Piston Rings Research Papers - Academia.edu (original) (raw)

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- Wear, IC ENGINES, Friction, Cylinder Liner

Nanocoating can help to improve performance and life
of automotive engine by reducing the wear between the engine
components. In this research have selected the proper material
for top piston ring and same material are to be selected for
preparation of pin for tribometer testing and material of cylinder
liner tested and fabricated the same material of tribometer disc.
Nanocoating by electroplated Chromium coating and Chromium
nitride using DLC method by PVD coating was done on
specimen pin and piston ring and this material which was used
tribometer testing.
Depleting fossil fuel resources, economic
competitiveness and environmental concerns has compelled to
explore newer avenues to improve efficiency of automotive
engines. Various techniques have been adapted to achieve this
goal.

This paper describes the structural analysis of four different aluminium alloy pistons, by using finite element method (FEM). The specifications used for designing the piston belong to four stroke single cylinder engine of Bajaj Pulsar 220cc and the parameters used for the simulation are operating gas pressure, temperature and material properties of piston. The results predict the maximum stress and strain on different aluminium alloy pistons using FEA. Modeling of various aluminium alloy piston are done using CATIA V5R20. Static structural analysis is performed by using ANSYS WORKBENCH 14.5. The best aluminum alloy material is selected based on stress analysis. The analysis results are used to optimize piston geometry of best aluminum alloy.

A B S T R A C T Textured surfaces have been shown to provide enhanced tribological performance in a variety of contacts. Numerical analysis and optimisation methods are combined for application-oriented texture optimisation. However, an analytical approach is advantageous in providing more generic in-depth understanding of the nature of the relationships between texture parameters and objective functions, such as enhanced load carrying capacity and reduced friction. The paper outlines such an approach to obtain a set of global optimum design parameters for partially textured surfaces. The optimised results are expressed in dimensionless form, which enables their use for a variety of applications. The performance of optimised partially textured sliding surfaces is compared with the other conventional bearing geometries in their optimum state.

- by Ramin Rahmani
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- Tribology (Engineering), Lubrication, Surface Texturing, Surface Engineering

The study of textured surface performance is one of the highly researched topics in recent times. This is mainly due to the advantages that such surfaces can potentially provide in practice, in mitigating adverse tribological conditions, such as friction and wear. However, considering the complexities found in practice, a methodological analysis and evaluation procedure is essential in order to gain an understanding of the benefits from utilising such features in a given contact. The current study provides a combined analytical and experimental approach towards an enhanced understanding of the behaviour of textured surfaces relative to their untextured counterparts. The developed analytical models are invaluable in providing an insight into the relationship between the many parameters involved in defining even simple surface texture feature geometry and the expected outcomes in practice, when corroborated with experimental results. The current study reports on such an endeavour. With the studied texture configuration, the results have shown the possibility of reducing friction by as much as 25%.

- by Ramin Rahmani
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- Tribology (Engineering), Lubrication, Surface Texturing, Tribology

Özet: Ağır vasıta araçlar için önemli bir bileşen olan hava kompresörleri aracın yolda güvenli hareketini sağlayan fren, süspansiyon ve debriyaj sistemleri için gerekli havanın basınçlandırılarak tanklara depo edilmesini sağlamaktadırlar. Kompresör, çalışma şartları ve düzenli servis bakım periyoduna bağlı olarak, bazen hava tanklarına ve oradan fren sistemi elemanlarına yağ taşınımı gerçekleşebilmektedir. Bu istenmeyen durum ise aracın hava ile çalışan aksamlarının çalışma verimliliğini azaltmakta, hatta arızalanmasına sebep olabilmektedir. Ana sanayi üreticilerinin servis kitapçıklarında belirtilen aşırı yükte çalışma durumu, giriş hattının bakımsız ve deforme olması sonucu görülen piston segman-gömlek aşınması gibi durumların arıza gerçekleştiği anda bilinmesi oldukça önemlidir. Böylelikle zamanında tanı konularak, cüzi ücretlerle gerekli servis bakımların yapılmasına katkı sağlamaktadır. Ortaya konulan bu çalışmada, kompresörlerde meydana gelebilecek bu derece önemli durumların önceden belirlenmesinde Rastgele Orman Algoritması'nın sınıflandırma performansı ve algoritmanın hiç tanımadığı verilerde tahmin yeteneği incelenmiştir.
Abstract: Compressor is an important component for heavy vehicles that ensure the safe movement of the vehicle on the road for the air required for brake, suspension and clutch systems is pressurized and stored in tanks. According to the working conditions of the compressor and regular service maintenance period, oil can be carried to the air tanks and from there to the brake system elements. This unexpected situation reduces the working efficiency of the parts of the vehicle driven by pressurized air and even causes malfunction. It is important to consider that conditions such as operating overload specified in the service manuals of the original equipment manufacturer or piston ring-liner wear in case of maintenance and deformation of the inlet line. In this way, it contributes to the necessary service maintenance with a low fee by making a timely diagnosis. In this study, the classification performance of the random forest algorithm and its ability to predict in the data that the algorithm does not recognize was examined in the prediction of such important situations that may occur in compressors.

