Piston Ring-cylinder Liner Research Articles

Techniques used to improve the tribological performance of the piston ring-cylinder liner contact

The mechanical assemblies in automotive engines are usually lubricated by a combination of oil and solid lubrication films. Consequently, the significant current challenges for developing the tribological behavior of vehicle engines need the lubricants that conform to different operating conditions by providing mechanisms for reducing friction and wear. This article summarily reviews the techniques used to improve the tribological performance for piston ring-cylinder liner contact and evaluates their effectiveness to provide the most assuring approaches to reduce friction and wear. The objective was to explore the areas where there are openings for further research contributions to achieving an improvement in the piston ring-cylinder contact in automotive engines.

TRIBOLOGICAL PERFORMANCE OF MODIFIED FLOCCULENT GRAPHITE AS LUBRICANT ADDITIVES

In this research, graphite has been found to have excellent tribological properties as a lubricant additive. To reduce high friction and wear in cylinder liner piston ring friction pairs, modified flocculent graphite have been prepared via chemical technology. The morphology and microstructure of modified flocculent graphite were investigated via SEM, EDS, XRD and IR. In this study, varying concentrations (0.1, 0.5, and 0.9 wt.%) within modified flocculent graphite were dispersed at 350 SN lubricant for Gasoline Engine. Suspension stability of the lubricating oils with modified flocculent graphite and graphite as determined by ultraviolet-visible light (UV-VIS) spectrophotometry. The friction and wear characteristics of lubricants containing materials of modified flocculent graphite were evaluated under reciprocating test conditions to simulate contact. The morphology and microstructure of the friction pair tribofilms produced during frictional contact were investigated via SEM, EDS and a 3D surface profiler. The results show that scratching, pits, furrows and adhesive wear took place, respectively, on the worn surfaces of friction pairs. But, modified flocculent graphite showed excellent friction reducing and anti-wear performance and subsequently has great potential for the application of anti-wear.

Synthesis of oil-soluble WS2 nanosheets under mild condition and study of their effect on tribological properties of poly-alpha olefin under evaluated temperatures

Abstract A liquid phase method was adopted to encapsulate tungsten disulfide (WS2) nanosheets with oleylamine (OA) at a relatively lower temperature of 200 °C so as to acquire good solubility in organic lubricant base oil. The effect of OA-modified WS2 nanosheets on the tribological properties of poly-alpha olefin (PAO6) in a wide temperature range was examined with a four-ball machine and a UMT TriboLab test rig in a piston ring-cylinder liner contact mode. Results indicate that the OA-modified WS2 nanosheets added in PAO6 oil are able to improve the tribological properties of the lubricant base oil significantly at elevated temperatures; and they are advantageous over zinc dialkyldithiophosphates in improving the anti-wear ability of PAO6 from room temperature to 300 °C.

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.

Effects of thread groove width in cylinder liner surface on performances of diesel engine

The performance of diesel cylinder liner-piston ring (CLPR) friction pairs with different surface textures are very important and affect the service life, reliability, and economy of diesel engines. The aim of this study was to gain insights into interactions between thread groove surface texture (TGT) and the friction and wear behavior of a marine diesel CLPR. Four kinds of TGT with different widths, including 1, 2, 3, and 4 mm, were designed and machined on cylinder liners and then tested using a four-stroke CLPR friction and wear tester. The cylinder liner pressure, contact resistance between cylinder liner-piston ring, and worn surface morphologies of cylinder liners were obtained to examine cylinder liner performance with different width TGT. Compared with untextured cylinder liners, the experimental results showed that TGT significantly affected tribological behavior and consequently affected sealing performance of CLPR systems. Specifically, 3 mm TGT had the clearest effect on CLPR system performance, as the CLPR antifriction performance showed an average friction reduction of 30.9%, oil film lubrication performance, reflected by contact resistance, increased by 33.3%, and sealing performance improved by 14.4%. These results aided in the understanding of specific applications of surface texture on wear performance in CLPR friction pairs which could be applied in slower sliding long stroke marine engines.

