Search Results (17)

Improving the thermal efficiency of internal combustion engines plays a crucial role in reducing fuel consumption and engine emissions. Studies have shown that the friction loss caused by the piston ring–cylinder liner pair accounts for approximately 30–40% of the engine’s total mechanical friction. The key to improving mechanical and thermal efficiency lies in reducing frictional losses through advanced solutions. However, as engine intensification increases, the growing thermal and mechanical loads lead to out-of-round deformation of the cylinder liner. This deformation reduces the sealing conformity of the piston rings, leading to increased blow-by and elevated particulate matter (PM) emissions. To address this, a dynamic–static deformation testing system for cylinder liners, combined with a multi-physics simulation for data validation, has been developed to achieve energy conservation and emission reduction in engines. Based on established strain gauge and eddy current displacement sensors, this study developed a dynamic deformation testing system, modified for a specific type of diesel engine, and analyzed the cylinder liner deformation under fired conditions. Test results show that under engine speeds ranging from 700 rpm to 1100 rpm, the overall radial out-of-roundness of the cylinder liner increased, with a maximum deformation of 49.2 μm. The second-order component of out-of-roundness also increases with speed, showing a maximum rise of 28.9 μm, while the third-order and fourth-order components exhibit relatively minor changes. These findings suggest that the overall radial deformation under fired conditions is mainly dominated by second-order out-of-roundness, with third-order and fourth-order components contributing marginally. Full article

The mechanisms of in-service damage caused to the cylinder units of internal combustion engines (ICE) during their operation are analyzed. Long-term operation under harsh conditions, failure to comply with operating conditions, and breach of design and technology standards were found to be the major reasons for the initiation and propagation of in-service defects. The life of ICE cylinder liners is proposed to be extended by forming regular microreliefs. This represents a promising surface engineering strategy. Axial lines of the regular microrelief’s grooves were considered using analytical dependencies, which helped determine their coordinates and those of their equidistant. The authors simulated the pattern according to which the groove axes of type II regular microrelief could be aligned on the inner surface of the cylinder liner. To this end, a tool with three deforming elements was used. Technical means have been developed to implement this technology on the working surfaces of the liner–piston group’s mating parts. Full article

In order to improve the wear resistance of Al-Si alloy cylinder liners, surface treatment is usually used. The Al-Si alloy cylinder liner samples were prepared by mechanical grinding and laser finishing. The mechanical grinding samples were carried out by the independent design and development of a grinding machine. The laser finishing samples were laser-heated by a CO₂ continuous transverse-flow laser. Both of the two surface treatments could provide the surfaces of protruding silicon particles with round edges to improve the wear resistance. However, in the exposure height of silicon particles with round edges, the study was lacking. The exposure height of silicon particles is important to the tribological properties of the Al-Si alloy cylinder liner, and should be analyzed in detail. The wear tests were completed by a contraposition reciprocating wear test rig under lubrication. It was found that when the silicon particles were exposed on the surface of the Al-Si alloy cylinder liner sample by 1.2 μm, the mechanical grinding samples and laser finishing samples all exhibited minimum friction coefficients and weight losses. This paper confirms that a suitable exposure height of silicon particles would reduce the probability of adhesion wear and abrasive wear of Al-Si alloy cylinder liners and increase the lubrication. It presents an excellent tribological property. However, when the exposure height of silicon particles is too high, the silicon particle is easily prone to plastic deformation or even falls off during the friction process due to the high stress and larger plastic contact index. Full article

With the marine industry’s demands for carbon reduction and increased reliability, the friction and wear performance of marine engines is becoming increasingly important. MAX phase materials show great potential in marine engine tribopair materials due to their unique microstructure and performance. The typical MAX phase material Ti₃AlC₂ was combined with MoDTC and added to the lubricant containing ZDDP additive for the tribopair composed of chromium-based ceramic composite coated steel (CKS) piston rings and cast iron cylinder liners under impact-sliding conditions. Compared to Ti₃AlC₂ alone, the friction coefficient and wear depth of the designed composite additive MoDTC/Ti₃AlC₂ were reduced by 36.9% and 41.4%, respectively. The worn surface lubricated with the Ti₃AlC₂/MoDTC composite additive showed fewer scratches with significantly less plastic deformation and clearer honing grooves. The multi-component tribofilm containing FeS, MoS₂, MoO₃, ZnO, TiO₂, Al2O₃, unoxidised particles, short-chain phosphates, and some ZnS was present on the worn cylinder liner surface. The synergistic effect of Ti₃AlC₂, MoDTC and ZDDP additives in the lubricant can isolate the mutual contact, generate a solid tribofilm and reduce the scratching. This can provide some guidance for the development of high-performance lubricant additives under impact-sliding conditions. Full article