- by Gökselhan Kula and +1
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- Machine Learning, Compressor, Piston Rings, Random Forest Algorithm

A fluid solid interaction model (FSI) developed for two different structural cylinder patterns in order to simulate the frictional performance of piston ring–cylinder liner systems for marine engines. Computational fluid dynamics (CFD) analysis is used to solve the Navier Stokes equations. A fully flooded inlet and outlet conditions are assumed taking into account the piston ring elasticity. Honing and wave-cut cylinder geometries were compared while the pressure distribution along the ring thickness and the lubricant film is determined for each crank angle. The present results demonstrate that the honed cylinder geometry improves the friction results increasing the oil film thickness. Further, the artificially textured piston rings with the honed cylinder liner were investigated. As a result, we propose the operational function between the textured rings with the modified cylinder liners in marine engines.

Minimisation of parasitic losses in the internal combustion engine is essential for improved fuel efficiency and reduced emissions. Surface texturing has emerged as a method palliating these losses in instances where thin lubricant films lead to mixed or boundary regimes of lubrication. Such thin films are prevalent in contact of compression ring to cylinder liner at piston motion reversals because of momentary cessation of entraining motion. The paper provides combined solution of Reynolds equation, boundary interactions and a gas flow model to predict tribological conditions, particularly at piston reversals. The results of the analyses are validated against measurements using a floating liner for determination of in-situ friction of an engine under motored condition. Very good agreement is obtained. The validated model is then modified to include the effect of surface texturing which can be applied to the surface of the liner at compression ring reversals under fired engine conditions. The predictions show that some marginal gains in engine performance can be expected with laser textured chevron features of shallow depth under certain operating conditions.

- by Nicholas Morris and +1
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- Tribology (Engineering), Lubrication, Surface Texturing, Tribology

IC engines contribute to global warming through extensive use of fossil fuel energy and emission of combustion by-products. Innovative technologies such as cylinder de-activation (CDA), after-exhaust heat treatment, surface texturing and coatings are proposed to improve fuel economy and reduce emissions of the vehicle fleet. Therefore, study of coating technology through a comprehensive multi-physics analytical model of engine top compression ring is important to ascertain ways of promoting energy savings. This paper presents a multi-scale, multi-physics model of the compression ring-cylinder bore conjunction, using three alternative bore surfaces. The model comprises ring dynamics, contact tribology, heat transfer and gas blow-by. Tribological and thermal properties of advanced coatings, such as Nickel Nanocomposite (NNC) and diamond-like carbon (DLC) are compared with an uncoated steel bore surface as the base line configuration. Such a comprehensive analysis has not hitherto been reported in open literature, particularly with original contributions made through inclusion of salient properties of alternative bore materials for high performance race engines. Power loss and FMEP are evaluated in a dynamometric test, representative of the Worldwide harmonised Light vehicles Test Cycle (WLTC). The NNC coating shows promising tribological improvements. The DLC coating is detrimental in terms of frictional power loss and FMEP, although it can effectively improve sealing of the combustion chamber. The differences in power loss of nominated bore surfaces are represented as fuel mass and CO emissions, using theoretical and empirical relations. For the first time the paper shows that advanced coatings can potentially mitigate the adverse environmental impacts of spark ignition (SI) engines, with significant repercussions when applied to the global gasoline-powered vehicle fleet.

Reciprocating and low-speed sliding contacts can experience increased friction because of solid boundary interactions.
Use of surface texturing has been shown to mitigate undue boundary friction and improve energy efficiency. A combined
numerical and experimental investigation is presented to ascertain the beneficial effect of pressure perturbation caused
by micro-hydrodynamics of entrapped reservoirs of lubricant in cavities of textured forms as well as improved microwedge
flow. The results show good agreement between numerical predictions and experimental measurements using a
precision sliding rig with a floating bed-plate. Results show that the texture pattern and distribution can be optimised for
given conditions, dependent on the intended application under laboratory conditions. The translation of the same into
practical in-field applications must be carried out in conjunction with the cost of fabrication and perceived economic gain.
This means that near optimal conditions may suffice for most application areas and in practice lesser benefits may accrue
than that obtained under ideal laboratory conditions.