A quantitative wear measurement method on production engine parts: Effect of DLC thin films on wear

The automotive industry is facing worldwide pressure to reduce carbon emission to meet the Paris Accord target of 2 °C increase in global average temperature by the end of the century. One way to reduce carbon emission is to improve fuel economy of cars and trucks. Recent emergence of ultralow viscosity lubricants has shown significant fuel economy benefits. However, the resulting low oil film may cause increased surface contacts and could lead to increased wear. The ability to measure the initiation phase of wear before it accelerates towards failure is an important issue today. Quantitative measurement of wear in engine parts has always been a challenge. In today’s fuel efficient engines, coatings increasingly being introduced into engine component manufacturing, wear metrology of small amount of wear spread over a large area of rough surfaces presents even a greater challenge.This paper describes the development of a quantitative measurement technique to measure mild wear over a relatively large area of rough production engine surfaces. One of the critical engine sliding components is the piston ring vs cross-hatched cylinder liner contact interface. The availability of a quantitative wear measurement technique would allow comparison of various materials, including coated rings, and liner surface treatments. In this study, production rings and liners were obtained from cooperative engine manufacturers under non-disclosure agreements. A reciprocating ring-liner test rig was used to conduct the wear tests, using a newly developed cyclic wear test procedure, sequence of speed and load cycles were used for simulating sliding motions. Mini-cycles (a constant speed with varying loads from 160 N to 240 N) at 120 °C, and at 6 Hz reciprocating frequency were used. An experimental 0 W-16 lubricant, which has gone through engine testing, was used in the wear tests. A dual white light interferometric microscope (Z resolution 1 Å) was used to measure the liner wear. An analytical balance with 1 µg resolution was used to measure the ring segment weight loss. After the wear measurement procedure was established, diamond-like carbon (DLC) coated rings were also used to assess the effect of the DLC on the wear, and the measurement technique. A digital 3D surface topography subtraction technique was successfully developed to measure quantitative wear of the liner. This technique can be used for other wearing engine parts.

Effect of additives on a surface textured piston ring–cylinder liner system

ABSTRACTLaser texturing of the surface is a known approach to improve the tribological performance of mechanical systems. Many studies focused on optimising surface texture parameters for the piston-ring cylinder liner (PRCL) system. However, little attention is given to explore the effect of the textured surface on additive film formation. In the present work, the effect of a laser textured surface on the formation of additives tribochemical films and its impact on the tribological performance of PRCL system is studied. Commercially available steel piston ring and grey cast iron cylinder liner are used as samples to carry out the experiments using linear reciprocating tribometer. Experiments are carried out at 75 N load, 0.1 Hz frequency and 80°C temperature, using polyalphaolefin as base oil mixed with different additives. It is found that dimples are interfering in the formation of tribo-chemical films. However, the hydrodynamic effect of dimples is contributing to the improvement of lubrication performance even in the presence of additives.

Frictional behaviors in piston ring-cylinder liner system of diesel engine with solid particles considered

The abnormal wear of diesel engine cylinder often occurs due to the solid particles introduced along with the gas intake, as well as the product of fuel combustion. The main purpose of this research is to develop an unsteady-state liquid–solid model to predict the dynamic and lubrication behaviors of the piston ring-cylinder liner with the consideration of the surface roughness, operating load, material properties, and solid particles. Based on the Reynolds boundary condition, the unsteady-state liquid–solid lubrication model is solved with finite difference method. The accuracy of such model is verified upon the comparison with experimental results from a reciprocating friction test workbench at different working frequencies. The test uses actual piston ring specimens sliding on segments of cylinder liner to simplify the engine operation. Finally, the model is applied for a four-stroke diesel engine to reveal the effects of particle properties. It has found that particle diameter, concentration and yield strength have some significant influences on piston ring-cylinder liner system tribological property.

Influence of Surface Groove Width on Tribological Performance for Cylinder Liner–Piston Ring Components

Surface groove width is of great significance to the performance of the cylinder liner–piston ring (CLPR) with the different surface textures in marine diesel. However, little is understood about the specific application (e.g., the geometric parameters of surface textures and operating conditions) of surface texture in actual marine diesel engines. To address this issue, different surface groove textures including grooves structures with 1-, 2-, 3-, and 4-mm widths were designed based on previous results related to marine diesel engine applications. A series of experimental tests was conducted in a reciprocation tester, and data on the friction characteristics were obtained under different operating conditions. Comparative studies on the friction coefficients, worn surface features, and oil film characteristics were performed. Results showed that the 2-mm groove structure of the cylinder liner was more favorable for improving the wear performances at low speed, whereas a 3-mm groove structure of the cylinder liner was more suitable for improving the wear performance at higher speeds, though its wear performance needs to be improved under high load. These results help to understand the specific application of surface texture on the wear performance of the CLPR pair.

