Piston Ring Surface Research Articles

Tribofilm distribution and tribological analysis of piston ring-cylinder liner interfaces under realistic engine conditions

The study investigates tribofilm distribution and tribology performance on piston ring-cylinder liner surfaces under realistic internal combustion (IC) engine conditions. By examining the effects of load, temperature, and oil film thickness ratio, the research reveals that the tribofilm is significantly greater on the cylinder liner surface compared to the piston ring surface. The findings highlight that a specific excitation pressure is necessary for tribofilm formation. An oil film thickness ratio of 1.8041 is evaluated as an accurate boundary for tribofilm distribution on the cylinder liner surface. These insights provide valuable data for designing piston ring-cylinder liner interfaces and improving IC engine performance.

Novel Approach to Analyzing Friction Losses by Modeling the Microflow of Lubricating Oil between the Piston Rings and Cylinder in Internal Combustion Engines

This work focuses on the evolution of lubrication wedge shaping in internal combustion piston engines, taking into account liquid microflows on curved surfaces and coating microgeometries. It introduces a new approach to the analysis of friction losses by simulating the microflow of lubricating oil between the surfaces of piston rings cooperating with the cylinder surface. The models used take into account three types of microgeometry and material expansion. Key results indicate that microirregularities with a stereometry of 0.1–0.2 µm significantly influence the distribution of oil film thickness in the phase of maximum working pressure, which is critical for the functioning of the seal ring. The innovation of the work consists of demonstrating that, despite small changes in the friction force and power in the piston rings, changes in the minimum values of the oil film thickness are significant. The work highlights the failure to take into account microgeometry parameters in friction models, which leads to significant errors in the simulation results, especially in terms of oil film continuity and the contribution of mixed friction. The simulations also indicate that advanced geometric models with high mesh resolution are necessary only for the assessment of changes in oil film thickness during the highest pressure increase in the combustion chamber and taking into account various mixed friction conditions. The results suggest significant progress in engine design and performance, confirming the importance of advanced fluid and mixed friction models in piston engine lubrication research.

Synergistic effects of graphene additives and piston ring surface treatment on friction properties of engine oil

The use of nano-additives improves the performance of lubricants by minimizing energy loss due to friction and wear. In this study, tribological properties of cylinder liner-piston ring were improved by modifying monolayer graphene with surfactants. Additionally, surface chemical chromium coating and chemical heat treatment were conducted on the friction surfaces of specially made piston ring samples to further enhance the friction of piston ring. From the comparison of experimental results, the best lubrication performance was exhibited by the use of 0.05 wt% modified graphene nano-lubricant, which reduced the friction coefficient by approximately 31.1% and improved the anti-wear performance by approximately 59.6% compared to the base oil. In addition, the effect of the graphene nano-lubricant on the friction performance of chromium-coated samples was more substantial than that of the chemically heat-treated samples. Under high-temperature and heavy-load conditions, the corresponding friction coefficient was reduced by 15.5% and 34%, respectively, when compared to the base oils. This can be attributed to the porous surface of the chromium-coated sample, which promotes the storage of the graphene nano-lubricant. The results highlight the synergistic effect of graphene additives and piston ring surface treatment on the tribological performance.

Effects of different surface textures on tribological performances of the cylinder liner-piston ring: An experimental study

The tribological performance of internal combustion engines (ICEs) has an important impact on fuel efficiency and power consumption, and the wear of cylinder liner-piston ring (CLPR) system affects the operation reliability. The surface texture of CLPR can significantly improve the tribological performance of ICEs. Aiming at the friction and wear of CLPR, the different textures (dimple, equilateral triangle and square) are generated on the CLPR using laser processing, and the different tests are conducted on the UMT-TriboLab tester. The coefficient of friction, wear topography, surface roughness parameters and profiles are measured. The results show that, compared with the non-textured surface, the dimple texture surface of piston ring or cylinder liner has better tribological performance. If the textures coexist on the cylinder liner and piston ring, the tribological performances are better than single surface texture. Furthermore, the mixed textures can significantly improve the surface lubrication performance and the ability to store abrasive particles, and better surface quality can be obtained at the same operating conditions to enhance the tribological performance. This study can provide guidance for reducing the friction and wear of CLPR system of ICEs, and achieve energy saving and emission reduction of ICEs.