- by Nicholas Morris
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- Tribology (Engineering), Surface Texturing, Tribology, Laser Surface Texturing

The current study uses Reynolds equation and the cross-film flow velocity profile to analytically determine pertinent locations for texture feature positioning in sliding hydrodynamic contacts. The position of textures is shown to have a significant effect on the lubricant film thickness, thus the load carrying capacity and generated friction and power loss. It is shown that textures, residing after the inlet lubricant recirculation boundary and prior to the position of maximum contact pressure enhance film thickness and reduce friction in the contact of real rough sliding surfaces. The methodology is applied to partial surface texturing of a thin compression ring of a high performance race engine, with the predicted results confirming the utility of the expounded analytical technique and its conformance to the findings of others reported in literature. The time-efficient analytical and fundamental approach constitutes the main contribution of the paper to furtherance of knowledge.

- by Ramin Rahmani and +1
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- Tribology (Engineering), Internal Combustion Engines, Lubrication, Surface Texturing

Thin lubricant films and cavitation to ring–bore contact have a directly correlation between wear and emissions output of internal combustion engines. Thus, there is a need to develop innovate engineering solutions such as surface texturing. In particular, micro textures are manufactured in order to keep more lubricant in weakly lubricated contact. An isothermal mixed-hydrodynamic analysis was developed for textured compression rings, which utilised the effects of two-phase flow using Navier–Stokes equations, vapour transport and asperity interaction. Realistic boundary conditions are used from a real motorbike engine. This paper employs a computational model including multiphase flow of the ring–bore conjunction in order to predict the effects of surface texturing of the barrel face ring around the dead centres. The model is validated using numerical and experimental results from the literature. Additionally, flow simulations have been performed, on how micro-dimples shape and depth on the ring liner affect on the total friction and minimum lubricant film.

- by Anastasios Zavos and +1
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- Surface Texturing, Computational Fluid Dynamics (CFD) modelling and simulation, Cavitation, Piston Rings

The surface condition of the piston ring-cylinder system affects significantly its performance. Simultaneously, the oil condition and its viscosity play an important role in these tribological components. In this study a Fluid Structure Interaction (FSI) analysis is used in order to solve the Navier Stokes equations, calculating the hydrodynamic field. The surface irregularities are measured of two stroke single cylinder engine that already have been worked about 4000 hours. The measurements are made by a CMM Tesa machine with accuracy of 1μm per axis. Several models of oils viscosities are introduced. Hydrodynamic friction force is predicted using the above combinations of surface condition and oil. Results show that the wavy piston ring reduces the friction while the mechanical stresses increased.

- by Anastasios Zavos and +1
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- Computational Fluid Dynamics (CFD) modelling and simulation, Piston Rings, Surface irregularities, Oil Viscosity

This article provides solution for isothermal mixed hydrodynamic conjunction of the compression ring to cylinder liner. This is obtained using the average flow model representation of Reynolds equation based on pressure- and shear-induced flow factors. In particular, the effects of compression ring axial profile along its face-width and surface topography of contiguous solids are investigated. It is shown that ring geometry may be optimized to improve lubrication, whilst care should be taken in order to avoid oil loss or degradation resulting from any loss of sealing. In predicting friction, it is shown that appropriate surface parameters should be used in-line with the state of wear of the ring. For a new ring against a plateau honed liner, boundary friction contribution during the initial running-in wear phase should be predicted according to the average asperity peak heights protruding above the plateau, whilst the plateau height also takes into account the valleys within the surface roughness or grooves created by any cross-hatch honing would be the appropriate measure of topography for worn rings. The main contributions of the article are in providing an analytic solution as well investigation of ring face-width geometry and effect of wear upon friction. However, it is acknowledged that generated heat, inlet boundary starvation and circumferential non-conformity of ring to the bore surface would affect the film thickness and exacerbate generated friction accordingly. These further considerations would require a numerical solution, rather than an analytical one presented here.

- by Nicholas Morris
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- Tribology, IC ENGINES, Piston Rings

Technically the system that is the subject of research in this paper is a reciprocating compressor. The goal of the research presented in this paper was to examine the reliability of operation reciprocating compressor with a single cylinder. This study is based on monitoring diagnostic parameters of axial clearance and temperature on tested ball bearings, which are located on the crankshaft of the compressor. The reliability in the work was analyzed observed through monitoring of axial clearance and the temperature of ball bearings and was performed in the laboratory conditions testing. Results of the research on the tested ball bearings show that the size of the axial clearance correspond to the sizes and the temperature before the period of notice that condition and are a good indicator of the reliability of the technical system. The most general type of technical system with rotating elements is certainly the compressor that is used in the field of launching of many mechanical installations. Piston compressors use the pistons, which are moving directly by means of the piston mechanism transforming rotary motion into oscillatory motion of the rotor 1. They sucked the gasses from a reservoir, of penstock or the environment and propulsion still (with a significant increase in of pressure) and the other were

- by Blaza Stojanovic
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- Engineering, Mechanical Engineering, Tribology (Engineering), Tribology

Tribological parameters such as friction, lubrication and wear influence strongly the engine component's life. In this study, a piston ring-cylinder system simulated taking into account the surface modifications under fully flooded lubrication and normal engine conditions. The hydrodynamic pressure field solved based on the Navier Stokes equations by Fluid Structure Interaction analysis. A real experimental data of piston ring-cylinder was used from a two stroke motor engine 50 cc. The surface irregularities are measured by 3D coordinate measurement machine while the engine has been worked about 4000 hours. The friction force, the hydrodynamic pressure, the oil film and the mechanical stresses were predicted for different engine conditions. Results show that the worn profile ring reduces the friction as well as the mechanical stresses increased. Surface condition of worn top ring was observed after a metallurgical profile analysis.

