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The paper presents results of research performed to find the most suitable cylinder-liner-lubricating-oil feed rates for lubrication of long-stroke, slow-speed marine engines to reduce cylinder oil consumption and reduce engines' maintenance costs. Obtained research data can be used to increase engines' reliability, reduce operational costs of the vessels, and improve energy efficiency on board ships. Using analysis of under-piston scavenge drain oil, research has been performed to find the relationship between various engines' operational factors and the wear intensity of cylinder liners and piston rings. Prediction models of the most suitable cylinder oil feed rates depend on the brand of cylinder oil and fuel actually in use, and the sulfur content in the fuel oil Verified in operation, the presented practical model can be used by engines' operators to set up cylinder oil feed rates with satisfactory cylinder liner and piston ring wear rates and cylinder oil consumption. It is underlined that analysis of scavenge drain oil properties gives an answer whether reduction of the cylinder oil lubricating feed rate is possible, information about the quality of lubrication of cylinder liners and piston rings, and can be used as a maintenance tool to maintain the serviceability and reliability of marine slow-speed engines. [ABSTRACT FROM AUTHOR]

Numerical simulation of hydrodynamic processes accompanying the formation and propagation of vortex rings produced by a piston generator has been performed. The influence of the characteristics of a vortex ring on the transfer of a passive impurity is considered. Numerical calculations were carried out using nonstationary Navier– Stokes equations and adaptive grid structures. The geometric and dynamic characteristics of the vortex ring are obtained which correspond to the self-similar law of its dynamics and experimental data. [ABSTRACT FROM AUTHOR]

The oil storage effect of textures is beneficial for lubrication performance under starved lubrication. When the larger of the two surfaces in friction pairs is textured, the moving textures should be considered because the boundary conditions are transiently changed at each moment. This is especially for the cross‐hatched textures, which are manufactured on the cylinder liner while not on the piston ring. However, it means that the calculation cost will be very expensive for engineering friction pairs because the required calculation scale is very large and the required time step is very small. So the dynamic characteristics of moving textures on engineering surfaces are normally neglected in the existing researches. In this study, a starved lubrication model of the piston ring‐cylinder liner (PRCL) system is established considering the oil storage effect, local hydrodynamic effect and dynamic characteristics of the moving cross‐hatched textures. To speed up the calculation, an efficient parallel algorithm is developed. The results show that there is a significant difference in minimum oil film thickness (MOFT), wear load and oil film boundaries between stationary textures and moving textures, so the moving textures should not be simplified. This is helpful to find a better design of textures for engineering friction pairs. [ABSTRACT FROM AUTHOR]

The objective of this study is to characterize and understand the evolutionary processes that the effect of surface texture has on the tribology properties of the Chrom-Keramik-Schicht (CKS) piston ring/cast iron cylinder liner system under high intensifying. Surface dimple textures with an area density of 3–9% were prepared on the CKS piston ring by YAG laser, and the antifriction and antiscuffing properties were tested on a reciprocating test rig at 200 °C and 80 MPa. The minimum friction coefficient and wear loss were both obtained at the area density of 5%, compared with the untextured cylinder liner–piston ring (CLPR). The friction coefficient decreased by 0.013 to 0.086, and the wear loss for the piston ring and cylinder liner decreased by 41% and 46%, respectively. The sharp decrease of the friction force induced by surface polishing of the cylinder liner is taken as a sign to indicate the cylinder scuffing under starved lubrication. The scuffing time for the piston ring/cylinder liner system reached a maximum value of 18 min at an area density of 3%, which is extended about 41% compared with that of the untextured piston ring. The dimple surface texture on the piston ring could extend the scuffing time by delaying the occurrence of polishing behavior on the surface of cylinder liner. It is found that the retarded surface polishing played a major role for the modification of the antiscuffing property of the friction pairs according to the friction curves and wear morphologies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper contains the results of the transient flow of piston ring conjunction of a single-cylinder motorbike engine. Calculations of piston ring forces, asperity contact and gas blow-by are determined in computational fluid dynamics. The stochastic model of Greenwood-Tripp approach is used to predict the load of asperities. The hydrodynamic friction is also calculated by means of computational fluid dynamics including the multi-phase flow through Rayleigh–Plesset equation and a discrete phase model for simulating nanoparticles interaction. The major contribution of this analysis is to specifically investigate the impact of the lubricant with additives and the corresponding transient effects such as hydrodynamic pressure, cavitation and lubricant film within the contact. The results indicate that to investigate realistic mechanisms of multi-phase flow in piston ring-liner contact, the contribution of nanoparticles should be matched with the type of lubricants. In addition, this advanced computational fluid dynamics model showed that nanoparticles motion is important in reciprocating line contacts, leading to lower boundary friction in the order of 8.8% than a simple model where cavitation and nanoparticles are ignored. [ABSTRACT FROM AUTHOR]

