Yes / A laser induced fluorescence system has been developed to visualise the oil film thickness between the piston ring and cylinder wall of a fired gasoline engine via a small optical window mounted in the cylinder wall. A fluorescent dye was added to the lubricant in the sump to allow the lubricant to fluoresce when absorbing laser radiation. The concentration of the dye did not disturb the lubricant chemistry or its performance. Degraded engine oil samples were used to investigate the influence of lubricant quality on ring pack lubricant film thickness measurements. The results show significant differences in the lubricant film thickness profiles for the ring pack when the lubricant degrades which will affect ring pack friction and ultimately fuel economy.

No description available.

<p>This study focuses on the wear of piston rings in a hydraulic radial piston motor. The piston ring has to satisfy increasing demands for reliability and longer service life. It has two contacting surfaces, the face and the flank, and operates under a boundary lubrication state.</p><p>This first part of the project aimed to detect and characterise piston ring wear. Measurement by weighing gives an overall value for wear defined as loss of mass. Two-dimensional form and surface roughness measurements show the distribution of wear on the piston ring face in contact with the cylinder bore and the piston ring flank in contact with the piston groove. Three-dimensional analyses, both quantitative and qualitative, allow the wear mechanisms to be identified.</p><p>The wear of piston rings from an actual hydraulic motor was characterised. As well, rig testing was performed in two different test rig set-ups, one simulating the sliding movement of the piston ring and the other the tilting movement at the end of the strokes. Wear during the running-in period was investigated, and the findings indicate that the period when this takes place is of short duration. In the long term, mild wear makes the surfaces smoother than they were when new, resulting in a very low wear coefficient. Significant levels of wear were measured on both contacting surfaces of the piston ring. In cases in which the flank exhibits more wear than the face, the wear on the flank can be reduced by proper design of the piston groove.</p><p>The second part of the project aimed to evaluate use of a textured surface for the cylinder bore counter surface and a coated surface for the piston ring. Three modelling experiments were performed to characterise the friction and wear properties under lean boundary lubrication conditions. Under such conditions, textured surfaces have the advantage of retaining more lubricant and supplying it over a longer time. Stable friction was also a distinctive feature of the textured surface. Use of a coating could also possibly reduce the amount of wear. Though a smooth surface, like a polished one, is hard to beat for a working texture, a coated surface is far ahead of a smooth uncoated one. Different manufactured and commonly used cylinder bore surfaces, including textured ones, were evaluated in the sliding movement test rig. That allowed favourable wear properties, such as lowest wear coefficient, to be determined with the use of a roller burnished surface.</p><p>A final part of the research involved simulating wear on the piston ring face throughout the entire service life of a hydraulic motor. This allowed us to determine the roles of surface roughness and coating in prolonging service life and achieving acceptable and secure piston ring operation. The model is simple and realistic, but still needs to be refined so as to correspond even better to reality.</p>

This study focuses on the wear of piston rings in a hydraulic radial piston motor. The piston ring has to satisfy increasing demands for reliability and longer service life. It has two contacting surfaces, the face and the flank, and operates under a boundary lubrication state. This first part of the project aimed to detect and characterise piston ring wear. Measurement by weighing gives an overall value for wear defined as loss of mass. Two-dimensional form and surface roughness measurements show the distribution of wear on the piston ring face in contact with the cylinder bore and the piston ring flank in contact with the piston groove. Three-dimensional analyses, both quantitative and qualitative, allow the wear mechanisms to be identified. The wear of piston rings from an actual hydraulic motor was characterised. As well, rig testing was performed in two different test rig set-ups, one simulating the sliding movement of the piston ring and the other the tilting movement at the end of the strokes. Wear during the running-in period was investigated, and the findings indicate that the period when this takes place is of short duration. In the long term, mild wear makes the surfaces smoother than they were when new, resulting in a very low wear coefficient. Significant levels of wear were measured on both contacting surfaces of the piston ring. In cases in which the flank exhibits more wear than the face, the wear on the flank can be reduced by proper design of the piston groove. The second part of the project aimed to evaluate use of a textured surface for the cylinder bore counter surface and a coated surface for the piston ring. Three modelling experiments were performed to characterise the friction and wear properties under lean boundary lubrication conditions. Under such conditions, textured surfaces have the advantage of retaining more lubricant and supplying it over a longer time. Stable friction was also a distinctive feature of the textured surface. Use of a coating could also possibly reduce the amount of wear. Though a smooth surface, like a polished one, is hard to beat for a working texture, a coated surface is far ahead of a smooth uncoated one. Different manufactured and commonly used cylinder bore surfaces, including textured ones, were evaluated in the sliding movement test rig. That allowed favourable wear properties, such as lowest wear coefficient, to be determined with the use of a roller burnished surface. A final part of the research involved simulating wear on the piston ring face throughout the entire service life of a hydraulic motor. This allowed us to determine the roles of surface roughness and coating in prolonging service life and achieving acceptable and secure piston ring operation. The model is simple and realistic, but still needs to be refined so as to correspond even better to reality. / QC 20101007

