Compression Ring Research Articles

Effect of iron oxides on sliding friction of thermally sprayed 1010 steel coated cylinder bores

In-situ Raman spectroscopy was performed on 1010 steel coatings thermally sprayed on an Al-Si alloy on A 380 (Al-9.0% Si) cylinder bore and subjected to reciprocating sliding against various coated rings to investigate the progression of iron oxide formation during sliding. The coatings evaluated for the top compression ring (TCR) included diamond-like carbon (DLC) and chromium nitride (CrN). The reciprocating tests were conducted under unlubricated and boundary lubricated conditions. During unlubricated sliding, a running-in period was observed with increasing coefficient of friction (COF) values which corresponded to the conversion of the initial FeO, present in the as-deposited coating, to Fe3O4 and then to Fe2O3 as identified by changes in Raman spectra obtained at short intervals during the test. Once a Fe2O3 layer was formed, a steady state regime was obtained with a COF of 0.4 that was accompanied by the adhesion of the oxide debris generated during sliding to the counterfaces. The DLC coated TCR provided low steady state COF (0.18) and volumetric wear of 1010 steel, with negligible debris formation. Boundary lubricated sliding tests, with an initial period of unlubricated sliding, resulted in low steady state COF value of 0.10 for DLC and 0.16 for CrN. The low friction and wear of 1010 coatings observed during boundary lubricated sliding against DLC coated TCR was due to a composite tribolayer consisting of an amorphous carbon layer on top of an oil residue layer that was formed on the sliding surfaces.

Calculating Failure Pressure Under Different Failure Modes in the Roof-to-Shell of a Vaulted Tank

In this study, two failure modes, yield buckling of the compression ring section and strength failure in the roof-to-shell of the tank, have been proposed for a vertical vaulted tank. The failure criteria of the two failure modes in the roof-to-shell of vault tanks are established via finite element analysis of three tanks of 640 m3, 3200 m3, and 6800 m3 in volume. The finite element models are built with axisymmetric elements and spatial multi-elements. Based on the strength failure criterion, the failure pressure formula in the vaulted tank roof-to-shell is derived. The maximum relative error between the theoretical calculation and numerical simulation is 9.7%. Finally, we verify the strength failure criterion through a tank failure test; the maximum relative error between the test and theoretical calculation is 9.6%. The failure pressure of both failure modes has been compared and analyzed. The failure pressure of the yield buckling in the compression ring section is about 1.65 times that of the strength failure in the roof-to-shell of the tank.

The effect of cylinder liner operating temperature on frictional loss and engine emissions in piston ring conjunction

Despite extensive research into alternative methods, the internal combustion engine is expected to remain as the primary source of vehicular propulsion for the foreseeable future. There are still significant opportunities for improving fuel efficiency, thus directly reducing the harmful emissions. Consequently, mitigation of thermal and frictional losses has gradually become a priority. The piston-cylinder system accounts for the major share of all the losses as well as emissions. Therefore, the need for an integrated approach, particularly of a predictive nature is essential. This paper addresses this issue, particularly the role of cylinder liner temperature, which affects both thermal and frictional performance of the piston-cylinder system. The study focuses on the top compression ring whose critical sealing function makes it a major source of frictional power loss and a critical component in guarding against further blow-by of harmful gasses. Such an integrated approach has not hitherto been reported in literature. The study shows that the cylinder liner temperature is critical in mitigating power loss as well as reducing Hydrocarbon (HC) and Nitrogen Oxide (NOx) emissions from the compression ring – cylinder liner conjunction. The results imply the existence of an optimum range for liner working temperature, independent of engine speed (at least in the studied cases) to minimise frictional losses. Combined with the study of NOx and HC emissions, the control of liner temperature can help to mitigate frictional power loss and reduce emissions.

Optimisation of the piston compression ring for improved energy efficiency of high performance race engines

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.

A systematic analysis of controlled clinical trials using the NiTi CAR™ compression ring in colorectal anastomoses.

