ANALISIS PERUBAHAN KEKERASAN YANG TERJADI PADA CINCIN TORAK AKIBAT PERUBAHAN JARAK TEMPUH PADA MOTOR YAMAHA MIO SOUL GT

In a four stroke combustion engine, there are three piston rings, namely two compression piston rings and one lubrication control piston ring. The piston compression ring serves to maintain the combustion pressure, while the piston ring lubrication regulator functions to lubricate the combustion chamber during the energy change process so that the piston will run back and forth in the combustion chamber smoothly. Damage that occurs to the piston ring can be in the form of a broken piston ring, or a scratched or worn piston ring. These things can reduce the quality of the energy transfer process. The piston ring is broken because the ring is too brittle. Vibration that occurs in the piston when combustion occurs at full load increases the possibility of a fracture process in the piston ring. The brittleness of the piston ring is strongly influenced by the material used. To overcome this, a hard but not stiff material is needed. Keywords: Hardness, mileage, Vicker test

Cavitation shapes measurements in piston-ring lubrication and their link to lubricant properties

The emissions control regulations introduced by governments are set to improve engine quality and reduce the impact automobiles have on the planet. The regulations imposed on the manufactures have proven very difficult to meet. To this effect some of the leading names in the industry were pushed to invest significant funding in research, development and optimisation of combustion, powertrain and tribology inside the ICE. Their goal is reduction of fuel consumption and emissions while increasing performance and durability. The piston-ring and cylinder-liner interaction is the major source of frictional losses for reciprocating ICEs and so, it is important to avoid any failure of piston-rings to effectively control lubricant transport from the sump onto the cylinder walls and further to the combustion chamber. This lubricant will participate in the emissions through absorption and desorption of fuel in the oil film at the cylinder walls, also resulting in lubricant contamination and consumption. The objective of this project is to assist with the investigation of phenomena occurring in the cylinder liner and piston-ring interaction under different operating conditions. The following investigations have been carried out, flow and cavitation visualisation in a model lubricant rig and cavitation visualisation in a newly designed optical engine.

Modeling the Fatigue Wear of the Cylinder Liner in Internal Combustion Engines during the Break-In Period and Its Impact on Piston Ring Lubrication

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.

Piston-ring performance: limitations from cavitation and friction

Purpose Cavitation in piston-ring lubrication is studied as part of the performance of piston-ring assemblies. Cavitation degrades performance in engineering applications and its effect is that it alters the oil film pressure, generated at the converging-diverging wedge of the interface. Studies tried to shed light to the phenomenon of cavitation and compare it with cavities that have been identified in bearings. The paper aims to discuss this issue. Design/methodology/approach Lubricant formulations were used for parametric study of oil film thickness (OFT) and friction providing the OFT throughout the stroke and LIF for OFT point measurements. Lubricant formulation affects cavitation appearance and behaviour when fully developed. Findings Cavitation affects the ring load carrying capacity. Different forms of cavitation were identified and their shape and size (length and width) is dictated from reciprocating speed and viscosity of the lubricant. A clear picture is given from both techniques and friction results give quantifiable data in terms of the effect in wear and cavitation, depending on the lubricant properties. Research limitations/implications Engine results are limited due to manufacturing difficulties of visualisation windows and oil starvation. Therefore, full stroke length sized windows were not an option and motoring tests were implemented due to materials limitations (adhesive and quartz windows). Lubricant manufacturer has to give data regarding the chemistry of the lubricants. Originality/value The contribution of cavitation in piston-ring lubrication OFT, friction measurements and lubricant parameters that try to shed light to the different forms of cavitation. A link between viscosity, cavitation, shear thinning properties, OFT and friction is given.

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

Purpose The purpose of this paper is to investigate the coupling mechanism of the roughness distribution characteristic and surface textures on the cylinder liner. Design/methodology/approach The 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. Findings The 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/value Although 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.

A mass-conserving algorithm for piston ring dynamical lubrication problems with cavitation

Purpose Piston ring dynamic problem plays an important role in the lubricant characteristics of a reciprocating engine, which lead to engine wear and the increased consumption of lubricating oil. A cavitation analysis of the piston ring lubrication with two-dimensional Reynolds equation has rarely been reported owing to the complex working condition. The purpose of this study is to establish a precise model that can provide guidance for the design of the piston ring. Design/methodology/approach In this paper, a cavitation model and its effect on the piston ring lubrication was studied in a simulation program based on the mass-conserving theory which is solved by means of the Newton–Raphson method. In this study, some models such as mixed lubrication, asperity contact, blow-by/blow-back flow and cavitation have been coupled with the lubrication model. Findings The established model has been compared with the traditional model that deals with cavitation by using the Reynolds boundary condition algorithm. The cavitation zone, pressure distribution and density distribution between the piston ring and the cylinder have also been predicted. Studies of the changing trend for the pressure distribution and the cavitation zone at few typical crank angles have been listed to illustrate the cavitation changing rule. The analysis of the results indicates that the developed simulation model can adequately illustrate the lubrication problem of the piston ring system. All the analyses will provide guidance for the oil film rupture and the reformation process. Originality/value A two-dimensional cavitation model based on the mass-conserving theory has been built. The cavitation-forming and -developing process for the piston ring–liner lubrication has been studied. Non-cavitation occurs in the vicinity of top dead center and bottom dead center. The non-cavitation period will be longer in the vicinity of 360° of crank angle. The density distribution in the cavitation zone can be obtained.

The effect of friction force and cavitation on wear in piston-cylinder assemblies

Both in engines and test rigs, cavitation in piston-ring lubrication is a subject studied by many researchers in the past. Although there is no sufficient evidence of cavitation erosion on the surface of the liner, this phenomenon is studied as part of the lubricant transport process. During the transport process the lubricant enters the combustion chamber. The combustion products of consumed oil might contribute to exhaust gas emissions and with emission legislation becoming more stringent, it is important that oil consumption is reduced to the lowest level possible. The role of the piston-rings is becoming more complex with the imposed requirements for lower oil consumption and friction. The piston-ring pack role on engine performance, durability and wear, is becoming on the other hand, more demanding. Between the piston-ring and cylinder liner, cavitation occurs as a result of two-phase liquid flow. Cavitation has long been recognized to degrade performances in most engineering applications and its effect in piston-ring lubrication is that it alters the oil film pressure profile, generated at the converging-diverging wedge of the piston-ring. An area of the piston-ring surface is void, corresponds to subatmospheric pressures and thus, the piston-ring load capacity is altered. Two experimental rigs were used, a simplified single-ring test rig that simulates the piston-ring liner movement at speeds corresponding to idle but the movement is reversed and a single cylinder diesel engine that was used for visualization results only, after the necessary modifications.