No description available.

Piston rings cause significant friction losses within internal combustion engines. Especially the first compression ring, which is pressed onto the liner by high cylinder pressure, contributes significantly to the total friction loss of the piston assembly. The tribological behavior of the oil scraper ring is mainly related to the pretensioning force and can lead to high losses even at low and idle speed. Due to this, there is always a markable risk of wear for the contact surfaces of the piston rings and the cylinder. “Diamond-like carbon” coatings on the surface of the piston rings can prevent wear and are able to reduce friction in the ring-liner-contact. The purpose of this work was to investigate the tribological benefit of this coating-system on the compression and oil scraper ring. Experimental studies were carried out on a fired single-cylinder engine using the Indicated Instantaneous Mean Effective Pressure-method (IIMEP) for the crank angle-resolved detection of the piston assembly’s friction force. To be able to determine the component-related fractions of the friction loss and to quantify the hydrodynamic and asperity related parts locally and time dependent, an EHD/MBS model of the engine was created in AVL EXCITE and a simulative investigation was performed. This simulation was validated by the experimental work and provided detailed information about the individual contact conditions and gap height of each tribological contact of the piston group. The combined approach of measurement and simulation enabled the prediction of tribological aspects and performance in parameter studies on a virtual engine test bed.

Due to climate changes and an increasing global temperature, the maritime transport sector has taken upon a mission to reduce their share of greenhouse gas emissions by 50% until 2050. Combustion engines used in ships mainly run on carbon-based fuels, but to achieve the reduction of emissions it is crucial to investigate the possibility of alternative fuels. Ammonia is an alternative fuel with a carbon free chemical composition that shows big potential, with several initiatives to put ammonia driven ship engines on the market in the near future. For ships to be able to run on ammonia fuel, the engine materials have to withstand the corrosive effect of ammonia whilst still ensuring that the motor runs properly. In this study, two piston ring materials are investigated with regards to long-term effects of exposure to ammonia solution. The piston ring materials investigated were comprised of a cast iron substrate covered with either a chromium ceramic coating or a with a cermet coating, the latter also coated with an aluminium-bronze based running in layer on top. The materials were submerged in 25% ammonia solution for different time intervals up to 12 weeks, with a solution change every fourth week. After exposure to ammonia, the materials were tribologically tested in a reciprocal sliding test rig. The surfaces, both inside and outside of the wear tracks, were analysed with SEM and EDS, as well as with CSI. The chromium ceramic coating did not seem to get affected by, or interact chemically, with the ammonia solution. Exposing the material to ammonia did not seemingly affect the tribological properties. However, two different behaviours were observed when analysing the cermet coated samples with a running-in layer of aluminium-bronze. These samples reacted with the ammonia solution in two different ways, resulting in the series being split into two. In both cases precipitates were formed, but the colour changes of the solutions differed for the series. The coatings were also worn differently, as in one case a flattening effect was observed throughout all time intervals, whereas in the other case the worn volume and track depth seemed to increase with exposure to ammonia solution.

