O presente estudo descreve as alterações metalúrgicas e topográficas do cilindro de blocos de motor de combustão interna fabricados em ferro fundido cinzento, após a realização de testes de durabilidade em dinamômetro. O motor testado tem tecnologia Flex-Fuel, e pode ser operado com qualquer proporção de mistura gasolina comum/etanol. Um motor foi testado com combustível etanol e o outro com gasolina comum, buscando-se assim representar duas condições extremas de trabalho em termos de combustível. A pesquisa constituiu-se da revisão bibliográfica e da parte prática que envolveu: a realização de testes de durabilidade de motor em dinamômetro; a caracterização metalúrgica e topográfica do cilindro após teste com ambos os combustíveis, utilizando técnicas de microscopia eletrônica de varredura, metalografia por microscopia óptica, perfilometria e quantificação de parâmetros de rugosidade, entre outros; a análise crítica, discussão dos resultados e apresentação da conclusão. / The present study approaches the metallurgical and topographical alterations on the cylinder of an internal combustion engine block made of gray cast iron, after durability dynamometer tests. The tested engine has flexible fuel technology (Flex-Fuel), and is capable to work with both gasoline/ethanol fuels, in any mixture proportion. One engine has been tested with ethanol and another one tested with gasoline, and so representing two extreme conditions on which the engine may work in terms of fuel. The research has been developed basically through the conceptual approach by the bibliographic review and the experimental steps that involved: general engine durability test at dynamometer bench; metallurgical and topographic characterization analysis at laboratory, after the test with both fuels, applying Scanning Electronic Microscopy SEM, optical microscopy metallography, profilometer and roughness parameters quantification, and so forth; critical analysis on the results, discussion and final conclusion.

Despite years of research in high speed boundary layer flow, there is still a need for insightful experiments to realize key features of the flow like boundary layer response to different conditions and related transition mechanisms. Volumes of data on the these problems point to the fact that there is still much to be understood about the nature of boundary layer instability causing transition and growth of boundary layer in different conditions. Boundary layer stability experiments have been found to be more useful, in which the boundary layer is perturbed and its behavior observed to infer useful conclusions. Also, apart from the stability part, the effect of various changes in boundary layer due to the perturbation makes interesting observation to gain more insight into the understood and the not so understood facets of the same. In view of the above, the effect of a steady axisymmetric thermal bump is investigated on a hypersonic boundary layer over a 60º sharp cone cylinder model. The thermal bump, placed near tip of the cone, perturbs the boundary layer, the behavior of which is observed by recording the wall heat flux on the cone and cylinder surface using platinum thin film sensors. The state of the boundary layer is qualitatively assessed by the wall heat flux comparisons between laminar and turbulent values. The same thermal bump also acts as a heat addition source to boundary layer in which case this recorded data provides a look into the effect of the heat addition to the wall heat flux. To gain a larger view of heat addition causing changes to the flow, effects of change in enthalpy are also considered. Experiments are performed in the IISc HST2 shock tunnel facility at 2MJkg−1 stag-nation enthalpy and Mach number of 8,with and without the thermal bump to form comparisons. Some experiments are also performed in the IISc HST3 free piston driven shock tunnel facility at 6MJkg−1, to investigate the effect of change in stagnation enthalpy on the wall heat flux. To support the experimental results theoretical comparisons and computational studies have also been carried out. The results of experiments show that the laminar boundary layer over the whole model remains laminar even when perturbed by the thermal bump. The wall heat flux measurements show change on the cone part where there seems to be fluctuation in the temperature gradients caused by the thermal bump, which decrease at first and then show an increase towards the base of the cone. The cylinder part remains the same with and without the thermal bump, indicating heavy damping effects by the expansion fan at cone cylinder junction. A local peak in wall heat flux is observed at the junction which is reduced by 64% by the action of the thermal bump. The possible reason for this is attributed to the increased temperature gradients at the wall due to delayed dissipation of heat that is accumulated in the boundary layer as a result of the thermal bump action. The comparison of data for enthalpies of 2MJkg−1 and 6MJkg−1 show that there are negligible real gas effects in the higher enthalpy case and they do not affect the wall heat flux much. Also it is found that the thermal bump fails to dump heat into the flow directly though it creates heat addition virtually by mere discontinuity in the surface temperature and causes temperature gradients fluctuation in the boundary layer. Considering the thermal bump action and the change in stagnation enthalpy of the flow, there seems to be no change in both cases that can be attributed to a common observation resulting from the factor of change in heat inside the boundary layer.