Anastomotic leak following colorectal surgery can be a devastating adverse event. The ideal stapling device should be capable of rapid creation of an anastomosis with serosal apposition without the persistence of a foreign body or a foreign body reaction which potentially contribute to early anastomotic dehiscence or late anastomotic stricture. A systematic review was performed examining available data on controlled randomized and non-randomized trials assessing the NiTi compression anastomosis ring-(NiTi CAR™) (NiTi Solutions, Netanyah Israel) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) standards. A protocol for this meta-analysis has been registered on PROSPERO (CRD42016050934). The initial search yielded 45 potentially relevant articles. After screening titles and abstracts for relevance and assessment for eligibility, 39 of these articles were eventually excluded leaving 6 studies for analysis in the review. Regarding the primary outcome measure, the overall anastomotic leak rate was 2.2% (5/230) in the compression anastomosis group compared with 3% (10/335) in the conventional anastomosis group; this difference was not statistically significant (RR 0.75, 95% CI 0.25-2.24; participants=565; studies=6; I 2=0%). There were no statistically significant differences between compression and conventional anastomoses in any of the secondary outcomes. This review was unable to demonstrate any statistically significant differences in favor of the compression anastomosis technique over conventional manual or stapled mechanical anastomoses.

On the Transient Three-Dimensional Tribodynamics of Internal Combustion Engine Top Compression Ring

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.

A combined analytical‐experimental investigation of friction in cylinder liner inserts under mixed and boundary regimes of lubrication

AbstractIt is necessary to develop an analytical solution in order to combine predictions with measured tribological parameters and fundamentally understand the mechanism of lubrication in a typical region of engine cycle, using tribometric studies. This paper deals with the development of such a representative approach. An analytical, rather than a numerical approach is expounded, as it is shown to suffice for the purpose of precise time‐efficient predictions, which conform well to the measurements. The effect of surface topography, material and operating conditions are ascertained for the representative case of top compression ring—cylinder liner contact at the top dead centre reversal in transition from the compression to power stroke. Stainless steel uncoated surface used as press fit cylinder liners for niche original equipment manufacturer applications are compared with those furnished with a Nickel‐Silicon Carbide wear‐resistant coating of choice in high performance motorsport. © 2017 The Authors Lubrication Science Published by John Wiley & Sons Ltd.

Thermo-mixed lubrication analysis of coated compression rings with worn cylinder profiles

PurposeCompression rings are the main sources of frictional losses in internal combustion engines. The present paper aims to present a thermo-mixed hydrodynamic analysis for coated top compression rings. To understand the coating effects, the main tribological parameters are investigated into a ring-cylinder conjunction in a motorbike engine. Furthermore, flow simulations have been carried out on how different worn profiles on the cylinder inner liner affects friction, lubricant film and localized contact deformation of the coated compression rings.Design/methodology/approachIn this paper, the basic geometrical dimensions of the top compression ring-cylinder system are obtained from a real motorbike engine. A 2D axisymmetric CFD/FLOTRAN model is created for coated compression rings. Flow simulations are performed by solving the Navier-Stokes and the energy equations. The load capacity of the asperities is also taken into account by Greenwood and Tripp contact model. Realistic boundary conditions are imposed to simulate the in-plane ring motion. The simulation model is validated with analytical and experimental data from the literature. Under thermal considerations, the contribution of worn cylinder profiles in conjunction with different coated compression rings is presented.FindingsThis research shows that because of thermal effects, the boundary friction is higher at reversals and the viscous friction is lower because of reduced oil viscosity. As regards to the isothermal case, the viscous friction is greater because of a higher lubricant viscosity. In the case of chromium-plated ring, boundary friction was 16 per cent lower than a grey cast iron ring taking into account thermal effects. Regarding the localized contact deformation, the coated compression rings showed lower values under different worn cylinder shapes. In particular, hard wear-resistant (Ni-Cr-Mo) coating showed the slighter local deformation. Therefore, the worn cylinder profiles promote boundary/mixed lubrication regime, whereas the lobed profile of cylinder inner liner becomes more wavy.Originality/valueThe solution of the thermo-mixed lubrication model, concerning the piston ring and worn cylinder tribo pair by taking into account the coating of the top compression ring.

