Modeling of Piston Ring Dynamics, Crevice Gas Flow, and Hydrodynamic Lubrication in Internal Combustion Engines PDF Download
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Author: Riadh Namouchi
Publisher:
ISBN:
Category :
Languages : en
Pages : 308
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Author: Riadh Namouchi
Publisher:
ISBN:
Category :
Languages : en
Pages : 308
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Author: Liang Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 143
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(Cont.) This model predicts the inter-ring gas pressure and 3-D displacements of the three rings at various circumferential locations. Model results show significant variations of the dynamic behavior along ring circumference. In the ring-pack lubrication model, an improved flow continuity algorithm is implemented in the ring/liner hydrodynamic lubrication, and proves to be very practicable. By coupling the ring/liner lubrication with the in-plane structural response of the ring, the lubrication along the entire ring circumference can be calculated. Model results show significant variations of lubrication along the circumference due to the non-axisymmetric characteristics of the power cylinder system. Bore distortion was found to have profound effects on oil transport along the liner. Particularly, it stimulates the occurrence of oil up-scraping by the top ring during compression stroke. Because the oil evaporation on the liner affects the liner oil film thickness, a sub-model for liner evaporation with consideration of multi-species oil is incorporated with the lubrication model. With consideration of oil transport along the liner, the prediction of evaporation is more precise. The combination of these models is a complete package for piston ring-pack analysis. It is computationally robust and efficient, and thus has appreciable practical value.
Author: Yang Liu (S.M.)
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ISBN:
Category :
Languages : en
Pages : 109
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Nowadays, a rapid growth of internal combustion (IC) engines is considered to be a major contributor to energy crisis. About 20% of the mechanical loss in internal combustion engines directly goes to the friction loss between piston ring pack and liner finish. A twin-land oil control ring (TLOCR) deterministic model was developed by Chen et al. and it helps the automotive companies investigate the effects of liner finish, rings, and lubricants on friction and oil control of the TLOCR [2]. This work focuses on application of the TLOCR model and extension of the deterministic model to the top two rings. First, there are some practical challenges in the application of Chen's TLOCR deterministic model. Due to different wear condition on the same liner, surface roughness varies from spot to spot. A small patch of measurement cannot provide enough information and the change of plateau roughness makes the contact model unreliable. As a result, a multi-point correlation method was proposed to combine the information of different spots from the same liner and this method was shown to give better match to the experimental results. A top-two-ring lubrication cycle model was developed based on the multiphase deterministic model by Li. et al [30] and previous top-two-ring lubrication model by Chen. Et al [2][31]. The model is composed with two parts. First, the deterministic model is used to generate a correlation between the hydrodynamic pressure/friction and the minimum clearance with prescribed oil supply from the deterministic oil control ring model. It was found that within reasonable accuracy, the gas pressure effect on the hydrodynamic lubrication of the top two rings can be decoupled from the hydrodynamic lubrication. Thus, only single-phase deterministic model was needed to generate the correlation. This decoupling significantly reduces the computation time. Then, a cycle model was developed utilizing the correlation of hydrodynamic pressure/friction and the minimum clearance. The cycle model considers the effect of gas pressure variations in different ring pack regions as well as the dynamic twist of the top two rings. Finally, the models were used to examine the friction and lubrication of three different liner finishes in an actual engine running cycle.
Author: Mikhail Aleksandrovich Ejakov
Publisher:
ISBN:
Category : Internal combustion engines
Languages : en
Pages : 386
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Author: Fiona McClure
Publisher:
ISBN:
Category :
Languages : en
Pages : 241
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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:
Publisher:
ISBN:
Category : Internal combustion engines
Languages : en
Pages : 660
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Author: Zhen Meng (Ph.D.)