A multi-objective optimization study and sensitivity analysis of a SI engine piston-rings pack using dynamics analysis software (AVLExcite Piston&Rings) and optimizer software (modeFRONTIER) are presented. The effects of changing the piston rings' tangential force and face profile on the oil and gas flow behavior inside the piston-rings pack are investigated by calculating the lubrication oil consumption, blow-by, and power losses. The feasibility of the simulation model was determined by comparing it to empirical data obtained from experimental testing of the engine to estimate the amount of oil consumption and blow-by gas flow. Using the statistical modeling algorithm SS-ANOVA, multi-objective optimization investigates the individual and interaction effects of the three rings' tangential forces. This method significantly reduces the time and cost required to find the optimal design, an approach not reported in previous studies. The results showed a strong correlation between simulation and experimental test results, indicating an acceptable match during model validation. Furthermore, the predictions show that tangential forces affect sealing performance; thus, modifying the tangential force resulted in a 30% reduction in oil consumption and less than a 0.8 percent increase in friction. Furthermore, the LKZ oil control ring model efficiently reduces oil consumption by 25% while slightly increasing friction (about 10 percent without face coating). [ABSTRACT FROM AUTHOR]

This study investigated the wear behavior of cylinder liners and piston rings under various speed-load conditions through systematic wear tests. The wear mechanism of the cylinder liner under different parameter combinations was analyzed using a scanning electron microscope (SEM), X-ray energy dispersive spectrometer (EDS), and transmission electron microscope (TEM). The cylinder liner was categorized into various wear states based on wear rate and the evolution of wear mechanisms. A speed-load wear map of the cylinder liner was developed using the partition fitting method. The results demonstrate that the tribofilm on the cylinder liner plays a significant anti-wear role in the mild wear state, reducing the wear rate of the substrate material. The transition from mild to severe wear involves an intermediate stage where cracks form independently. Severe wear conditions are primarily characterized by delamination wear. Furthermore, lubricating oil that infiltrates the crack gaps forms a tribofilm, accelerating the propagation of fatigue cracks and the generation of debris. [Display omitted] • The wear rule of the cylinder liner and piston ring under varying speed-load was studied. • The wear process of the cylinder liner was divided into different wear states. • The wear state conversion mechanism of cylinder liner was clarified. • The wear model of the cylinder liner was established by the partition fitting method. [ABSTRACT FROM AUTHOR]

With increasing demands for friction reduction and wear resistance in heavy-duty diesel engines, the design of surface textures in reciprocating contact zone of the cylinder liner and piston ring (CLPR) has been a major concern. Through designed orthogonal tests for optimizing the double-sided textured CLPR, a maximum reduction in the friction coefficient of 12.63 % was achieved for the superior double-sided textured CLPR compared to the untextured surface, with corresponding reductions in the wear depth of the cylinder liner and piston ring of 16.73 % and 18.25 %, respectively. The relative position variation between the CLPR microtextures at the sliding contact area caused different stress values and stress distribution. Compared to the inferior double-sided textured CLPR, superior double-sided textured CLPR with lower stress concentration and symmetrical distribution within the contact area generated smoother and flatter worn platforms and non-spalling dimple edges with less abrasive wear. It can provide some insight into the matching design of double-sided CLPR surfaces under heavy load conditions. • Electrolytic double-sided microtextures were prepared on cylinder liner and piston ring. • Geometric parameters of double-sided microtextures were optimized with orthogonal tests. • Double-sided microtextures with balanced stress distribution inhibited spalling and scratches. [ABSTRACT FROM AUTHOR]

In this simulation-based research, the authors investigate the influence of the contacting profile and its tilting orientation of original compression piston rings on their hydrodynamic properties in internal combustion engines (ICEs). They employ a systematic approach, detailing the computational framework and simulation parameters. Three different original piston rings belonged to the same engine are used for the simulation and corresponding experimental validation in this publication. Results and discussions highlight the directional dependence of hydrodynamic conditions, with distinct differences for individual rings. Original smoothed profiles are compared with substitute geometries like quadratic parabola and circular arc fits. The research contributes insights into the complex dynamics of compression rings in ICEs, providing a foundation for optimizing ring profiles for enhanced hydrodynamic properties. • Implementation of an EHD simulation of the piston ring - cylinder liner contact in the Open Source software Netgen/NGSolve. • Use of original measured ring profiles for the simulation and experimental validation. • Investigation of the influence of the piston ring profile on the lubrication film formation. • Analysis of piston ring tilting angle on the lubrication film formation. [ABSTRACT FROM AUTHOR]

