model, Hertzian contact and revised deterministic dry contact model by Professor A.A. Lubrecht. The predicted contact between liner finish and piston ring is then combined with hydrodynamic pressure caused by lubricant which was examined using TLOCR deterministic model by Chen. et al to get total friction resulted on the surface of liner finish. Finally, contact model is used to examine friction of different liners in an actual engine running cycle.
Author: Chongjie Gu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Nowadays, more constraints are required for design of internal combustion engines, to meet the energy saving and the emissions standards in the new era. Engine emissions and engine durability are two of the most important factors in the development of IC engines.
Author: Riadh Namouchi
Publisher:
ISBN:
Category :
Languages : en
Pages : 308
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