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Os desenvolvimentos de novos motores têm resultado no aumento constante dos carregamentos mecânicos e térmicos dos componentes. Além de estarem expostos a condições desfavoráveis ao desgaste, os novos componentes do motor devem garantir desempenho similar, ou muitas vezes superior, aos dos componentes atuais. Para os anéis de pistão, o desempenho é dado pela sua capacidade de vedação e raspagem, que podem ser mensurados em motor pelos resultados de consumo de óleo lubrificante (COL) e fluxo de gases para o cárter (blow-by). Sendo assim, a proposta desse trabalho foi a de avaliar-se a influência do tratamento superficial a laser para endurecimento da pista de desgaste do anel de pistão de segundo canalete, em termos do desempenho de vedação e raspagem. Foram comparados dois protótipos, utilizando como padrão um anel de pistão de produção corrente, comercialmente fornecido a clientes. O efeito do tratamento térmico a laser nos anéis foi avaliado em relação a distorções dimensionais. Após isto, foram realizados testes tribológicos de bancada com o objetivo de conhecer o comportamento do anel depois do tratamento laser. De maneira geral o tratamento superficial por laser na superfície de anéis de pistão mostraram resultados significativos no aspecto aumento de dureza, com alguns deméritos no aspecto dimensional que pode interferir na boa funcionalidade do sistema tribológico anel lubrificante cilindro. / The new engine developments are providing engine mechanical and thermal loads increase on the components. Besides the unfavorable wear conditions, the components should provide similar or improved performance compared with current baselines. For piston rings, the performance is given by the ring capacity of sealing and scrapping. These performances can be measured in a engine by the results of lube oil consumption (LOC) and Blow-by. So, the proposal of this work is to evaluate the influence of laser hardening on the second ring wear and verify the sealing and scrapping performance. It was compared two prototypes, being as parameter the current piston ring supplied to customer. Firstly, it was compared the dimensional of the laser hardening effect. After that, it were tested these prototypes in bench tests in order to know the ring performance after laser hardening. In general terms, the superficial treatment by laser on the piston rings surface have showed significant results in the hardness aspects, with some demerits in the dimensional aspect that can interfere in the good functionality of the tribological system, piston rings lubricant cylinder liner.

A partir de registros de dois testemunhos, KF-12 localizado na Bacia de Campos e KF-18 na Bacia de Santos, ambos na margem continental sudeste brasileira, realizou-se a caracterização do Último Interglacial s.l., de 60 a 130 ka atrás. Primeiramente, estabeleceu-se um Modelo de Idade para o KF-12 tendo como referência a curva do KF-18 que já possuía uma boa cronologia. Com a curva do plexo Menardii, determinou-se as biozonas de Ericson e Wollin (1968) e constatou-se a diferença existente entre os limites da Zona X e do estágio isotópico marinho 5. Os limites inferidos para a biozona X foram 135,6 ka AP (limite inferior), e 82,3 ka AP (limite superior) para o testemunho KF-18 e; para o KF-12, 133,5 ka AP (limite inferior) a 88,4 ka AP (limite superior). O estágio isotópico marinho (MIS) 5, na região de estudo, compreende o intervalo entre 129,5 e 71,1 ka AP, em ambos os testemunhos. Também foram utilizados outros dados, tais como, razão isotópica em foraminífero planctônico, fauna, teor de carbonato, razão Ti/Ca e Fe/Ca através dos quais pôde-se estimar paleotemperaturas da superfície do mar, aporte de material terrígeno de acordo com as condições úmidas/seca da região de estudo durante o intervalo de interesse. Por fim, verificou-se que tanto os dados isotópicos de oxigênio (δ18O) do testemunho de gelo da Groenlândia (NGRIP) quanto os da razão de deutério da Antártica variaram de forma semelhante aos δ18O de foraminíferos bentônicos do KF-12 e KF-18, confirmando o sincronismo de tais registros. / The Last Interglacial Cycle s.l. (between 60 and 130 ky ago) was characterized through registers of two different cores in the Brazilian continental shelf, KF-12, located in Campos Basin and KF-18, located in Santos Basin. First an \"age model\" was established for KF-12, from the KF-18 curve that already had a good cronology. Using Menardii group curve, the biozones from Ericson e Wollin (1968) were established and the difference between the X Zone and the marine isotope stage 5 edges was noticed. The inferred limits for X biozone were 35,6 ky BP (inferior limit) and 82,3 ky BP (superior limit) for KF-18 core and 133,5 and 88,4 ky BP for KF-12 core. In both cores the marine isotope stage (MIS) 5 was between 129,5 and 71,1 ky BP. Other data were also used in the study, such as isotope ratio in planktonic foraminifera, fauna, carbonate content, Ti/Ca and Fe/Ca ratios whereby humidity/dry conditions and continental runoff were inferred. Lastly, the study showed that both the oxygen isotope data from Greenland ice core (NGRIP) and the Antarctic deuterium ratio ranged in a similar way of the δ18O benthonic foraminifera from KF-12 and KF-18, confirming the data synchronism.

