•The online condition monitoring and repairing strategies in diesel CLPR are reviewed.•It provides theoretical guarantee for reliable operation to marine diesel.•Future trends for online monitoring ...and maintenance technology of CLPR are predicted.
As vital components of diesel engines, failure issues of cylinder liner-piston ring components (CLPRs), which work under harsh conditions of high temperature, high pressure, and heavy load, become a technical shortcoming of performance improvement and service life for diesel engines. Online condition monitoring and maintenance based on the operating conditions of CLPRs are considered an effective method for ensuring normal diesel engine operation. For this reason, a comprehensive overview for condition-monitoring technologies, including lubricating oil and vibration condition monitoring, and wear-repairing strategies was necessary. However, such an overview, to the best of our knowledge, is needed in related research fields of condition monitoring and maintenance regarding diesel engines and its components. This paper systematically reviewed the research progress of online condition monitoring and self-repairing techniques for in-service diesel CLPRs from the perspective of tribosystems. To contextualize this concern, an initial review of various condition-monitoring techniques, such as lubricating oil, mechanical vibration, essential state parameters, and acoustic emission technology were specifically discussed. Subsequently, real-time maintenance strategies based on lubricating oil self-repairing additives were comprehensively summarized. Finally, this review concluded with a brief discussion of shortcomings and plausible future trends for various techniques. This study tackled wear-induced failure issues of CLPRs by reviewing online condition techniques and in-time maintenance methodology, providing a theoretical foundation and technical assistance for the development of operation and maintenance guarantee systems for marine diesel engines and intelligent engine rooms in the near future.
Surface texturing has gained great attention in the tribological community since precisely defined surface features can help to reduce friction and/or wear irrespective of the acting lubrication ...regime. The ability to positively influence tribological performance under different lubrication conditions makes surface texturing particularly interesting for machine elements since they may experience different conditions over the lifetime or sometimes even over one cycle/stroke. However, despite the great effort by both researchers and industry to introduce surface texturing in machine elements, many questions remain unclear regarding the optimal design of surface textures, as well as the positive and negative effects on the component's performance. The aim of this review article is to critically summarize the state of the art of surface texturing applied to machine elements, with a special emphasis on piston rings, seals, roller bearings, and gears. After a brief introduction, the first section focuses on surface texturing in sliding components (piston rings and seals), whereas the second section deals with surface texturing in rolling components (roller bearings and gears). Based upon the main evidence from the literature, the final section provides more general design guidelines for surface texturing in machine elements.
Surface texturing has gained great attention in the tribological community since precisely defined surface features can help to reduce friction and/or wear irrespective of the acting lubrication regime. This review aims at summarizing the latest developments in the field of surface texturing applied to machine components with a special emphasis on piston rings, seals, roller bearings, and gears.
Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a ...common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets' interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation.
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.
•Ni-P-TiN coated piston rings were prepared by electroless plating.•The tribological performances of the coated piston ring-cylinder liner pair were investigated.•Synergistic effects between the coatings and the nano-additives were found.•The corresponding antiwear mechanisms were illuminated.
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.
Continuous optimization of advanced coatings is required to achieve technology advances and strict emission standards in automotive systems. Integration of conventional ceramic coatings and hard ...amorphous graphite-like carbon (GLC) with low friction is an economically feasible way of achieving superior efficiency of oil and durability as well as scuffing resistance. This work evaluates the scuffing resistant capacity and durability of engineered coating materials. The presence of GLC not only combats the scuffing damage and running instability effectively for conventional chromium-based coatings, and also improves the reliability and robustness of the piston rings. The scuffing mechanism of the engineered rings with and without GLC surface will be discussed by the observation of the damaged characteristics and the chemistry of the rubbing parts. This will potentially benefit to optimize the coating material in the piston assembly of engine.
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•Integration of traditional ceramic coatings and hard low friction surface is proposed.•The load-carrying capacity of engineered coating materials is evaluated by the scuffing tests.•Amorphous carbon improves reliability and robustness of chromium-based surface during rubbing.
The dangerousness of ultrafine particles will require to regulate the emissions of sub-23 nm particles, from all engines.