A Mixed Lubrication Model of Piston Rings on Cylinder Liner Contacts Considering Temperature-Dependent Shear Thinning and Elastic–Plastic Contact

This work develops a numerical methodology for predicting the performance of an automotive piston ring system by considering contact and lubrication mechanics. The rough surface contact mechanics and lubrication occurs on a scale much smaller than the size of the piston rings and therefore the key aspect of the model is an algorithm that simultaneously solves the multiple mechanisms at different scales. The finite element method will be used to model the mechanical deformations of the piston ring surfaces at large scales. The quasi-steady state model includes heat generation due to solid and viscous friction. This heat generation will then be used to predict the temperature rise and thermal effects in the lubricant and component. A statistical rough surface method that renders asperities as elastic–plastic wavy surfaces predicts the solid contact area. The modified Reynolds equation will be solved to consider the effects of mixed hydrodynamic lubrication while using flow factors formulated for actual piston and ring surfaces. The lubricant viscosity depends both on temperature and shear rate. This will allow for the regimes of boundary, mixed, and full-film lubrication to be considered. The model predicts friction for various loads and speeds that are then compared to experimental measurements. Although the contacts operate mostly in the mixed lubrication regime, the model and experiments show changes in friction with load, speed, and temperature.

Design, manufacturing, and testing of a laser textured piston ring surface reinforced with a CuCoBe–diamond composite by hot-pressing

A CuCoBe–diamond composite was used to reinforce a laser textured 410 stainless steel piston ring by hot-pressing. Different hot-pressing parameters were used to optimize the sintering process of the CuCoBe particles (P = 25 and 50 MPa, T = 820 and 980 °C, and t = 15 and 30 min). The results showed an increase in the hardness of the hot-pressed samples (50.5% and 48.5% for P = 25 and 50 MPa, respectively). Three textures with different track widths and distances between them were produced by laser on the compression piston rings’ surface. The composite powders were used for the reinforcement of the textures by hot-pressing at the optimized sintering parameters (T = 980 °C, P = 25 and 50 MPa, and t = 15 min). The tribological results revealed that larger texture dimensions led to enhanced tribological performance.

Effect of Groove Texture on Deformation and Sealing Performance of Engine Piston Ring

During the present study, a double groove texture was designed on the surface of a piston ring to improve the sealing performance between the piston ring and cylinder liner. The experimental design method was used to fabricate the test plan according to the groove width, depth, and spacing. By using the thermal–structural coupling analysis method, the finite element analysis of the standard piston ring and the textured piston ring was carried out to simulate the deformation state of the cylinder liner system of the piston ring group during the working stroke. The piston rings with different parameters designed by the test scheme were manufactured by wire electrical discharge machining, and the self-made experiment device carried out the sealing test. The results showed that the groove texture could improve the sealing performance of the piston ring, and the analyzed results demonstrated that the groove texture had little effect on the maximum deformation of the piston ring. Still, it could significantly reduce the minimum deformation of the piston ring group. A piston ring with groove texture would improve the sealing performance and reduce the deformation during the work stroke. During the test, the average deformation of the No.7 piston ring group, with a groove depth of 1 mm, a groove width of 0.5 mm, and a groove spacing of 0.1 mm, was the smallest, about 29.6% lower than that of the standard piston ring group. The sealing performance of the No.7 piston ring group was the best, and the reduction rate of the top gas leakage rate was 52.18%. During the present study, the sealing performance of the piston ring was improved by designing the grooved structure on the piston ring surface, thereby improving the fuel economy and power performance of the engine. The present study could provide a reference for the engineering field to design a piston ring with high sealing performance.

STRUCTURE AND PROPERTIES OF POWDER GAS-PLASMA COATINGS BASED ON NICKEL

The development of modern technology requires a constant increase in reliability and durability of products. Widely used in the practice of domestic and foreign engineering coatings from electrolytic chromium for several hundred hours are triggered, they are unsatisfactorily working on friction and wear at high temperatures. The subject of the study were powder materials based on nickel PG-SR3 and PG-SR4. The work is devoted to the study of the formation of gas-plasma coatings on parts of the cylinder-piston group of internal combustion engines using self-fluxing powders based on nickel, as well as the structure and properties change after coating sputtering, its reflow, subsequent hardening. The purpose of this work is to study powder materials applied to the working surfaces of piston rings by gas-thermal spraying. The object of the study are processes of formation of the structure and properties of coatings from powder materials. The presence in the deposited layer of a solid solution based on nickel, carbide phase, borides of chromium and nickel, chromium silicides is established. The greatest macro- and microhardness is possessed by fused layers containing the greatest number of strengthening phases. The conducted researches and industrial tests allowed to introduce the coating into production.

