Piston Ring Surface Research Articles

A Review of Experimental Tribological Investigations of Piston Ring with Laser Surface Textured Dimples

In an automobile internal combustion engine plays a vital role but the efficiencies like thermal and mechanical efficiency of an internal combustion engine is relatively low. It is due to dissipation of large part of its fuel energy in the form of heat loss and loss for overcoming the friction. The friction between the piston ring and cylinder liner pair, rotating engine bearings, valve train etc. is responsible for the power loss in an engine. The attempts to reduce the friction between these interacting surfaces leads to the advantages like reduction in consumption of fuel, high power output, reduction in consumption of oil, reduction in exhaust emissions etc. The reduction of friction as well as wear can be achieved by the proper lubrication and proper surface treatment of the interacting components. The surface modification technique like laser surface texturing (LST) is mostly used for improving the tribological performance of interacting surfaces. Therefore the effect of laser surface textured dimples especially on piston ring surface to evaluate the performance of piston ring and cylinder liner tribological pair should be studied properly. Most of the researches carried out the theoretical study about this but very few have carried out the experimental investigations about the tribological evaluation of ring and liner pair. In this research work the review of the experimental work done for tribological investigation of piston ring with laser surface textured dimples on outer surface of ring and cylinder liner interface by various researchers was carried out. The review work in this paper describes the effect of various dimple parameters like shape, size and depth of dimple, area ratio load, speed etc. on the tribological performance of the ring and liner interface.

Tribotest of engine piston ring/cylinder liner pairs with different nanoparticles added into engine oil

Purpose Wear on internal combustion engines is a loss of material that occurs with the rubbing of the materials in contact with each other and significantly reduces the economic life of the engine. Even the smallest precaution that can be taken to prevent friction and wear in the engines can provide economical savings in very large quantities. Internal combustion engines are widely utilized in modem automobiles. Around 10 per cent of the total fuel energy is dissipated to heat due to mechanical friction, among which 20 per cent is caused by the contact between the cylinder liner and the piston rings. Design/methodology/approach In this study, real piston ring-cylinder specimens were tested with reciprocating tribometer by using five different nanoparticles added to engine oil to investigate their wear and friction behavior. Findings With regard to the experiments, it has been found that the best results were determined by TiO2 and single-walled carbon nanotubes according to boron nitride, multi-walled carbon nanotubes and graphene nanoparticles added to the engine oil, respectively. At the end of the tests, different wear mechanisms have been determined after the surface analyses on the piston ring and cylinder liner surface, and abrasive wear has been observed as the main wear mechanism. Originality/value This paper has an originality with regard to adding different nanoparticles into the commercial engine oil.

Tribological behavior of the boron succinimide on cylinder liner and piston ring surfaces

In this study, tribological performances of two types of anti-wear additive, boron succinimide anti-wear package and ZnDTPs, were investigated in the cylinder liner and piston ring tribological system with a reciprocating tribotest machine. The tribological performances of oils were evaluated in three main contexts including wear rates, surface tribofilm formation and friction. Results showed that NP-3 (boron succinimide containing) lubrication oil which was environment and catalyst friendly, can be an alternative lubrication oil with its tribological performance due to its friction and wear reduction capacity.

Development of Novel Fe-Based Coating Systems for Internal Combustion Engines

Nowadays, combustion engines are the most common way to power vehicles. Thereby, losses occur due to cooling, exhaust gas and friction. With regard to frictional losses, highest potentials for optimization can be found in the tribological system of the inner surface of combustion chamber and piston ring. Besides friction, corrosive stress increases, e.g., due to utilization of exhaust gas recovery. In order to save energy, reduce emissions and enhance the life span of combustion engines, the demand for innovative coating material systems, especially for the inner surface of combustion chamber, increases. This study focuses on the development of innovative iron-based coating materials for the combustion chamber. As a first step, the plasma transferred wire arc and rotating single wire arc (RSW) technologies were compared using 0.8% C-steel as a reference. Subsequently, RSW was used for coating deposition using an innovative iron-based feedstock material. In order to improve wear and corrosion resistance, boron and chromium were added to the feedstock material. After deposition, different honing topographies were manufactured and compared under tribological load. Furthermore, electrochemical corrosion tests were conducted using an electrolyte simulating the exhaust gas concentrate. Especially with regard to corrosion, the novel coating system FeCrBMn showed promising results.