• PTFE and carbon fibre improved piston ring composite materials show improved tribological behaviour in the piston ring tribocontact in the hydrogen compressor application. • Wear mechanism of the tribosystem was investigated in detail using FIB, TEM and EDX to analyse distribution of elements in a depth profile. • Wear mechanism changes to less wear with increased material deposition, in the investigated material pairings (steel vs high strength polymer composites). • Deposition can be optimized by adding PTFE into the polymer composite. The transistion to renewable energy production is a main component in achieving the climate targets defined in the 2015 Paris Agreement. Power-to-gas concepts, where electrical energy is stored as hydrogen gas, require the design and operation of state-of-the-art reciprocating compressor technology to realize high pressure ratios and high volumetric flow rates for gas supply demands. The main challenges in designing machines suited for these operating conditions are high thermo-mechanical stresses acting on the piston sealing rings. High shear loads and minimal ring gap sizes demand material pairings with excellent wear resistance and sliding properties. This work investigates the life cycle limiting wear mechanisms present in the piston compressor and develops advanced concepts for piston rings in cylinder tribo-contacts. PI and PPS polymers reinforced with carbon fiber were modified with dry lubricating PTFE to fulfil the requirements of this highly stressed tribo-system. Tribo-tests were performed against steel countersurfaces with a linear oscillating tribometer in pin-on-plate configuration. The failure mechanisms were analysed utilizing scanning electron microscopy on cross-sections cut into the depth of the countersurface material with focused ion beam milling. 2D scanning transmission electron microscopy mapping supported by energy dispersive X-ray spectroscopy were performed to analyze the depth profile of the deposited tribo-layer elements on the wear track. [ABSTRACT FROM AUTHOR]

• Tribological behavior of both combustion chamber geometries was investigated. • Significant reductions in soot emissions were found for NCC geometry compared to SCC. • Especially at the operation end, the presence of elements such as Fe and Al increased engine wear. • SEM/EDX analysis of the piston rings showed a significant difference between the first and second rings for the two geometries. It was found that the wear lines were deeper and more visible in the standard geometry than in the new geometry. Changes to the piston bowl geometry directly affect engine performance, exhaust emissions, combustion characteristics and air/fuel mixture formation. In this study, a new combustion chamber (NCC) geometry for a single cylinder direct injection diesel engine is presented, and experimentally compared with the standard combustion chamber (SCC) geometry. Each combustion chamber was fitted to the engine and performed long-term test for 100 h. The effect of combustion chamber bowl geometry on piston rings and lubricating oil was investigated. Firstly, soot was measured in the engine, and the NCC geometry reduced soot emission by approximately 12.32 % compared to the standard bowl geometry type at part load. With the NCC geometry, homogeneity fresh charge and flame propagation were achieved by providing wall-guided flow. The tribological effect of bowl geometry on the lubricating oil was investigated. In the oil analysis, Al,Ca,Co,Cr,Cu,Fe,Mg,Mn,Mo,Ni and Zn elements were higher in the SCC geometry than in the NCC geometry. Especially at the end of the 100th hour of operation, the presence of elements such as Fe and Al showed an increase in engine wears. The lubricating oil kinematic viscosity for SCC was 111.9 mm2/s at 40 °C and 127.9 mm2/s for NCC. In the new geometry, the flash point temperature of the lubricating oil was measured as 232 °C, while this value in the standard geometry was measured as 222 °C. This showed that the volatility and degree of contamination of the oil was lower with the new geometry. SEM/EDX analysis of the piston rings showed a significant difference between the first and second rings for the two geometries. The wear lines in the standard geometry were found to be deeper and more visible than in the new geometry. [ABSTRACT FROM AUTHOR]