Structure and properties of powder gas-plasma coatings based on nickel

Problem. The development of modern technology requires a constant increase in reliability and durability of products. Widely used in the practice of domestic and foreign engineering coatings from electrolytic chromium for several hundred hours are triggered, they are unsatisfactorily working on friction and wear at high temperatures. The subject of the study were powder materials based on nickel PG-SR 3 and PG-SR 4. The work is devoted to the study of the formation of gas-plasma coatings on parts of the cylinder-piston group of internal combustion engines using self-fluxing powders based on nickel, as well as the structure and properties change after coating sputtering, its reflow, subsequent hardening. Goal. The purpose of this work is to study powder materials applied to the working surfaces of piston rings by gas-thermal spraying. The object of the study are processes of formation of the structure and properties of coatings from powder materials. Methodology. Plasma sputtering modes were carried out with the following constant parameters: sample rotation speed - 45 rpm, linear speed of sample movement relative to the plasma jet - 18.4 m/min; the diameter of the charge line in the anode nozzle is 2 mm; the distance from the place of introduction of the powder to the cut of the nozzle is 4 mm; the axis of the plasma jet is perpendicular to the axis of rotation of the sample. Radiographically, a multiphase structure is registered in the initial powder. The most fully presented solid solution lines based on nickel and carbide phase Cr23С6 type. But many lines cannot be clearly identified. A match can be found with the main lines of chromium and nickel borides, chromium silicides. The X-ray pattern of the fused layer quite completely coincides with the X-ray pattern of the powder. Chromium carbide lines and the strongest lines of other phases are preserved on the radiograph of the unmelted layer. Preservation of phase lines in the deposited layer without reflow and the layer after quenching indicates that these phases are formed during primary crystallization. This is confirmed by the metallography of the original powder and the original layer. In the structure of the powder, crystals are visible, as well as a dispersed mixture of phases between them. Electron microscopic studies show that in the area of coarse mixtures, oriented areas are observed, in the area of fine mixtures - non-oriented, less dispersed. Results. The presence in the deposited layer of a solid solution based on nickel, carbide phase, borides of chromium and nickel, chromium silicides is established. The greatest macro- and microhardness is possessed by fused layers containing the greatest number of strengthening phases. Originality. Gas-thermal sputtering of powder materials applied to the working surfaces of piston rings is used, which significantly increases their operational properties in comparison with other methods. Practical value. The conducted researches and industrial tests allowed to introduce the coating into production. Conclusions. As a result of the conducted researches on surfacing and heat treatment of coatings made of PG-SR powders, it was confirmed that the best properties have fused coatings. For coatings made of PG-SR powders, heat treatment is undesirable, as it deteriorates the structure and properties of the coating.

Experimental analysis of Nd3+:YAG laser-assisted ablation on piston ring surface in an environmentally friendly underwater ambiance

The present work focuses on the nanosecond pulsed Nd3+:YAG laser-assisted ablation on the chromium-coated piston ring surface. The influence of laser pulse energies and the number of laser pulses on dimple size at different ambient conditions such as air, underwater (still condition) and underwater (flowing condition) is studied. An underwater laser ablation setup was developed especially to perform underwater laser machining (surface texturing) aimed at avoiding the metallic vapor pollution formed when the laser beam irradiates the target surface. The dimple diameter was maximum with underwater (still condition) followed by air and underwater (flowing condition) for all the corresponding laser pulse energies. The dimple depth was maximum with air ambiance followed by flowing underwater ambiance and still underwater ambiance for all the corresponding laser pulse energies. In underwater ambiances, the re-deposition layer around the dimple was lesser. A part of the melt pool formed in underwater ambiance (still condition) might be dissolved in water. The remaining melt pool is distributed around the dimple as a thin layer. In the case of the underwater flowing ambient condition, flowing water distributes the re-deposition layer further away compared to the underwater still ambiance. The re-deposition layer was substantially minimized around the dimple in both the underwater laser ablation conditions. An increase in compressive residual stress is observed around the dimple formed in underwater laser ablation both in still and flowing conditions. Though the underwater laser ablation (flowing) is more complex, it is found to be more beneficial compared to ablation in air ambiance.

Simulation on the effect of cylinder liner and piston ring surface roughness on friction performance

Considering the surface roughness of piston ring and cylinder liner and deformation of cylinder liner, the friction dynamics calculation model of cylinder liner-piston ring friction pair was established. The effects of top ring, other piston rings and cylinder liner surface roughness on friction performance were analyzed by grouping comparison and Box-Behnken response surface methodology. The calculation results show that when the surface roughness of the piston ring increases, the friction of the asperity increases slightly, the friction of the fluid decreases, and the total friction loss decreases. When the surface roughness of the cylinder liner increases, the friction of the asperity decreases slightly, the friction of the fluid increases, and the total friction loss increases.