The anti-wear efficiency of boron succinimide on engine cylinder liner and piston ring surfaces

Anti-wear additives are important components of the lubricating oils which protect the sliding surfaces from wear. Researches on developing the non-phosphorus catalysis-friendly anti-wear additive still continue due to government’s regulations. One way to provide non-phosphorus anti-wear additive is boron and sulfur addition to succinimides. In this study, boron succinimide used as an anti-wear additive is compared with ZDDPs in a real engine environment by the engine bench tests. Anti-wear performances were evaluated by microscopic and spectroscopic surface analyses on engine cylinder liner and piston rings after 100-h engine running periods for each anti-wear additive. SEM/EDX and XPS analyses were used to evaluate the tribochemical analyses of tribofilms. SEM and AFM were used to evaluate wear mechanisms on cylinder liner and piston ring surfaces. Results showed that boron succinimide can be an alternative anti-wear additive of ZDDPs from the perspective of anti-wear efficiency.

Investigation on generation of laser assisted dimples on piston ring surface and influence of dimple parameters on friction

In the present work, pulsed laser assisted texturing of the piston ring and its influence on tribology characteristics were studied experimentally and theoretically. Influence of laser wavelengths of 532nm and 1064nm on surface morphology of dimples, formed on the piston ring samples was studied. Subsequently, the laser wavelength of 532nm was used for texturing to generate dimples with different sizes, aspect ratio and area density. Tribological characteristics of textured samples consisting of dimples with size, aspect ratio and area density ranging from 40μm to 130μm, 0.1 to 0.3 and 5% to 38%, respectively were measured experimentally by using reciprocating tribometer. The results showed that the aspect ratio concerning minimum friction varied with dimple size. The results also indicated that the area density of 16% showed low friction compared to other fractions for all the dimple diameters considered for the analysis. A reduction in cylinder liner wear rate of 72% was observed when tested with textured ring sample of the desired dimension compared to the liner tested with the non-textured ring. A theoretical model based on Reynolds equation was used to determine lubricant film thickness between textured surface and a non-textured counter surface. The experimental studies on friction coefficient were then compared with the theoretical results on film thickness.

Investigation of different piston ring curvatures on lubricant transport along cylinder liner in large two-stroke marine diesel engines

A theoretical investigation of the hydrodynamic lubrication of the top compression piston ring in a large two-stroke marine diesel engine is presented. The groove mounted piston ring is driven by the reciprocal motion of the piston. The ring shape follows a circular geometry and the effect of changes in radii is analysed. A numerical model based on the finite difference method in 1D has been developed for solving Reynolds equation in combination with the load equilibrium equation together with flow continuity between the piston ring surface and liner for analysis of the lubricant transport. The cyclic variation throughout one stroke is presented for the minimum film thicknesses at different interesting locations of the piston ring surface together with the friction and the pressure distribution history. The aforementioned parameters have been investigated numerically. The numerical results are presented and discussed.

Piston ring performance in two-stroke marine diesel engines: Effect of hydrophobicity and artificial surface texturing on power efficiency

In the present work, an algorithm for the solution of the Reynolds equation incorporating the Elrod–Adams cavitation model and appropriately modified to account for hydrophobic surfaces has been developed and solved by means of the finite difference method. The algorithm has been utilized to calculate the frictional characteristics of piston rings of a large two-stroke marine diesel engine, and to evaluate their performance, in terms of minimum film thickness, friction force, and power loss over a full-engine cycle, including time-dependent phenomena. For improving frictional behavior, two surface treatments of the piston ring surface have been studied, namely hydrophobicity and artificial surface texturing, which are introduced at appropriate parts of the ring face. Following a parametric analysis, optimal texturing and hydrophobicity design parameters have been identified for operation with maximum value of minimum film thickness and minimum friction losses. The present results demonstrate that substantial performance improvement can be achieved if hydrophobicity or artificial surface texturing is properly introduced at the faces of a piston ring.

Comparison of Heavy-Duty Scuffing Behavior between Chromium-Based Ceramic Composite and Nickel-Chromium-Molybdenum-Coated Ring Sliding against Cast Iron Liner under Starvation

A running-in and starved lubrication experiment is designed to investigate the heavy-duty scuffing behavior of piston ring coatings against cast iron (Fe) cylinder liner using the piston ring reciprocating liner test rig. The scuffing resistance of the piston ring with the chromium-based ceramic composite coating (CKS), and that with the thermally sprayed nickel-chromium-molybdenum coating (NCM) is compared at different nominal pressures (40~100 MPa) and temperatures (180~250 °C). With the failure time as a criterion, the rank order is as follows: NCM/Fe > CKS/Fe. Before the scoring occurs at the interface of the piston ring and cylinder liner (PRCL), the cast iron liner enters into a “polish wear” stage, and iron-based adhesive materials begin to form on the piston ring surface. With the macroscopic adhesion formation, the plastic shearing cycle causes surface damages mainly due to abrasive effects for the CKS/Fe pairs and adhesive effects for the NCM/Fe pairs.

