Zeitschriftenartikel: „Piston ring dynamics“

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Knoll, G., H. Peeken, R. Lechtape-Gru¨ter und J. Lang. „Computer-Aided Simulation of Piston and Piston Ring Dynamics“. Journal of Engineering for Gas Turbines and Power 118, Nr. 4 (01.10.1996): 880–86. http://dx.doi.org/10.1115/1.2817009.

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A numerical computer simulation program was developed, aiding in finding optimum design parameters in the multibody-system piston, piston-rings, and cylinder with respect to optimum sealing, minimal friction, and minimum noise stimulation (impact impulse). In the simulation of piston secondary movement and piston ring motion, forces arising from the combustion process, subsonic/supersonic gas flow between the combustion chamber and the crank case, inertial forces and forces resulting from the hydrodynamic lubrication between cylinder liner and piston shaft and piston rings and between piston ring flanks and piston grooves are considered. In addition it is possible to account for effects of global, three-dimensional ring deformation as well as local piston deformation, roughness effects in lubricated contacts, and variable viscosity and variable oil supply. The governing differential equations for the pressure as well as the deformation are solved via finite element techniques, while initial value problems are solved by efficient implicit time integration schemes. The application of the developed computer code is presented in examples.

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Tian, T., L. B. Noordzij, V. W. Wong und J. B. Heywood. „Modeling Piston-Ring Dynamics, Blowby, and Ring-Twist Effects“. Journal of Engineering for Gas Turbines and Power 120, Nr. 4 (01.10.1998): 843–54. http://dx.doi.org/10.1115/1.2818477.

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A ring-dynamics and gas-flow model has been developed to study ring/groove contact, blowby, and the influence of ring static twist, keystone ring/groove configurations, and other piston and ring parameters. The model is developed for a ring pack with three rings. The dynamics of the top two rings and the gas pressures in the regions above the oil control ring are simulated. Distributions of oil film thickness and surface roughness on the groove and ring surfaces are assumed in the model to calculate the forces generated by the ring/groove contact. Ring static and dynamic twists are considered, as well as different keystone ring/groove configurations. Ring dynamics and gas flows are coupled in the formulation and an implicit scheme is implemented, enabling the model to resolve detailed events such as ring flutter. Studies on a spark ignition engine found that static twist or, more generally speaking, the relative angle between rings and their grooves, has great influence on ring/groove contact characteristics, ring stability, and blowby. Ring flutter is found to occur for the second ring with a negative static twist under normal operating conditions and for the top ring with a negative static twist under high-speed/low-load operating conditions. Studies on a diesel engine show that different keystone ring/groove configurations result in different twist behaviors of the ring that may affect the wear pattern of the keystone ring running surfaces.

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Novotný, Pavel, Peter Raffai, Jozef Dlugoš, Ondřej Maršálek und Jiří Knotek. „Role Of Computational Simulations In The Design Of Piston Rings“. Journal of Middle European Construction and Design of Cars 13, Nr. 1 (01.06.2015): 1–6. http://dx.doi.org/10.1515/mecdc-2015-0001.

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Abstract The paper presents computational approaches using modern strategies for a dynamic piston ring solution as a fluid structural problem. Computational model outputs can be used to understand design parameter influences on defined results of a primarily integral character. Piston ring dynamics incorporates mixed lubrication conditions, the influence of surface roughness on oil film lubrication, the influence of ring movement on gas dynamics, oil film formulation on a cylinder liner and other significant influences. The solution results are presented for several parameters of SI engine piston rings.

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Ahmed Ali, Mohamed Kamal, Hou Xianjun, Richard Fiifi Turkson und Muhammad Ezzat. „An analytical study of tribological parameters between piston ring and cylinder liner in internal combustion engines“. Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 230, Nr. 4 (03.08.2016): 329–49. http://dx.doi.org/10.1177/1464419315605922.

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This paper presents a model to study the effect of piston ring dynamics on basic tribological parameters that affect the performance of internal combustion engines by using dynamics analysis software (AVL Excite Designer). The paramount tribological parameters include friction force, frictional power losses, and oil film thickness of piston ring assembly. The piston and rings assembly is one of the highest mechanically loaded components in engines. Relevant literature reports that the piston ring assembly accounts for 40% to 50% of the frictional losses, making it imperative for the piston ring dynamics to be understood thoroughly. This analytical study of the piston ring dynamics describes the significant correlation between the tribological parameters of piston and rings assembly and the performance of engines. The model was able to predict the effects of engine speed and oil viscosity on asperity and hydrodynamic friction forces, power losses, oil film thickness and lube oil consumption. This model of mixed film lubrication of piston rings is based on the hydrodynamic action described by Reynolds equation and dry contact action as described by the Greenwood–Tripp rough surface asperity contact model. The results in the current analysis demonstrated that engine speed and oil viscosity had a remarkable effect on oil film thickness and hydrodynamic friction between the rings and cylinder liner. Hence, the mixed lubrication model, which unifies the lubricant flow under different ring–liner gaps, is needed via the balance between the hydrodynamic and boundary lubrication modes to obtain minimum friction between rings and liner and to ultimately help in improving the performance of engines.

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Mahmoud, Kamel G., Oliver Knaus, Tigran Parikyan, Guenter Offner und Stjepan Sklepic. „An integrated model for the performance of piston ring pack in internal combustion engines“. Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 232, Nr. 3 (25.10.2017): 371–84. http://dx.doi.org/10.1177/1464419317736676.

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Piston rings are important components in internal combustion engines. Their primary function is to seal dynamically the gap between moving piston and cylinder liner surface in order to prevent the combustion gases from penetrating into the crankcase. The rings also control the oil leakage from the crankcase to the combustion chamber. The performance of the piston ring pack impacts the engine efficiency, durability and emissions. The recognition of the impact of the ring-pack performance on the engine design resulted in a sustained effort of research and development aimed at understanding the operation of the piston ring pack. Most of the published models developed in this field are two-dimensional assuming that the ring and liner are perfect circles for the purpose of modelling the axial and radial dynamics. Although this approach has proved to be useful, there exist a number of asymmetrical characteristics of the power cylinder system that can be crucial to the ring-pack performance and therefore it is considered to be appropriate. In this work, an integrated methodology that handles the complex ring-pack mechanism is presented. The physics of the ring-pack mechanism covers the three-dimensional piston ring dynamics of asymmetric engine cylinder due to bore distortion, the mixed lubrication at ring running face as well as the ring flanks and the interring gas dynamics. The modelling method is verified in two steps. In the first step, the dynamic behaviour of the three-dimensional ring model is verified against a commercial finite element software by comparing the eigenmodes up to a frequency of about 1 kHz. In the second step, the ring-pack modelling approach using three-dimensional ring models is also verified against a commercial ring dynamics program, which is based on the two-dimensional modelling. It is shown that the three-dimensional ring dynamics modelling method has advantages over the two-dimensional modelling approach as it facilitates studying the influence of the non-uniform twist along its circumference (ring winding), the effect of bore distortion on blow-by, ring friction, friction power losses and wear.