The cylinder liner bears alternating thermal load and mechanical load, and evaluating the cylinder liner deformation is a key issue in the design stage of an engine. In this work, the shape and position tolerance of the cylinder liner to various loads were studied based on the finite element method, the simplex algorithm and the least square method. Firstly, the heat transfer boundary conditions of the cylinder liner were obtained through combustion simulation. Combined with the mechanical load, the transient deformation of the cylinder liner under the thermo-mechanical load was obtained. Subsequently, the out-of-roundness and coaxiality were selected to evaluate the shape and position changes in the cylinder liner. Finally, the transient tolerance analysis of the cylinder liner under alternating thermo-mechanical load was carried out. The results show that the maximum out-of-roundness of the cylinder liner under thermal load, mechanical load and thermos-mechanical load was 15.12, 43.40 and 51.76 μm, respectively. The maximum coaxiality under thermal load, mechanical load and thermos-mechanical load were 6.17, 80.49 and 80.22 μm. The side thrust was more likely to cause uneven deformation of the cylinder liner section, the liner coaxiality was mainly affected by the cylinder burst pressure, and the liner shape tolerance was much more sensitive to the mechanical load than the mechanical load. Full article

For future internal combustion engines, driven by regenerative fuels, efficiency is more important than ever. One approach to reduce the losses inside the piston cylinder unit (PCU) is to improve the alignment of the liner and the piston. Therefore, a cylinder liner with a free form was developed at the Institute of Technical Combustion (ITV) of the Leibniz University Hannover which compensates radial and linear deformations along the stroke. The layout is based on a FEM simulation. The liner was manufactured by the Institute of Production Engineering and Machine Tools (IFW) of Leibniz University of Hannover with a novel turn-milling process. The liner was investigated on the heavy-duty Floating-Liner engine of ITV with a displacement of 1991 ccm and a bore diameter of 130 mm. The experimental results show improvement in the friction losses over the whole engine map in the range of 9% and up to 17.3% compared to a serial liner. Sealing efficiency could be improved up to 28.8%, depending on the operational point. Overall, the investigation aims for lower fuel consumption which would in result fewer emissions. Full article

Hydrogen storage is a crucial factor that limits the development of hydrogen energy. This paper proposes using a split liner for the inner structure of a hydrogen storage cylinder. A self-tightening seal is employed to address the sealing problem between the head and the barrel. The feasibility of this structure is demonstrated through hydraulic pressure experiments. The influence laws of the O-ring compression rate, the distance from the straight edge section of the head to the sealing groove, and the thickness of the head on the sealing performance of gas cylinders in this sealing structure are revealed using finite elements analysis. The results show that when the gas cylinder is subjected to medium internal pressure, the maximum contact stress on the O-ring extrusion deformation sealing surface is greater than the medium pressure. There is sufficient contact width, that is, the arc length of the part where the stress on the O-ring contact surface is greater than the medium pressure, so that it can form a good sealing condition. At the same time, increasing the compression ratio of the O-ring and the head’s thickness will help improve the sealing performance, and reducing the distance from the straight edge section of the head to the sealing groove will also improve the sealing performance. Full article

To improve the friction and wear performance of the piston-cylinder liner friction pair, inspired by earthworms and leeches, 27 kinds of pistons with cylindrical pit arrays are designed and processed. Through a friction test, four superior textured pistons are optimized, and wear, life and thermal imaging tests are performed. Finite element analysis of the friction pair model is performed, and the friction and wear mechanisms are discussed. The results show that the pistons with cylindrical pit arrays have excellent friction and wear performance, less heat generation by friction, longer lives and less scratches on the cylinder liner. The temperature of the optimized textured pistons was reduced by around 5–10 °C. The wear amount of some textured pistons was reduced by over 50%, resulting in an improvement in their lifespan of at least 30% or more. The results of the finite element analysis indicate that the textured piston exhibited reduced deformation and favorable stress–strain distribution and satisfied the required contact pressure. Full article