Tribological Investigations of Silicon Nitride Lubricated by Ionic Liquid Aqueous Solutions

Water-lubricated ceramic components are promising material combinations for tribological applications because they are wear resistant and can exhibit low coefficients of friction under different loads. The aim of the work was to show in model tribological experiments with silicon nitride that the lubricating properties of water can be improved by adding water-soluble ionic liquids (ILs). The geometry used and the experimental parameters were selected to approximately simulate a piston ring–cylinder liner contact. We found that the addition of 1% IL tributyl methyl phosphonium acetate [P4441][OAc] leads to a reduction of the maximum friction work by 58% compared to pure water lubrication and even by 96% compared to oil-lubricated steel. It was shown that suitable running-in conditions and sufficient cooling by the lubricant at an early stage are important prerequisites for achieving low friction and wear values. In addition, the chemical interaction of water and IL with silicon nitride strongly affects the tribological behavior. As increasing demands on sustainability (green tribology) become more important due to environmental aspects, this work provides important insights for the development of novel water-based lubricant systems.

Synergistic effects of electroless piston ring coatings and nano-additives in oil on the friction and wear of a piston ring/cylinder liner pair

To enhance the tribological performance of piston ring-cylinder liner pair in engines, Ni-P-TiN coated piston rings were prepared by electroless plating technology, and novel Fe3O4@MoS2 nanocomposites were used as lubricating additives in oil. The tribological behavior of the coated friction pairs was evaluated on a multifunctional piston ring-cylinder liner tribometer. The results show that the concentration of TiN nanoparticles in the coatings has an important effect on the tribological performances. The coated piston ring-cylinder liner contact presented a mild abrasive wear with the concentration of TiN nanoparticles at 1.5 g/L. The coated piston rings did not increase the wear loss the cylinder liner due to the lubricating roles of TiN nanoparticles and the formation of transfer layer. The friction coefficient and wear loss of the Ni-P-1.5TiN coatings reduced by 23.8 ± 3.1 wt% and 64.3 ± 1.8 wt%, respectively, comparing to that of the Ni-P coating. Compared with nano-MoS2 and nano-Fe3O4, the Fe3O4@MoS2 nanocomposites as oil additives have a better effect on reducing the friction and wear of the Ni-P-TiN composite coating, mainly due to the synergistic effects of the coatings and the nanocomposite additives.

The influence of roughness distribution characteristic on the lubrication performance of textured cylinder liners

PurposeThe purpose of this paper is to investigate the coupling mechanism of the roughness distribution characteristic and surface textures on the cylinder liner.Design/methodology/approachThe cylinder liner-piston ring lubrication model with non-Gaussian roughness distribution surface was proposed in this paper to find the optimum cylinder liner surface. The motored engine tests were carried out to verify the simulation results.FindingsThe calculation and experiment results show that the large negative skewness surface has the optimal lubrication performance in the un-textured liner, while in the textured liner, the small negative skewness surface is more appropriate, which means surface textures couple with small negative skewness surface can improve the lubrication performance.Originality/valueAlthough there are some works related to liner surface roughness and textures, the combine of roughness distribution and surface textures is not usually taken into account. Therefore, this research is different from others, as the present model considers with real non-Gaussian roughness distribution liners.

Laser-induced improvement in tribological performances of surface coatings with MoS2 nanosheets and graphene

To deal with the corrosive property of bio-oil, laser-induced coatings were synthesized on the typical cylinder liner rubbing surfaces. Two nano-additives including MoS2 nanosheets and graphene were introduced into the coatings. The tribological performances of the coated surfaces were tested on a multifunctional cylinder liner-piston ring tribometer. The surfaces before and after sliding were characterized with modern surface analysis technology including Raman spectra, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and etc. The results show that the nickel-based coated surfaces can effectively prevent the corrosion of the bio-oil. In addition, the laser-induced coatings had better antifriction and antiwear performances than the corresponding traditional electroless plating coatings. With the introduction of MoS2 nanosheets or graphene, the tribological performances of the coatings were further enhanced. Laser irradiation increased the concentration of the nano-additives in the coatings and the thickness of the tribo-layers, which accounted for their outstanding tribological performances.