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Khramtsov, I. V., P. V. Pisarev, V. V. Palchikovskiy, R. V. Bulbovich und V. V. Pavlogradskiy. „Numerical Analysis of Gasdynamic Characteristics of Vortex Ring“. Applied Mechanics and Materials 770 (Juni 2015): 483–88. http://dx.doi.org/10.4028/www.scientific.net/amm.770.483.

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In the framework of the research the authors have solved the problem of formation and dynamics of the vortex ring. Intensive turbulent vortex rings produced by piston generators have been considered. The research has been carried out on the basis of numerical simulations in fluid dynamics program ANSYS CFX using the high-performance computing system. We have obtained the dynamic and geometrical characteristics of the vortex ring on the basis of numerical experiments. The results are in agreement with self-similar law of vortex ring dynamics and experimental results. The authors have analyzed the influence of piston velocity on the vortex ring properties. The structure of the generated vortex ring has been found to be stable, which is important for experimental studies of acoustic properties of this object.

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Zhou, Xiao Rong, Meng Tian Song und Gan Wei Cai. „Research of Internal Combustion Engine Piston Skirt Profile Line Effect Based on Dynamics and Tribological Coupling Model“. Applied Mechanics and Materials 373-375 (August 2013): 3–6. http://dx.doi.org/10.4028/www.scientific.net/amm.373-375.3.

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This paper mainly based on the coupling relationship between tribological and dynamic behaviors of cylinder liner-piston system to establish dynamics and tribology coupling model of cylinder linerpiston-piston ring, and to analyze the effect of piston skirt profile based on it, providing theoretical basis for determining the effect of piston skirt profiles to piston dynamics and lubrication performance.

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Li, Wanyou, Yibin Guo, Tao He, Xiqun Lu und Dequan Zou. „Interring Gas Dynamic Analysis of Piston in a Diesel Engine considering the Thermal Effect“. Mathematical Problems in Engineering 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/176893.

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Understanding the interaction between ring dynamics and gas transport in ring pack systems is crucial and needs to be imperatively studied. The present work features detailed interring gas dynamics of piston ring pack behavior in internal combustion engines. The model is developed for a ring pack with four rings. The dynamics of ring pack are simulated. Due to the fact that small changes in geometry of the grooves and lands would have a significant impact on the interring gas dynamics, the thermal deformation of piston has been considered during the ring pack motion analysis in this study. In order to get the temperature distribution of piston head more quickly and accurately, an efficient method utilizing the concept of inverse heat conduction is presented. Moreover, a sensitive analysis based on the analysis of partial regression coefficients is presented to investigate the effect of groove parameters on blowby.

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Wannatong, Krisada, Somchai Chanchaona und Surachai Sanitjai. „Simulation algorithm for piston ring dynamics“. Simulation Modelling Practice and Theory 16, Nr. 1 (Januar 2008): 127–46. http://dx.doi.org/10.1016/j.simpat.2007.11.004.

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Novotný, Pavel, Václav Píštěk und Lubomír Drápal. „Modeling of piston ring pack dynamics“. Journal of Middle European Construction and Design of Cars 9, Nr. 2 (01.11.2011): 8–13. http://dx.doi.org/10.2478/v10138-011-0008-y.

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SHRNUTÍ Pístní kroužky hrají důležitou roli při mazání spalovacích motorů se značnými důsledky na opotřebení motoru, třecí ztráty a spotřebu oleje. Výpočtové řešení dynamiky pístních kroužků představuje značný problém a vyžaduje využití numerických přístupů s množstvím vhodných vstupů. V případě tohoto článku jsou použity numerické postupy pro řešení dynamiky pístních kroužků za podmínek smíšeného mazání se vstupy z virtuálního motoru a vhodných experimentů. Výpočtový algoritmus je rovněž zpracován do uživatelského prostředí a je k dispozici pro průmyslové využití. Výsledky řešení jsou prezentovány na vznětovém přeplňovaném motoru v konfiguraci s třemi pístními kroužky.

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Srinivas, E. Krishna. „Design and Analysis of Piston Rings by Using Hyper Elastic Materials of Dynamic Engine Assembly“. International Journal for Research in Applied Science and Engineering Technology 9, Nr. VII (20.07.2021): 1808–15. http://dx.doi.org/10.22214/ijraset.2021.36704.

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The piston ring is one of the main components of an internal combustion engine. Its main purposes are to seal the combustion chamber of engine. The main objective of this work is to develop the design modeling and then analysis of stress and deformation of the piston rings by using different materials like Grey cast iron, elastomer and Titanium alloy by using ansys software and to investigate these three materials behavior which are used for the piston ring. The project shows the components involved in the single cylinder engine assembly and their operation. Finally we are checking out three materials behaviors which are used for piston rings. This research paper deals with to reduce the friction of a piston ring while maintaining a Large oil film load-carrying capacity, an approach comprising of the inverse method, modeling and analysis of piston rings using Structural and rigid dynamics is deliberated in order to quantify the stress that the rings can bear. Many researchers had considered that the entire surface of the ring was enveloped in an oil film, but much experimental research has discovered that not all the entire surface was soaked. The various parameters studied under structural analysis are displacement and ultimate stress limit using three Different composition materials. A cumulative analysis is performed which considers the combined effect of mechanical and load for determination of the dimensions of the rings.

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Liu, Xiao Ri, Guo Xiang Li, Shu Zhan Bai und Yu Ping Hu. „Mixed Lubrication and Friction Power Loss of Piston Ring Pack“. Applied Mechanics and Materials 668-669 (Oktober 2014): 205–8. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.205.

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With consideration of asperity contact, the minimum oil film thickness and friction power loss are calculated by simultaneous solution of the dynamics, blow-by and lubrication of piston ring pack. Take the piston ring pack in the first cylinder from the free end of a six-cylinder diesel engine for example, results show that the asperity contact takes place at all of the compression rings and oil ring; the minimum oil film thickness is 1.04μm at the top ring; the total friction loss power is 0.94kW, the top ring accounts for 37.2%, the second ring accounts for 33.0%, the oil ring accounts for 29.8%.

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Dlugoš, Jozef, und Pavel Novotný. „Computational Modelling of Piston Ring Dynamics in 3D“. Journal of Middle European Construction and Design of Cars 12, Nr. 3 (01.12.2014): 1–7. http://dx.doi.org/10.2478/mecdc-2014-0009.

