Search Results (132)

With the implementation of the ISO 8217-2024 marine fuel standard, the use of high-concentration biofuels in ships has become viable. However, relatively few studies have been conducted on the effects of biofuels on cylinder lubrication performance in low-speed, two-stroke marine diesel engines. In this study, catering waste oil was blended with 180 cSt low-sulfur fuel oil (LSFO) to prepare biofuels with volume fractions of 24% (B24) and 50% (B50). These biofuels were evaluated in a MAN marine diesel engine under load conditions of 25%, 50%, 75%, and 90%. The experimental results showed that, at the same engine load, the use of B50 biofuel led to lower kinematic viscosity and oxidation degree of the cylinder residual oil, but higher total base number (TBN), nitration level, PQ index, and concentrations of wear elements (Fe, Cu, Cr, Mo). These results indicate that the wear of the cylinder liner–piston ring interface was more severe when using B50 biofuel than when using B24 biofuel. For the same type of fuel, as the engine load increased, the kinematic viscosity and TBN of the residual oil decreased, while the PQ index and the concentrations of Fe, Cu, Cr, and Mo increased, reflecting the aggravated wear severity. Ferrographic analysis further revealed that ferromagnetic wear particles in the oil mainly consisted of normal wear debris. When using B50 biodiesel, a small amount of fatigue wear particles were detected. These findings offer crucial insights for optimizing biofuel utilization and improving cylinder lubrication systems in marine engines. Full article

Improving the reliability and durability of internal combustion engines in marine vessels is a complex issue. The vibrations generated in these engines significantly affect their proper operation. One of the current research challenges is identifying effective methods to reduce, among other things, torsional vibrations generated within the crank–piston system. To mitigate these vibrations, viscous dampers are commonly used. The selection of a viscous damper for a high-power multi-cylinder engine, such as those in marine power plants, requires a thorough understanding of the thermo-hydrodynamic properties of oil films formed in the spaces between the damper housing and the inertial mass. The description of the phenomena involved is complicated by the variable positioning of the inertial mass center relative to the housing during operation. Most previous studies assume a concentric alignment between these components. The main novelty of this work lies in highlighting the combined effect of the eccentric motion of the inertial ring on both hydrodynamic resistance and thermal characteristics, which has not been fully addressed in existing studies. This article defines the oil flow resistance coefficients and develops static characteristics of the dampers. Additionally, it evaluates the impact of the size of the frontal and cylindrical surfaces of the damper on its heat dissipation capacity. The presented characteristics can be utilized to assess the performance parameters of this type of damper. Full article

The lubrication performance of the cylinder liner–piston ring (CLPR) is crucial for the energy efficiency and operating reliability of marine diesel engines. To enhance the boundary lubrication of marine engine oil, a 1,3-diketone fluid HPTD (1-(4-hexylphenyl) tridecane-1,3-dione, HPTD) was introduced as an ash-free friction modifier. Besides that, octadecylamine-functionalized nanocopper particles (ODA-Cu) were also added to the marine oil to improve its anti-wear behavior. Through cylinder-on-disk friction tests, the appropriate contents of HPTD and ODA-Cu were determined, which then formed hybrid additives and modified the engine oil. The tribological performance of the modified oil was analyzed under various normal loads, reciprocating frequencies, and testing temperatures. Based on the synergy of the tribochemical reaction of HPTD and the mending effect of ODA-Cu on the sliding surface, the modified oil not only had lower sulfated ash content but also exhibited superior lubrication performance (i.e., reduced coefficient of friction by 15%, smaller wear track by 43%, and higher maximum non-seizure load by 11%) than the pristine engine oil. The results of this study would be helpful for the design of novel hybrid eco-friendly additives for marine engine oil. Full article

The use of combustion engines on agricultural vehicles will persist much longer than on-road vehicles. Introducing new technologies in agricultural engines is crucial to mitigating emissions while accounting for customer cost-sensitivity, harsh operation conditions, and typically sub-optimal maintenance. This work describes the use of CrN and tetrahedral amorphous carbon (ta-C) DLC-coated rings in small agricultural diesel engines. Compared with the gas nitride rings, the CrN and the ta-C DLC coatings exhibited, respectively, 74% and 86% lower wear in rig tests. The DLC also presented a very low coefficient of friction and high resistance to scuffing. A similar wear trend was observed on durability engine tests, where the CrN top ring showed an 80% lower wear rate than the GNS used in a similar engine. Wear on the DLC oil ring was below the measurement capability. Liner radial wear was measured on the piston ring reversal points in four angular positions, and except for one position, was lower than 3 µm. At the end of the test, engine performance and emissions are nearly identical to those at the test’s start, demonstrating that the use of advanced tribological solutions can significantly contribute to emissions mitigation in agricultural engines. Full article