In India, with the increase in the number of industries and vehicles the environment is getting more and more polluted. More than industries it is the rapid growth of vehicles which causes serious environmental crisis in the form of air pollution and has become alarming particularly in cities. The industrial and vehicular growth cannot be neglected, as the country’s economic and social well being is largely dependent on them. But this should not come at the cost of our health and eco system. The industrial and vehicular emissions must be controlled in order to keep our air clean. Continued efforts in this direction are being taken up across the globe to investigate an efficient and economical technique. There are many air pollutants being emitted from both natural and manmade sources. The major air pollutants identified as hazardous to human health are nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM), volatile organic compounds (VOC), and sulfur dioxides (SOx). Among these, nitrogen oxides are considered to be difficult to remove. The sources of NOx are thermal power plants, stationary and mobile diesel engines, gasturbine engine, ironore sintering plants and various other smallscale utilities. There are conventionally available technologies to remove NOx such as chemical scrubbing, catalysis etc. But these techniques are either difficult to operate or do not bring down the level of NOx to the required norms imposed by the government. The failure of conventional techniques to remove NOx to the expected limit led to the development of alternative nonconventional techniques. Prominent among these new alternative techniques is electric discharge plasma, where the gas is partially ionized and temperature of electrons is considerably higher than that of ions and background gas molecules. Diesel engines are getting popular due to their inherent merits and their number is increasing considerably. Unfortunately, the exhaust of diesel engine being complex with high oxygen content makes the existing pollution control techniques insufficient particularly with regard to removal of NOx. So there is a need for investigating better technology which can effectively abate the pollutants from diesel engine exhaust. Electric Discharge plasma is one such alternative technique which has been very successful in large volumes of flue gas cleaning and hence, its potential is being explored in the cleaning of small volumes of vehicular exhausts, in particular, diesel engine exhaust. In the present work we investigated the relative performance of different electric discharge plasma reactors, with different type of voltages like AC, DC and pulse. The reactors were evaluated for NOx removal efficiency and NO conversion. This research work is a feasibility study to find whether electric discharge plasma can be used more effectively as an alternative technology for the after treatment of diesel engine exhaust in cascade with some cheaper adsorbents, if necessary. The scope of this qualitative experimental study can briefly be summarized as below: . • To study different reactors for NO conversion and NOx removal . • To study the effect of dielectric pellets in enhancing the radical production which in turn will have a bearing on the chemical reactions . • To study the effect of different types of voltages on the cleansing process . • To propose an efficient reactor system subject to the experimental conditions studied.

Size and distribution of mount deformation are the main topics discussed in this thesis, using different static loading. The thesis’ primary focus is to show how deformation and stress of the engine block with cylinder liner are affected in the assembly order of the cylinder head. The calculation and evaluation of the solution are calculated by using method finite element, software Ansys. In addition other methods are discussed which can also measure the deformation of the engine block.

This paper presents a conceptual study aiming to improve the compactness of electro-hydraulic compact drives (ECD ). In most current ECD architectures, gas accumulators are used as volume compensators for the flow imbalance emerging whenever asymmetric single rod cylinders are used. To stay within a required reservoir pressure range typically from two to four bar, a large gas volume is required, compromising system compactness. Combining conventional ECD architectures with a bootstrap reservoir offers a greater degree of freedom in system design, which enables downsizing or avoidance of the gas volume. Another potential benefit by including a bootstrap reservoir is the possibility of elevating the backpressure of the ECD thus enhancing drive stiffness, expanding the application range and market acceptance. Based on an open analysis of the solution space occurring when introducing a bootstrap reservoir, three system architectures are selected for a conceptual study. The results show that the downsizing potential is strongly dependent on the maximum friction force and the area ratio of the bootstrap reservoir pistons, while a linear analysis reveals that for some system architectures the bootstrap reservoir may severely influence the system dynamics. Simulation results confirm the functionality of the proposed system architectures, and show that a potential for downsizing/avoiding the gas volume, as well as increasing the ECD stiffness is present.

The high price of batteries in working machines with electric drives offer a potential for investment in energy-saving hydraulic systems. The decentralized power network opens up new approaches for hydraulic- and hybrid circuits. In addition, the regeneration of energy can be used at any point of the machine. For the example of an excavator arm drive with a double cylinder two compact hydraulic circuits are presented, which relieve a central hydraulic system.