- by Anastasios Zavos and +1
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- Fluid structure interaction, Navier-Stokes Equations, Motorcycle Engines, Piston Rings

A multi-physics integrated analysis of piston top compression ring of a high-performance internal combustion engines is presented. The effects of transient ring elastodynamics, thermal gas flow through piston crevices upon chamber leakage pressure and parasitic frictional losses are investigated. The multi-physics analysis comprises integrated flexible ring dynamics, ring-liner thermo-mixed hydrodynamics and gas blow-by, an approach not hitherto reported in literature. The predictions show close conformance to frictional measurements under engine motored dynamometric conditions. It is shown that power losses due to gas leakage can be as much as 6 times larger than frictional losses, which are usually considered as the main sources of inefficiency.

- by Ramin Rahmani and +2
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- Tribology (Engineering), Internal Combustion Engines, Lubrication, Tribology

In I.C. Engine, piston is most complex and important part therefore for smooth running of vehicle piston should be in proper working condition. Pistons fail mainly due to mechanical stresses and thermal stresses. Analysis of piston is done with boundary conditions, which includes pressure on piston head during working condition and uneven temperature distribution from piston head to skirt. The analysis predicts that due to temperature whether the top surface of the piston may be damaged or broken during the operating conditions, because damaged or broken parts are so expensive and difficult to replace and generally are not easily available. The main purpose of the preliminary analyses presented in the book is to compare the behaviour of the combustion engine piston made of different type of materials under thermal load. FEA analysis is carried out using ANSYS software. Development of the FEA model is also presented. Geometrical CAD model of the piston is developed based on the actual engine piston of TATA MOTORS four stroke diesel engine. The piston is loaded by a temperature field inside it. Appropriate averaged thermal boundary conditions such as temperatures and heat fluxes were set on different surfaces of the FEA model. In this study, firstly, thermal analyses are investigated on a conventional diesel piston, made of structural steel for design 1. Secondly, thermal analyses are performed on optimized piston, made of aluminium alloy and titanium alloy material by means of using a commercial code, namely ANSYS. The proposed new material is characterized by a low density, high thermal conductivity, easy machinability, high reliability and very good recycling characteristics. The results obtained for the piston made of a new material are compared with those for the current standard material. The analysis is carried out to reduce the stress concentration on the upper end of the piston i.e. (piston head/crown and piston skirt and sleeve) so as to increase life of piston.

- by Atul D Dhale
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- Engineering, Modeling and Simulation, FEA with ANSYS, Automotive

Up to 90% of the combustion chamber pressure applied on the top compression ring during the combustion cycle. The main functions of the compression rings are to prevent the passage of the combustion gas and to absorb the heat between piston and cylinder wall. Thus, the main priority is to improve the structural integrity and the shape of top rings. In this study, a computational fluid dynamics (CFD) model is performed for top ring-cylinder contact condition. A combined thermo-mixed lubrication model is implemented solving simultaneously the Navier-Stokes and the energy equations. Realistic boundary conditions are also taken into account from a four stroke motorbike engine. Consequently, for the warm idle engine conditions, the effects of chromium plated and uncoated compression piston rings, in the minimum lubricant thickness, in the total friction force and the average oil temperature at the contact area are investigated and presented.

- by Anastasios Zavos and +1
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- CFD Analysis, Piston Rings, Piston Ring Coating

There are increasing pressures upon the automotive industry to reduce harmful emissions as well as meeting the key objective of enhanced fuel efficiency, while improving or retaining the engine output power. The losses in an internal combustion (IC) engine can be divided into thermal and parasitic as well as due to gas leakage because of untoward compression ring motions. Frictional losses are particularly of concern at low engine speeds, assuming a greater share of the overall losses. Piston–cylinder system accounts for nearly half of all the frictional losses. Loss of sealing functionality of the ring pack can also contribute significantly to power losses as well as exacerbating harmful emissions. The dynamics of compression ring is inexorably linked to its tribological performance, a link which has not been made in many reported analyses. A fundamental understanding of the interplay between the top compression ring three-dimensional elastodynamic behavior, its sealing function and contribution to the overall frictional losses is long overdue. This paper provides a comprehensive integrated transient elastotribodynamic analysis of the compression ring to cylinder liner and its retaining piston groove lands’ conjunctions, an approach not hitherto reported in the literature. The methodology presented aims to aid the piston ring design evaluation processes. Realistic engine running conditions are used which constitute international drive cycle testing conditions.