Piston ring–cylinder liner is one of the most important friction pairs in internal combustion engines. The surfaces of the piston ring and the cylinder liner are affected by high temperature and high pressure, and the influence mechanism of temperature and pressure on their microscopic morphology parameters is yet to be revealed. In this paper, high temperature friction and wear experiments on the piston ring and cylinder liner are carried out to obtain the microscopic morphology of the cylinder liner and piston ring at different temperatures and pressures, and their changes under different temperatures and pressures are investigated by using two methods, namely, fractal dimension and three-dimensional surface roughness characterization. The results show that, as the temperature increases, the texture patterns on the cylinder liner’s friction surface become simpler, with the fractal dimension showing a decreasing trend while the roughness shows an increasing trend. Compared to the condition at 80 °C, the surface roughness (Sa) of the cylinder liner increased by approximately 58.43% at 190 °C, while that of the piston ring increased by about 96.5%. With increasing pressure, both the fractal dimension and the roughness of the friction surface first decrease and then increase. Full article

High-temperature fretting wear typically occurs on mechanical contact surfaces in high-temperature environments, with displacement amplitudes generally in the micrometer range (≤300 μm), such as the turbine disks and blades in aerospace engines, and the piston rings in automotive engines. The study performed tangential fretting wear tests between superalloy specimens and Si₃N₄ balls under 700 °C to investigate the influence of ground and milled surface morphologies on the high-temperature fretting wear behavior. The experimental results show distinct wear mechanisms for the two surface types: ground specimens exhibit adhesive and oxidative wear, while milled specimens experience fatigue and abrasive wear. Both wear modes intensify with increasing load and fretting frequency. A comprehensive surface morphology characterization method, combining fractal dimension (FD) and surface roughness, is proposed. The study reveals that the roughness parameters Sa and Ra are strongly correlated with the Coefficient of Friction, while FD is strongly correlated with the wear volume. This study provides a novel approach to characterizing the evolution of surface morphology during high-temperature fretting wear. Full article

This experimental study investigates the critical role and impact of additive concentration in enhancing the tribological performance of castor oil as a biolubricant for agricultural tractor engines. Friction and wear are major contributors to reduced engine efficiency, highlighting the need for effective lubrication strategies. While biolubricants like castor oil offer environmental benefits, they often require additives to achieve optimal performance. However, the concentration of these additives is crucial, as an imbalance can negatively impact the lubrication system, leading to a higher coefficient of friction, increased wear, and reduced engine efficiency and lifespan. This study examines the effects of varying concentrations of a mixture of propyl gallate (PG) and ionic liquid (IL) additives on the tribological performance of castor oil. The tribological behaviour of lubricated top compression piston ring and cylinder liner samples was evaluated under simulated engine conditions using a Bruker UMT Tribolab test rig, in accordance with the ASTM G181 standard. The experimental results revealed an influence of additive concentration on the coefficient of friction and wear behaviour. This emphasises the importance of optimising additive formulations to minimise engine wear and friction. Notably, a 0.5% volume concentration of the additive mixture led to a remarkable 34.8% reduction in the average coefficient of friction (COF) and a lower wear rate. Full article

In this work, 1,3-diketone synthesized via the Claisen condensation method and nano-copper particles modified by the Brust–Schiffrin method were added into a commercial marine medium-speed diesel engine cylinder piston oil to evaluate their effects on boundary lubrication performance. Friction and wear tests conducted on CKS-coated piston ring and cast-iron cylinder liner samples demonstrated significant reductions in both friction and wear with the addition of 1,3-diketone and nano-copper particles. Compared to the original oil without additives, the friction force was reduced by up to 16.7%, while the wear of the piston ring and cylinder liner was decreased by up to 21.6% and 15.1% at 150 °C, respectively. A worn surface analysis indicated that the addition of 1,3-diketone and functionalized nano-copper particles influenced the depolymerization and tribo-chemical reactions of the anti-wear additive ZDDP (zinc dialkyldithiophosphate) in the original engine oil. This modification enhanced the oil’s anti-friction and anti-wear properties, offering valuable insights into the development of eco-friendly lubricants for energy-efficient systems. Full article