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Shrnutí Pokročilé výpočtové modely pístní skupiny na základě virtuálních prototypů vyžadují mimo jiné i detailní popis dynamického chování pístního kroužku. Z tohoto hlediska je zřejmé, že pístní kroužky pracují v podmínkách, které obecně nelze zjednodušit na často využívaný osově symetrický model. Píst a vložka válce nemají dokonale kruhový tvar především v důsledku výrobních tolerancí a vnějšího tepelně-mechanického zatížení. V případech, kdy kroužek nedokáže kopírovat deformace vložky, nastane lokální ztráta kontaktu a následně i zvýšený profuk spalin a spotřeba oleje. V současné době využívané výpočtové modely nejsou schopné zahrnout všechny podstatné efekty. Článek se zaměřuje na tvorbu 3D poddajného modelu pístního kroužku s využitím Timoshenkovy teorie prutů a Multibody systému (MBS). Vytvořený výpočetní model je porovnán s numerickým řešením na základě metody konečných prvků (FEM).

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Ortjohann, Timo, A. P. J. Voncken und Stefan Pischinger. „Piston ring dynamics simulation based on FEA software“. MTZ worldwide 69, Nr. 12 (Dezember 2008): 36–41. http://dx.doi.org/10.1007/bf03226936.

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Hongwei, Yan, Yang Jin und Zhang Baocheng. „Analysis of the Influences of Piston Crankshaft Offset on Piston Secondary Movements“. Open Mechanical Engineering Journal 9, Nr. 1 (07.10.2015): 933–37. http://dx.doi.org/10.2174/1874155x01509010933.

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This paper takes dynamics analysis on the piston and the dynamic lubrication theory on the skirt and the ring of piston as the basis. Using AVL Glide software, through the establishment of the analysis model of the piston secondary movements, this study focuses on the effects of the crankshaft bias on piston secondary movements’ characteristics. This paper takes 5 different offsets, by comparing the piston lateral displacement, transverse movement speed, transverse acceleration, swinging angle, swing angular velocity and angular acceleration, finds out the relationships between crank offset value and the piston “slap”, piston impact energy and piston skirt friction loss, thus, provides the basis for the design of internal combustion engines.

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SULLIVAN, IAN S., JOSEPH J. NIEMELA, ROBERT E. HERSHBERGER, DIOGO BOLSTER und RUSSELL J. DONNELLY. „Dynamics of thin vortex rings“. Journal of Fluid Mechanics 609 (31.07.2008): 319–47. http://dx.doi.org/10.1017/s0022112008002292.

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As part of a long-range study of vortex rings, their dynamics, interactions with boundaries and with each other, we present the results of experiments on thin core rings generated by a piston gun in water. We characterize the dynamics of these rings by means of the traditional equations for such rings in an inviscid fluid suitably modifying them to be applicable to a viscous fluid. We develop expressions for the radius, core size, circulation and bubble dimensions of these rings. We report the direct measurement of the impulse of a vortex ring by means of a physical pendulum.

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Shih, L. K., und D. N. Assanis. „Effect of Ring Dynamics and Crevice Flows on Unburned Hydrocarbon Emissions“. Journal of Engineering for Gas Turbines and Power 116, Nr. 4 (01.10.1994): 784–92. http://dx.doi.org/10.1115/1.2906886.

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A significant source of unburned hydrocarbon emissions from internal combustion engines originates from the flow of unburned fuel/air mixture into and out of crevices in the piston-cylinder-ring assembly. During compression, fuel vapor flows into crevice regions. After top dead center, the trapped fuel vapor that returns into the cylinder escapes complete oxidation and contributes to unburned hydrocarbon emissions. In this work, the crevice flow model developed by Namazian and Heywood is implemented into KIVA-II, a multidimensional, reacting flow code. Two-dimensional, axisymmetric simulations are then performed for a 2.5 liter gasoline engine to investigate the effects of engine speed and selected piston-ring design parameters on crevice flows and on unburned hydrocarbon emissions. Results suggest that engine-out unburned hydrocarbon emissions can be reduced by optimizing the ring end gap area and the piston-cylinder side clearance.

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Tian, T. „Dynamic behaviours of piston rings and their practical impact. Part 2: Oil transport, friction and wear of ring/liner interface and the effects of piston and ring dynamics“. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 216, Nr. 4 (01.04.2002): 229–48. http://dx.doi.org/10.1243/135065002760199970.

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The paper discusses several important processes that have great impact on the lubrication between the top two rings and the liner. The analysis is conducted on the basis of the calculation results on a heavy-duty (HD) diesel engine using theoretical models. Oil supply mechanisms to different liner regions are analysed, and emphasis is given to the oil transport to the top liner region that is found critical to friction, wear and oil consumption in HD diesel engines. Additionally, the paper discusses the oil supply to the second ring, its uncertainties and the effect on the prediction of the performance of the top two rings. Furthermore, the effects of dynamics of the piston and rings on friction, wear and oil transport are illustrated and the effects of bore distortion on oil transport are discussed. For practical purposes, a formula to describe the second ring running surface profile is given based on simple geometrical constraint. A new truncation method is rendered for plateau surface roughness in order to effectively use the existing mixed lubrication models.

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Selmani, Erjon, Cristiana Delprete und Arian Bisha. „Cylinder liner deformation orders and efficiency of a piston ring-pack“. E3S Web of Conferences 95 (2019): 04001. http://dx.doi.org/10.1051/e3sconf/20199504001.

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One of the several losses of a combustion chamber is the gas leakage toward the crankcase due to imperfect sealing of the rings. It is commonly known as blow by and it affects efficiency and emissions. The paper initially describes a bibliographic review of the phenomenon, together with the equations of the system. A typical piston ring pack for internal combustion engine is proposed to be analysed and solved using ©Ricardo RINGPAK Solver. A specific issue such as Bore distortion orders were used to investigate the sealing capacity of the ring-pack in terms of ring dynamics, inter-ring pressures and mass flows. Bore distortion orders and their magnitude showed to affect the ring pack behavior. Order zero distortion resulted to be the most important order due to the highest amount of gas lost in the crankcase, while orders three and four resulted to generate high blow-by values, even if their magnitude of distortion is lower in comparison to other orders.

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Gulwadi, S. D. „A Mixed Lubrication and Oil Transport Model for Piston Rings Using a Mass-Conserving Algorithm“. Journal of Engineering for Gas Turbines and Power 120, Nr. 1 (01.01.1998): 199–208. http://dx.doi.org/10.1115/1.2818076.

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A numerical study of the interactions between hydrodynamic/boundary lubrication, oil transport, and radial dynamics of a piston ring using a mass-conserving (cavitation) algorithm is presented. The scheme outlined in this investigation facilitates the calculation of the volume of oil accumulating at the leading and trailing edges of the piston ring as it scrapes against the line. The calculation of this oil accumulation is important in the estimation of lubricating oil consumption in engines. The numerical procedure employed in this study is capable of depicting the transition between the various modes of piston ring lubrication (hydrodynamic, mixed, and boundary) over an engine cycle, including the detachment of oil film from the ring and its subsequent re-attachment. Additionally, the effects of (a) liner lubricant availability and (b) ring face profiles on the oil accumulation are also discussed.