Diesel engine emissions of oxides of nitrogen and particulate matter can be reduced simultaneously through the use of high levels of exhaust gas recirculation (EGR) to achieve low temperature combustion (LTC). Although the potential benefits of diesel LTC are clear, the main challenges to its practical implementation are the requirement of EGR levels that can exceed 60%, high fuel consumption, and high unburned hydrocarbon and carbon monoxide emissions. These limit the application of LTC to medium loads. In order to implement the LTC strategy in a passenger vehicle engine, a transition to conventional diesel operation is required to satisfy the expected high load demands on the engine. The investigation presented in this thesis was therefore aimed at improving the viability of the high-EGR LTC strategy for steady-state and transient operation. An experimental investigation was carried out on a single cylinder high-speed direct injection diesel engine. This thesis presents research on engine in-cylinder performance and engine-out gaseous and particulate emissions at operating conditions (i.e. EGR rate, intake pressure, fuel quantity, injection pressure) likely to be encountered by an engine during transient and steady-state operation. At selected operating points, further investigation in terms of in-cylinder spray and combustion visualization, flame temperature and soot concentration measurements provided deeper insight into the combustion and emissions phenomena. Increased intake pressure at single injection high-EGR LTC operation was investigated as a strategy to reduce the emissions of partial combustion by-products and to improve fuel economy. The higher intake pressure, although effective in reducing partial combustion by-products emissions and improving fuel economy, increased the EGR requirement to achieve LTC. A split fuel injection strategy with advanced injection timing on the other hand was effective in reducing the EGR requirement for LTC from 62% with single injection to 52% with split injections at 120 kPa (absolute) intake pressure. Unburned hydrocarbon emissions and fuel economy were particularly sensitive to intake oxygen mass fraction, and injection and dwell timings with the split injection strategy. In-cylinder soot formation and oxidation mechanisms with the split injection strategy were found to be significantly different from the single injection high-EGR LTC case. Transient simulation of an engine during combustion mode transition identified engine operating parameters on a cycle-by-cycle basis. Steady-state investigation of these test conditions provided significant insight into the combustion conditions and their effect on emissions and performance. The results from this thesis demonstrated the importance of optimizing both the air handling system performance and the fuel injection system during engine transients. The increased emissions and impaired performance due to slow response of the EGR and turbocharger systems during transitions to and from LTC modes can in part be mitigated through split injections optimized for the specific transient point. This provides a clear direction for engine developers to pursue in optimizing engine calibration when running with LTC-conventional diesel dual-mode strategies.

Wave energy converters of point absorber type have been developed and constructed. Full scale experiments have been carried out at sea and electricity has been successfully delivered. Linear permanent magnet generators together with a subsea substation and buoys of various geometric shapes have been investigated theoretically and experimentally. The design has in large extent an electronic approach, keeping the mechanical part of it as simple as possible, due to the long life span and reliability of electric components. Because of the nature of a linear generator, the internal translator with permanent magnets has a limited stroke length which will be reached when the buoy is exposed to large wave heights. Internal springs at the top and bottom of the generator prevent the translator from hitting the generator hull. Inertial forces due to the mass and velocity of the translator and the buoy and its heave added mass compresses the spring. The added mass is a rather large part of the total moving mass. Simulations of a converter with a vertical cylindrical buoy and with a toroidal buoy were conducted, as well as real sea experiments with converters with cylindrical buoys of two different sizes and a toroidal buoy. The overloads are likely to affect the design and service life of the generator, the buoy and the wire which interconnects them. Buoy shapes with as much excitation force as possible and as little heave added mass as possible were sought. A toroidal buoy caused less overloads on the generator at sea states with short wave periods and relatively large wave height, but for sea states with very long wave periods or extremely high waves, the magnitude of the overloads was mainly determined by the maximum displacement of the buoy. Snap loads on the interconnecting wire, as the slack wire tensed up after a very deep wave trough, were found to be greater but of the same order of magnitude as forces during the rest of the wave cycle. During a 4 day period at various wave conditions, two converters with cylindrical buoys proved efficiency between 11.1 % and 24.4 %. The larger buoy had 78 % larger water plane area than the other buoy which resulted in 11 % more power production. Short wave period was beneficial for the power production. Infinite frequency heave added mass was measured for a cylindrical buoy at real sea and found to be greater than the linearly calculated theoretical added mass.

Composite materials are usually multi-phase materials, made up from two or more phases, which are combined to provide properties that the individual constituents cannot. This technology represents an economical way to improve product performances avoiding the use of expensive materials. Composite materials can be obtained as films by means of the electrolysis of electroplating solutions in which micrometre- or submicrometre-size particles are suspended: variable amounts of these particles become incorporated in the electrochemically produced solid phase, to which they impart enhanced properties. The main aims of the present work contributing to this thesis are the study of different parameters influencing the electroco-deposition process in order to promote and improve the applicability of such a technology in the high speed electroplating industry. Following a comprehensive review on the electroco-deposition of composite coatings, the phenomena have been analysed moving from a microscopic point of view i. e. the role of the metal ions present in the electrolyte and adsorption on the inert particles and their interactions with the growing metal layer, to a macroscopic point of view i. e. the electrolyte agitation, its influence on particle motion and all the issues related to the presence of particles in an electrolyte during electroplating. In particular the inert particle influence in terms of geometry, dimension and chemical nature (spherical polystyrene particles vs. irregular alumina particles with different dimensions), the metal matrix influence (nickel, copper and zinc), the influence of electrolyte agitation (using a Rotating Cylinder Electrode cell system) and the influence of the coating thickness on particle content in the final coating, using different deposition times, have been examined. The importance of the particle shape has been highlighted showing how incorporating irregular geometries gave higher particle incorporation densities than regular geometries. The influence of the substrate finishing in terms of imperfections has been related to the particle incorporation rate showing how small surface imperfections enhanced the incorporation of particles. Different hydrodynamic regimes have been analysed resulting three different regimes being discerned: laminar, transitional and turbulent. The consequence, in terms of particle incorporation levels, has been found showing how the amount of particles in the coating changed from one regime to another. Different rate-determining steps were related to the hydrodynamics: when the regime is laminar, particles were incorporated as agglomerates and the process was under particle transfer control, whilst in the turbulent zone, the rate determining step was the velocity of reduction of the ions adsorbed on the particle surface.