Friction and wear reduction in internal combustion engines are crucial for improving efficiency and durability. This study investigates the effect of microtextured surfaces on friction power loss in an engine’s piston ring-cylinder system. A numerical analysis was conducted on piston rings equipped with dimple-shaped microtextures using AVL Excite Piston & Rings, modelling a hard chromium-coated piston ring and a cast iron cylinder. The goal was to determine the optimal surface texture parameters that minimize friction power loss under typical urban driving conditions with SAE 0W-30 oil. A two-step Design of Experiments (DoE) approach was employed, where the first step involved mapping the effects of texture parameters, i.e., dimple depth (A = 0.5, 1, 1.5 µm), dimple distance (B = 120, 160, 240 µm), and dimple diameter (C = 50, 60, 70 µm), to identify influential factors. The second step aimed at locating a parameter configuration with minimal friction power loss. The results demonstrated that the optimized texture parameters can significantly reduce friction power loss. The lowest friction power loss of 8.96 W was achieved with a dimple depth of 2 µm, distance of 80 µm, and diameter of 60 µm, which contributed to an 8.3% improvement over the reference surface. The model built to describe the investigated texturing approach exhibited a strong correlation with an R² value of 0.93, and the deviation between predicted and measured values was below 1%. Future work will involve tribometer tests to experimentally validate the optimized parameters and confirm the simulation results. Full article

With the global shift in energy structure and the advancement of the “double carbon” strategy, methanol has gained attention as a clean low-carbon fuel in the engine sector. However, the corrosion–wear coupling failure caused by acidic byproducts, such as methanoic acid and formaldehyde, generated during combustion severely limits the durability of methanol engines. In this study, we employed a systematic approach combining the construction of a corrosion liquid concentration gradient experiment with a full-load and full-speed bench test to elucidate the synergistic corrosion–wear mechanism of core friction pairs (cylinder liner, piston, and piston ring) in methanol-fueled engines. The experiment employed corrosion-resistant gray cast iron (CRGCI), high chromium cast iron (HCCI), and nodular cast iron (NCI) cylinder liners, along with F38MnVS steel and ZL109 aluminum alloy pistons. Piston rings with DLC, PVD, and CKS coatings were also tested. Corrosion kinetic analysis was conducted in a formaldehyde/methanoic acid gradient corrosion solution, with a concentration range of 0.5–2.5% for formaldehyde and 0.01–0.10% for methanoic acid, simulating the combustion products of methanol. The results showed that the corrosion depth of CRGCI was the lowest in low-concentration corrosion solutions, measuring 0.042 and 0.055 μm. The presence of microalloyed Cr/Sn/Cu within its pearlite matrix, along with the directional distribution of flake graphite, effectively inhibited the micro-cell effect. In high-concentration corrosion solutions (#3), HCCI reduced the corrosion depth by 60.7%, resulting in a measurement of 0.232 μm, attributed to the dynamic reconstruction of the Cr₂O₃-Fe₂O₃ composite passive film. Conversely, galvanic action between spherical graphite and the surrounding matrix caused significant corrosion in NCI, with a depth reaching 1.241 μm. The DLC piston coating obstructed the permeation pathway of formate ions due to its amorphous carbon structure. In corrosion solution #3, the recorded weight loss was 0.982 mg, which accounted for only 11.7% of the weight loss observed with the CKS piston coating. Following a 1500 h bench test, the combination of the HCCI cylinder liner and DLC-coated piston ring significantly reduced the wear depth. The average wear amounts at the top and bottom dead centers were 5.537 and 1.337 μm, respectively, representing a reduction of 67.7% compared with CRGCI, where the wear amounts were 17.152 and 4.244 μm. This research confirmed that the HCCI ferrite–Cr carbide matrix eliminated electrochemical heterogeneity, while the DLC piston coating inhibited abrasive wear. Together, these components reduced the wear amount at the top dead center on the push side by 80.1%. Furthermore, mismatches between the thermal expansion coefficients of the F38MnVS steel piston (12–14 × 10⁻⁶/°C) and gray cast iron (11 × 10⁻⁶/°C) resulted in a tolerance exceeding 0.105 mm in the cylinder fitting gap after 3500 h of testing. Notably, the combination of a HCCI matrix and DLC coating successfully maintained the gap within the required range of 50–95 μm. Full article

This study evaluates the tribological characteristics of quasi-monolithic engine cylinder coatings and piston rings using a custom-built linear reciprocating tribometer. The coatings were deposited on an Al-Si alloy cylinder bore using the Plasma Transfer Wire Arc (PTWA) and Electrolytic Jet Plasma Oxidation (EJPO) processes. The coatings’ tribological performances were investigated in the boundary lubrication regime. The performance of conventional chrome-coated cast iron piston rings was tested and compared to that of EJPO- and PTWA-coated engine cylinder samples that were extracted from a cast Al-Si engine block. Scanning electron microscopy and profilometry were used to compare the evolution of wear and the prevalent wear mechanism. This paper also presents the verification and repeatability analysis of a custom-built tribometer against a standard industry-calibrated tribometer. The wear test results showed that the EJPO coating had 0.05% to 10.35% lower wear rates than its PTWA counterpart throughout a wide range of loading conditions and sliding distances. The variation in the counter-face behavior is likely due to the different surface topographic parameters such as skewness, kurtosis, and porosity. Full article