• The real-time coupled tribo-dynamics calculation of piston-cylinder liner and piston ring-cylinder liner is realized. • Modeling is based on unified global coordinates, making the coupling and solution between lubrication and dynamics more efficient. • The influencing mechanism of piston deformation on the ring tribo-dynamics properties is given. • The effect of the assembly position on the ring tribo-dynamics properties is revealed, and the worst assembly position is discovered. Research on the tribo-dynamics of the piston-cylinder liner (PCL) and piston ring-cylinder liner (PRCL) is vital due to their role in generating over 50 % of total engine friction loss and the impact on carbon emissions. Traditional studies, hindered by the structural and functional differences between pistons and rings, required separate simulation models, often overlooking crucial coupling characteristics. A unified tribo-dynamics modeling method for the piston-ring-liner (PRL) system is proposed in this paper, integrating the ring pack and piston into one multi-body system. This article models with global coordinates, unifying the form of governing, film thickness, and load equations of discontinuous lubrication domains for more efficient dynamics-lubrication coupling. The described method is applied to a marine engine, and the new tribology characteristics discovered after calculations are exhibited. It shows how piston deformation impacts ring tribology, indicating that increased profile height reduces the squeezing effect by allowing more ring movement. Additionally, ring assembly position significantly affects tribology parameters' circumferential distribution. Installing the ring with the end gap facing the piston pin side should be avoided, as it maximizes the negative impact of elastic force and secondary motion, deteriorating lubrication. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on the characteristics of engine working conditions, the ring/liner reciprocating friction tests were conducted to research the effects of three typical cylinder liner surface topographies (honed surface, large dimple texture and small dimple texture) on the tribological performance of production piston ring pack. The experimental results demonstrated the effects of liner textures are different between three kinds of piston rings: for the barrel‐shaped ring‐liner pair, the large or small dimple texture has its specific working condition; for the taper‐faced ring‐liner pair, the oil scraping efficiency and oil distributing stability can be improved by texturing small dimples on liner surface; while the dimple textures have little influence on the friction force of oil control ring‐liner pair. In addition, texturing micro‐dimples on liner is conducive to reducing the surface wear caused by abrasive wear, and the anti‐wear effect of small dimple texture is much better. [ABSTRACT FROM AUTHOR]

In every process of the manufacturing and service industry, there exist variations. Quality practitioners desire to avoid these variations to maintain and improve the quality level of products and services. The control charts are commonly applied under the assumption of normality, however, when the underlying assumption is not valid, nonparametric (NP) control charts become alternatives for quality engineers and practitioners. In this article, an NP progressive mean control chart based on Wilcoxon signed-rank statistic (NPPM-SR) has been proposed for prompt detection of shifts in the process target. The NPPM-SR chart proves in-control robust and much effective performance in spotting deviations in the process location for heavy-tailed and skewed distributions. The run-length distribution performance of the proposed NPPM-SR chart for some selected continuous symmetrical distributions; normal, t, Laplace, logistic and contaminated normal distributions are evaluated under zero- and steady states using average run length (ARL) and some other run-length characteristics. The proposed NPPM-SR chart is compared with existing NP counterparts such as; NP exponentially weighted moving average sign (NPEWMA-SN) chart, NP EWMA based on Wilcoxon signed-rank statistic (NPEWMA-SR) chart and NP cumulative sum based on Wilcoxon signed-rank statistic (NPCUSUM-SR) chart. For the comparative analysis, the parametric competitors such as; traditional EWMA (EWMA- X ¯ ) chart and Double EWMA- X ¯ (DEWMA- X ¯ ) control charts are also included in this study. The proposed NPPM-SR charting scheme under zero-state has been found efficient as compared to steady-state and its existing counterparts. The piston rings data and simulated data have been taken for the illustration of the proposal. [ABSTRACT FROM AUTHOR]

This paper is respecting the evaluation of stress distribution on IC engine (four-stroke) piston ring and analysis of finite element by using FEA software. The purpose of this analysis is to calculate strain for SiC reinforced ZrB2, A360, A2618 and deformation resulting through ring elastic pressure and gas pressure. The total deformation and strain on the piston ring have been obtained in this project. The characteristics of such vibrations are analyzed with the help of solid works software and analysis of finite element is performed on the Ansys workbench software. The material used is Silicon Carbide reinforced Zirconium Diboride (SiC reinforced ZrB2), Aluminium alloy (A360), Aluminium alloy (A2618). This is a ceramic matrix composite (CMC) which has good safety factor and lower cost. The experiment is conducted on three types of composites to evaluate the strain on SiC reinforced ZrB2, A360, A2618 resulting from the total deformation and strain. Compressive strength has also been analyzed for the structural model of the piston ring. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The friction and wear properties, as well as the scuffing resistance, of different piston-ring coatings mating with a chrome-plated cylinder liner were investigated. Interrupted wear tests under the lubricant starvation condition were conducted to examine the wear behavior of Cr-diamond coating (GDC) and diamond-like coating (DLC). The results indicated that the DLC coating had outstanding tribological properties (small coefficient of friction and wear loss) at 150 °C, while the GDC coating exhibited better performance at an elevated temperature (240 °C). The DLC coating had a better scuffing resistance; no material adhesion occurred for 70 min under the unlubricated condition. The interrupted wear behaviors revealed that the scuffing process of the GDC coating involved the consumption of lubricant oil with relatively stable wear, a reduction in the friction force, and the occurrence of scuffing, in sequence. In contrast, although the friction force also increased after a short period of weak friction, no scuffing was observed. This is attributed to the formation of a mixed oxide and graphitic C tribolayer. [ABSTRACT FROM AUTHOR]