The piston ring in a marine two-stroke diesel engine operates in demanding conditions, involving high temperatures and pressures. Its main purposes are to seal the combustion chamber of the engine, minimize the frictional contact against the cylinder liner and transfer heat from the piston. The development of new piston ring designs for marine diesel engines is mainly based on engineering knowledge and expertise but is somewhat unstructured. A new method which may be used to overcome this lack of structure is to simulate the working conditions for the piston ring. This is the main objective of this thesis work, to invent a simulation method which allows accurate and distinct results to be obtained and thereby knowledge about piston ring performance. The simulation method is based on a three-dimensional geometric model of the piston ring, where the radial geometry should be described by the lathe curve from industry. It should also be implemented and function automatically as a simulation tool. In short terms, the calculated stresses and strains in the material, the contact pressure against the cylinder liner and the piston ring twist should be evaluated. The simulation tool should be able to model two different types of piston ring designs, namely straight cut design and CPR design, and both with optional dimensions. Validation of the results are performed with a simulation model which uses fewer dimensions, but also utilizes engineering knowledge from the marine industry. In addition to this, some more advanced investigations have been performed in order to demonstrate the capacity and power of the simulation tool. The simulation method appears to perform well and according to the simple model, but it also shows good prediction in more advanced investigations. For example, piston rings in overheated engines tend to twist more than usual, which could be seen in real investigations, and the behavior is easily recreated with the simulation tool. Also investigations with reduced cross sections, which is well known within high-speed engines, are performed. The method is executed automatically with the developed simulation tool which is based on ANSYS, a commercial simulation software. This software, that is commonly used in development work, uses a finite element method to solve the problem. The simulation tool is used as an external input which configures the geometry, finite element formulation and the result rendering. / Kolvringen i en marin tvåtaktsmotor arbetar under krävande förhållanden i form av hög temperatur och högt tryck. Dess huvudsyften är att täta motorns förbränningskammare, minimera friktion mot cylindern och transportera värme från kolven. Utvecklingen av nya kolvringsmodeller för marint bruk är huvudsakligen baserat på ingenjörskunskap och expertkunnande vilket dock lett till en viss osäkerhet. En modern metod för att bemästra denna osäkerhet är att simulera kolvringen och dess förhållanden i motorn. Det huvudsakliga målet är att skapa en simuleringsmetod som ger noggranna och tydliga resultat och därav kunskap om kolvringens påfrestningar och egenskaper under drift av motorn. Simuleringsmetoden är skapad för en tredimensionell geometri som är beskriven av bl.a. den svarvkurva som används inom industrin. Metoden skall även vara implementerad och fungera automatiskt som ett beräkningsverktyg vilket inom en rimlig tidsrymd skall beräkna intresseområden såsom spänningar, kontakttryck och twist. Det skall även vara konstruerat så att två olika kolvringmodeller skall kunna simuleras, nämligen rakskuren ring och gastät ring, och båda med valbara dimensioner. Simuleringsmetoden är bekräftad genom att jämföra med en enklare simuleringsmodell samt teknisk kunskap och resonemang. Utöver att bekräfta modellen genomförs även en del mer avancerade undersökningar för att kunna återge simuleringsverktygets verkliga effektivitet. Resultaten återger rätt karaktär och i rätt storleksordning i jämförelse med den enklare modellen men visar även på sanningenliga resultat vid mer avancerade tester. Exempelvis har överhettade motorer ofta en förstärkt twist, vilket är uppmärksammat vid mätningar, och sådana effekter kan återges med simuleringsverktyget. Även tester med förändrade tvärsnittsprofiler, vilka ofta används inom fordonsindustrin, och vilken effekt dessa profiler får på twistningen har genomförts. Metoden och det automatiska simuleringsverktyget är implementerat i den kommersiella programvaran ANSYS. Programmet använder sig av finita elementmetoden för att lösa problem och är ett vanligt program inom flera olika utvecklingsområden. Verktyget används som en extern inläsning till programmet vilket konfigurerar geometrin, finita elementformuleringen och resultatrenderingen.