An experimental study on fuel energy saving in gasoline engines using GNP as a lubricant additive

This study concentrates on enhancing the performance of the gasoline engine through nano-lubrication. The effect of Graphene nano-platelets (GNP) as lubricant additives in SAE 15W40 oil on the fuel energy consumption and piston ring wear is investigated. GNP-filled lubricating oil boosted the brake strength, engine torque, and mechanical efficiency, whereas the gasoline engine’s brake specific fuel consumption (BSFC) decreased by 5.3%–6.5% due to a 1.7%–3.46% improvement in engine mechanical efficiency. Further, emission results showed that the GNP-filled lubricating oil reduced the emissions of the engine by approximately 3%–6% as compared to the virgin lubricating oil. Furthermore, the piston ring wear was found to reduce by using GNP-filled nano-lubricant. The characterization of the worn piston ring surfaces showed that the tribo-film formed on wear tracks resulted in the improved performance of the engine thereby reducing abrasive wear and surface roughness. From these studies, an attempt has been made to co-relate engine performance characteristics with tribological perception to contribute in the direction of energy savings and fuel economy.

Effects of Ring Pack Friction Heat on Temperature Fields of Piston Set-Liner

To investigate the temperature fields of piston set-liner under the friction heat of ring pack, it is established a friction heat allocation model of ring pack based on the heat transfer theory of semi-infinite body. In this model, the piston ring, lubrication film and liner are treated as a three-layer medium. Furthermore, the distribution model of ring pack friction heat, the unsteady heat-mixed lubrication and friction model of piston ring-liner, and the heat transfer model of piston assembly-liner are also built and coupled with the allocation model to develop a coupled heat transfer model of piston set-liner. Employing the model for 6110 diesel engine, the effects of ring pack friction heat on the temperature fields of piston set-liner are simulated. Numerical results demonstrate that the friction heat allotted to the piston ring, lubrication film and liner accounts for nearly 47 %, 21 % and 32 % of ring pack friction heat, respectively. Due to the effects of friction heat, the maximum temperature rises on the piston ring, piston and liner surfaces run approximately up to 8.5 °C, 5 °C and 5 °C, separately. The established allocation and distribution models related to friction heat in this paper can be applied to any type of piston set-liner and provide the theoretical foundation for the optimal design of piston ring-liner.

Modeling of piston ring wear

A theoretical study of piston ring wear in large two-stroke engines is presented. Piston rings in combustion engines are manufactured with an initially defined shape of the surface contacting the cylinder liner. Further the ring surface working against the cylinder liner is coated with layers of ceramic materials to accommodate the running-in process. Most rings have a nonflat shape (parabolic) when delivered from the ring supplier. After running in which is typically many hours of operation( >1000 h) the ceramic layers are worn and the ring geometry is typically changed significantly by surface wear. It is shown in the present study that the geometry of the worn ring depends on the operation scheme of the engine. Both the load pattern and the order in which the loads are applied influences the final shape of the piston ring surface.

Effects on lubricating oil and piston rings of the different operating parameters in a DI diesel engine

Biodiesel is an alternative fuel that can be produced from renewable sources such as vegetable and animal fats. It is available as fuel in diesel engines. Also, biodiesel fuel is a type of environmentally friendly fuel that is non-toxic, not perishable in nature. A single cylinder, four-stroke, air-cooled, direct-injection diesel engine was used in the study. In the engine is used as fuel of diesel fuel and 10%, COME (Canola Oil Methyl Ester) was added to diesel fuel.The piston rings between the engine parts are critical in term of leakage and lubrication. The fuel used affects engine performance and emissions as well as the surface structure of the piston rings. In this study, Antor 3LD510 diesel engine was run with 10% canola oil methyl ester blended fuel and the engine carried out subjected to long term 150 hours’ endurance test. The engine was operated at 1500 rpm and under part load. SEM (Scanning Electron Microscope) and EDX (Energy Dispersive Spectrometry) analysis of the first, second and third piston rings were performed. As a result, after the operation of the engine with both fuels, the Cr element was largely determined on the surface of the first piston ring and the structure was not disturbed. When the second piston ring surface distribution of COME10 fuel compared to diesel fuel is examined, it is seen that besides the wear elements, combustion and fuel chemistry in the engine are more effective on the surface. The surface of the third piston ring was found to be close to each other after the operating of engine.