O objetivo deste projeto de mestrado é estudar o escoamento bidimensional ao redor de um cilindro isolado oscilando forçadamente e apoiado em base elástica através de simulações computacionais utilizando o Método de Elementos Espectrais. Este tópico suscita grande interesse no meio tecnológico, pois esta configuração aparece com bastante freqüência em estruturas marítimas, como os \"risers\" de produção e umbilicais de plataformas de exploração de petróleo, e também no meio acadêmico, uma vez que se trata do estudo de fenômenos complexos originados do escoamento ao redor de uma geometria simples: cilindro circular. A pesquisa tem seu principal enfoque na avaliação da utilização do método espectral de elementos finitos para solução do escoamento bidimensional no limite do regime de esteira laminar, Re < ou = 200 , ao redor de um cilindro oscilando forçadamente e apoiado em base elástica. As simulações do escoamento ao redor de um cilindro oscilando forçadamente são realizadas com duas amplitudes de oscilação do cilindro: 0.15D e 0.40D . Para cada amplitude são utilizadas dez freqüências de oscilação: 0.8 s f , 0.85 s f , 0.9 s f , 0.95 s f , 0.975 s f , 0.9875 s f , 1.025 s f , 1.05 s f , 1.075 s f e 1.1 s f ; onde D é o diâmetro do cilindro e s f é a freqüência de desprendimento de vórtices para cilindro fixo. O objetivo destas simulações é a tentativa de observação do fenômeno da mudança brusca do ângulo de fase entre a força transversal à direção da corrente e o deslocamento do cilindro, \"phase-jump\", obtendo, deste modo, uma base para comparação com trabalhos já existentes sobre o mesmo tema, avaliando o método numérico utilizado para o caso do escoamento ao redor de um cilindro oscilando. As simulações do escoamento ao redor de um cilindro apoiado em base elástica (livre para oscilar) foram feitas com apenas um grau de liberdade: a direção transversal ao escoamento incidente (eixo y no caso estudado). O resultado mais importante deste tipo de configuração, do ponto de vista prático (projetos de \"risers\", e outras estruturas cilíndricas), é a curva max A / D versus r V , isto, devido à dependência da vida útil destas estruturas à máxima amplitude de oscilação. Para reproduzir a curva max A / D versus r V , foram escolhidos os seguintes valores de velocidade reduzida: 1.0, 2.0, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, e 10.0. / The goal of this work is to study through numerical simulations using the Spectral Elements Method the two-dimensional the flow past a single circular cylinder that is either in simple harmonic cross-flow oscillation or elastically mounted. This is a very important topic for the technological environment because this configuration is identical to offshore structures, like risers of oil production platform and is also important to scientific environment due to the study of complex phenomena originated from the flow past a very simple geometry: a circular cylinder. The focus of this research is to evaluate the use of Spectral Element Method for solution of two-dimensional flow past a circular cylinder that is either in simple harmonic cross-flow oscillation or elastically mounted, at the laminar wake limit, Re < or = 200 . Two oscillation amplitudes were employed for the forced oscillations simulations: 0.15D e 0.40D . And, for each amplitude, were selected ten frequencies: 0.8 s f , 0.85 s f , 0.9 s f , 0.95 s f , 0.975 s f , 0.9875 s f , 1.025 s f , 1.05 s f , 1.075 s f e 1.1 s f ; where D is the cylinder diameter and s f is the vortex shedding frequency. The phase jump phenomenon, e.g., the fast change of phase angle, is observed and compared with existents works evaluating the Spectral Elements Method for forced oscillations cases. In the elastically mounted simulations the most important result, for the practical point of view (risers design), is the max A / D x r V curve, e.g., maximum amplitude versus velocity ratio, due to the relation of risers lifetime with maximum oscillation amplitude. To build the max A / D x r V curve were selected the follow values of velocity ratio: 1.0, 2.0, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, e 10.0.