Au sein des parties statiques d’une turbine à gaz, l’étanchéité du système d’air derefroidissement est couramment assurée par un montage de segments. De par sa rigiditéélevée, ce type de joint s’adapte mal aux pièces avec lesquelles il entre en contact. Uneméthodologie, associant métrologie et calcul éléments finis, a effectivement montré quel’ouverture, à l’interface entre un segment et sa piste, est très supérieure à celle qui caractériseun contact simplement rugueux. Une analyse en ordres de grandeur a révélé que lesmécanismes d’écoulement du gaz, sur un champ d’ouverture typique de l’interface entre la pisteet le segment, sont conditionnés par deux nombres adimensionnels. Trois régimes peuvent êtredistingués en fonction des valeurs prises par ces nombres. L’un d’eux, le régime laminairecompressible inertiel, est particulièrement intéressant car il est présent dans les zones de laturbine où l’étanchéité est cruciale. Un modèle quasi analytique a été développé pour décrire cerégime. En l’associant à un modèle de déformation, on aboutit à un outil prédictif du débit degaz induit par un segment. Des essais sur banc partiel ont permis de le valider et de démontrersa précision. L’outil développé fournit le moyen de quantifier l’impact du champ de température,du champ de pression et des écarts géométriques, propres à un stator de turbine, sur lesperformances de l’étanchéité. Ce travail a débouché sur des règles de dimensionnement et deconception qui portent notamment sur l’obturation du jeu inter-extrémités, sur le choix dunombre de segments et du sens de serrage. / The sealing of gas turbine static parts is usually performed using piston rings.Because of its high stiffness, this type of gasket does not adapt itself to the parts with which it isdue to be in contact. A method involving metrology and a FEM actually revealed that the ringboreor ring-piston contact aperture is far larger than the one within a rough contact. Using ascale analysis, we showed that gas flow mechanisms, through the aperture field of the contactbetween the ring and the inner or outer part (i.e. the piston or the bore), depend on twodimensionless numbers. Three regimes can be distinguished depending on the values of thesenumbers. One of them, the compressible inertial laminar regime, is of particular interestbecause of its relevance in turbine areas where sealing is strongly critical. A quasi analyticalmodel was developed to describe this regime. By a coupling with a strain model, it wasupgraded to a predictive tool of leakage through a piston-ring or bore-ring contact. Acomparison with measurements carried out on a partial test rig allowed to prove its accuracy.This tool made it possible to quantify the influence of temperature field, pressure field andgeometrical defects, which are typical of a turbine stator, on sealing performance. This worklead us to propose design rules concerning, in particular, the ring gap type, number of rings tobe mounted and choice of tightening direction.

The constant pursuit in the automotive industry to increase the engines performance, new solutions are always developed and tested to reduce the friction and increase the efficiency in the engine. One component that contributes to friction losses is the piston ring pack where the top compression stands for up to 40 %. This master thesis collaborated with Scania’s material science department Basic engine and covers the friction and wear of four different materials on the cylinder liner surface against the top compression ring.The four tested materials were grey cast iron with different honing quality and three atmospheric plasma sprayed coatings with titanium oxide, chromium oxide and Metco’s mixture F2071 which is a stainless steel mixed with a ceramic. A martensitic steel piston ring with a chromium coated sliding surface was used for all the testing in the Cameron-Plint TE77 test-rig. This is a pin-on-disc test method and the parameters used for testing is set to replicate the environment the ring is exposed to at the top dead centre.The test-rig has been in Scania’s possession for a long time and has not always given a satisfying result. An uneven contact between the ring and liner has been a problem resulting in only worn edges of the liner specimen. The piston ring holder was therefore redesigned to be able to adjust the radius of the ring. This allowed a good conformability between the ring and liner to be obtained.The tested materials were evaluated according to friction and wear. Friction was measured with the test-rig and the wear was calculated with surface profiles that were measured before and after testing. Worn surfaces were studied in a SEM to verify which wear mechanism that was active. The changes of the surfaces was studied with the use of following surface parameters Ra, Rk, Rpk, Rvk and if there was a connection between these parameters and friction and wear coefficient.Independent of honing quality showed the grey cast iron lowest friction coefficient just under 0.13, the F2071 liner showed a friction coefficient just above 0.13. Both oxide layers showed similar friction where the chromium oxide had a friction just below 0.15 and the titanium oxide lay just above 0.15. Lowest wear coefficient had the chromium oxide followed by F2071, titanium oxide and the bad honed grey cast iron. These three liners showed almost the exact same wear coefficient. Worst wear coefficient had the grey cast iron with a good honing quality. A mild abrasive wear mechanism was active during the wear test and vague wear marks was found on the surface. There is no connection between wear coefficient and friction and the change in surface roughness during the test does not affect the friction.