Modeling the Effects of Liner Pores on Piston Ring Lubrication in Internal Combustion Engines PDF Download
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Author: Jérôme Sacherer
Publisher:
ISBN:
Category :
Languages : en
Pages : 72
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Book Description
Automotive manufacturers are increasingly replacing traditional cast iron liners in the internal combustion engines of commercial vehicles with spray-coated liners. While not the original intention, these new, porous liners are suspected to reduce hydrodynamic friction. The interaction of pores with piston ring and liner lubrication is studied in this work. Preliminary computational fluid dynamics simulations are performed on a single, idealized pore geometry, including surface tension but no cavitation due to computational cost limitations. Potential mechanisms for displacement of oil out of the pore are investigated, as this would improve subsequent ring lubrication. Pressure-driven flow is found to dominate this process, though surface tension also has an impact: it can trap air bubbles in the pore and level out accumulated oil back into the evacuated pore. A deterministic model exists to predict hydrodynamic pressure and friction for rough and honed liner surfaces. This model, however, assumes fully flooded boundary conditions. A modification to the governing equation for the regions beyond the full film boundaries is developed by introducing a diffusive velocity profile. The diffusion provides a transition between an oil film on the liner experiencing uniform flow to full film Couette flow. This change enables the large pore geometry to be accommodated by the model without unrealistic premature film attachment all the while maintaining the continuous transition between full film and cavitation. Results from the model indicate that the pore can act as an oil supply, extending the wetting region beneath the ring and consequently allowing for greater pressure generation and larger, desirable load carrying capacity. Cavitation also plays a critical role in the pore interaction; early cavitation in the pore can split the full film region, significantly compromising the load carrying capacity. Cavitation is also found to potentially make use of the pore's oil supply to redistribute oil onto the liner. In general, the pore causes a substantial drop in lift force, increasing the coefficient of friction as a result, though in some cases an extended wetting region can counter this effect.
Author: Jérôme Sacherer
Publisher:
ISBN:
Category :
Languages : en
Pages : 72
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Book Description
Automotive manufacturers are increasingly replacing traditional cast iron liners in the internal combustion engines of commercial vehicles with spray-coated liners. While not the original intention, these new, porous liners are suspected to reduce hydrodynamic friction. The interaction of pores with piston ring and liner lubrication is studied in this work. Preliminary computational fluid dynamics simulations are performed on a single, idealized pore geometry, including surface tension but no cavitation due to computational cost limitations. Potential mechanisms for displacement of oil out of the pore are investigated, as this would improve subsequent ring lubrication. Pressure-driven flow is found to dominate this process, though surface tension also has an impact: it can trap air bubbles in the pore and level out accumulated oil back into the evacuated pore. A deterministic model exists to predict hydrodynamic pressure and friction for rough and honed liner surfaces. This model, however, assumes fully flooded boundary conditions. A modification to the governing equation for the regions beyond the full film boundaries is developed by introducing a diffusive velocity profile. The diffusion provides a transition between an oil film on the liner experiencing uniform flow to full film Couette flow. This change enables the large pore geometry to be accommodated by the model without unrealistic premature film attachment all the while maintaining the continuous transition between full film and cavitation. Results from the model indicate that the pore can act as an oil supply, extending the wetting region beneath the ring and consequently allowing for greater pressure generation and larger, desirable load carrying capacity. Cavitation also plays a critical role in the pore interaction; early cavitation in the pore can split the full film region, significantly compromising the load carrying capacity. Cavitation is also found to potentially make use of the pore's oil supply to redistribute oil onto the liner. In general, the pore causes a substantial drop in lift force, increasing the coefficient of friction as a result, though in some cases an extended wetting region can counter this effect.
Author: Haijie Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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Book Description
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: Haijie Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 119
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Book Description
(cont.) These key parameters include the surface wavelength of the plateau part, the frequency of deep valleys and the honing cross-hatch angle. This thesis work has opened a window on the deterministic study of the functionality of cylinder liner surface texture.
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: Rosalind Kazuko Takata
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Book Description
The piston ring-pack contributes approximately 25% of the mechanical losses in an internal combustion engine. Both lubricant viscosity and surface texturing were investigated in an effort to reduce this ring-pack friction and increase engine efficiency. While both optimizing viscosity and surface texturing are predicted to cause a reduction in ring/liner friction individually, a combined approach may cause an even greater friction reduction while mitigating unwanted side-effects such as oil consumption and wear. Existing MIT models, with some modifications and supplementary programs to allow investigation of the parameters of interest, were used to conduct this research. A ring-pack model based on average flow-factor Reynolds analysis was used for both studies, with a modified form of this program, along with a supplementary deterministic model for surface analysis, used for the study of surface texturing. Although these advanced models are applicable in a wide range of cases, the surface textures studied in this research are very different than a typical cylinder liner surface, and can be represented only approximately by the averaged Reynolds analysis upon which the ring simulation is based.