Effect of bio-lubricant on wear characteristics of cylinder liner-piston ring and cam-tappet combination in simulated environment

The present investigation focuses on need of bio-based lubricants which are biodegradable and environmental-friendly along with improved oxidative stability. The global demand for lubricants is expected to increase as the demand for engine oil for new motor vehicle increases with the increase in number of vehicles. The depleting nature of mineral oils and its adverse impacts on environment has raised the attention of scientists towards the utilisation of renewable bio-based lubricants. The increased environmental awareness is a primary driving force for the new technological developments. In the present study, waste cooking oil (WCO) biodiesel is used as a feedstock for blending with lubricating oil as it is the economical source for the production of biodiesel. WCO was chemically modified by transesterification process. The effect of friction and wear behaviour on performance of cylinder liner-piston and cam-tappet in valve train under lubricating condition has been studied using high frequency reciprocating test rig (HFRR) and pin on disc tester (POD). In addition, the investigations of lubricant variants after the test were also carried out with analytical ferrography to analyse the wear debris in the lubricants. The 10% blending of SAE20W40 with WCO biodiesel exhibits improved results in terms of coefficient of friction and wear scar diameter (WSD).

Experimental Study on Wear Performance and Oil Film Characteristics of Surface Textured Cylinder Liner in Marine Diesel Engine

It is of a vital importance to reduce the frictional losses in marine diesel engines. Advanced surface textures have provided an effective solution to friction performance of rubbing pairs due to the rapid development of surface engineering techniques. However, the mechanisms through which textured patterns and texturing methods prove beneficial remains unclear. To address this issue, the tribological system of the cylinder liner-piston ring (CLPR) is investigated in this work. Two types of surface textures (Micro concave, Micro V-groove) are processed on the cylinder specimen using different processing methods. Comparative study on the friction coefficients, worn surface texture features and oil film characteristics are performed. The results demonstrate that the processing method of surface texture affect the performance of the CLPR pairs under the specific testing conditions. In addition the micro V-groove processed by CNCPM is more favorable for improving the wear performances at the low load, while the micro-concave processed by CE is more favorable for improving the wear performances at the high load. These findings are in helping to understand the effect of surface texture on wear performance of CLPR.

Research of the Frictional Characteristics of Piston Ring - Cylinder Liner Based on GT-Suite

Establish the piston ring-cylinder liner frictional model using the software of GT-Suite combine both of the frictional condition and lubrication, analyze and compute the thickness of oil film between piston ring and cylinder liner, the distribution of oil stress, and the force and power of the friction in rated condition. Then, mainly analyze the thickness of oil film and power of friction at the first piston ring under different temperatures of lubrication oil and different speeds. The results indicate that: The lubrication effect at first piston ring is poor, and the consumption of frictional power is high. The frictional power is significantly reduced with the oil temperature increases. However, the thickness of the oil film will decrease with the oil temperature increases, which is bad to the lubricational condition. Considering both of the lubrication condition and the frictional power, the frictional characteristics are better when the oil temperature is maintained at 80-90°C. With the increase of rotational speed, the oil film thickness and frictional power increase, but comparing with the influence on the frictional power, the change of rotational speed has less influence on the oil film.

Modeling and Analysis of the Tribological Evaluation of Bearing Materials under the Influence of Nano Based Marine Lubricant Using D-Optimal Design

The journal bearing is considered to be an important element of all rotating machinery. The journal and bearing are separated by a thin film lubricating oil, thus preventing metal-to-metal contact. In general, the journal bearing is a significant tribological component next to the piston ring-cylinder liner tribo pair in any of the marine diesel engines. The friction and wear of the journal bearing system is reduced by proper lubricating oil. The usage of fuel oil was considerably increased due to the rapid development in marine diesel engine which increases the operating cost. The power of the marine diesel engine is greatly improved by reducing frictional power which in turn rely on the tribological behavior between bearing materials and lubricants combination. In the present study, Response Surface Methodology (RSM) based D-optimal design was used to estimate the tribological behavior of various journal bearing materials (Bronze, AlSn40 and White metal) under the influence of nano based marine lubricants (SN 500 base oil). The pin on disc tribometer was used to estimate the frictional and wear characteristics of the various journal bearing materials lubricated with SN 500 base oil containing various concentrations of nano CuO. The experiments were conducted by selecting a various load and speed as numerical factors and journal bearing materials/nano based marine lubricants as categorical factors to perform the tribological behavior such as frictional coefficient and specific wear rate. From the present study, it was observed that the bronze bearing material with SN 500 base oil containing 0.5 wt% nano CuO showed the minimum frictional coefficient of 0.072 and minimum specific wear rate of 1.54X10-10mm3/Nm as compared with the other bearing materials/lubricating oil combination for a sliding speed of 2 m/s and bearing load of 100 N. Additionally the scanning electron microscopy (SEM) examination was conducted to estimate the worn surfaces of the tested pin (bearing) material, and it is showed that the bronze bearing material lubricated with the SN 500 base oil containing 0.5 wt% nano CuO is smoother wear surface than the other bearing materials/lubricants combination.