This article describes a technology for the thermomechanical treatment of stainless-steel piston rings. This technology makes it possible to obtain rings with an optimal combination of plastic and strength properties that is essential for piston rings. The following thermomechanical treatment is suggested for piston rings manufacturing: quenching at 1050 °C, holding for 30 min and cooling in water, then straining by the HPT method for eight cycles at cryogenic temperature and annealing at a temperature up to 600 °C. The resulting microstructure consisted of fine austenite grains sized 0.3 μm and evenly distributed carbide particles. Annealing above this temperature led to the formation of ferrite in the structure; however, preserving the maximum fraction of austenitic component is very important, since the reduction of austenite in the structure will cause a deterioration of corrosion resistance. The strength properties of steel after such treatment increased by almost two times compared with the initial ones: microhardness increased from 980 MPa to 2425 MPa, relative elongation increased by 20%. The proposed technology will improve the strength and performance characteristics of piston rings, as well as increase their service life, which will lead to significant savings in the cost of repair, replacement and downtime. [ABSTRACT FROM AUTHOR]

Historically, the engine crankcase has been made of gray cast iron due to that material's high machinability, damping ability, thermal conductivity, and sensible cost. Despite these advantages and the long-term use of gray cast iron, the vehicle manufacturers predominately use cast aluminum as material of choice for the engine block due to aluminum's density being almost a third of that of gray cast iron, and the aluminum engines have the same durability as gray cast iron while weighing considerably less. However, due to the low wear resistance of aluminum, efforts are needed to improve internal working surfaces such as the use of cast iron cylinder liners or the application of a protective coat is applied to the aluminum surface to increase its resistance. The purpose of this study is to examine which ring materials have the lowest friction with the Twin Wire Arc (TWA) aluminum cylinder liner. An Ansys simulation model accomplishes the experimental work. The steel ring material obviously had the lowest friction with twin wire arc spray aluminum cylinder liner as opposite to the cast iron material which was the worst. [ABSTRACT FROM AUTHOR]

A piston-rings-cylinder (PRC) assembly determines the blowby, engine oil consumption, and friction and wear processes accompanying the system's operation. Thus, it is crucial for the whole IC engine efficiency and lifetime. A lot of research effort is put into increasing the performance of this complex and highly dynamic system. Advanced, comprehensive models play an important role in understanding and improving the PRC system. In the presented work, the effect of load on the operation of the ring pack of an automotive gasoline engine is analyzed. A comprehensive model that covers the gas flow through the crevices of the PRC system, ring displacements in the groove, and ring lubrication was used for this analysis. The results of the simulations show that the local thickness of the oil film, especially near the piston top dead center is compared to the height of the combined surface roughness of a cylinder liner and piston rings, and friction-related asperity contact strongly increases as the engine load increases. The simulations also show that the engine load affects the axial displacements of the rings in the grooves but practically does not affect the thickness of the oil film left by the ring pack on the cylinder liner. [ABSTRACT FROM AUTHOR]