Les moteurs à pistons utilisent en général l’air ambiant comme comburant. Cet air est composé principalement d’azote et d’oxygène mais aussi de vapeur d’eau. La présence de cette vapeur modifie le processus de combustion de façon plus ou moins significative. S’agissant des moteurs, l’addition d’eau modifie les performances et diminue les émissions d’oxydes d’azote. Cependant très peu de travaux traitent de ces effets. Ce travail a donc pour objectif d’étudier expérimentalement et numériquement l’influence de l’humidité de l’air sur la combustion et plus particulièrement sur le fonctionnement des moteurs à pistons. L’approche numérique, menée de front avec l’approche expérimentale, modélise une flamme laminaire de prémélange. L’outil numérique qui a été utilisé est le logiciel de calcul de cinétique chimique COSILAB® pour du méthane et de l’isooctane. L'approche expérimentale utilise deux bancs d'essais. Le premier banc est un brûleur bec Bunsen à fente qui a été entièrement conçu et validé au cours de cette étude afin de mesurer des vitesses de flamme laminaire. Une attention particulière a été portée à la métrologie et à l'estimation quantitative des incertitudes de mesures. Ces mesures obtenues à pression atmosphérique sur ce brûleur, pour une humidité spécifique pouvant atteindre 80 g.kg-1, ont permis de valider les résultats obtenus numériquement. Les calculs ont ensuite été portés à des conditions de pression et température représentatives d'un fonctionnement moteur. Un banc d'essai moteur recherche a été utilisé pour confirmer les tendances observées dans le cas des flammes laminaires. Les résultats obtenus montrent une forte diminution de la vitesse de flamme ainsi que des émissions d'oxydes d'azote lorsque l'humidité augmente. Par exemple pour une humidité spécifique de 110 g.kg-1, la vitesse de flamme chute de 55% et les émissions de NOX chutent de 70%. Les essais au banc moteur ont montré une augmentation de l'avance à l'allumage optimale et des émissions d'hydrocarbures imbrûlés lorsque l'humidité augmente. Ils confirment également la forte diminution des émissions d'oxydes d'azote ; par exemple pour une augmentation de l'humidité de 30 g.kg-1, les NOX baissent de 35% / Manquant

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / Includes bibliographical references. / by David L. Akin. / M.S.

A partir de registros de dois testemunhos, KF-12 localizado na Bacia de Campos e KF-18 na Bacia de Santos, ambos na margem continental sudeste brasileira, realizou-se a caracterização do Último Interglacial s.l., de 60 a 130 ka atrás. Primeiramente, estabeleceu-se um Modelo de Idade para o KF-12 tendo como referência a curva do KF-18 que já possuía uma boa cronologia. Com a curva do plexo Menardii, determinou-se as biozonas de Ericson e Wollin (1968) e constatou-se a diferença existente entre os limites da Zona X e do estágio isotópico marinho 5. Os limites inferidos para a biozona X foram 135,6 ka AP (limite inferior), e 82,3 ka AP (limite superior) para o testemunho KF-18 e; para o KF-12, 133,5 ka AP (limite inferior) a 88,4 ka AP (limite superior). O estágio isotópico marinho (MIS) 5, na região de estudo, compreende o intervalo entre 129,5 e 71,1 ka AP, em ambos os testemunhos. Também foram utilizados outros dados, tais como, razão isotópica em foraminífero planctônico, fauna, teor de carbonato, razão Ti/Ca e Fe/Ca através dos quais pôde-se estimar paleotemperaturas da superfície do mar, aporte de material terrígeno de acordo com as condições úmidas/seca da região de estudo durante o intervalo de interesse. Por fim, verificou-se que tanto os dados isotópicos de oxigênio (δ18O) do testemunho de gelo da Groenlândia (NGRIP) quanto os da razão de deutério da Antártica variaram de forma semelhante aos δ18O de foraminíferos bentônicos do KF-12 e KF-18, confirmando o sincronismo de tais registros. / The Last Interglacial Cycle s.l. (between 60 and 130 ky ago) was characterized through registers of two different cores in the Brazilian continental shelf, KF-12, located in Campos Basin and KF-18, located in Santos Basin. First an \"age model\" was established for KF-12, from the KF-18 curve that already had a good cronology. Using Menardii group curve, the biozones from Ericson e Wollin (1968) were established and the difference between the X Zone and the marine isotope stage 5 edges was noticed. The inferred limits for X biozone were 35,6 ky BP (inferior limit) and 82,3 ky BP (superior limit) for KF-18 core and 133,5 and 88,4 ky BP for KF-12 core. In both cores the marine isotope stage (MIS) 5 was between 129,5 and 71,1 ky BP. Other data were also used in the study, such as isotope ratio in planktonic foraminifera, fauna, carbonate content, Ti/Ca and Fe/Ca ratios whereby humidity/dry conditions and continental runoff were inferred. Lastly, the study showed that both the oxygen isotope data from Greenland ice core (NGRIP) and the Antarctic deuterium ratio ranged in a similar way of the δ18O benthonic foraminifera from KF-12 and KF-18, confirming the data synchronism.