The electron cyclotron resonance–chemical vapor deposition (ECR-CVD) plasma coating method was employed to bombard steel surfaces to achieve high-strength carbon-based structures. The surfaces to be coated were rotated using an Arduino-controlled rotation system at different orientations to ensure a homogeneous coating. The samples were fixed 10 mm away from the plasma gun (CH₄/N₂ plasma). The samples were characterized via XRD, EDX, Raman spectroscopy, SEM, and AFM. The coated surfaces were then subjected to tribological tests, including the wear rate, coefficient of friction, and surface hardness–roughness. Thermally reduced graphene oxide with an average nanocrystalline size of 5.19–24.58 nm and embedded carbon nanotube structures with sizes ranging from 150 to 600 nm were identified, as well as less-defective microcrystallines and nanodiamonds. The results demonstrated that carbon coating in the presence of N₂ gas led to a maximum reduction of 66% in the average wear rate, 14% improvement in the average surface hardness, 40% enhancement in the average coefficient of friction, and 48% enhancement in the average surface roughness. Consequently, a high-adhesion carbon-based coating deposited via plasma is likely to be a good candidate in the context of manufacturing engineering steels with a low friction coefficient, low wear rate, and long service life. Full article

At present, the improvement of anti-wear performance of piston rings remains a challenge. In this article, Ni-SiC composite coatings fabricated at 3, 9, and 15 g/L SiC were denoted as NSc-3, NSc-9, and NSc-15 coatings. Meanwhile, the influence of SiC concentration on the surface morphology, phase structure, microhardness, and anti-wear performance of electrodeposited Ni-SiC composite coatings were investigated utilizing scanning electron microscopy, X-ray diffraction, a microhardness tester, and a friction–wear tester, respectively. The SEM images presented NSc-9 coatings with a compact, flat, or cauliflower-like surface morphology. The cross-sectional morphology and EDS results showed that the Si and Ni elements were uniformly distributed in the NSc-9 coatings with dense and flat microstructures. Moreover, the average grain size of the NSc-9 coatings was only 429 nm. Furthermore, the microhardness and indentation path of the NSc-9 coatings were 672 Hv and 13.7 μm, respectively. Also, the average friction coefficient and worn weight loss of the NSc-9 coatings were 0.46 and 29.5 mg, respectively, which were lower than those of the NSc-3 and NSc-15 coatings. In addition, a few shallow scratches emerged on the worn surfaces of the NSc-9 coatings, demonstrating their outstanding anti-wear performance when compared to the NSc-3 and NSc-15 coatings. Full article

This research follows closely previous findings in flow characteristics and phenomena that take place in the piston ring and cylinder liner interface during motoring and firing engine operation, and also compares results between different optical engine set-ups. Cavitation visualisation in a simulating lubrication single-ring test rig and oil transport and cavitation visualisation in custom made cylinder assemblies of optical engines are the tools used to quantify the transport process under the piston ring and cylinder liner. Simplification of the interface is an essential technique that enhances the researcher’s confidence in results interpretation. Engine complexity and severe oil starvation are impeding the analysis of the experimental results. Visualisation experiments constitute an effective way to test various lubricant types and assess their overall performance characteristics, including their properties and cavitation behaviour. The repeatability of the visualisation method establishes the parametric study effects and offers valuable experimental results. As a further step towards the lubricant composition effect, a link between the lubricant formulation and the operating conditions could be established as the oil performance is assessed with a view to its transport behaviour. Image processing is used to quantify the impact of cavitation on piston ring lubrication in conjunction with varied operating and lubricant parameters. The characteristics of the lubricant and the working environment have an impact on these types of cavities. Viscosity, cavitation, oil film thickness (OFT), lubricant shear-thinning characteristics and friction are all linked. Full article

Piston top rings in the combustion engine play a crucial role in the overall hydrodynamic performance of engines, such as power loss, minimum film thickness and friction forces, by ensuring sealing and minimizing the leakage of burnt gases. This present paper examines the influence of four key parameters of the top ring, such as ring width, ring temperature, ring tension, and ring surface roughness on the hydrodynamic behavior at the ring/cylinder contact. These parameters play a significant role in the formation and maintenance of the oil film, directly influencing hydrodynamic indicators such as the minimum oil film thickness, friction force, power loss, oil pressure, and the ring angle twist. This article relies on hydrodynamic models and numerical simulations performed using GT-SUITE version 6 software to analyze these effects. The pressure curve used in this simulation is experimentally validated for an engine speed of 2000 RPM. It was found that an increase in the top ring temperature reduces the oil’s viscosity, decreasing the film thickness and increasing the risk of metal-to-metal contact. Increasing the roughness of the ring enhances oil film stability, especially at the bottom dead center (BDC) points during each phase of the operating cycle. Further, three different types of ring profiles were investigated for friction forces by varying the speed of the engine. Full article