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ISBN:
Category :
Languages : en
Pages : 121
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The piston pin joins the piston and the connecting rod to transfer the linear force on the piston to rotate the crankshaft that is the eventual power outlet of the engine. The interfaces between the piston pin and the pin bore as well as the connecting rod small end are one of the most heavily loaded tribo pairs in engines. Piston pin seizure still occurs often in the engine development and the solution often comes from applying expensive coatings. Furthermore, it has been found that the friction loss associated with the pin can be a significant contributor to the total engine mechanical loss. Yet, there lacks a basic understanding of the lubrication behavior of the pin interfaces. This work is aimed to develop a piston pin lubrication model with consideration of all the important mechanical processes. The model predicts the dynamics of the pin and the lubrication of the interfaces between the pin and pin bore as well as small end. The model couples the dynamics of the pin with the structural deformation of the mating parts, the hydrodynamic and boundary lubrication of all the interfaces, and oil transport. The model is successfully implemented with an efficient and robust numerical solver with the second order accuracy to compute this highly stiff system. The preliminary results applying the model to a gasoline engine show that the boundary lubrication is the predominant contributor to the total friction. As a result, the interface with more asperity contact tends to hold the pin with it. Thus, the pin friction loss is coming from the interface with less contact. Solely from friction reduction point of view, ensuring efficient hydrodynamics lubrication in one interface is sufficient. Furthermore, as the heavy load is supported in several small areas, mechanical and thermal deformation of all the parts are critical to load distribution, oil transport, and the generation of hydrodynamic and asperity contact pressure, providing the necessity of the elements integrated in the model. This work represents the first step to establishing a more comprehensive engineering model that helps the industry understand the pin lubrication and find cost-effective solutions to overcome the existing challenges.
Author: Camille Baelden
Publisher:
ISBN:
Category :
Languages : en
Pages : 218
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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: Haijie Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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Piston ring packs are used in internal combustion engines to seal both the high pressure gas in the combustion chamber and the lubricant oil in the crank case. The interaction between the piston ring pack and the cylinder bore contributes substantially to the total friction power loss for IC engines. The aim of this thesis work is to advance the understanding of the ring liner lubrication through numerical modeling. A twin-land oil control ring lubrication model and a top two-ring lubrication model are developed based on a deterministic approach. The models take into consideration the effect of both the liner finish micro geometry and the ring face macro profile. The liner finish effect is evaluated on a 3D deterministically measured liner finish patch, with fully-flooded oil supply condition to the oil control rings and starved oil supply condition to the top two rings. Correlations based on deterministic calculations and proper scaling are developed to connect the average hydrodynamic pressure and friction to the critical geometrical parameters and operating parameters so that cycle evaluation of the ring lubrication can be performed in an efficient manner. The models can be used for ring pack friction prediction, and ring pack/liner design optimization based on the trade-off of friction power loss and oil consumption. To provide further insights to the effect of liner finish, a wear model is then developed to simulate the liner surface geometry evolution during the break-in/wear process. The model is based on the idea of simulated repetitive grinding on the plateau part of the liner finish using a random grinder. The model successfully captures the statistic topological features of the worn liner roughness. Combining the piston ring pack model and the liner finish wear model, one can potentially predict the long term ring pack friction loss. Finally the thesis covers the experimental validation of the twin-land oil control ring model using floating liner engine friction measurements. The modeled ring friction is compared with the experimental measurement under different ring designs and liner finishes. The result shows that the model in general successfully predicts the friction force of the twin-land oil control ring/liner pair.
Author: Ke Jia (S. M.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 129
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Oil flows through ring/groove interface play a critical role in oil transport among different regions the piston ring pack of internal combustion engines. This thesis work is intended to improve the understanding and modeling capability on this important oil transport mechanism for better analysis in engine oil consumption. A model incorporating ring dynamics, gas flow, and oil flow was developed to study oil transport in the piston ring-pack system. The major new element of this new model is adaptation of a mass conserved two phase oil/gas flow sub-model. Doing so, the present model can describe the oil flows through the ring/groove interface in a consistent manner. The model was applied to a heavy duty diesel engine at maximum power condition and to a SI engine at engine-braking and moderate load conditions. In the diesel application, the model demonstrates that oil can be released through the second ring/groove interface during second ring flutter and ring/groove interface plays positive role in reducing oil consumption and oil residence time. On the other hand, oil can be pumped up into the top ring groove and combustion chamber through the top ring/groove interface at engine braking conditions in the SI engine. Both applications show that oil flow rate through ring/groove interface is most prominent during the period of the engine cycle when the ring motion and gas pressure exhibit dynamic behaviors, and thus show that the coupling of the ring dynamics and gas/oil flows in the present model is essential to predict the oil pumping through ring/groove interface.