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Delprete, Cristiana, und Abbas Razavykia. „Piston ring–liner lubrication and tribological performance evaluation: A review“. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, Nr. 2 (25.04.2017): 193–209. http://dx.doi.org/10.1177/1350650117706269.

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Internal combustion engines are at present used as the major power sources for transportation and power generator. Improvement of the internal combustion engine efficiency is expected due to strict environmental standards and energy costs. Any reduction in oil consumption, friction power losses and emissions results in improving engines’ performance and durability. Automotive industries have intense passion to increase engines’ efficiency to meet the fuel economy and emission standards. Many studies have been conducted to develop reliable approaches and models to understand the lubrication mechanisms and calculate power losses. This review paper summarizes the synthesis of the main technical aspects considered during modeling of piston ring–liner lubrication and friction losses investigations. The literature review highlights the effects of piston ring dynamics, components geometry, lubricant rheology, surface topography and adopted approaches, on frictional losses contributed by the piston ring-pack.

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Risse, Konstantin, Matthias Schorgel, Dirk Bartel, Bernhard Karpuschewski und Florian Welzel. „Resource-efficient piston ring/cylinder liner pairing“. Industrial Lubrication and Tribology 71, Nr. 1 (14.01.2019): 154–63. http://dx.doi.org/10.1108/ilt-06-2018-0250.

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Purpose The purpose of this paper is to investigate the influence of different finish processes on the surface integrity and tribological behaviour of cylinder running surfaces for internal combustion engines. Design/methodology/approach The cutting force during finishing and the resulting surface topography was measured for a variety of cylinder running surfaces made of EN-GJL-250, EN-GJV-400 and thermal sprayed aluminium alloy. A separate conditioning tool was developed and tested. Different analysis methods (SEM, EDX, SIMS and FIB) for the characterisation of the boundary conditions were used. By an oscillating friction wear test and a single cylinder floating liner engine, the running-in and frictional behaviour was rated. Findings It was shown that honing with low cutting forces and silicon carbide cutting material decreases the friction in operation. The characteristics of the boundary layers after running-in depend on the finish machining process. A preconditioning with a separate tool can adjust the boundary layer and running-in behaviour. Based on the experimental results, a multi-body and computational fluid dynamics simulation was developed for the floating liner engine. Originality/value The results demonstrate the potential of finishing with low process forces to reduce friction and the need for a complete consideration of the tribological system piston ring/cylinder liner surface.

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Priest, M., D. Dowson und C. M. Taylor. „Theoretical modelling of cavitation in piston ring lubrication“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, Nr. 3 (01.03.2000): 435–47. http://dx.doi.org/10.1243/0954406001523092.

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Mathematical models of piston ring dynamics and lubrication are sensitive to the boundary conditions adopted to describe the cavitation occurring in the diverging outlet region of the lubricant film between the piston ring and cylinder wall. In this paper, such sensitivity is investigated by applying different models of gaseous cavitation, flow separation and fluid film reformation to the analysis of a single compression ring from a diesel engine. Significant differences are predicted in hydrodynamic pressure profiles, lubricant film boundaries, lubricant film thickness, oil flow and friction. Such indications of substantial differences in piston ring operating characteristics associated with the distinct cavitation boundary conditions considered highlights the need for further research in this field. However, the lack of detailed experimental data to validate the predictive models suggests that future progress must be based upon combined theoretical and experimental approaches to the problem. It is postulated that boundary conditions based upon Reynolds cavitation and fluid film reformation may be applicable at high loads, and fluid film separation of a form proposed by Coyne and Elrod at low loads.

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Kurbet, S. N., und R. K. Kumar. „A finite element study of piston tilt effects on piston ring dynamics in internal combustion engines“. Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 218, Nr. 2 (Juni 2004): 107–17. http://dx.doi.org/10.1243/146441904323074567.

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Tian, T., und V. W. Wong. „Modeling the Lubrication, Dynamics, and Effects of Piston Dynamic Tilt of Twin-Land Oil Control Rings in Internal Combustion Engines“. Journal of Engineering for Gas Turbines and Power 122, Nr. 1 (18.03.1999): 119–29. http://dx.doi.org/10.1115/1.483183.

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A theoretical model was developed to study the lubrication, friction, dynamics, and oil transport of twin-land oil control rings (TLOCR) in internal combustion engines. A mixed lubrication model with consideration of shear-thinning effects of multigrade oils was used to describe the lubrication between the running surfaces of the two lands and the liner. Oil squeezing and asperity contact were both considered for the interaction between the flanks of the TLOCR and the ring groove. Then, the moments and axial forces from TLOCR/liner lubrication and TLOCR/groove interaction were coupled into the dynamic equations of the TLOCR. Furthermore, effects of piston dynamic tilt were considered in a quasi three-dimensional manner so that the behaviors of the TLOCR at different circumferential locations could be studied. As a first step, variation of the third land pressure was neglected. The model predictions were illustrated via an SI engine. One important finding is that around thrust and anti-thrust sides, the difference between the minimum oil film thickness of two lands can be as high as several micrometers due to piston dynamic tilt. As a result, at thrust and anti-thrust sides, significant oil can pass under one land of the TLOCR along the bore, although the other land perfectly seals the bore. Then, the capabilities of the model were further explained by studying the effects of ring tension and torsional resistance on the lubrication and oil transport between the lands and the liner. The effects of oil film thickness on the flanks of the ring groove on the dynamics of the TLOCR were also studied. Friction results show that boundary lubrication contributes significantly to the total friction of the TLOCR. [S0742-4795(00)01801-9]

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Su, Wen Gui, Xiao Gang Han, Kui Hua Geng, Jing Guo, Wei Wei, Xin Yan und Chun Hong Li. „The Comparison between Swing-Constrain Reciprocating Piston Oil-Free Air Compressor and Traditional Compressor“. Applied Mechanics and Materials 551 (Mai 2014): 108–14. http://dx.doi.org/10.4028/www.scientific.net/amm.551.108.

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This paper gives the comparison of structure and motion characteristics between the new swing-constrain reciprocating piston oil-free air compressor (new compressor) and traditional compressor through mechanism, kinematics and dynamics analysis. By comparison, the new compressor has more parts, more manufacturing and maintenance costs and less machine height that is benefit to reduce storage and transportation cost. Furthermore, reversing knocking strength between piston and cylinder is released ,friction loss is decreased dramatically between seal ring and cylinder and so the service time of seal ring is prolonged.

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Piao, Y., und S. D. Gulwadi. „Numerical Investigation of the Effects of Axial Cylinder Bore Profiles on Piston Ring Radial Dynamics“. Journal of Engineering for Gas Turbines and Power 125, Nr. 4 (01.10.2003): 1081–89. http://dx.doi.org/10.1115/1.1610016.