This paper describes the design and execution of a wavemaker system (piston type) in the Dokuz Eylül University Hydraulic Laboratory flume to perform hydraulic model tests using regular and irregular waves. In this study, we will focus on generating the irregular waves from the target JONSWAP spectrum using an adjusted random phase method; also, the control software of the wavemaker is described. An identical numerical channel wave to the physical flume was modeled to compare and observe the irregular wave profile using Flow 3D, one of the advanced computational fluid dynamics (CFD) software. The paddle movement was validated by comparing the experimentally converted irregular wave surface elevations to the wave spectrum to the numerical models of several waves. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to explore the thermal load change of the diesel engine piston under transitional conditions, and the influence of the position of cooling gallery on the heat transfer characteristics of the piston. An off-road high-pressure common-rail diesel engine is chosen as the research object. The sequence coupling method is used to establish the fluid–solid coupling heat transfer simulation model of the piston-gallery under the transition conditions of cold start, urgent acceleration and rapid deceleration. The Pareto optimization algorithm is introduced to optimize the position of the cooling gallery to reduce the maximum temperature and maximum thermal stress of the piston. The results show that the maximum temperature of the piston can be reduced by reducing the distance between the cooling gallery and the throat area under the maximum torque condition, and that the maximum thermal stress of the piston can be reduced by reducing the distance between the cooling gallery and the throat area or by increasing the distance between the cooling gallery and the ring area. Compared with the original design, the maximum temperature of Design A decreases by 1.28 °C while the maximum thermal stress decreases by 2.07 MPa. The maximum temperature and maximum thermal stress of Design B decreases by 0.22 °C and 0.5 MPa, respectively. The maximum thermal stress of Design C decreases by 2.67 MPa when the maximum temperature increases by 1.15 °C. The maximum change in temperature of the three typical designs and the original design of the piston throat under cold start, urgent acceleration and rapid deceleration conditions reached 207.29 °C, 136.78 °C and 9.89 °C, and the maximum change of thermal stress reached 8.62 MPa, 20.43 MPa, 4.08 MPa, respectively. The maximum change in temperature of the piston first ring groove under cold start, urgent acceleration and rapid deceleration conditions reached 172.00 °C, 83.52 °C and 7.36 °C, and the maximum change in thermal stress reached 22.96 MPa, 43.10 MPa, 5.72 MPa, respectively. The conclusions obtained can provide boundary conditions for further study of the thermal load change law of the same type of pistons, and also provide a theoretical basis for diesel engine piston structure optimization and the performance improvement. [ABSTRACT FROM AUTHOR]

—Hydrodynamic lubrication is simulated under the contact conditions that the direction of contact velocity reverses with a sudden high applied load in the contact of piston top ring and cylinder liner. Hydrodynamic lubrication film formation and pressure between piston ring and cylinder liner at the top dead center (TDC) location are investigated in detail because most friction loss and wear damage happen at this location due to the thin-film thickness resulting from the slow-down and reversal contact velocities as well as high applied load. The surface roughness on the cylinder liner by the honing process that is similar scale to the lubrication film thickness at TDC location is considered. Around the TDC location, laser surface textured (LST) surface that is larger scale than the surface roughness is designed for the favorable film formation. These two surface roughness parameters are simulated to study the effects of favorable film formation and less frictional loss of piston top ring at TDC location where most of damage and friction loss occur. Frictional power loss and minimum film thickness of the cylinder surfaces of the honed roughness are compared with those of patterned designs. [ABSTRACT FROM AUTHOR]

Tribological interactions between the piston groove and ring in combustion engines have a significant influence on mechanical friction losses. Based on the analysis of the distribution of forces acting on the piston, the conditions for the friction tests were selected. The research was carried out on composites reinforced with silicon carbide (SiCp), glassy carbon (GCp), and a hybrid mixture of particles (SiCp + GCp). Tribological tests were carried out under extremely unfavorable dry sliding conditions using a pin-on-block tester. The friction of coefficient and wear values of the matrix alloy, composites, and iron were compared. Profilometry was used to perform quantitative and qualitative analyses of the wear tracks formed on the tested surfaces. The effect of the presence of reinforcing particles on the geometry of working surfaces was also evaluated. The obtained results show that AlSi12CuNiMg/SiCp and AlSi12CuNiMg/SiCp + GCp composites provided satisfactory effects towards stabilizing the friction coefficient and reducing the wear of tested tribological couples. This may provide a new solution dedicated to an important system, which is the piston groove/piston ring in diesel engines. [ABSTRACT FROM AUTHOR]

The condition monitoring of piston–cylinder‐reciprocating machinery usually relies on vibration and acoustic sensors installed on the outer surface of cylinders. However, vibration and acoustic signals are susceptible to external interference from other accessories, and require an external power supply, which limits its widespread application. Herein, based on the lateral sliding mode of triboelectric nanogenerator (TENG), a novel reciprocating device with condition‐monitoring and self‐powering capabilities is proposed, called piston–cylinder triboelectric nanogenerator (PCTN). The effects of different factors, including mean piston speed, number of piston rings, materials of piston ring and cylinder, on the output characteristics of PCTN are investigated, respectively. Two typical fault cases, that is, piston ring missing and coil fracture, are investigated to verify the condition‐monitoring capability of PCTN. Piston ring missing faults can be effectively identified based on the variations in peak and root‐mean‐square (RMS) values of short‐circuit current (Isc). Coil fracture faults can be identified and located by analyzing changes in time–domain curve and time–‐frequency spectrum of Isc. Herein, a theoretical and experimental basis for the widespread application of PCTN in reciprocating machinery is provided. [ABSTRACT FROM AUTHOR]