- by Ramin Rahmani
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- Mechanical Engineering, Structural Dynamics, Energy, Tribology (Engineering)
- by Anastasios Zavos and +1
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- Surface Texturing, Computational Fluid Dynamics (CFD) modelling and simulation, Lubricants Additives, Piston Rings

Ball bearings are an integral part of many machines and mechanisms and often determine their performance limits. Vibration, friction and power loss are some of the key measures of bearing performance. Therefore, there have been many predictive analyses of bearing performance with emphasis on various aspects. The current study presents a mathematical model, incorporating bearing dynamics, mechanics of rolling element-to-races contacts as well as the elastodynamics of the bearing outer ring as a focus of the study. It is shown that the bearing power loss in cage cycles increases by as much as 4% when the flexibility of the outer ring is taken into account as a thick elastic ring, based on Timoshenko beam theory as opposed to the usual assumption of a rigid ring in other studies. Geometric optimisation has shown that the lifetime power consumption can be reduced by 1.25%, which is a significant source of energy saving when considering the abundance of machines using rolling element bearings. The elastodynamics of bearing rings significantly affects the radial bearing clearance through increased roller loads and generated contact pressures. The flexible ring dynamics is shown to generate surface waviness through global elastic wave propagation, not hitherto taken into account in contact dynamics of rollers-to-raceways which are generally considered to be subjected to only localised Hertzian deflection. The elastodynamic behaviour reduces the elastohydrodynamic film thickness, affecting contact friction, wear, fatigue, vibration, noise and inefficiency.

- by Ramin Rahmani
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- Vibrations, Elasticity (Solid Mechanics), Contact Mechnics, Elastodynamics

The ring-pack is the main part of parasitic losses in the engine. In particular, the major contribution of the top compression ring friction is approximately 15-20% of the total friction due to the piston-ring pack. The object of this paper is to measure the piston-ring pack friction during the cold start-up period of a single-cylinder motorbike engine under firing conditions. The basic geometric dimensions of the piston assembly system are measured using a coordinate measuring machine. Strain gauges are used along the cylinder liner and the extracted signals are analyzed using the Labview software. The engine test for friction measurement is taken for a short time of 5 min in order to simulate the cold start-up driving condition. The cylinder temperature is measured using a high-performance thermo camera. A fresh multigrade oil is used during the engine test. The lubricant properties are measured using a capillary tube viscometer from deltalab. In the present study, CFD simulations are carried out in order to predict the friction produced for a new compression ring sliding against a plateau crossed hatched cylinder. The analysis considers a mixed lubrication model combining the Navier-Stokes and Rayleigh-Plesset equations. The contribution of asperity contact in thin lubricant films is obtained. The numerical results are compared with experiments under idle rotational speed. Good agreement is observed between experimental and numerical predictions.
Keywords— CFD compression ring, engine cold start-up, friction, strain gauges

- by Anastasios Zavos and +1
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- Lubrication and Friction, Strain Gauges, Piston Rings

The paper presents direct measurement of in-cylinder friction from a single cylinder motocross race engine under motored conditions and compares the same with a new analytical predictive method. These conditions are encountered in piston-cylinder system with the application of cylinder deactivation (CDA) technology, which is a growing trend. The analytical method takes into account the various regions within instantaneous contact of compression ring-cylinder liner, including lubricant film rupture, cavitation zone and the subsequent lubricant film reformation. The analysis also includes the effect of boundary friction and lubricant rheology. The predictions and direct measurements of cyclic friction show good agreement and indicate dominance of viscous friction under the investigated engine running conditions. In particular, it is shown that the compression ring contribution to in-cycle friction is most pronounced in the region of high cylinder pressures because of combined Poiseuille friction and some boundary solid interactions. The combined experimental-analytical approach has not hitherto been reported in literature.

- by Ramin Rahmani
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- Tribology (Engineering), Internal Combustion Engines, Lubrication, Friction Models

The design of piston ring pack is a major subject on the internal combustion engines. The current trend focused on thin piston rings and the improvements of profile to oil consumption and lubrication in each engine stage. In this paper, an investigation of piston ring shapes in modern combustion engines was performed. The geometrical dimensions of piston ring pack-cylinder tribo pair were obtained from a four stroke motor engine. A 2D axisymmetric model of ring pack-cylinder was created using the finite element method. The minimum oil thickness, the combustion gas pressures and the asperities contribution were updated for each crankshaft position in quasi static manner. The fluid field was solved based on the Navier Stokes approach, as well as the piston ring balance was performed. Several shape profiles for top ring were examined and compared. Lower curvature height improved the minimum lubricant thickness, thus the total friction force decreased near to top dead center.