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The role of cylinder bore shapes in engine performance has been the subject of several studies in recent years. In particular, the influence of bore distortion on oil consumption under high speed conditions has generated significant interest. In this paper, the effect of an axial bore profile on radial dynamics of a ring is investigated. Radial ring motions within grooves due to the axial bore profile can generate significant inertial effects and also have an impact on ring end-gap sizes and lubrication conditions at the ring-liner interfaces. The magnitude of such effects is dependent on the ring-pack configuration, engine operating conditions (speed and load) and axial bore profile details. These issues are investigated in this study due to their implication on engine oil consumption, friction and blow-by. The authors have developed an analytical expression to account for the effects of radial ring inertia due to an axial bore profile for implementation in a piston ring-pack simulation tool RINGPAK. Simulation results from a gasoline engine study are presented to illustrate the effects of engine speeds, ring tensions, and characteristics of axial bore profiles on ring radial dynamics and ring-liner lubrication. Relevant qualitative comparisons are made to experimental measurements available in the literature.

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Keribar, R., Z. Dursunkaya und M. F. Flemming. „An Integrated Model of Ring Pack Performance“. Journal of Engineering for Gas Turbines and Power 113, Nr. 3 (01.07.1991): 382–89. http://dx.doi.org/10.1115/1.2906242.

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This paper describes an integrated model developed for the detailed characterization and simulation of piston ring pack behavior in internal combustion engines and the prediction of ring pack performance. The model includes comprehensive and coupled treatments of (1) ring-liner hydrodynamic and boundary lubrication and friction; (2) ring axial, radial, and (toroidal) twist dynamics; (3) inter-ring gas dynamics and blowby. The physics of each of these highly inter-related phenomena are represented by submodels, which are intimately coupled to form a design-oriented predictive tool aimed at the calculation of ring film thicknesses, ring motions, land pressures, engine friction, and blowby. The paper also describes the results of a series of analytical studies investigating effects of engine speed and load and ring pack design parameters, on ring motions, film thicknesses, and inter-ring pressures, as well as ring friction and blowby.

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Selmani, Erjon, und Arian Bisha. „Engine Speed and Load on the Sealing Capacity of a Piston Ring-Pack“. European Journal of Engineering Research and Science 5, Nr. 3 (17.03.2020): 304–13. http://dx.doi.org/10.24018/ejers.2020.5.3.1775.

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The combustion chamber is ought to be perfectly sealed, however, part of the air and fuel mixture can escape from it. Among the several losses there is the gas flow from the inter-ring crevices, which is always present. This leakage is known as blow-by, and affects efficiency, correct lubrication and emissions. The amount of leakage is dependent on many factors, and among the most important are the engine speed and load, which are able to affect the system through the forces applied on it. The aim of this paper was to understand in a more detailed way how the engine speed and load could affect the sealing efficiency of a ring-pack. For this purpose, a complete range of speeds and loads were used in the simulations. The equations of the ring motions and gas dynamics has been implemented and solved in ©Ricardo RINGPAK solver. The results showed that inertia and inter-ring gas pressures drives the sealing behavior of the rings. The blow-by trend showed to decrease with the speed and increase with the load, exception made for the idle condition where the values were different to the other cases, especially at higher speeds. Among the two parameters, the engine speed resulted to affect more significantly the blow-by trend.

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He, Tao, Xiqun Lu, Dequan Zou, Yibin Guo, Wanyou Li und Minli Huang. „Thermomechanical Fatigue Life Prediction for a Marine Diesel Engine Piston considering Ring Dynamics“. Advances in Mechanical Engineering 6 (Januar 2014): 429637. http://dx.doi.org/10.1155/2014/429637.

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HETTEL, M., F. WETZEL, P. HABISREUTHER und H. BOCKHORN. „Numerical verification of the similarity laws for the formation of laminar vortex rings“. Journal of Fluid Mechanics 590 (15.10.2007): 35–60. http://dx.doi.org/10.1017/s0022112007007677.

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From analytical investigations it is well known that the roll-up of an inviscid plane vortex sheet which separates at the edge of a body is a self-similar process which can be described by scaling laws. Unlike plane vortices, ring vortices have a curved rotational axis. For this special vortex type experimental investigations as well as calculations in the literature suggest that the scaling laws are only partially valid. The main goal of this work is to clarify how far these similarity or scaling laws are also valid for the formation of viscid laminar vortex rings. Therefore, the formation process of laminar vortex rings was investigated numerically using a CFD (computational-fluid-dynamics) code. The calculations refer to an experimental setup for which detailed experimental data are available in the literature. In this setup, laminar ring vortices are generated by ejecting water from a circular tube into a quiescent environment by means of a piston. First, a case based on a constant piston velocity was investigated. Comparing calculated and measured data yields a very good agreement. Further calculations were made when forcing the velocity of the piston by three different time-dependent functions. The results of these calculations show that the formation laws for inviscid plane vortices are also valid for the formation process of viscid ring vortices. This applies to the normalized axial and radial position of the vortex centre as well as the normalized diameter of the vortex spiral. However, the similarity laws are valid only if the process is considered in a special frame of reference which moves in conjunction with the front of the jet and if the starting time of the formation process with respect to the starting time of the ejection is taken into account. Additionally, the formation of a ring vortex, which occurs during the start-up process of a free jet flow, was calculated. The results confirm a dependence for the motion of the jet front, which is known from analytical considerations and allows some interesting features to be identified.

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Le, Trung Bao, Iman Borazjani, Seokkoo Kang und Fotis Sotiropoulos. „On the structure of vortex rings from inclined nozzles“. Journal of Fluid Mechanics 686 (26.09.2011): 451–83. http://dx.doi.org/10.1017/jfm.2011.340.

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AbstractWe carry out numerical simulations to investigate the vortex dynamics of laminar, impulsively driven flows through inclined nozzles in a piston–cylinder apparatus. Our simulations are motivated by the need to provide a complete description of the intricate vortical structures and governing mechanisms emerging in such flows as documented in the experiments of Webster & Longmire (Phys. Fluids, vol. 10, 1998, pp. 400–416) and Troolin & Longmire (Exp. Fluids, vol. 48, 2010, pp. 409–420). We show that the flow is dominated by the interaction of two main vortical structures: the primary inclined vortex ring at the nozzle exit and the secondary stopping ring that arises due to the entrainment of the flow into the cylinder when the piston stops moving. These two structures are connected together with pairs of vortex tubes, which evolve from the continuous vortex sheet initially connecting the primary vortex ring with the interior cylinder wall. In the exterior of the nozzle the key mechanism responsible for the breakup of the vortical structure is the interaction of the stronger inclined primary ring with the weaker stopping ring near the longest lip of the nozzle. In the interior of the nozzle the dynamics is governed by the axial stretching of the secondary ring and the ultimate impingement of this ring on the cylinder wall. Our simulations also clarify the kinematics of the azimuthal flow along the core of the primary vortex ring documented in the experiments by Lim (Phys. Fluids, vol. 10, 1998, pp. 1666–1671). We show that the azimuthal flow is characterized by a pair of two spiral saddle foci at the long and short lips of the nozzle through which ambient flow enters and exits the primary vortex core.