<p>This thesis investigates the effects of swashplate vibration and slipper surface geometry on the performance of the slipper-swashplate interface. The lubricating interfaces within a swashplate type axial piston machine are the most complicated part of the design process. These interfaces are supposed to provide support to the significant loads they experience during operation and to prevent continuous contact of the sliding surfaces. Therefore a proper slipper-swashplate interface design ensures full film lubrication during operation and provides sufficient load support while minimizing viscous and volumetric losses at the same time. The effects of two factors on the performance of the slipper-swashplate are examined during this work; swashplate vibration and slipper surface micro-geometry. An already existing model of the slipper-swashplate interface was used to carry out the results for this work however some modifications were made to the model to suit the needs of this research. Swashplate vibration is a phenomenon that has not been implemented in the model before, therefore its effects on the performance of the interface were analyzed. Thickness of the fluid film in the lubricating regime corresponds with its performance and is directly affected by the micro-geometry of the sliding interfaces. Therefore the effects of slipper surface micro-geometry is crucial to study in order to find the optimal slipper-swashplate interface design.</p>

This Master Thesis has been performed at Atlas Copco Rock Drills AB, Örebro and at Linköping University, Sweden from February 2010 through August 2010.The project deals with performance improvement of hydraulic rock drill machine manufactured by Atlas Copco Rock Drills. Atlas Copco Rock Drills AB is a world leading supplier of percussive rock drilling equipment for surface and underground applications. HOPSAN, a software developed at Linkoping University, provides an integrated simulation environment for simulation of fluid power systems. During the work, a HOPSAN model of a piston accumulator has been developed and its performance with a rock drill has been studied. Furthermore, the fatigue strength calculations of a piston accumulator has been made on the basis of stress analysis performed using the ANSYS software. One of the rock drills of valveless type, developed at Atlas Copco Rocktec Division works at higher efficiency than the conventionally used rock drills. But the problem with this type of drill is that the piston swings between two large and highly pressurized oil volume which causes strength problems in the housing of the rock drill. The aim of this work is to achieve the higher efficiency of the rock drill without having any strength problems. Therefore, some study and research is proposed to replace the large oil volume by one or two piston accumulators. This thesis work involves modelling, simulation, design and fatigue strength calculations of a piston accumulator and its implementation to the rock drill. Optimization of the piston accumulator has also been conducted while working with the rock drill so that highest possible eciency could be achieved. The performance of the rockdrill with piston accumulator has been analyzed and results are studied. In the end, a short fatigue life calculations are performed and results are discussed. Prior to fatigue life calculations, a transient dynamic stress analysis has been performed and stress amplitudes are identified which contributes to the accumulated damage to piston in accumulator.

We study thoroughly Casimir energy and Casimir force in a rectangular cavity and piston with various boundary conditions, for both scalar field and electromagnetic (EM) field. Using the cylinder kernel approach, we find the Casimir energy exactly and analyze the Casimir energy and Casimir force from the point of view of closed classical paths (or optical paths). For the scalar field, we study the rectangular cavity and rectangular piston with all Dirichlet conditions and all Neumann boundary conditions and then generalize to more general cases with any combination of Dirichlet and Neumann boundary conditions. For the EM field, we first represent the EM field by 2 scalar fields (Hertz potentials), then relate the EM problem to corresponding scalar problems. We study the case with all conducting boundary conditions and then replace some conducting boundary conditions by permeable boundary conditions. By classifying the closed classical paths into 4 kinds: Periodic, Side, Edge and Corner paths, we can see the role played by each kind of path. A general treatment of any combination of boundary conditions is provided. Comparing the differences between different kinds of boundary conditions and exploring the relation between corresponding EM and scalar problems, we can understand the effect of each kind of boundary condition and contribution of each kind of classical path more clearly.

<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>