- by Anastasios Zavos and +1
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- Design, Computational Fluid Dynamics (CFD) modelling and simulation, Friction, Piston Rings

Fuel consumption is an extremely important parameter for the automotive industry today. In engines the piston system is the largest source of frictional losses, accounting for about 30% of the total frictional losses, thus it is important to optimize. The lost caused by friction and wear is huge. There is about 30% power of automobile engine lost because of friction, 19% of the power loss is come from the piston ring-cylinder liner pair. This important pair of engine often damaged because of wear. Lubricant film in an internal combustion engine (I.C. Engine) is an important factor in determining fuel economy and performance of the vehicle.

- by Hitesh Yadav
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- LST, Friction, Piston Rings

A novel integrated multi-physics assessment of the piston top compression ring of an internal combustion engine under normal operation mode, as well as subjected to cylinder deactivation is carried out. The methodology comprises ring-liner thermo-mixed hydrodynamics, elastodynamics of ring, as well as combustion gas blow-by and emissions. Therefore, the analysis provides prediction of ring-liner contact’s energy losses and gas power leakage across the piston and ring crevices, as well as the resulting emissions. Cylinder deactivation (CDA) technology reduces the unburnt fuel entering the ring-pack crevices, as well as the emissions. It is also shown that the frictional and gas leakage power losses are exacerbated under CDA by as much as 20%. Although this is much lower than the potential gains in fuel usage when using CDA. The optimisation of the piston compression ring would provide further fuel efficiency and improved emissions, an issue which has not hitherto received the attenti...

A novel integrated multi-physics assessment of the piston top compression ring of an internal combustion engine under normal operation mode, as well as subjected to cylinder deactivation is carried out. The methodology comprises ring-liner thermo-mixed hydrodynamics, elastodynamics of ring, as well as combustion gas blow-by and emissions. Therefore, the analysis provides prediction of ring-liner contact's energy losses and gas power leakage across the piston and ring crevices, as well as the resulting emissions. Cylinder deactivation (CDA) technology reduces the unburnt fuel entering the ring-pack crevices, as well as the emissions. It is also shown that the frictional and gas leakage power losses are exacerbated under CDA by as much as 20%. Although this is much lower than the potential gains in fuel usage when using CDA. The optimisation of the piston compression ring would provide further fuel efficiency and improved emissions, an issue which has not hitherto received the attention which it deserves. The in-depth analysis has also shown that CDA reduces the predicted CO, NOx and HC emissions by nearly as much as 8.5%, 10% and 8.7%, respectively.

- by Ramin Rahmani
- •
- Tribology (Engineering), Internal Combustion Engines, Automobile, Tribology

Aim: Design Analysis and Optimization of piston for various materials and Determination of its Thermal Stresses. To optimize stress concentration on piston. Study design: Analysis of the stress distribution in the various parts of the piston to know the induced stresses due to gas pressure and thermal variations of TATA MOTORS 4 stroke diesel engine piston using ANSYS. Methodology:The Piston of an engine is analysed and optimized by using graphics software. With using computer aided design, CATIAV5R17 software, the structural model of a piston is developed. Furthermore, analysis and optimization is performed using ANSYS11 software. Brief Results: Von misses stress is decreased from 56.14MPa to 33.3Mpa for aluminium Alloy and 26.25MPa for Titanium Alloy.

- by Nikita R Sukthankar
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- Modeling and Simulation, FEA with ANSYS, Automotive, Thermal Analysis

Piston rings are the most complicated component of the internal combustion engine. They are designed to seal the combustion chamber of the engine while minimizing the friction against the cylinder liner. Modern automobiles normally use three rings: two compressions rings and one oil ring. The first compression ring is the closest to the combustion chamber, so that it is exposed to the extreme conditions and rapidly changing loads associated with the combustion itself. Designs have been developed to improve ring friction and load carrying capacity by applying artificial surface texturing. Wear and lubrication also play a significant role in the life and performance of a ring.

- by Anastasios Zavos and +1
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- Use Wear Analysis, Computational Fluid Dynamics (CFD) modelling and simulation, Friction, Piston Rings

The quality of the surface of the piston ring and cylinder tribo pair affects significantly its performance and its dynamic characteristics. Manufacturing errors in terms of waviness and straightness can lead to a series of defects on the surfaces of the piston ring and the cylinder respectively. In this work a tribological model of a piston ring- cylinder package is presented using CFD analysis. In the proposed model, the piston ring waviness and cylinder straightness are included. Smooth and artificially textured surfaces of the ring are also considered. Configurations of the waves are formed as a sum of sinusoidal waves with different amplitude and length in order to study the relationship between the waviness of the ring and the cylinder bore. The results of the simulations carried out show the reduction of the friction force by increasing the percentage of the waviness or straightness amplitude.