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Rusu, Gabriela-Petruta, Mihai-Octavian Popp, Alexandru Bârsan und Mihaela Oleksik. „Crimping Profile Optimization on the Air Spring Using Finite Element Method“. ACTA Universitatis Cibiniensis 70, Nr. 1 (01.12.2018): 43–47. http://dx.doi.org/10.2478/aucts-2018-0007.

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Abstract Due to the fact that the requirements of the industry aim to improve the dynamics, the safety and the comfort during the use of the vehicles, it is recommended to use the finite element method for component quality optimization. The purpose of this paper is to provide an overview of the current state of analysis through the finite element method of the crimping process used to assemble air springs produced in the automotive industry. Starting from the prototype of an air spring, the researches are focused on the study of the assembly of the piston with the bellow and the crimping ring through the crimping process. After analysis with the finite element method and static tests, improvements were made to the piston, the results of the tests revealing an improvement as opposed the original variant of the piston.

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Lyubarskyy, Pavlo, und Dirk Bartel. „2D CFD-model of the piston assembly in a diesel engine for the analysis of piston ring dynamics, mass transport and friction“. Tribology International 104 (Dezember 2016): 352–68. http://dx.doi.org/10.1016/j.triboint.2016.09.017.

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Wen, Chengwei, Xianghui Meng und Wenxiang Li. „Numerical analysis of textured piston compression ring conjunction using two-dimensional-computational fluid dynamics and Reynolds methods“. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, Nr. 11 (31.01.2018): 1467–85. http://dx.doi.org/10.1177/1350650118755248.

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The Reynolds equation, in which some items have been omitted, is a simplified form of the Navier–Stokes equations. When surface texturing exists, it may unreasonably reveal the tribological effects in some cases. In this paper, both the two-dimensional computational fluid dynamics method, which is based on the Navier–Stokes equations, and the corresponding one-dimensional Reynolds method are adopted to analyze the performance of the textured piston compression ring conjunction. To conduct a comparison between these two methods, the modified Elrod algorithm for Jakobsson–Floberg–Olsson cavitation model is chosen to solve the Reynolds equation. The results show that the Reynolds method is somewhat different from the computational fluid dynamics method in the minimum oil film thickness, pressure distribution, and cavitation at given operating conditions. Moreover, for a low ratio of texture depth to length, the Reynolds equation is still suitable to predict the overall effects of the designed groove textures. The simulation results also reveal that it is not always beneficial for the tribological performance and sometimes may increase the total friction force when the ring is textured.

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O’Farrell, Clara, und John O. Dabiri. „Nested contour dynamics models for axisymmetric vortex rings and vortex wakes“. Journal of Fluid Mechanics 748 (01.05.2014): 521–48. http://dx.doi.org/10.1017/jfm.2014.199.

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AbstractInviscid models for vortex rings and dipoles are constructed using nested patches of vorticity. These models constitute more realistic approximations to experimental vortex rings and dipoles than the single-contour models of Norbury and Pierrehumbert, and nested contour dynamics algorithms allow their simulation with low computational cost. In two dimensions, nested-contour models for the analytical Lamb dipole are constructed. In the axisymmetric case, a family of models for vortex rings generated by a piston–cylinder apparatus at different stroke ratios is constructed from experimental data. The perturbation response of this family is considered by the introduction of a small region of vorticity at the rear of the vortex, which mimics the addition of circulation to a growing vortex ring by a feeding shear layer. Model vortex rings are found to either accept the additional circulation or shed vorticity into a tail, depending on the perturbation size. A change in the behaviour of the model vortex rings is identified at a stroke ratio of three, when it is found that the maximum relative perturbation size vortex rings can accept becomes approximately constant. We hypothesise that this change in response is related to pinch-off, and that pinch-off might be understood and predicted based on the perturbation responses of model vortex rings. In particular, we suggest that a perturbation response-based framework can be useful in understanding vortex formation in biological flows.

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Weinstein, Michael, Christian Nowroth, Jens Twiefel und Jörg Wallaschek. „Identification of the Effect of Ultrasonic Friction Reduction in Metal-Elastomer Contacts Using a Two-Control-Loop Tribometer“. Applied Sciences 11, Nr. 14 (07.07.2021): 6289. http://dx.doi.org/10.3390/app11146289.

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Pneumatic cylinders are widely used in highly dynamic processes, such as handling and conveying tasks. They must work both reliably and accurately. The positioning accuracy suffers from the stick-slip effect due to strong adhesive forces during the seal contact and the associated high breakaway forces. To achieve smooth motion of the piston rod and increased position accuracy despite highly variable position dynamics, sliding friction and breakaway force must be reduced. This contribution presents a specially designed linear tribometer that has two types of control. Velocity control allows the investigation of sliding friction mechanisms. Friction force control allows investigation of the breakaway force. Due to its bearing type, the nearly disturbance-free detection of stick-slip transients and the dynamic contact behavior of the sliding friction force was possible. The reduction of the friction force was achieved by a superposition of the piston rod’s movement by longitudinal ultrasonic vibrations. This led to significant reductions in friction forces at the rubber/metal interface. In addition, the effects of ultrasonic frequency and vibration amplitude on the friction reduction were investigated. With regard to the breakaway force, significant success was achieved by the excitation. The force control made it possible to identify the characteristic movement of the sealing ring during a breakaway process.

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Kim, C. G., C. S. Bae und S. M. Choi. „Importance of inter-ring crevice volume as a source of unburned hydrocarbon emissions-numerical considerations“. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 214, Nr. 4 (01.04.2000): 395–403. http://dx.doi.org/10.1243/0954407001527718.

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The influence of the inter-ring crevice, the volume between the top and the second piston rings, on unburned hydrocarbon (UHC) emissions has been numerically investigated with the aid of experimental results. The main goal of this study was to estimate the level of UHC emissions induced by the blow-up of the unburned gas trapped in the inter-ring crevice (inter-ring mixture). For this purpose, the relationship between the inter-ring mixture and UHC emissions was established from the experimental results. A physical flow model integrated with a ring dynamics model was constructed to predict the gas flows through the inter-ring crevice. Calculated results showed that some of the inter-ring mixture returned to the combustion chamber, while the cylinder pressure fell below the inter-ring pressure late in the expansion stroke. The amount of inter-ring mixture returning to the combustion chamber after exhaust valve open was calculated and converted to the corresponding UHC emissions using the relationship between the inter-ring mixture and UHC emissions obtained from the experiments. The calculated level of UHC emissions caused by the inter-ring mixtures was 10-30 per cent of the entire UHC emissions over a range of speeds (1250—3500 r/min) and loads [185—556 kPa brake mean effective pressure (b.m.e.p.)]. The contribution was highest at the medium speed and medium load (2500 r/min and 432 kPa b.m.e.p.) for the test condition, which corresponds to the engine condition frequently required for normal running. These findings confirm the importance of inter-ring crevice volume in the UHC emissions in spark ignition engines.