Author: Chongjie Gu
Publisher:
ISBN:
Category :
Languages : en
Pages : 108
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Book Description
Internal combustion engines are widely utilized in modem automobiles. Around 10% of the total fuel energy is dissipated to heat due to mechanical friction, among which 20% is caused by the contact between the cylinder liner and the piston rings. The wear of cylinder liner not only leads to surface damage, but also results in the change of liner lubrication conditions. Therefore, a large number of tests are performed by researchers to investigate the liner wear process and its impact on engine lubrication. This work is the first step toward developing a wear model to predict the evolution of liner roughness and ring pack lubrication during break-in period. A physics-based liner wear model is built in this work, with focus on two mechanisms: surface plastic flattening and fatigue wear. Both mechanisms are simulated through a set of governing equations and are coupled together to complete the algorithm of the liner wear model. Simulations of break-in wear are performed to different liner surfaces finishes, with different external normal pressures. Simulation results indicate that the liner wear rate depends on the size and shape of liner surface asperities, which may provide guidance for surface manufacturing. The results also show consistence with the Archard's wear law, describing the proportional correlation between normal pressure and steady state wear rate. This wear model is then used to study the influence of liner wear on engine lubrication. Through the friction for entire engine cycles, simulated results are compared with experimental friction measurements. The comparison shows that the calculated friction evolution during break-in has the same trend and comparable magnitude as the measurements, indicating the efficiency of the wear model. Some initial work of modeling of third-body abrasive wear is also discussed in this thesis.
Author: Tianshi Fang
Publisher:
ISBN:
Category :
Languages : en
Pages : 136
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Book Description
The consumption of lubricating oil in internal combustion engines is a continuous interest for engine developers and remains to be one of the least understood areas. A better understanding on oil transport is critical to an optimization of engine designs, and advanced analytical tools are essential to the achievement of reduced frictions without compromising oil consumption. Oil transport from piston lands to a liner, hereafter called "bridging", has been observed in engine tests. The additional oil transferred to the liner becomes a potential source of oil consumption through ring-liner interaction. Thus, it is important to develop more quantitative models to better analyze bridging. The objective of this work is to obtain a more in-depth understanding on the oil transport between piston lands and liner and provide quantitative models of the oil transport mechanisms. Multiphase Computational Fluid Dynamics (CFD) was employed together with analyses of experimental observations. Three categories of bridging were identified: assisted bridging, self-sustained bridging, and reverse bridging. While assisted bridging involves an axial oil flow across an entire piston land, the other two phenomena are localized and become prominent at low engine speeds. The mechanisms of each phenomenon were analyzed in this work. Correlations and theoretical models were developed to associate the risk of bridging with geometrical designs of a piston and operating conditions of an engine. Particularly, the theoretical model of self-sustained bridging contributes to the optimization of geometrical designs of the third land of a piston ring pack. This work constitutes a major step towards a further quantification of oil transport. Some findings and models presented in this work can readily contribute to providing optimal solutions to certain piston regions. Furthermore, the results of this work serve broader purposes in providing boundary conditions to other interactions in a piston ring pack.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The piston ring-pack contributes approximately 25% of the mechanical losses in an internal combustion engine. Both lubricant viscosity and surface texturing were investigated in an effort to reduce this ring-pack friction and increase engine efficiency. While both optimizing viscosity and surface texturing are predicted to cause a reduction in ring/liner friction individually, a combined approach may cause an even greater friction reduction while mitigating unwanted side-effects such as oil consumption and wear. Existing MIT models, with some modifications and supplementary programs to allow investigation of the parameters of interest, were used to conduct this research. A ring-pack model based on average flow-factor Reynolds analysis was used for both studies, with a modified form of this program, along with a supplementary deterministic model for surface analysis, used for the study of surface texturing. Although these advanced models are applicable in a wide range of cases, the surface textures studied in this research are very different than a typical cylinder liner surface, and can be represented only approximately by the averaged Reynolds analysis upon which the ring simulation is based.
Author: Yang Liu (S.M.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 109
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Book Description
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: Liang Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 143
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Book Description
(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.