Natural Gas engines play a relevant role toward de-carbonization from ...transport sector. Considered as particulate matter-free, they have to become compliant with upcoming regulations. Several solutions are under development, but engine-side improvements represent a viable way to keep their competitiveness.
The present work investigates on the relationship among piston-liner oil leakage, engine operations and particle emission over the World Harmonized Transient Cycle.
The performance of an Euro VI spark ignition natural gas engine is compared with the one of a prototype version of the same engine.
The results evidenced a correlation of particle emissions with some phases of the cycle, in correspondence to the passage from long idle periods to speed/load increments, where particle emissions proved to be more than 90% of the total.
Literature analysis revealed that the reverse blow-by during high vacuum conditions appears the main driver of instantaneous oil consumption, corroborating the hypothesis of a correlation between instantaneous oil leakage and particle emission spikes during specific driving maneuvers.
The piston ring pack design improvement greatly affects such phenomena, providing, as demonstrated in this work, relevant reduction of particle emissions.
•Particles emissions from CNG engine mainly related to fast transient maneuvers.•Relationship among piston-liner oil leakage, engine operations and particle emission.•Oil leakage as main source of particle emissions.•Ring pack design is a crucial feature to approach ultra-low PN from CNG engine.
The piston rings are responsible for a large portion of the fuel consumption in heavy duty diesel engines. In this work a high speed component test rig for evaluation of piston ring friction is used. ...A number of different piston rings and cylinder liners are evaluated based on their friction performance. Shear thinning of typical multi grade oil is investigated by comparing it to single grade oil. Experimental simulation of higher speeds by decreasing the viscosity is evaluated. A method for indication of effects on oil consumption, without combustion, for different oil control rings is presented. Finally, a numerical simulation model for the oil control ring is validated by comparing the friction predicted with the model to the experimental results.
•Halved friction for the oil control ring with kept sealing capability is found.•Effect on friction from piston ring design and cylinder liner roughness are studied.•The effect on friction from multi grade oil is compared to single grade oil.•Stribeck like curves are produced for investigation of DLC coated piston rings.•Good correlation between a numerical model and experimental results are showed.
Applying surface texture to piston liners may provide an effective means of controlling friction and hence improving engine efficiency. However, little is understood about the mechanisms by which ...pockets affect friction, primarily because of a lack of reliable experimental measurements. To address this, the influence of surface texture on film thickness and friction force was measured simultaneously in a convergent-divergent bearing, under conditions that closely replicate an automotive piston ring-liner conjunction. Film thicknesses were measured using a modified version of the ultra-thin film optical interferometry approach, enabling film thicknesses <50nm to be measured under transient, mixed lubrication conditions. This involved using the out-of-contact curvature of the specimens in place of a spacer layer and analysing multiple interference fringes to avoid fringe ambiguity. Tests were performed on both a textured sample (with features oriented normal to the direction of sliding) and a non-textured reference sample, while angular velocity, applied normal load and lubricant temperature were controlled in order to study the effect of varying lubrication regime (as typically occurs in service). Results showed that the presence of surface pockets consistently enhances fluid film thickness in the mixed lubrication regime by approximately 20nm. Although this is only a modest increase, the effect on friction is pronounced (up to 41% under these conditions), due to the strong dependence of friction on film thickness in the mixed regime. Conversely, in the full film regime, texture caused a reduction in film thickness and hence increased friction force, compared with the non-textured reference. Both textured and non-textured friction values show nearly identical dependence on film thickness, (showing that, under these conditions, texture-induced friction reduction results entirely from the change in film thickness). These results are important in providing film thickness data to validate piston-ring lubrication models and also in helping to understand the effect of surface roughness on texture performance.
•Under full film lubrication conditions, the effect of surface texture is shown to reduce film thickness, which causes an increase in lubricant shear rate and hence increases friction.•Under mixed and boundary conditions, the effect of surface texture is shown to increase film thickness, causing a reduction in asperity contact and hence reduces friction. Although this film thickness increase is small (~28%), its effect on friction is significant (~41% in this study), due to steep gradient of the Stribeck curve in this regime.
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.
•Thread groove surface texture can significantly improve performance of the cylinder liner-piston ring.•The relationship of the sealing performance and tribological properties is investigate.•Experimental basis for improving performance of the cylinder liner on slower sliding long stroke marine engines is proposed.
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