Climate change is exacerbated by vehicle emissions. Furthermore, vehicle pollution contributes to respiratory and cardiopulmonary diseases, as well as lung cancer. This requires a drastic reduction in global greenhouse gas emissions for the automobile industry. To address this issue, researchers are required to reduce friction, which is one of the most important aspects of improving the efficiency of internal combustion engines. One of the most important parts of an engine that contributes to friction is the piston ring cylinder liner (PRCL) coupling. Controlling the linear deformation enhances the performance of the engine and, as a result, contributes positively to its performance. The majority of the tests to study the conformability between cylinder liner and piston were carried out on cylinder liners made of cast iron. It is possible to improve the performance of piston ring cylinder liner couplings by implementing new and advanced manufacturing techniques. In this work, a validated finite element model was used to simulate the performance when advanced manufactured materials were adapted. The deformation of the cylinder liner due to thermal and mechanical loads is simulated with five different additive manufactured materials (Inconel 625, Inconel 718, 17-4PH stainless steel, AlSi10Mg, Ti6Al4V). Simulated roundness and straightness errors, as well as maximum deformation, are compared with conventional grey cast iron liner deformation. Some additive manufactured materials, especially Ti6Al4V, show a significant reduction in deformation compared to grey cast iron, both in bore and circumferential deformation. Results show that Ti6Al4V can reduce maximum liner deformation by 36%. In addition, the roundness improved by 36%. The straightness error when Ti6Al4V was used also improved by 44% on one side, with an average of 20% over the four sides. Numerical results indicate that additive manufactured materials have the potential to reduce friction within the piston liner arrangement of internal combustion engines. Full article

The tribo-dynamics performance of the piston–cylinder system is affected by multiple physical fields. The current work presents a novel multiphysics coupling method to model and analyze the lubricated piston skirt–cylinder interface considering the cylinder liner vibration. This method is implemented by coupling multibody dynamics of the crank-connecting rod–piston–cylinder system, the heat transfer of the cylinder and piston, hydrodynamics lubrication on the skirt–cylinder interface, vibration of the cylinder liner, and thermal as well as elastic deformation in the piston–cylinder system together with rheological characteristics of lubricating oil. The proposed method is adopted into a four-stroke gasoline engine to predict its dynamics and tribological characteristics, with the purpose of revealing the influence of cylinder liner vibration on the tribo-dynamics implementation of the piston–cylinder system. The results indicate that increasing the stiffness and damping coefficient of the cylinder is beneficial to suppress the vibration of the system, but it has little effect on the tribological characteristics of the piston skirt–cylinder interface. Full article

During the present study, a double groove texture was designed on the surface of a piston ring to improve the sealing performance between the piston ring and cylinder liner. The experimental design method was used to fabricate the test plan according to the groove width, depth, and spacing. By using the thermal–structural coupling analysis method, the finite element analysis of the standard piston ring and the textured piston ring was carried out to simulate the deformation state of the cylinder liner system of the piston ring group during the working stroke. The piston rings with different parameters designed by the test scheme were manufactured by wire electrical discharge machining, and the self-made experiment device carried out the sealing test. The results showed that the groove texture could improve the sealing performance of the piston ring, and the analyzed results demonstrated that the groove texture had little effect on the maximum deformation of the piston ring. Still, it could significantly reduce the minimum deformation of the piston ring group. A piston ring with groove texture would improve the sealing performance and reduce the deformation during the work stroke. During the test, the average deformation of the No.7 piston ring group, with a groove depth of 1 mm, a groove width of 0.5 mm, and a groove spacing of 0.1 mm, was the smallest, about 29.6% lower than that of the standard piston ring group. The sealing performance of the No.7 piston ring group was the best, and the reduction rate of the top gas leakage rate was 52.18%. During the present study, the sealing performance of the piston ring was improved by designing the grooved structure on the piston ring surface, thereby improving the fuel economy and power performance of the engine. The present study could provide a reference for the engineering field to design a piston ring with high sealing performance. Full article