Effect of grooved cylinder liner depths on the tribological performances of cylinder liner-piston ring

PurposeFrictions in cylinder liner-piston ring often cause an inevitable loss of energy loss in the diesel engine. This study aims at evaluating the effect of depths in the cylinder liner groove texture on friction, wear and sealing performances.Design/methodology/approachFive depths of groove texture cylinder liners (50, 100, 150, 200, 250 µm) were fabricated, and experiments were carried out using a special-purpose diesel engine tester. Comparative analyses of cylinder liner contact resistances, piston ring wear losses and surface appearances were conducted with respect to different surface textures and applied loads.FindingsUnder no-load conditions, the cylinder liner with a 100 deep thread groove can significantly improve sealing and optimize its lubrication performance. On the other hand, the sealing is highly correlated with the depth of groove and the load within the cylinder liner. Under loaded conditions, the thread groove has less effect on the sealing performance.Originality/valueThe findings can provide feasible basis for the tribological design and production of diesel engines.

Оцінка властивостей зміцнених нанопокриттям маслоз'ємних поршневих кілець оптико-математичним методом

The paper presents an optical-mathematical evaluation of the physic-mechanical properties of the D100 diesel-generator oil scraper piston ring surface hardened by multi-layer ion-plasma nanocoating TiN/CrN. The application parameters of multilayer nanocoating and the sequence of its layers are shown. The values of wear and microhardness of the hardened and serial rings are given. The increase in wear resistance of the hardened product is shown to be 12 times in weight and 4 times in the degree of increase in the size of its friction surface. A method for evaluating properties using the mathematical operators of the laplacian and divergences in their different variations is proposed. A correlation between the properties of the results of tests for friction and wear with using a mathematical description of structure formation was revealed. The minimal difference of the friction zone and the initial surface of the hardened ring, which does not exceed 16 %, is revealed. The difference between the initial surface and the friction zone in the serial ring is shown, which reaches up to 42 % on average in terms of indicators. A substantial deviation of the values of the friction zone mathematical operators of the serial ring from the TiN/CrN hardened by ion-plasma nanocoating was confirmed, which in some cases reaches up to 42 % on average.

Оптико-математический анализ моделирования структуризации упрочнённых поверхностей поршневых колец при эксплуатации

Оптико-математический анализ моделирования структуризации упрочнённых поверхностей поршневых колец при эксплуатации

Influence of positive texturing on friction and wear properties of piston ring-cylinder liner tribo pair under lubricated conditions

Purpose In an internal combustion engine, piston ring-cylinder liner tribo pair is one among the most critical rubbing pairs. Most of the energy produced by an internal combustion engine is dissipated as frictional losses of which major portion is contributed by the piston ring-cylinder liner tribo pair. Hence, proper design of tribological parameters of piston ring-cylinder liner pair is essential and can effectively reduce the friction and wear, thereby improving the tribological performance of the engine. This paper aims to use surface texturing, an effective and feasible method, to improve the tribological performance of piston ring-cylinder liner tribo pair. Design/methodology/approach In this paper, influence of positive texturing (protruding) on friction reduction and wear resistance of piston ring surfaces was studied. The square-shaped positive textures were fabricated on piston ring surface by chemical etching method, and the experiments were conducted with textured piston ring surfaces against un-textured cylinder liner surface on pin-on-disc apparatus by continuous supply of lubricant at the inlet of contact zone. The parameters varied in this study are area density and normal load at a constant sliding speed. A comparison was made between the tribological properties of textured and un-textured piston ring surfaces. Findings From the experimental results, the tribological performance of the textured piston ring-cylinder liner tribo pair was significantly improved over a un-textured tribo pair. A maximum friction reduction of 67.6 per cent and wear resistance of 81.6 per cent were observed with textured ring surfaces as compared to un-textured ring surfaces. Originality/value This experimental study is helpful for better understanding of the potency of positive texturing on friction reduction and wear resistance of piston ring-cylinder liner tribo pair under lubricated sliding conditions.

Femtosecond laser assisted generation of micro-dimples on moly-chrome film for improving its tribology

Femtosecond laser ablation of the moly-chrome deposited piston ring and the influence of laser fluence and number of laser pulses on dimple morphology and geometry were analysed. The increase of laser fluence and pulse numbers beyond 8.4 J/cm2 affected the dimple surface by inducing severe cracks due to heat accumulation. Based on the experimental investigation, the ablation threshold for moly-chrome film was found to be 0.36 J/cm2. Textured surface was formed on the moly-chrome film with laser fluence near the ablation threshold and the tribological characteristics were studied. The piston ring surface was textured with dimple diameter of 100 μm and dimple aspect ratio of 0.2. Effect of different dimple area ratios, such as 2%, 16% and 38% were analysed by reciprocating type tribology testing. The textured surface with 16% dimple area ratio showed a reduction in friction compared to the plain and the remaining textured piston rings.