Computational fluid dynamics analysis of top compression ring in mixed lubrication

The top compression ring design of an internal combustion engine has an impact on ring in-plane motion and its lubrication conditions at the ring-cylinder liner contact. In this paper, the geometrical dimensions of the top compression piston ring-cylinder system were obtained from an actual four-stroke motorbike engine. The top ring tribological behaviour was characterized by a Computational Fluid Dynamics (CFD) simulation including the effects of asperity contact. Based on the numerical solution of the Navier–Stokes equations and taking into account realistic engine running conditions, the effect of the in-plane top ring motion in quasi-static equilibrium was determined. The simulation model was validated by the numerical and experimental results of similar investigations of other researchers. Good predictions were achieved by solving the Navier-Stokes equations because the pressure gradient into the lubricant film was accounted for. The effects of ring curvature at the ends of the stroke were studied. The results show that a flatter ring profile has a sufficient minimum lubricant thickness at reversal points, showing reasonably lower boundary friction than that of the higher curvature. Higher heights of the curvature profile promote significantly mixed lubrication, in which the power losses and the burning of excess lubricating oil are increased. The proposed simulation model can be expanded to any set of compression rings where a minimum simulation time is required.

Effect of cylinder de-activation on the tribological performance of compression ring conjunction

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.

Effects of honed cylinder liner surface texture on tribological properties of piston ring-liner assembly in short time tests

The experiments were conducted using an oscillating wear tester under lubricated conditions. Specimens were cut from cylinder liners made of gray cast iron. As the results of honing and/or plateau honing various surface textures of cylinder liners were obtained. Counter-specimens were cut from chromium-coated compression ring. Short time tests were carried out at temperature of 80°C, stroke was 3mm. The other operating parameters, like normal load and frequency varied. Before and after tests surface topographies of liners were measured by a white light interferometer. It was found that one-process textures led to smaller coefficients of friction than two-process topographies for test duration of 0.5h. The frictional resistance increased when honing angle increased.

Injection method of barrier bucket supported by off-aligned electron cooling for CRing of HIAF**Supported by New Interdisciplinary and Advanced Pilot Fund of Chinese Academy of Sciences

A new accelerator complex, HIAF (the High Intensity Heavy Ion Accelerator Facility), has been approved in China. It is designed to provide intense primary and radioactive ion beams for research in high energy density physics, nuclear physics, atomic physics as well as other applications. In order to achieve a high intensity of up to 5×1011 ppp 238U34+, the Compression Ring (CRing) needs to stack more than 5 bunches transferred from the Booster Ring (BRing). However, the normal bucket to bucket injection scheme can only achieve an intensity gain of 2, so an injection method, fixed barrier bucket (BB) supported by electron cooling, is proposed. To suppress the severe space charge effect during the stacking process, off-alignment is adopted in the cooler to control the transverse emittance. In this paper, simulation and optimization with the BETACOOL program are presented.

Modeling and simulation of frictional energy loss in mixed lubrication of a textured piston compression ring during warm-up of spark ignition engine

Road vehicles account for a substantial portion of energy consumed by transportation. A large amount of this energy is lost to overcome friction within vehicle engines, in which the piston compression rings are a major source of such parasitic losses. The internal losses of engines increase several times in the case of unfavorable warm-up conditions. Recent developments in surface modification showed promising results in improving the frictional behavior of piston rings. Analyses are often idealized, such as isothermal conditions and unrealistic engine operating conditions. This study presents a numerical investigation of the frictional behavior of mixed-hydrodynamic interaction in a textured piston compression ring–cylinder liner during the warm-up process. The transient Reynolds equation is solved with a mass-conserving cavitation algorithm, realistic oil rheology, and practical engine operating conditions. Several multigrade and monograde oils are considered to draw comprehensive conclusions. The results show that ring surface texturing substantially reduces energy loss during the entire warm-up phase.

Investigation of friction characteristics in segmented piston ring liner assembly of IC engine

Summary The friction at the piston ring cylinder liner assembly (PRLA) is a major contributor in the total friction losses in the I.C. engine. New materials, coatings and high-tech machining processes that previously were considered to be too expensive and therefore only used in complex applications are today becoming more affordable. A significant amount of the total power loss in a modern automotive engine is due to the Friction interaction between the top compression ring and the cylinder liner, especially at the TDC and BDC where boundary lubrication exists. The change in piston speed is accompanied with change the lubrication regime in the cylinder, which results change in friction between the ring and the liner during the entire stroke of the piston. Theoretical modelling of friction force from the various sources of friction will be compared to experimental results for analysing the tribological characteristics. The appropriate sample of piston ring and cylinder liner pair is developed for studying the different tribological parameters on Reciprocating Tribometer. The variable parameters are engine speed, oil viscosity, and load. The experimental results and observations are studied under different operating conditions in speed ranges from 300 rpm to 1500 rpm with constant load of 60 N. It can be seen that as speed increases, the friction force and friction coefficient also decreases.