The present study aims to analyze the secondary movement of the piston considering the deformations present in the piston skirt, the hydrodynamic lubrication, and the effects of the clearances in the connecting rod bearings. The analysis of the piston movement is performed by developing a mathematical model, which was used to evaluate the dynamic characteristics of the piston movement, the slap force on the piston skirt, the effect of the secondary piston movement on the connecting rod, and the influence of clearances in the connecting rod bearings and in the piston. For the study, the geometric of the crankshaft-connecting rod–piston system of a single-cylinder diesel engine is taken as a reference. The deformation model of the piston was carried out by means of a symmetric finite element model (FEM), which was integrated into the mathematical model of the piston. MATLAB^® software (The MathWorks Inc., Natick, MA, USA) is used for the development of model simulations. The obtained results show that during the combustion cycle, there are six changes of direction in the secondary movement of the piston with lateral and angular velocities that can reach a magnitude of 0.13 m/s and 4 rad/s. The lateral and angular movement of the piston during its travel causes the appearance of impacts on the piston skirt with the cylinder liner, which produces an increase of approximately 500 N in the hydrodynamic forces in the connecting rod bearings. The force analysis shows that the range of the maximum magnitudes of these forces is between 1900 N and 3480 N. The increase in clearance between the cylinder liner and the piston skirt (Cpc) causes a greater lateral displacement and an increase in the angle of inclination of the piston. Analysis of the change in connecting rod bearing clearance shows that there are critical values in relation to clearance Cpc. The model presented allows us to analyze the different characteristics of the secondary movement of the piston, which involve the interaction between the piston skirt and the cylinder liner. Additionally, the influence of this movement on the connecting rod bearings is considered. The foregoing can be used as an analysis tool for the study of designs and/or modifications in the engine in such a way that greater durability of the components, reductions in acoustic emissions, and reduction in friction losses are achieved. Full article

Reducing friction is an important aspect to increase the efficiency of internal combustion engines (ICE). The majority of frictional losses in engines are related to both the piston skirt and piston ring–cylinder liner (PRCL) arrangement. We studied the enhancement of the conformation of the PRCL arrangement based on the assumption that a suitable conical liner in its cold state may deform into a liner with nearly straight parallel walls in the fired state due to the impact of mechanical and thermal stresses. Combining the initially conical shape with a noncircular cross section will bring the liner even closer to the perfect cylindrical shape in the fired state. Hence, a significant friction reduction can be expected. For the investigation, the numerical method was first developed to simulate the liner deformation with advanced finite element methods. This was validated with given experimental data of the deformation for a gasoline engine in its fired state. In the next step, initially conically and/or elliptically shaped liners were investigated for their deformation between the cold and fired state. It was found that, for liners being both conical and elliptical in their cold state, a significant increase of straightness, parallelism, and roundness was reached in the fired state. The combined elliptical-conical liner led to a reduced straightness error by more than 50% compared to the cylindrical liner. The parallelism error was reduced by 60% to 70% and the roundness error was reduced between 70% and 80% at different liner positions. These numerical results show interesting potential for the friction reduction in the piston-liner arrangement within internal combustion engines. Full article

A preliminary study on a double-acting hydraulic cylinder subject to high-pressure loading conditions (pressure = 350 bar) and with a bore diameter of 300 mm is presented. The substitution of the reference steel cylinder tube with a multi-material tube is investigated. In detail, a solution providing a steel thin inner liner wrapped by carbon composite materials is analytically and numerically tested in terms of weight reduction. The composite lay-up design and the component geometry are built to comply with manufacturing constraints for a relatively high-volume production. The alternative multi-material cylinder is designed to ensure the same expected performance as its steel counterpart. Firstly, the non-conventional hydraulic cylinder was designed by extending Lamé’s solution to composite materials, by adopting the micro-mechanics theory of composites in order to bear the maximum operating pressure by monitoring its radial and axial deformation. The selection of the most appropriate carbon reinforcement was investigated. The influence of the stiffness-to-weight and the strength-to-weight ratio of the reinforcement on the design is discussed. Secondly, finite element analyses were performed to evaluate the occurrence of buckling and the modal response of the actuator considering the fluid and of the cylinder own weight influence. The results confirm the validity of the new cylinder tube design compared to the reference steel component. The proposed barrel weights 80 kg compared to the 407 kg of the reference cylinder, with a weight reduction of ~80%. Furthermore, it has a compact design with a decrease of the barrel outer diameter of ~5.3%. Full article

In internal combustion engines, a significant portion of the total fuel energy is consumed to overcome the mechanical friction between the cylinder liner and the piston rings. The engine work loss through friction gradually reduces during the engine break-in period, as the result of liner surface topography changes caused by wear. This work is the first step toward the development of a physics-based liner wear model to predict the evolution of liner roughness and ring pack lubrication during the break-in period. Two major mechanisms are involved in the wear model: plastic deformation and asperity fatigue. The two mechanisms are simulated through a set of submodels, including elastoplastic asperity contact, crack initiation, and crack propagation within the contact stress field. Compared to experimental measurements, the calculated friction evolution of different liner surface finishes during break-in exhibits the same trend and a comparable magnitude. Moreover, the simulation results indicate that the liner wear rate or duration of break-in depends greatly on the roughness, which may provide guidance for surface roughness design and manufacturing processes. Full article