Wear behavior of the aluminum-silicon alloy cylinder liner wear against Chrom–Keramik–Schicht piston ring

The aluminum–silicon alloy cylinder liner shows great potential for engine cylinder liner applications as its excellent castability, light weight, and good thermal conductivity. In order to improve the capability of the whole friction system further, the friction performance of the piston rings wear against cylinder liner should be discussed in details. In this paper, the wear behavior of the aluminum–silicon alloy cylinder liner wear against Chrom–Keramik–Schicht (CKS) piston ring was carried out by the contraposition reciprocating test rig under lubrication. The surface morphology was characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. When CKS piston ring wears against aluminum–silicon alloy cylinder liner, comparing with sprayed molybdenum piston ring, the friction coefficient reduced nearly 10%. Besides, the weight loss of cylinder liner and piston ring reduced nearly 95%. In the process of friction, aluminum was rolled repeatedly on the surface of cylinder liner. And the honing roads were still visible clearly on the worn surface. The coating of CKS piston ring is dense, lower roughness and higher hardness, and not easy to fall off. While the worn surface of CKS piston ring was smooth in the process of adhesive wear. When the aluminum–silicon alloy cylinder liner wears against CKS piston ring, the matched pair presents an excellent wear behavior.

Tribological assessment of coated piston ring-cylinder liner contacts under bio-oil lubricated conditions

To alleviate high friction and corrosive wear in piston ring and cylinder liner friction pairs lubricated with bio-oil, four kinds of coatings: Ni-P, Ni-P-MoS2, Ni-P-GO and Ni-P-MoS2-GO have been prepared via chemical nickel plating technology. A multi-functional engine piston ring-cylinder liner tribometer was employed to evaluate their tribological behaviors. Furthermore, the changes of the bio-oil under different frictional conditions were analyzed by Fourier transform infrared spectroscopy. The results show that adhesive wear, scratching, spalling and mild wear took place respectively on the worn surfaces of piston rings with Ni-P, Ni-P-MoS2, Ni-P-GO, and Ni-P-MoS2-GO coatings. Ni-P-MoS2-GO coated piston rings showed excellent friction-reducing and anti-wear performance and subsequently have great potential for accelerating the application of bio-oil in IC engines.

Influence of sliding surface roughness and oil temperature on piston ring pack operation of an automotive IC engine

In the paper a comprehensive model of a piston ring pack motion on an oil film has been presented. The local oil film thickness can be compared to height of the combined roughness of sliding surfaces of piston rings and cylinder liner. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works of Patir, Cheng and Greenwood, Tripp have been combined and used in this paper. The developed model takes the following phenomena into account: hydrodynamic and contact forces, spring and gas forces acting on piston rings. The rings motion concerning low and high temperature of cylinder surface has been compared. These results concern cases of hydrodynamic and mixed lubrication. Changes of oil wetted area and contact zone of piston rings have been shown. In addition the oil film thickness distribution along cylinder liner and all the forces acting on piston rings have been analysed and discussed. The results have been presented in form of relevant diagrams. The developed model and software can be utilized for optimization of piston rings design.

Surface and wear mechanisms analysis of phosphorous-free and conventional engine lubricants on cylinder liner and piston rings surfaces

Purpose – This paper aims to investigate the wear mechanisms, formations and effectiveness of tribofilms of new developed, antiwear additive which is called mercapthocarboxylate. The mercapthocarboxylate is a sulphur-based and non-phosphorus additive. Design/methodology/approach – The effectiveness of the additive was examined through a set of laboratory endurance tests that applied with single cylinder spark ignition engine. Two types of lubricants were used to compare the engine tests which were thiophosphate (ZDDP) containing engine lubricant (phosphorus containing) and mercapthocarboxylate containing non-phosphorus and non-ash crankcase oil. Lubricants were tested under identical operating conditions for 100 hrs. The surfaces of cylinder liner and piston rings were inspected through optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. Findings – Catalysis-friendly and sulphur-based mercapthocarboxylate additive can be an alternative antiwear additive package for lubrication oil due to better wear performance when compared to ZDDP. Originality/value – Sulphur-based mercapthocarboxylate is a new developed antiwear additive and was applied to lubrication oil in this study. This lubrication oil was tested in the real engine environment by using 100-hr engine bench tests.