This current study deals with the tribological property of piston rings of cast iron coated with (CrC)X+(Mo+Fe)+NiCrX alloy with plasma spray coatings. The sample coating was prepared in increasing CrC composition from 10% to 50% in the interval of 10% by keeping Mo+Fe composition constant for each test sample. The coefficient of friction and wear rate of the deposited coating was studied with constant load and varying CrC%. With the increase of CrC%, the coefficient of friction decreases at load 50 N, 60 N, and 70 N. The wear rate also decreased with increasing CrC% at each load. For the investigation of Tribological property of coating, Pin-on-Disc tribometer was used. Coating morphology was characterised by SEM, EDS & XRD. It was found that a coating with 30% CrC had a drastic reduction in specific wear rate. [ABSTRACT FROM AUTHOR]

The oil supply at the interface between the top ring and the cylinder liner (TRCL) plays a major role in an internal combustion engines efficiency. In particular, the interface forms a trade-off between the serving of enough lubricant for sufficient lubrication conditions and emissions through subsequent combustion. This can lead to deficient top ring lubrication conditions. In this study, a new developed reciprocating long-stroke tribometer, enabling the variation of oil supply, is used to investigate such application-like starved lubrication conditions of the TRCL interface. With the simulative investigations, a comparison with the fired engine is possible. The performance of diamond-like carbon coatings is compared to standard nitrided piston rings. It was found that the tetrahedral amorphous carbon (ta-C) coatings exhibit up to 31% reduced friction as well as a lower wear under starved lubrication conditions. Simulative investigations show a good correlation between engine friction and tribometer measurements for selected oil supply conditions. [ABSTRACT FROM AUTHOR]

The running-in of cylinder liner-piston rings (CLPRs) is the most important process that must be performed before a marine diesel engine can be operated. The quality of running-in directly affects the reliability of a CLPR. The surface texture of a CLPR has been proven to significantly affect its lubrication performance. In this study, the tribological behavior of a CLPR during running-in is investigated. Three types of surface textures are generated on the CLPR via laser processing: dimple texture on piston rings, groove texture on cylinder liners, and co-texture on both sides. Subsequently, a series of tests are performed on a slice tester. A load of 300 N (1.64 MPa) is applied, and two speeds (50 and 100 rpm) are adopted. The CLPR running-in quality is characterized based on three parameters, i.e., the friction coefficient, contact resistance, and wear topography. Experimental results show that, compared with a non-textured surface, the three types of surface textures mentioned above improved the friction performance during running-in. The lubricant supply capacity of the dimple texture on the piston ring, as a mobile oil reservoir, is stronger than that of the groove texture on the cylinder liner serving as a static oil reservoir. By contrast, the wear resistance of the dimple texture, as a movable debris trap on the piston ring, is weaker than that of the groove texture on the cylinder liner, which serves as a static debris trap. It is demonstrated that the co-texture combines the advantages of dimples and groove textures. Compared with non-textured surfaces, the friction coefficient decreased the most at 100 rpm (44.5%), and the contact resistance improved the most at 50 rpm (352.9%). The coupling effect provides the surface with improved running-in quality by optimizing the tribological performance, particularly at the dead center. This study provides guidance for the tribological design and manufacturing of CLPR in marine diesel engines. [ABSTRACT FROM AUTHOR]

To solve the brake caliper disc brake piston sealing ring in the high temperature, pressure, and changeful, complex working environments, such as vibration failure cause brake short service life, low reliability, in the original brake piston O seal ring and cross section, the research, based on the standard of sealing ring, such as special-shaped seal structure is put forward in order to improve the reliability of the caliper disc brake piston sealing performance. Based on the basic concept of time-varying reliability and the theoretical basis of stress-strength interference model, the time-varying reliability model of the plum blossom seal ring of the brake piston under shear stress failure and leakage failure modes was established. The reliability of the plum blossom seal ring under single failure mode and multiple failure modes is obtained. The results show that under the same conditions, the reliability of the plum blossom seal ring is greater than that of the O seal ring, and its sealing performance is better than that of the O seal ring. [ABSTRACT FROM AUTHOR]