Investigation of a friction-grip connection in laminated glass

Friction-grip bolted connections are theoretically well suited for the introduction of in-plane loads in glass structures because they distribute the load over a relatively large area and thus avoid critical stress concentrations. However, the performance of friction-grip connections for laminated glass may be jeopardised over time due to viscoelastic behaviour of the interlayers and gaskets used. More specifically, the latter may lead to preload losses in the connection. However, only a few technical papers have dealt with the use of friction-grip connections in laminated glass. Experimental tests were thus performed to study the time-dependent behaviour and the slip resistance of an existing connection. The latter consisted of a polyvinyl butyral laminated glass plate bolted to steel skew plates with preloaded bolts. Different materials (e.g. styrene butadiene rubber, nylon and polyoxymetheylene(-copolymer)) were investigated for the gasket, used to avoid direct contact between glass and steel. Specimens with and without a compression ring laminated between both glass panels were compared. The investigation very clearly demonstrated the importance of gasket design as well as the negative effect of interlayer creep on the performance of the investigated friction-grip connection.

Cavitation effects on textured compression rings in mixed lubrication

Cavitation effects on textured compression rings in mixed lubrication

Fast Cyclic Compression Installation for Conversion of Light Hydrocarbons

A description of the installation for adiabatic compression in a cyclic process is presented here. Experimental results of conversion of light hydrocarbons by this process are given. New structural design solutions and ceramic coatings obtained by applying the technology of microarc oxidation were used in the compression unit of the chemical compression reactor (the piston–cylinder assembly). This allowed us to forego the use of compression rings and lubricant, to achieve a high compression ratio, and to obtain the pressure and temperature required in the reaction zone for oxidative conversion.

Surface-specific flow factors for prediction of friction of cross-hatched surfaces

The paper presents a combined numerical and experimental study of generated sliding friction at low sliding speeds and high load intensity, typical of the top compression ring–cylinder liner conjunction at top dead centre in the compression stroke of high performance race engines. Frictional losses in the transition from compression to power stroke represent a significant portion of cyclic cylinder losses. The cylinder liner is cross-hatch honed with non-Gaussian topography, including larger groove features and a fairly smooth plateau roughness. Surface-specific flow factors are derived to closely represent the actual real rough conjunction. The predictions closely agree with the representative reported precision tribometric study of measured friction.

Mixed lubrication of piston compression ring with deformed cylinder liner during warm-up of spark ignition engine

Emerging clearances caused by out-of-round cylinder bores alter the tribological performance of piston compression rings. This change in performance intensifies during engine warm-up. To analyze the development of tribo-characteristics, a 2D mixed lubrication model is considered in the simulation of piston ring conjunction with a distorted bore during the entire warm-up period of a four-stroke spark ignition engine. Piston ring axial dynamics and conformability analyses are incorporated in the simulation. Oil film thickness, frictional loss, asperity interaction, and lubricant flow to the combustion chamber are investigated. The effect of the magnitude of bore distortion on ring conformability, oil transport, and energy loss per warm-up is also evaluated. Variations in oil transport and energy loss per warm-up per unit change in bore distortion are subsequently analyzed. Results show that despite the high film thickness, frictional losses remain substantially high during the initial warm-up phase. An uneven lubricating film resulting from bore non-circularity reduces this energy loss, but drastically increases the already augmented oil transport during the cold engine start-up. The temperature-dependent variation in performance is sensitive to bore distortions.

Cable Erection of Krasnodar Stadium Suspended Roof

The Krasnodar Stadium, hosting FC Krasnodar of Russian Premier League, has a capacity of 36.260 seats. The stadium roof is designed as a typical looped cable roof containing two compression rings and one tension ring. The roof is covered by a folded membrane, the inner perimeter towards the pitch is built as a 7m wide glass roof to improve the natural lighting of the pitch. The radial cables run along 56 axes from compression to tension rings. All cables forming the tension ring are connected by couplers, thus creating round cables. Redaelli took part in the project providing the supply, installation and big lift of 416 steel ropes, for a total mass of 500 tons including sockets and cast ring connectors.