On the running-in behavior of rough surface of piston rings in mixed lubrication regime

Purpose – The purpose of this paper is to study the real-time change of surface roughness at different small regions of piston rings during running-in process. Meanwhile, the effects of real-time change of the rough surface topography on the lubrication and friction of piston rings are investigated. Design/methodology/approach – An uneven wear model has been developed to research the running-in behavior at the different small regions of piston rings. The model is verified by comparing the simulation results with the experimental results on a reciprocating friction and wear test rig. Findings – This research shows that the wear process of piston ring surface is uneven during running-in. At most time of the operating cycle except the vicinity of top dead center and bottom dead center, the minimum oil film thickness ratio increases while the friction force and power loss decrease after the running-in period. Originality/value – Through this research, the running-in behavior of piston rings is investigated in detail. The interaction between the running-in and the lubrication and friction of piston rings is understood more deeply.

Pulsed electrochemical micromachining for generating micro-dimple arrays on a cylindrical surface with a flexible mask

Abstract Micro-dimple arrays play an important role in improving the performance and reliability of mechanical systems, and micro-dimples on the surfaces of piston rings and sliding bearings may reduce friction. Although many methods can be employed to create micro-dimples on cylindrical surfaces, it is still a challenge to generate micro-dimple arrays on cylindrical surfaces with high efficiency and low cost. In this paper, a patterned polydimethylsiloxane (PDMS) mask with good flexibility is introduced as a mask in through-mask electrochemical micromachining (TMEMM) for generating micro-dimple arrays on a cylindrical surface, in which thousands of micro-dimples can be fabricated in tens of seconds. In addition, the reusability of the PDMS mask is experimentally verified. To enhance removal of the product, the use of a pulsed current is introduced into TMEMM of micro-dimples. The experimental results show that the pulse duty cycle plays a significant role in enhancing the removal of product and improving the uniformity of the micro-dimple arrays. And the effect was weakened with increasing pulse duty cycle. Compared with duty cycles of 40, 60, and 80%, the highest current efficiency with a duty cycle of 20% is obtained at a frequency of 10 kHz. Finally, micro-dimple arrays with a diameter of approximately 110.6 μm and a depth of 11 μm are successfully generated on the cylindrical surface.

High Temperature Cylinder Sleeve Design Research Self-Lubricating Materials

Cylinder Liner design innovation goal is energy conservation. As the main friction parts engine cylinder liner, reducing friction energy is energy saving basic requirements. Materials research cylinder sleeve is one of the main cylinder liner saving research. Through the piston ring and cylinder liner surface friction dual material hard phase, self-lubricating phase, toughening phase analysis, select compatibility, high strength, heat resistance, good high temperature performance, ease of manufacture, price rational matrix material and an appropriate proportion of nanoscale hard material, self-lubricating materials, ductile materials, using appropriate methods cladding and processing, design developed high-temperature self-lubricating cylinder sets of advanced materials. The latest international high temperature, wear-resistant, self-lubricating materials research: modern nanoα-Al2O3+Ni-base alloy composite materials, Ti2B/Fe metal-ceramic composites, metals and ceramics NiCr-Cr3C2 particles CaF2 self-lubricating composite alloy powder material, NiCr/Cr3C2-WS2 self-lubricating wear-resistant materials were studied and found to TiC, Al2O3 is hard reinforcing phase, CaF self-lubricating phase, NiCr/TiC eutectic toughening phase, high-temperature self-lubricating wear-resistant nanocomposite, and Cr18Ni9 class alloy as base material, by laser cladding method enables conventional cylinder liners manufacturing technological breakthroughs, has practical value.

The relationship between flake graphite orientation, smearing effect, and closing tendency under abrasive wear conditions

Plastic deformation of the matrix during the wear process results in closing the graphite flakes. In this study, the relationship between the deformation of the matrix and the closing tendency of flake graphite was investigated, both qualitatively and quantitatively. Two representative piston rings, which belonged to the same two-stroke marine engine but were operated for different periods of time, were studied. Initial microstructural observations indicated a uniform distribution of graphite flakes on unworn surfaces, whereas worn surfaces demonstrated a tendency towards a preferred orientation. Approximately 40% of the open flakes of the unworn surfaces were closed during sliding, which may result in the deterioration of the self-lubricating capability of cast iron. Moreover, flakes within the orientation range of 0 to 30° relative to the sliding direction showed a maximum closing tendency when subjected to sliding. The closing tendency gradually decreased as the angle increased, approaching a minimum between 30 and 70°. A slight increase in the closing tendency was observed for flakes with orientations between 70 and 90°. A similar trend was observed on both rings. Furthermore, SEM and EDS analysis indicated substantial deformation of the matrix in the area around the flakes. An insignificant corrosion attack was observed on both worn piston ring surfaces.