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Kurbet, S. N., und R. Krishna Kumar. „Finite element modelling of piston-ring dynamics and blow-by estimation in a four-cylinder diesel engine“. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221, Nr. 11 (November 2007): 1405–14. http://dx.doi.org/10.1243/09544070jauto177.

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SHADDEN, S. C., K. KATIJA, M. ROSENFELD, J. E. MARSDEN und J. O. DABIRI. „Transport and stirring induced by vortex formation“. Journal of Fluid Mechanics 593 (23.11.2007): 315–31. http://dx.doi.org/10.1017/s0022112007008865.

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The purpose of this study is to analyse the transport and stirring of fluid that occurs owing to the formation and growth of a laminar vortex ring. Experimental data was collected upstream and downstream of the exit plane of a piston-cylinder apparatus by particle-image velocimetry. This data was used to compute Lagrangian coherent structures to demonstrate how fluid is advected during the transient process of vortex ring formation. Similar computations were performed from computational fluid dynamics (CFD) data, which showed qualitative agreement with the experimental results, although the CFD data provides better resolution in the boundary layer of the cylinder. A parametric study is performed to demonstrate how varying the piston-stroke length-to-diameter ratio affects fluid entrainment during formation. Additionally, we study how regions of fluid are stirred together during vortex formation to help establish a quantitative understanding of the role of vortical flows in mixing. We show that identification of the flow geometry during vortex formation can aid in the determination of efficient stirring. We compare this framework with a traditional stirring metric and show that the framework presented in this paper is better suited for understanding stirring/mixing in transient flow problems. A movie is available with the online version of the paper.

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Nouri, Jamshid, Ioannis Vasilakos, Youyou Yan und Constantino-Carlos Reyes-Aldasoro. „Effect of Viscosity and Speed on Oil Cavitation Development in a Single Piston-Ring Lubricant Assembly“. Lubricants 7, Nr. 10 (09.10.2019): 88. http://dx.doi.org/10.3390/lubricants7100088.

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A high-speed camera has been used to produce unique time-resolved images of high quality to describe the dynamics of the lubricant flow and cavitation characteristics in a sliding optical liner over a fixed single piston-ring lubricant assembly for three lubricants with different viscosities to establish their impact on cavitation formation and development. The images were obtained at two cranking speeds (or liner sliding velocity) of 300 rpm (0–0.36 m/s) and 600 rpm (0–0.72 m/s), at a lubricant temperature of 70 °C and a supply lubricant rate of 0.05 L/min. A special MATLAB programme has been developed to analyse the cavitation characteristics quantitatively. The dynamic process of cavities initiation was demonstrated by time-resolved images from fern cavity formation to fissure cavities and then their development to the sheet and strings cavities at a liner sliding velocity of around 0.17 m/s. The results for both up- and down-stroke motions showed that the cavities reach their fully developed state downstream of the contact point when the liner velocity reaches its highest velocity and that they start to collapse around TDC and BDC when the liner comes to rest. Within the measured range, viscosity had a great influence on length of cavities so that a decrease in viscosity (from Lubricant A to C) caused a reduction in length of cavities of up to 35% for Lubricant C. On the other hand, an increase in speed, from 300 rpm to 600 rpm, have increased the number of string cavities and also increased the length of cavities due to thicker oil film thickness with the higher speed. Overall, the agreement between the processed data by MATLAB and visualisation measurements were good, but further thresholds refinement is required to improve the accuracy.

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Nikolakopoulos, Pantelis, Stamatis Mavroudis und Anastasios Zavos. „Lubrication Performance of Engine Commercial Oils with Different Performance Levels: The Effect of Engine Synthetic Oil Aging on Piston Ring Tribology under Real Engine Conditions“. Lubricants 6, Nr. 4 (09.10.2018): 90. http://dx.doi.org/10.3390/lubricants6040090.

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To further improve efficiency in automotive engine systems, it is important to understand the generation of friction in its components. Accurate simulation and modeling of friction in machine components is, amongst other things, dependent on realistic lubricant rheology and lubricant properties, where especially the latter may change as the machine ages. Some results of research under laboratory conditions on the aging of engine commercial oils with different performance levels (mineral SAE 30, synthetic SAE10W-40, and bio-based) are presented in this paper. The key role of the action of pressure and temperature in engine oils’ aging is described. The paper includes the results of experiments over time in laboratory testing of a single cylinder motorbike. The aging of engine oil causes changes to its dynamic viscosity value. The aim of this work is to evaluate changes due to temperature and pressure in viscosity of engine oil over its lifetime and to perform uncertainty analysis of the measured values. The results are presented as the characteristics of viscosity and time in various temperatures and the shear rates/pressures. This paper also includes a Computational Fluid Dynamics (CFD) model, applying the experimental results in the piston ring tribology problem.

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Ye, Zi Bo, Sheng Guan Qu, Xing Feng Fu, Yong Hu, Guang Hong Wang und Zhong Hui Luo. „Friction Process Analysis and Ring Structure Improvement of Piston Rings in MTU396 Diesel“. Applied Mechanics and Materials 329 (Juni 2013): 234–38. http://dx.doi.org/10.4028/www.scientific.net/amm.329.234.

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Based on combustion pressure, the dynamic model was established by using AVL Excite Piston and Rings. Relative axial position and wear loss of rectangular piston ring in a work circulation were analyzed. Based on the shape of the rectangular ring outer side after abrasion, the piston ring cross sections were designed to barrel and tapered shape. Results indicate that improved gas rings are suffered substantially decreased friction. The friction of the first gas ring is less than 100N, and the second ring is even less than 20N. At the upper dead point in the compression stroke, the oil film thickness reaches the minimum value and the piston rings do not pump oil to the cylinder combustion chamber.

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Ye, Zi Bo, Sheng Guan Qu, Yong Hu und Guang Hong Wang. „Study on Wear Mechanism of Chromium Carbide Coating Reinforced Cast Iron Cylinder Sleeve“. Applied Mechanics and Materials 273 (Januar 2013): 124–28. http://dx.doi.org/10.4028/www.scientific.net/amm.273.124.

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In tribological system of internal combustion engine, cylinders and pistons were in high temperature, pressure and load working status. An SRV IV wear tester was used to measure dynamic coefficient of friction by simulating working condition of cylinder liner and piston ring. The worn surface topography was observed through scanning electron microscope and metallography. The results show that loads had little effect on the friction coefficient under oil lubrication. Cylinder with the high-chromium carburizing ring in pairs displayed wear in the form of plastic deformation, while cylinder with the phosphide cast iron ring in pairs displayed adhesive wear. The piston ring was subjected to shear stress and tensile force under dry friction condition and deformed into tapering burr. Lubricants played a bearer role under lubrication condition; therefore, surface borderline of piston ring was relatively flat.