- by Anastasios Zavos and +1
- •
- Surface Texturing, Computational Fluid Dynamics (CFD) modelling and simulation, Piston Rings, Waviness

The primary function of the piston compression ring is to seal the combustion chamber from the bottom end of the engine. As a result, its conformance to the cylinder liner surface is of prime importance. This close-contact contiguity results in increased friction, making this contact conjunction responsible for a significant proportion of energy losses. The frictional losses can be as much as 2–6% of the expended fuel energy, which is quite significant for such a diminutive contact. Under these conditions, the geometrical profile, the surface topography and the inertial properties of the ring assume significant importance. The paper presents an integrated mixed-hydrodynamic analysis of the compression ring– cylinder liner contact with multi-parameter optimisation, based on the use of a genetic algorithm. The multi-objective functionality includes minimisation of the parasitic energy loss, reduction in the incidence of asperity level interactions as well as minimisation of the ring mass. Both cold running engine conditions and hot running engine conditions in line with the New European Drive Cycle were considered. Hitherto, such an approach has not been reported in the literature.

- by Ramin Rahmani and +1
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- Automotive Systems Engineering, Energy, Tribology (Engineering), Internal Combustion Engines

Compression rings are mechanical components with specific interest for the internal combustion engines. Various studies focusing on the tribology of compression rings have been used in order to estimate friction and lubricant film thickness, including gas blow-by, surface treatments and thermal effects. In this paper, a combined experimental and numerical study was presented to study frictional performance of a new thin compression ring of a four-stroke motorbike engine, particularly for realistic speeds. The contribution of friction due to top compression ring conjunction was measured using a strain gauge with minimal cylinder modification. The limitations and the repeatability of the strain gauge method to obtain actual friction measurements was also described. The experimental results were compared with the predictions of a CFD model by including mixed-lubrication theory. The present CFD tool for mixed-hydrodynamic lubrication analysis was performed by solving the Navier-Stokes and Rayleigh-Plesset equations. The actual compression ring profile, the gas flow and the realistic lubricant properties of fresh multigrade oil were also included. Generally good agreement was seen when comparing the measured friction data and the CFD predictions. The results show the transient nature of the thin compression ring conjunction, especially the boundary/mixed regimes of lubrication at TDC reversal.

- by Anastasios Zavos and +1
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- CFD Analysis, Surface topography, Friction, Piston Rings

The paper presents transient thermal-mixed-hydrodynamics of piston compression ring–cylinder liner conjunction for a 4-cylinder 4-stroke gasoline engine during a part of the New European Drive Cycle (NEDC). Analyses are carried out with and without cylinder de-activation technology in order to investigate its effect upon the generated tribological conditions. In particular, the effect of cylinder deactivation upon frictional power loss is studied. The predictions show that overall power losses in the piston–ring cylinder system worsen by as much as 10% because of the increased combustion pressures and liner temperatures in the active cylinders of an engine operating under cylinder deactivation. This finding shows the down-side of this progressively employed technology, which otherwise is effective in terms of combustion efficiency with additional benefits for operation of catalytic converters. The expounded approach has not hitherto been reported in literature.

- by Ramin Rahmani
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- Tribology (Engineering), Internal Combustion Engines, Lubrication, Tribology

Energy losses in an internal combustion engine are either thermal or parasitic. The latter are the mechanical inefficiencies, chiefly as the result of generated friction. Nearly half of these losses are attributed to the piston–cylinder system. During idle and at low engine speeds, friction is the major contributor to the overall engine losses. In particular, the rather small top compression ring accounts for a disproportionate share. Therefore, detailed understanding of compression ring tribology/dynamics (referred to as tribodynamics) is essential. Moreover, the ring’s primary sealing function may be breached by its elastodynamic behavior. The reported analyses in literature do not account for the transient nature of ring elastodynamics, as an essential feature of ring–bore tribology. The transient in-plane dynamics of incomplete rings are introduced in the analysis and verified using a finite element analysis (FEA) model, in order to address this shortcoming. The methodology is then coupled with the tribological analysis of the top compression ring. Comparison is made with experimental measurements which show the validity of the proposed method. The radial in-plane elastodynamic response of the ring improves the accuracy of the frictional power loss calculations.

- by Ramin Rahmani
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- Structural Dynamics, Internal Combustion Engines, Tribology, Energy efficiency
- by Chennakesava Reddy A
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- Piston Rings

A novel integrated multi-physics assessment of the piston top compression ring of an internal combustion engine under normal operation mode, as well as subjected to cylinder deactivation is carried out. The methodology comprises ring-liner thermo-mixed hydrodynamics, elastodynamics of ring, as well as combustion gas blow-by and emissions. Therefore, the analysis provides prediction of ring-liner contact's energy losses and gas power leakage across the piston and ring crevices, as well as the resulting emissions. Cylinder deactivation (CDA) technology reduces the unburnt fuel entering the ring-pack crevices, as well as the emissions. It is also shown that the frictional and gas leakage power losses are exacerbated under CDA by as much as 20%. Although this is much lower than the potential gains in fuel usage when using CDA. The optimisation of the piston compression ring would provide further fuel efficiency and improved emissions, an issue which has not hitherto received the att...