Effect of Lubricant contaminated with Waste Ayurvedic Oil Biodiesel on Tribological Behavior of Cylinder Liner-Piston Ring Tribo pair Material

Depletion of fossil fuels and environmental problems are triggering the researches on alternative fuels. Biodiesel becomes very attractive fuel and easy to produce to replace the commercially available petroleum based fossil fuels. The waste management system and processes play a vital attention to the researchers because the utilization of wastes may lead reduction in the original feed stocks used. Waste oils were high pollutant material that needs responsible management. Waste oil will cause more damages to the environment when it dumped into the ground or into water streams including sewers. Among many waste oils (waste cooking oils, waste transformer oils, waste engine oils) the Waste Ayurvedic Oil (WAO) is observes a major attention as alternate fuels utilized. In a year more than one lakh liters of ayurvedic oil getting wasted in India and to dispose the oil becomes very tedious process. In this article we report the utilization of Waste Ayurvedic Oil energy source as biodiesel for compression ignition engines. The WAO had undergone simple transesterification process to convert as Waste Ayurvedic Oil Methyl Ester (WAOME) and the blends were prepared viz., B10, B15, and B20. Additionally, engine lubricating oil (SAE 15W40) was contaminated with a known percentage of prepared biofuel blends in order to simulate the fuel dilution effect. Further the compatibility of cylinder liner/piston ring tribo pair material is analyzed using Pin-On-Disc Tribometer under standard test condition. The disc was made out of engine cylinder liner material (i.e.) AISI-316 and the pin was made out of piston ring material (i.e.) AISI-304. The tribological experiments were carried out in accordance with ASTM G99 with an applied load of 5Kg; sliding speed 300 rpm and for the period of one hour. Under similar experimental conditions, B20 blend exhibited excellent tribological behavior in comparison with the other blends and diesel. The wear surfaces of pin morphology were examined using Scanning Electron Microscopy (SEM). The image gives a positive impact that the compatibility of pin material was good and less wear scars were observed in blend B20 than other blends and diesel. Thus, the results prove that the liner ring pair material of AISI-316 and AISI-304 along with WAOME Blended fuel were adaptable for diesel engines.

Effects of the array modes of laser-textured micro-dimples on the tribological performance of cylinder liner–piston ring

A mixed lubrication model of textured cylinder liner–piston ring was built to investigate the effects of four array modes namely, square array, stagger array, stretching, and shortening along liner axis array of micro-dimples on the tribological properties of cylinder liner–piston ring pair. The simulation results indicate that micro-dimples can enhance the hydrodynamic effects of lube oil, improving the film bearing capability. However, the effects differ significantly under the four dimple array modes: for square array, the cylinder liner–piston ring pair is well lubricated due to the synergistic effects of uniformly spaced micro-dimples that form homogeneous bearing film even around the fired top dead center where the lubrication condition is harsh; while the film of stagger array is the thinnest among the four schemes, which means its lubrication is also the worst. From square array mode, to shortening and stretching along liner axis array, then to stagger array mode, the total friction force of cylinder liner–piston ring shows an upward trend. By utilizing laser surface texturing method, square array, stretching along liner axis array, and stagger array of micro-dimples were textured on the gasoline engine cylinder bores, followed by a set of engine bench tests. The experimental results demonstrate that the engine motored torque of the three array modes increases in turns, which validates that the anti-friction effect of square array is optimal whereas that of stagger array is the most inefficient.

Friction performance of MoDTP and ester‐containing lubricants between CKS piston ring and cast iron cylinder liner

AbstractThe friction performance of MoDTP in the existence of ester was investigated. Tribological experiments were performed on reciprocating test rig between CKS piston ring and cast iron cylinder liner. Experimental results show that ester concentration is a key factor that influences the performance of MoDTP, the competitive effects between MoDTP and ester also vary with test temperature and load, and the “V” shape friction coefficient curve is caused by the change in friction surface states. During friction, when the surface roughness decreased and liner surface is covered by the friction layer, fresh metal is less likely to expose to lube oil, which reduces the activity of MoDTP in the existence of high concentration ester.