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Tian, T. „Dynamic behaviours of piston rings and their practical impact. Part 1: Ring flutter and ring collapse and their effects on gas flow and oil transport“. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 216, Nr. 4 (01.04.2002): 209–28. http://dx.doi.org/10.1243/135065002760199961.

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This paper describes the physics of two major dynamic behaviours of the piston rings, namely ring flutter and ring collapse, and their effects on gas flow and oil transport. The analysis was conducted by applying a theoretical model in a spark ignition engine and a heavy-duty diesel engine. Parameters that have great influence on these dynamic behaviours are discussed for these two different types of engine and different rings. Specifically, the importance of ring twist, torsional stiffness and ring-groove clearance to ring flutter are discussed in detail. For ring radial collapse, the paper presents a simple formula that determines value of the critical parameters to eliminate ring radial collapse. Emphases are placed on the importance of mechanical designs in changing the performance of the piston ring pack in blowby and oil consumption.

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Zhang, Jia, Yuxuan Zheng, Fenghua Zhou und Jun Liu. „Experimental Technique for Dynamic Fragmentation of Liquid-Driving Expanding Ring“. EPJ Web of Conferences 183 (2018): 02034. http://dx.doi.org/10.1051/epjconf/201818302034.

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Expanding ring experiment is an important method for dynamic fragmentation of solid under 1D tensile loading. Based on the split Hokinson pressure bar (SHPB), a liquid-driving experimental technology was developed for conducting expanding ring tests. The loading fixture includes a hydraulic cylinder filled with water, which is pushed by a piston connected to the input bar. As the water is driven, it expands the metallic ring specimen in the radial direction. The approximately incompressible property of the water makes it possible to drive the specimen in very high radial velocity by low velocity movement of piston, according to the large sectional area ratio of the cylinder to specimen. Using liquid-driving expanding ring device, 1060 aluminum rings (ductile materials)/PMMA rings (brittle materials) were fragmented and the fragments were recovered. Impact deformation of free-flying fragments was avoided through the use of “sample soft-capture” technology. The fragmentation process was observable by high speed camera through modifying the driving direction of the water. From the observations of the fracture morphology and the residual internal cracks of the recovered fragments, it is concluded that the fracture of the rings is caused by the circumferential tensile stress.

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Chernobryvko, Marina V., Konstantin V. Avramov, Valentina N. Romanenko, Tatiana J. Batutina und Ulan S. Suleimenov. „Dynamic instability of ring-stiffened conical thin-walled rocket fairing in supersonic gas stream“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, Nr. 1 (19.06.2015): 55–68. http://dx.doi.org/10.1177/0954406215592171.

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The assumed-modes method is applied to obtain the dynamical model of the ring-stiffened conical shells in a supersonic gas stream. The pressure acting on the shell is described by the piston theory. The displacements of the rings are functions of the shell displacements. The kinetic and the potential energies of the structure are obtained as the functions of the shell displacements. It is suggested the approach to calculate the shell spatial mode, when the shell dynamic stability is lost. The free vibrations of the structures with different numbers of the rings are analyzed. The loss of the structure dynamic stability is investigated.

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Xin, Dianbo, Jianmei Feng, Liqing Ding, Donghui Yang und Xueyuan Peng. „Experimental investigation of pressure distribution between the piston rings and its formation in reciprocating compressors“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, Nr. 11 (09.02.2012): 2701–12. http://dx.doi.org/10.1177/0954406212438151.

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The severe non-uniformity of pressure distribution has been suggested as the essential reason for the premature failure of piston rings in reciprocating compressors. A test rig was built to investigate the dynamic pressure distribution and its formation process, so that the root cause of the non-uniform pressure distribution could be revealed. The experimental results showed that the pressure distribution between the rings was always significantly non-uniform under various test conditions and the first ring bore more than 75% of the total pressure difference. Further analysis of the experimental data indicated that when the suction pressure was not higher than that in the crank case, the first piston ring switched its contact position with the piston ring groove twice in one cycle, at the angles of around 63° and 170°, respectively, while the others switched contact positions at about 90° and 270°. If the suction pressure was higher than the pressure in the crank case, the first ring still switched its contact position twice in a cycle, at the crank angle of about 47° and 195°, respectively, but the other rings no longer changed their positions. The experimental results also demonstrated that the formation of pressure difference on different rings was not synchronous, which indicated that the rings could not work until their pressure difference reached a critical value.

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Xin, Dian Bo, Jian Mei Feng, Yan Jing Xu und Xue Yuan Peng. „Study of the Pressure Distribution between the Piston Rings in Reciprocating Compressors“. Advanced Materials Research 383-390 (November 2011): 6048–52. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.6048.

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Piston ring is one of the most important sealing components that can be easily damaged in reciprocating compressors. The severe non-uniformity of the pressure distribution was suggested to be the essential reason for the premature failure of the piston rings. Therefore, a test rig was set up to measure the pressure distributions as well as the build-up of the dynamic pressure difference, which could reveal the root cause for the non-uniformity of the pressure distributions. The results showed that the build-ups of the pressure differences between different rings were not simultaneous; there existed a threshold pressure, and the latter ring could work only when the pressure before the former ring reached to the threshold value. The pressure distributions were also investigated at the start-up and shut-down of the compressor, which further validated the cause of the premature failure of the first ring.

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Hu, Yuanzhong, Herbert S. Cheng, Takayuki Arai, Yoichi Kobayashi und Shunichi Aoyama. „Numerical Simulation of Piston Ring in Mixed Lubrication—A Nonaxisymmetrical Analysis“. Journal of Tribology 116, Nr. 3 (01.07.1994): 470–78. http://dx.doi.org/10.1115/1.2928867.

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The assumption of axisymmetry, employed by most of studies on piston ring lubrication, probably gives a too idealistic model for the real situation. A theoretical model for a nonaxisymmetrical analysis of piston ring lubrication has been established in the present study. When a piston ring with an arbitrary free shape is fitted into the cylinder bore, the determination of ring deflection and contact load has been modeled mathematically as a Linear Complementary Problem (LCP). By combining LCP solution with lubrication analysis, the film thickness and contact load distribution over the circumference are obtained, leading to a more realistic simulation for piston ring lubrication. The friction force between piston ring and cylinder bore is predicted by the mixed lubrication model including the effects of surface roughness and asperity contact. The static distortion of cylinder bore, gas pressure variation, and lubricant starvation are also considered in the simulation. Results show that the contact pattern and film thickness between piston ring and cylinder bore are not exactly axisymmetrical. The main reason for the nonuniform contact is the asymmetry of ring elasticity, the static distortion and dynamic load created by the secondary movement of piston skirt.

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