- by atul dhale
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- Engineering, Mechanical Engineering, Modeling and Simulation, FEA with ANSYS

Thin curved rings used mostly as seals, including in internal combustion engines undergo complex elastodynamic behavior when subjected to a combination of normal radial loading and tangential shear with friction. In turn, their complex modal behavior often results in loss of sealing, increased friction, and power loss. This paper presents a new finite difference approach to determine the response of thin incomplete circular rings. Two interchangeable approaches are presented; one embedding mass and stiffness components in a unified frequency-dependent matrix, and the other making use of equivalent mass and stiffness matrices for the ring structure. The versatility of the developed finite difference formulation can also allow for efficient modification to account for multiple dynamically changing ring support locations around its structure. Very good agreement is observed between the numerical predictions and experimental measurements, particularly with new precision noncontact measurements using laser Doppler vibrometry. The influence of geometric parameters on the frequency response of a high performance motorsport engine's piston compression ring demonstrates the degree of importance of various geometrical parameters on ring dynamic response.

- by Ramin Rahmani and +1
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- Computational Mechanics, Elasticity (Solid Mechanics), Modal Analysis, Mathematical Modelling

The piston compression ring's primary function is to seal the combustion chamber, thus mitigating gas leakage to the crankcase and avoiding loss of pressure loading. As a result, the ring is meant to conform closely to the cylinder surface which promotes increased friction. The compression ring is subjected to combustion pressure loading, ring tension, varying inertial force and friction. It is a slender ring of low mass, thus undergoes complex elastodynamic behaviour, when subjected to a multitude of forces. These motions occur in the ring's radial in-plane and axial out-of-plane dynamics, which comprise flutter, ring axial jump, compression-extension, ring twist and rotational drag. An implication of these motions can be loss of sealing, gas blow-by, loss of power and lubricant degradation/oil loss, to name but a few. Consequently, understanding and accurately predicting ring dynamic behaviour under transient conditions is an important step in any subsequent modelling for evaluation of cylinder system efficiency. There have been a plethora of investigations for ring dynamics, often decoupling the ring behaviour in its in-plane and out-of-plane motions. This approach disregards any transfer of dynamic energy from one degree of freedom to another which is only applicable to rectangular ring cross-sections. Alternatively, there are computationally intensive approaches such as finite element analysis which are not conducive for inclusion in any subsequent system level engine modelling where ring response alters in an instantaneous manner. This would require embedded finite element analysis within a transient analysis. This paper presents a finite difference numerical analysis for coupled in-plane and out-of-plane motions of compression rings with practical cross-sectional geometries, which are mostly not rectangular. The formulated method can be integrated into a system level transient cyclic analysis of ring-bore contact. The presented approach takes into account the energy transfer between different degrees of freedom. The predictions are validated against precise non-contact measurements of ring elastodynamic behaviour under amplitude-frequency sweeps. This approach has not hitherto been reported in literature and constitutes the main contribution of the paper.

- by Ramin Rahmani
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- Piston Rings
- by Izhak Etsion
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- Materials Engineering, Mechanical Engineering, LST, Friction

This paper presents a wear process analysis of piston‐cylinder set in internal combustion engines.Piston mechanism is a very important factor in the proper lubrication of the engine, but also a potential cause of increased consumption of oil. There are very important kinematic ‐ tribological properties of piston mechanisms in this regard. From the point of reliability and functionality, critical parts of this circuit are the piston rings. Wear is most pronounced in the first piston ring, since it is exposed to the highest pressure and temperature, as well as the direct impact of fuel and combustion products. The intensity of wear of piston ‐ cylinder set depends on many factors, but the most influential ones are: construction, materials used for the production of the parts of this assembly, production technology and conditions of use.

Performance enhancements by laser surface texturing (LST) of parallel-thrust bearings is experimentally investigated. Test results are compared with a theoretical model and good correlation is found over the relevant operating conditions. A comparison of the performance of unidirectional and bi-directional partial-LST bearings with that of a baseline, untextured bearing is presented showing the benefits of LST in terms of increased clearance and reduced friction.

- by Izhak Etsion
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- Materials Engineering, Mechanical Engineering, LST, Friction
- by Nicholas Morris
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- Mechanical Engineering, Heat Transfer, Internal Combustion Engines, Tribology

- by Ramin Rahmani
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- Mechanical Engineering, Internal Combustion Engines, Lubrication, Tribology