This is the second and final part of a review of the impact of LST on piston rings and cylinder liner tribological characteristics. Part 1 was published in this journal, 2021, 99(5), 231-237, and traced the development of the laser surface texturing process for materials. Part 2 reviews the development and application of the process to piston-cylinder ring liner contact situations. The future directions for automotive tribological research and desirable areas for research goals related to friction, fuel efficiency, emissions are also discussed. The numbering of figures follows on from those in Part 1, and, like Part 1, the complete reference list is given to enable easy concurrent reading of both parts. [ABSTRACT FROM AUTHOR]

This study comparatively investigates the influence of graphite nano-flakes (GNF) and graphene nano-platelets (GNP) additives on the performance characteristics of 4-stroke 3-cylinder gasoline engine (GE) viz., brake power (BP), mechanical efficiency (ME), engine torque (ET), brake specific fuel consumption (BSFC), and piston ring wear in engine oil grade SAE 15W40. The BP, ET, and ME of the engine using 0.1 wt.% GNP + SAE 15W40 and 0.1 wt.% GNF + SAE 15W40 enhanced by 3.7–4.8%, 3.1–6.3% and 2%; and by 1.8–3.8%, 2.3–5.2%, and 1.4% compared to virgin SAE 15W40, respectively. However, the BSFC and emissions were reduced by 1.7–3.8% and 2.0–4.0% for 0.1 wt. % GNP + SAE 15W40 and by 1.2–3.4% and 1–3% for 0.1 wt. % GNF + SAE 15W40, respectively. The 0.1 wt. % GNP dispersed SAE 15W40 showed improved performance of GE than 0.1 wt. % GNF dispersed SAE 15W40 and base oil SAE 15W40. Further, the piston ring wear was also evaluated and observed to decrease using 0.1 wt. % GNP/SAE 15W40. The formation of tribo-film on the wear track of the piston ring resulted in the reduction of abrasive wear and surface roughness, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this study is to build a parametric algorithm combining analytical results and Machine Learning in order to improve the tribological performance of coated piston rings and thrust bearings in mixed lubrication using different synthetic lubricants. The friction models for piston ring conjunction and pivoted pad thrust bearing consider the basic lubrication theory, the detailed contact geometry and the complete lubricant action for a wide range of speeds. The data produced from the analytical solutions are used as input for the training of regression models. The effect of TiN, TiAlN, CrN and DLC coatings on friction coefficient are investigated through multi-variable quadratic regression and support vector machine models. The optimum selection is considered when the minimum friction coefficient is predicted. Smooth TiN2 and TiAlN coatings seem to affect better the ring friction coefficient than rougher steel, TiN1 and CrN coatings using an uncoated or coated Nickel Nanocomposite (NNC) cylinder. Using an NNC cylinder for better durability, the friction coefficients were found to be higher by 31.3−58.8% for all the studied rings due to the rougher surface morphology. On the other hand, the results indicate that pads coated with DLC show lower friction coefficients compared to the common steel and TiAlN, CrN, and TiN applications. The multi-variable second-order polynomial regression models were demonstrated to be 1−6% more accurate than the quadratic support vector machine models in both tribological contacts. [ABSTRACT FROM AUTHOR]

The contact between the piston rings and the cylinder liner is an interface with a strong influence on the tribological behavior and, therefore, directly affects the useful life of the engine components and fuel consumption. Due to this importance, the present investigation carried out an analysis of the effects of dimples and the honing groove in the cylinder liner on the tribological characteristics. A tribological model was developed to study the friction forces, minimum film thickness, and friction coefficient for the present investigation. Similarly, a computational fluid dynamics model was built to determine the dynamic movement of the piston. The validation of the numerical model showed a close similarity with the real behavior of the engine, obtaining an average relative error of 14%. The analysis of the results showed that a 3% increase in dimples' density leads to a 3.79% increase in the minimum lubricant film and a 2.76% decrease in friction force. Additionally, it was shown that doubling the radius and depth of the dimple produces an increase of 3.86% and 1.91% in the thickness of the lubrication film. The most suitable distribution of the dimples on the surface of the cylinder liner corresponds to a square array. In general, the application of dimples and honing grooves in the cylinder liner are promising alternatives to reduce energy losses and minimize wear of engine components. [ABSTRACT FROM AUTHOR]