Measurement of oil film thickness between piston ring and liner using strain gauge

PurposeThe aim of this paper is to develop a technique to measure the oil film thickness between piston ring and liner throughout the stroke, without impairing the surface properties of the piston ring and liner. Mechanical properties of the piston ring, like ring stiffness, are also not altered. Effect of variation in bore on the movement of piston ring can be studied with the proposed technique.Design/methodology/approachThe gap Hmin between the cylinder liner and the piston ring is formed due to the hydrodynamic pressure generated by the presence of oil film between piston ring and liner. This gap can be inferred by measuring the movement of the inner surface of piston ring with reference to a sensor mounted on the piston at a fixed distance from the piston ring. The piston ring is connected to the sensor through reasonably rigid member. The underlying assumption here is that there is no elastic deformation of the piston ring due to the hydrodynamic pressure. The fundamental sensor to measure oil film thickness used in this setup is a set of strain gauges.FindingsIt is possible to measure oil film thickness by the proposed arrangement for the entire stroke without changing the surface properties. Mechanical properties of the piston ring, like ring tension, are not affected. The results possibly provide the correct picture of the piston ring movement throughout the stroke. The measurement at near zero speed can give information on the movement of the piston ring due to hydrodynamic action and to the variation in the bore. The measurement is not affected by engine vibrations. The proposed technique can be helpful in validating the theoretical models proposed in the literature.Originality/valueThe measurement is possible only in unfired condition. However, this attempt can be considered as the basis to measure OFT in fired condition with necessary improvements. It is not feasible to measure quantity of lubricant/extent of lubricant on leading or trailing edge of piston. Effect of temperature on the oil film thickness cannot be studied as the engine is not fired. It is assumed that the piston ring does not pass through elasto‐hydrodynamic lubrication regime. Debris/worn out particles in the oil may affect the indicated oil film thickness at local points.

20606 ピストンリング表面からのオイル消費に関する基礎的研究(OS7-2【環境と調和したエネルギー利用(2)】)

It is important problems for environment to suppress the oil consumption of spark ignition engine. We approached to clear the dispersion mechanism from the piston ring surface by means of adjust the surface tension of lubricating oil and wettability of a piston ring. Experimental results show oil consumption increase by using silicon coated piston ring. We propose the numerical calculation model to predict the behavior of oil droplets on the piston ring surface. Calculated results show that the increase of wettability angle of piston ring surface accelerates oil consumption and surface tension of oil effects on oil consumption.

The influence of start–stop transient velocity on the friction and wear behaviour of a hyper-eutectic Al–Si automotive alloy

As worldwide automotive ownership is set to exceed 2 billion vehicles by 2030 (Dargay et al., 2007 [1]), environmental and economical pressures on the automotive industry mean there is a trend to reduce harmful greenhouse gas emissions whilst simultaneously improving fuel economy. The use of electrical hybrid, start–stop idling and materials light-weighting are some of the technological solutions which can offer efficiency savings, however their combined use in a tribological context is less well understood. Interruption of piston sliding as a result of start–stop technology will simultaneously interrupt fluid film lubrication at the ring/liner interface. This could have implications on the friction and wear behaviour of Al–Si cylinder blocks, where scuffing can be an issue. In order to determine the effect of a start–stop velocity cycles on the lubricated friction and wear behaviour of a hyper-eutectic Al–Si liner, an interrupted reciprocating laboratory tribometer test programme was developed based upon the European Urban Cycle standard. Refined cast iron piston ring segments were slid at 23Hz frequency, 4MPa nominal contact pressure and 25mm stroke length against a conformal honed Alusil cylinder liner segment. Regular velocity interruptions at 60s intervals did not significantly inhibit the dynamic friction behaviour between the liner and the cast-iron piston ring segment, indicating that lubricant additive function was not significantly inhibited. However contact potential and FIB–SIMS depth profiles indicated that anti-wear tribo-film thickness was reduced as a result of start–stop cycling. Mass loss from the piston ring was also notably higher as a result of the interruption of elasto-hydrodynamic lubrication causing boundary conditions at re-start and subsequent 2-body abrasion by harder protruding Si particles. Specific wear rates for the Al–Si liner as a result of start–stop velocities were surprisingly lower compared to uninterrupted tests and was believed to be due to faster running-in of the piston ring surface. These results are discussed in terms of the viability of Al–Si as engine materials running start–stop technology.